,aeroplanes by ,j4 ,s4 ,zerbe ,scanned by ,charles ,keller with ,omni,page ,professional ,,ocr software ,,aeroplanes ,this work is not intended to set forth the exploits of aviators nor to give a history of the ,art4 ,it is a book of instructions intended to point out the theories of flying1 as given by the pioneers1 the practical application of power to the various flying structures2 how they are built1 the different methods of controlling them2 the advantages and disadvantages of the types now in use2 and suggestions as to the directions in which improvements are required4 ,it distinctly points out wherein mechanical flight differs from bird flight1 and what are the relations of shape1 form1 size and weight4 ,it treats of kites1 gliders and model aeroplanes1 and has an ,interesting chapter on the aeroplane and its uses ,in the great war4 ,all the illustrations have been specially prepared for the work4 ,every ,boy's ,mechanical ,library ,,aeroplanes ,,by ,j4 ,s4 ,,zerbe1 ,m4 ,e4 ,author of ,automobiles--,motors ,,copyright1 #aiae1 ,,by ,,cupples ,,leon ,,company ,,ny ,,contents ,,introductory ,,chapter ,i4 ,,theories ,,and ,,facts ,,about ,,flying ,the ,science of ,aviation4 ,machine ,types4 ,shape or ,form not ,essential4 ,a ,stone as a ,flying ,machine4 ,power the ,great ,element4 ,gravity as ,power4 ,mass and ,element in ,flying4 ,momentum a ,factor4 ,resistance4 ,how ,resistance ,affects ,shape4 ,mass and ,resistance4 ,the ,early ,tendency to ,eliminate ,momentum4 ,light ,machines ,unstable4 ,the ,application of ,power4 ,the ,supporting ,surfaces4 ,area not the ,essential ,thing4 ,the ,law of ,gravity4 ,gravity4 ,indestructibility of ,gravitation4 ,distance ,reduces ,gravitational ,pull4 ,how ,motion ,antagonizes ,gravity4 ,a ,tangent4 ,tangential ,motion ,represents ,centrifugal ,pull4 ,equalizing the ,two ,motions4 ,lift and ,drift4 ,normal ,pressure4 ,head ,resistance4 ,measuring ,lift and ,drift4 ,pressure at ,different ,angles4 ,difference ,between ,lift and ,drift in ,motion4 ,tables of ,lift and ,drift4 ,why ,tables of ,lift and ,drift are ,wrong4 ,langley's ,law4 ,moving ,planes vs4 ,winds4 ,momentum not ,considered4 ,the ,flight of ,birds4 ,the ,downward ,beat4 ,the ,concaved ,wing4 ,feather ,structure ,considered4 ,webbed ,wings4 ,the ,angle of ,movement4 ,an ,initial ,movement or ,impulse ,necessary4 ,a ,wedging ,motion4 ,no ,mystery in the ,wave ,motion4 ,how ,birds ,poise with ,flapping ,wings4 ,narrow- winged ,birds4 ,initial ,movement of ,soaring ,birds4 ,soaring ,birds ,move ,swiftly4 ,muscular ,energy ,exerted by ,soaring ,birds4 ,wings not ,motionless4 ,,chapter ,,ii4 ,,principles ,,of ,,aeroplane ,,flight ,speed as one of the ,elements4 ,shape and ,speed4 ,what ,square of the ,speed ,means4 ,action of a ,skipper4 ,angle of ,incidence4 ,speed and ,surface4 ,control of the ,direction of ,flight4 ,vertical ,planes4 ,,chapter ,,iii4 ,,the ,,form ,,or ,,shape ,,of ,,flying ,,machines ,the ,theory of ,copying ,nature4 ,hulls of ,vessels4 ,man ,does not ,copy ,nature4 ,principles ,essential1 not ,forms4 ,nature not the ,guide as to ,forms4 ,the ,propeller ,type4 ,why ,specially-designed ,forms ,improve ,natural ,structures4 ,mechanism ,devoid of ,intelligence4 ,a ,machine ,must ,have a ,substitute for ,intelligence4 ,study of ,bird ,flight ,useless4 ,shape of ,supporting ,surface4 ,the ,trouble ,arising ,from ,outstretched ,wings4 ,density of the ,atmosphere4 ,elasticity of the ,air4 ,air ,holes4 ,responsibility for ,accidents4 ,the ,turning ,movement4 ,centrifugal ,action3 ,the ,warping ,planes4 ,,chapter ,,iv4 ,,fore ,,and ,,aft ,,control ,the ,bird ,type of ,fore and ,aft ,control4 ,angle and ,direction of ,flight4 ,why ,should the ,angle of the ,body ,change4 ,changing ,angle of ,body not ,safe4 ,a ,non-changing ,body4 ,descending ,positions by ,power ,control4 ,cutting off the ,power4 ,the ,starting ,movement4 ,the ,suggested ,type4 ,the ,low ,center of ,gravity4 ,fore and ,aft ,oscillations4 ,application of the ,new ,principle4 ,low ,weight not ,necessary with ,synchronously- moving wings4 ,,chapteb ,v4 ,,different ,,machine ,,types ,,and ,,their ,,characteristics ,the ,helicopter4 ,aeroplanes4 ,the ,monoplane4 ,its ,advantages4 ,its ,disadvantages4 ,the ,bi-plane4 ,stability in ,bi-planes4 ,the ,orthopter4 ,nature's ,type not ,uniform4 ,theories ,about ,flight of ,birds4 ,instinct4 ,the ,mode of ,motion4 ,the ,wing ,structure4 ,the ,wing ,movement4 ,the ,helicopter ,motion4 ,,chapter ,,vi4 ,,the ,,lifting ,,surfaces ,,of ,,aeroplanes ,relative ,speed and ,angle4 ,narrow ,planes ,most ,effective4 ,stream ,lines ,along a ,plane4 ,the ,center of ,pressure4 ,air ,lines on the ,upper ,side of a ,plane4 ,rarefied ,area4 ,rarefaction ,produced by ,motion4 ,the ,concaved ,plane4 ,the ,center of ,pressure4 ,utilizing the ,rarefied ,area4 ,changing ,center of ,pressure4 ,plane ,monstrosities4 ,the ,bird ,wing ,structure4 ,torsion4 ,the ,bat's ,wing4 ,an ,abnormal ,shape4 ,the ,tail as a ,monitor4 ,,chapter ,,vii4 ,,abnormal ,,flying ,,stunts ,,and ,,speeds ,lack of ,improvements in ,machines4 ,men ,exploited and not ,machines4 ,abnormal ,flying of no ,value4 ,the ,art of ,juggling4 ,practical ,uses the ,best ,test4 ,concaved and ,convex ,planes4 ,how ,momentum is a ,factor in ,inverted ,flying4 ,the ,turning ,movement4 ,when ,concaved ,planes are ,desirable4 ,the ,speed ,mania4 ,uses of ,flying ,machines4 ,perfection in ,machines ,must ,come ,before ,speed4 ,the ,range of its ,uses4 ,commercial ,utility4 ,,chapter ,,viii4 ,,kites ,,and ,,gliders ,the ,dragon ,kite4 ,its ,construction4 ,the ,malay ,kite4 ,dihedral ,angle4 ,the ,common ,kite4 ,the ,bow ,kite4 ,the ,box ,kite4 ,the ,voison ,bi-plane4 ,lateral ,stability in ,kites1 not ,conclusive as to ,planes4 ,the ,spear ,kite4 ,the ,cellular ,kite4 ,tetrahedral ,kite4 ,the ,deltoid4 ,the ,dunne ,flying ,machine4 ,rotating ,kite4 ,kite ,principles4 ,lateral ,stability in ,kites4 ,similarity of ,fore and ,aft ,control4 ,gliding ,flight ,one of the ,uses of ,glider ,experiments4 ,hints in ,gliding4 ,,chapter ,,ix4 ,,aeroplane ,,construction ,lateral and ,fore and ,aft4 ,transverse4 ,stability and ,stabilization4 ,the ,wright ,system4 ,controlling the ,warping ,ends4 ,the ,curtiss ,wings4 ,the ,farman ,ailerons4 ,features ,well ,developed4 ,depressing the ,rear ,end4 ,determining the ,size4 ,rule for ,placing the ,planes4 ,elevating ,plane4 ,action in ,alighting4 ,the ,monoplane4 ,the ,common ,fly4 ,stream ,lines4 ,the ,monoplane ,form4 ,,chapter ,x4 ,,power ,,and ,,its ,,application ,features in ,power ,application4 ,amount of ,power ,necessary4 ,the ,pull of the ,propeller4 ,foot ,pounds ,small ,amount of ,power ,available4 ,high ,propeller ,speed ,important4 ,width and ,pitch of ,blades4 ,effect of ,increasing ,propeller ,pull4 ,disposition of the ,planes4 ,different ,speeds with ,same ,power4 ,increase of ,speed ,adds to ,resistance4 ,how ,power ,decreases with ,speed4 ,how to ,calculate the ,power ,applied4 ,pulling ,against an ,angle4 ,the ,horizontal and the ,vertical ,pull4 ,the ,power ,mounting4 ,securing the ,propeller to the ,shaft4 ,vibrations4 ,weaknesses in ,mounting4 ,the ,gasoline ,tank4 ,where to ,locate the ,tank4 ,the ,danger to the ,pilot4 ,the ,closed-in ,body4 ,starting the ,machine4 ,propellers with ,varying ,pitch4 ,,chapter ,,xi4 ,,flying ,,machine ,,accessories ,the ,anemometer4 ,the ,anemograph4 ,the ,anemometrograph4 ,the ,speed ,indicator4 ,air ,pressure ,indicator4 ,determining the ,pressure ,from the ,speed4 ,calculating ,pressure ,from ,speed4 ,how the ,figures are ,determined4 ,converting ,hours ,into ,minutes4 ,changing ,speed ,hours to ,seconds4 ,pressure as the ,square of the ,speed4 ,gyroscopic3,balance4 ,the ,principles ,involved4 ,the ,application of the ,gyroscope4 ,fore and ,aft ,gyroscopic ,control4 ,angle ,indicator4 ,pendulum ,stabilizer4 ,steering and ,controlling ,wheel4 ,automatic ,stabilizing ,wings4 ,barometers4 ,aneroid ,barometer4 ,hydroplanes4 ,sustaining ,weight of ,pontoons4 ,shape of the ,pontoon4 ,,chapter ,,xii4 ,,experimental ,,work ,,in ,,flying ,certain ,conditions in ,flying4 ,heat in ,air4 ,motion ,when in ,flight4 ,changing ,atmosphere4 ,ascending ,currents4 ,aspirate ,currents4 ,outstretched ,wings4 ,the ,starting ,point4 ,the ,vital ,part of the ,machine4 ,studying the ,action of the ,machine4 ,elevating the ,machine4 ,how to ,practice4 ,the ,first ,stage4 ,patience the ,most ,difficult ,thing4 ,the ,second ,stage4 ,the ,third ,stage4 ,observations ,while in ,flight4 ,flying in a ,wind4 ,first ,trials in a ,quiet ,atmosphere4 ,making ,turns4 ,the ,fourth ,stage4 ,the ,figure #h4 ,the ,vol ,plane4 ,the ,landing4 ,flying ,altitudes4 ,,chapter ,,xiii4 ,,the ,,propeller ,propeller ,changes4 ,propeller ,shape4 ,the ,diameter4 ,pitch4 ,laying ,out the ,pitch4 ,pitch ,rule4 ,laminated ,construction4 ,laying up a ,propeller ,form4 ,making ,wide ,blades4 ,propeller ,outline4 ,for ,high ,speeds4 ,increasing ,propeller ,efficiency4 ,,chapter ,,xiv4 ,,experimental ,,gliders ,,and ,,model ,,aeroplanes ,the ,relation of ,models to ,flying ,machines4 ,lessons ,from ,models4 ,flying ,model ,aeroplanes4 ,an ,efficient ,glider4 ,the ,deltoid ,formation4 ,racing ,models4 ,the ,power for ,model ,aeroplanes4 ,making the ,propeller4 ,material for the ,propeller4 ,rubber4 ,propeller ,shape and ,size4 ,supporting ,surfaces4 ,,chapter ,,xv4 ,,the ,,aeroplane ,,in ,,the ,,great ,,war ,balloon ,observations4 ,changed ,conditions in ,warfare4 ,the ,effort to ,conceal ,combatants4 ,smokeless ,powder4 ,inventions to ,attack ,aerial ,craft4 ,functions of the ,aeroplane in ,war4 ,bomb-throwing ,tests4 ,method for ,determining the ,movement of a ,bomb4 ,the ,great ,extent of ,modern ,battle ,lines4 ,the ,aeroplane ,detecting the ,movements of ,armies4 ,the ,effective ,height for ,scouting4 ,sizes of ,objects at ,great ,distances4 ,some ,daring ,feats in ,war4 ,the ,german ,taube4 ,how ,aeroplanes ,report ,observations4 ,signal ,flags4 ,how ,used4 ,casualties ,due to ,bombs ,from ,aeroplanes4 ,,glossary ,,introductory ,in preparing this volume on ,flying ,machines the aim has been to present the subject in such a manner as will appeal to boys1 or beginners1 in this field of human activity4 ,the art of aviation is in a most primitive state4 ,so many curious theories have been brought out that1 while they furnish food for thought1 do not1 in any way1 advance or improve the structure of the machine itself1 nor are they of any service in teaching the novice how to fly4 ,the author considers it of far more importance to teach right principles1 and correct reasoning than to furnish complete diagrams of the details of a machine4 ,the former teach the art1 whereas the latter merely point out the mechanical arrangements1 independently of the reasons for making the structures in that particular way4 ,relating the history of an art1 while it may be interesting reading1 does not even lay the foundations of a knowledge of the subject1 hence that field has been left to others4 ,the boy is naturally inquisitive1 and he is interested in knowing ,,why certain things are necessary1 and the reasons for making structures in particular ways4 ,that is the void into which these pages are placed4 ,the author knows from practical experience1 while experimenting with and building aeroplanes1 how eagerly every boy inquires into details4 ,they want the reasons for things4 ,one such instance is related to evidence this spirit of inquiry4 ,some boys were discussing the curved plane structure4 ,one of them ventured the opinion that birds' wings were concaved on the lower side4 ,but1 retorted another1 why are birds' wings hollowed8 ,this was going back to first principles at one leap4 ,it was not satisfying enough to know that man was copying nature4 ,it was more important to know why nature originated that type of formation1 because1 it is obvious1 that if such structures are universal in the kingdom of flying creatures1 there must be some underlying principle which accounted for it4 ,it is not the aim of the book to teach the art of flying1 but rather to show how and why the present machines fly4 ,the making and the using are separate and independent functions1 and of the two the more important is the knowledge how to make a correct machine4 ,hundreds of workmen may contribute to the building of a locomotive1 but one man1 not a builder1 knows better how to handle it4 ,to manipulate a flying machine is more difficult to navigate than such a ponderous machine1 because it requires peculiar talents1 and the building is still more important and complicated1 and requires the exercise of a kind of skill not necessary in the locomotive4 ,the art is still very young2 so much is done which arises from speculation and theories2 too much dependence is placed on the aviator2 the desire in the present condition of the art is to exploit the man and not the machine2 dare-devil exhibitions seem to be more important than perfecting the mechanism2 and such useless attempts as flying upside down1 looping the loop1 and characteristic displays of that kind1 are of no value to the art4 ,,the ,,author4 ,,aeroplanes ,,chapter ,i ,,theories ,,and ,,facts ,,about ,,flying ,,the ,,science ,,of ,,aviation4--,it may be doubted whether there is such a thing as a science of aviation4 ,since ,langley1 on ,may #f1 #ahif1 flew a motor-propelled tandem monoplane for a minute and an half1 without a pilot1 and the ,wright ,brothers in #aijc succeeded in flying a bi-plane with a pilot aboard1 the universal opinion has been1 that flying machines1 to be successful1 must follow the structural form of birds1 and that shape has everything to do with flying4 ,we may be able to learn something by carefully examining the different views presented by those interested in the art1 and then see how they conform to the facts as brought out by the actual experiments4 ,,machine ,,types4--,there is really but one type of plane machine4 ,while technically two forms are known1 namely1 the monoplane and the bi-plane1 they are both dependent on outstretched wings1 longer transversely than fore and aft1 so far as the supporting surfaces are concerned1 and with the main weight high in the structure1 thus1 in every particular1 conforming to the form pointed out by nature as the apparently correct type of a flying structure4 ,,shape ,,or ,,form ,,not ,,essential4--,it may be stated with perfect confidence1 that shape or form has nothing to do with the mere act of flying4 ,it is simply a question of power4 ,this is a broad assertion1 and its meaning may be better understood by examining the question of flight in a broad sense4 ,a ,,stone ,,as ,a ,,flying ,,machine4--,when a stone is propelled through space1 shape is of no importance4 ,if it has rough and jagged sides its speed or its distance may be limited1 as compared with a perfectly rounded form4 ,it may be made in such a shape as will offer less resistance to the air in flight1 but its actual propulsion through space does not depend on how it is made1 but on the power which propelled it1 and such a missile is a true heavier-than-air machine4 ,a flying object of this kind may be so constructed that it will go a greater distance1 or require less power1 or maintain itself in space at less speed2 but it is a flying machine1 nevertheless1 in the sense that it moves horizontally through the air4 ,,power ,,the ,,great ,,element4--,now1 let us examine the question of this power which is able to set gravity at naught4 ,the quality called energy resides in material itself4 ,it is something within matter1 and does not come from without4 ,the power derived from the explosion of a charge of powder comes from within the substance2 and so with falling water1 or the expansive force of steam4 ,,gravity ,,as ,,power4--,indeed1 the very act of the ball gradually moving toward the earth1 by the force of gravity1 is an illustration of a power within the object itself4 ,long after ,galileo firmly established the law of falling bodies it began to dawn on scientists that weight is force4 ,after ,newton established the law of gravitation the old idea1 that power was a property of each body1 passed away4 ,in its stead we now have the firmly established view1 that power is something which must have at least two parts1 or consist in pairs1 or two elements acting together4 ,thus1 a stone poised on a cliff1 while it exerts no power which can be utilized1 has1 nevertheless1 what is called potential energy4 ,when it is pushed from its lodging place kinetic energy is developed4 ,in both cases1 gravity1 acting in conjunction with the mass of the stone1 produced power4 ,so in the case of gunpowder4 ,it is the unity of two or more substances1 that causes the expansion called power4 ,the heat of the fuel converting water into steam1 is another illustration of the unity of two or more elements1 which are necessary to produce energy4 ,,mass ,,an ,,element ,,in ,,flying4--,the boy who reads this will smile1 as he tells us that the power which propelled the ball through the air came from the thrower and not from the ball itself4 ,let us examine this claim1 which came from a real boy1 and is another illustration how acute his mind is on subjects of this character4 ,we have two balls the same diameter1 one of iron weighing a half pound1 and the other of cotton weighing a half ounce4 ,the weight of one is1 therefore1 sixteen times greater than the other4 ,suppose these two balls are thrown with the expenditure of the same power4 ,what will be the result6 ,the iron ball will go much farther1 or1 if projected against a wall will strike a harder blow than the cotton ball4 ,,momentum ,a ,,factor4--,each had transferred to it a motion4 ,the initial speed was the same1 and the power set up equal in the two4 ,why this difference1 ,the answer is1 that it is in the material itself4 ,it was the mass or density which accounted for the difference4 ,it was mass multiplied by speed which gave it the power1 called1 in this case1 momentum4 ,the iron ball weighing eight ounces1 multiplied by the assumed speed of #ej feet per second1 equals #djj units of work4 ,the cotton ball1 weighing #a_/b ounce1 with the same initial speed1 represents #be units of work4 ,the term unit of work means a measurement1 or a factor which may be used to measure force4 ,it will thus be seen that it was not the thrower which gave the power1 but the article itself4 ,a feather ball thrown under the same conditions1 would produce a half unit of work1 and the iron ball1 therefore1 produced #hjj times more energy4 ,,resistance4--,now1 in the movement of any body through space1 it meets with an enemy at every step1 and that is air resistance4 ,this is much more effective against the cotton than the iron ball3 or1 it might be expressed in another way3 ,the momentum1 or the power1 residing in the metal ball1 is so much greater than that within the cotton ball that it travels farther1 or strikes a more effective blow on impact with the wall4 ,,how ,,resistance ,,affects ,,the ,,shape4--,it is because of this counterforce1 resistance1 that shape becomes important in a flying object4 ,the metal ball may be flattened out into a thin disk1 and now1 when the same force is applied1 to project it forwardly1 it will go as much farther as the difference in the air impact against the two forms4 ,,mass ,,and ,,resistance4--,owing to the fact that resistance acts with such a retarding force on an object of small mass1 and it is difficult to set up a rapid motion in an object of great density1 lightness in flying machine structures has been considered1 in the past1 the principal thing necessary4 ,,the ,,early ,,tendency ,,to ,,eliminate ,,momentum4-- ,builders of flying machines1 for several years1 sought to eliminate the very thing which gives energy to a horizontally-movable body1 namely1 momentum4 ,instead of momentum1 something had to be substituted4 ,this was found in so arranging the machine that its weight1 or a portion of it1 would be sustained in space by the very element which seeks to retard its flight1 namely1 the atmosphere4 ,if there should be no material substance1 like air1 then the only way in which a heavier-than-air machine could ever fly1 would be by propelling it through space1 like the ball was thrown1 or by some sort of impulse or reaction mechanism on the air-ship itself4 ,it could get no support from the atmosphere4 ,,light ,,machines ,,unstable4--,gradually the question of weight is solving itself4 ,aviators are beginning to realize that momentum is a wonderful property1 and a most important element in flying4 ,the safest machines are those which have weight4 ,the light1 willowy machines are subject to every caprice of the wind4 ,they are notoriously unstable in flight1 and are dangerous even in the hands of experts4 ,,the ,,application ,,of ,,power4--,the thing now to consider is not form1 or shape1 or the distribution of the supporting surfaces1 but ,,how to apply the power so that it will rapidly transfer a machine at rest to one in motion1 and thereby get the proper support on the atmosphere to hold it in flight4 ,,the ,,supporting ,,surfaces4--,this brings us to the consideration of one of the first great problems in flying machines1 namely1 the supporting surfaces1--not its form1 shape or arrangement1 7which will be taken up in their proper places71 but the area1 the dimensions1 and the angle necessary for flight4 ,,area ,,not ,,the ,,essential ,,thing4--,the history of flying machines1 short as it is1 furnishes many examples of one striking fact3 ,that area has but little to do with sustaining an aeroplane when once in flight4 ,the first ,wright flyer weighed #gda pounds1 had about #djj square feet of plane surface1 and was maintained in the air with a #ab horse power engine4 ,true1 that machine was shot into the air by a catapult4 ,motion having once been imparted to it1 the only thing necessary for the motor was to maintain the speed4 ,there are many instances to show that when once in flight1 one horse power will sustain over #ajj pounds1 and each square foot of supporting surface will maintain #ij pounds in flight4 ,,the ,,law ,,of ,,gravity4--,as the effort to fly may be considered in the light of a struggle to avoid the laws of nature with respect to matter1 it may be well to consider this great force as a fitting prelude to the study of our subject4 ,proper understanding1 and use of terms is very desirable1 so that we must not confuse them4 ,thus1 weight and mass are not the same4 ,weight varies with the latitude1 and it is different at various altitudes2 but mass is always the same4 ,if projected through space1 a certain mass would move so as to produce momentum1 which would be equal at all places on the earth's surface1 or at any altitude4 ,gravity has been called weight1 and weight gravity4 ,the real difference is plain if gravity is considered as the attraction of mass for mass4 ,gravity is generally known and considered as a force which seeks to draw things to the earth4 ,this is too narrow4 ,gravity acts in all directions4 ,two balls suspended from strings and hung in close proximity to each other will mutually attract each other4 ,if one has double the mass it will have twice the attractive power4 ,if one is doubled and the other tripled1 the attraction would be increased six times4 ,but if the distance should be doubled the attraction would be reduced to one-fourth2 and if the distance should be tripled then the pull would be only one-ninth4 ,the foregoing is the substance of the law1 namely1 that all bodies attract all other bodies with a force directly in proportion to their mass1 and inversely as the square of their distance from one another4 ,to explain this we cite the following illustration3 ,two bodies1 each having a mass of #d pounds1 and one inch apart1 are attracted toward each other1 so they touch4 ,if one has twice the mass of the other1 the smaller will draw the larger only one-quarter of an inch1 and the large one will draw the other three-quarters of an inch1 thus confirming the law that two bodies will attract each other in proportion to their mass4 ,suppose1 now1 that these balls are placed two inches apart1--that is1 twice the distance4 ,as each is1 we shall say1 four pounds in weight1 the square of each would be #af4 ,this does not mean that there would be sixteen times the attraction1 but1 as the law says1 inversely as the square of the distance1 so that at two inches there is only one-sixteenth the attraction as at one inch4 ,if the cord of one of the balls should be cut1 it would fall to the earth1 for the reason that the attractive force of the great mass of the earth is so much greater than the force of attraction in its companion ball4 ,,indestructibility ,,of ,,gravitation4--,gravity cannot be produced or destroyed4 ,it acts between all parts of bodies equally2 the force being proportioned to their mass4 ,it is not affected by any intervening substance2 and is transmitted instantaneously1 whatever the distance may be4 ,while1 therefore1 it is impossible to divest matter of this property1 there are two conditions which neutralize its effect4 ,the first of these is position4 ,let us take two balls1 one solid and the other hollow1 but of the same mass1 or density4 ,if the cavity of the one is large enough to receive the other1 it is obvious that while gravity is still present the lines of attraction being equal at all points1 and radially1 there can be no pull which moves them together4 ,,distance ,,reduces ,,gravitational ,,pull4--,or the balls may be such distance apart that the attractive force ceases4 ,at the center of the earth an object would not weigh anything4 ,a pound of iron and an ounce of wood1 one sixteen times the mass of the other1 would be the same1--absolutely without weight4 ,if the object should be far away in space it would not be influenced by the earth's gravity2 so it will be understood that position plays an important part in the attraction of mass for mass4 ,,how ,,motion ,,antagonizes ,,gravity4--,the second way to neutralize gravity1 is by motion4 ,a ball thrown upwardly1 antagonizes the force of gravity during the period of its ascent4 ,in like manner1 when an object is projected horizontally1 while its mass is still the same1 its weight is less4 ,motion is that which is constantly combating the action of gravity4 ,a body moving in a circle must be acted upon by two forces1 one which tends to draw it inwardly1 and the other which seeks to throw it outwardly4 ,the former is called centripetal1 and the latter centrifugal motion4 ,gravity1 therefore1 represents centripetal1 and motion centrifugal force4 ,if the rotative speed of the earth should be retarded1 all objects on the earth would be increased in weight1 and if the motion should be accelerated objects would become lighter1 and if sufficient speed should be attained all matter would fly off the surface1 just as dirt dies off the rim of a wheel at certain speeds4 ,a ,,tangent4--,when an object is thrown horizontally the line of flight is tangential to the earth1 or at right angles to the force of gravity4 ,such a course in a flying machine finds less resistance than if it should be projected upwardly1 or directly opposite the centripetal pull4 ,fig #a4 ,tangential ,flight ,,tangential ,,motion ,,represents ,,centrifugal ,,pull4--,a tangential motion1 or a horizontal movement1 seeks to move matter away from the center of the earth1 and any force which imparts a horizontal motion to an object exerts a centrifugal pull for that reason4 ,in ,fig4 #a1 let ,a represent the surface of the earth1 ,b the starting point of the flight of an object1 and ,c the line of flight4 ,that represents a tangential line4 ,for the purpose of explaining the phenomena of tangential flight1 we will assume that the missile was projected with a sufficient force to reach the vertical point ,d1 which is #djjj miles from the starting point ,b4 ,in such a case it would now be over #eejj miles from the center of the earth1 and the centrifugal pull would be decreased to such an extent that the ball would go on and on until it came within the sphere of influence from some other celestial body4 ,,equalizing ,,the ,,two ,,motions4--,but now let us assume that the line of flight is like that shown at ,e1 in ,fig4 #b1 where it travels along parallel with the surface of the earth4 ,in this case the force of the ball equals the centripetal pull1--or1 to put it differently1 the centrifugal equals the gravitational pull4 ,the constant tendency of the ball to fly off at a tangent1 and the equally powerful pull of gravity acting against each other1 produce a motion which is like that of the earth1 revolving around the sun once every three hundred and sixty-five days4 ,it is a curious thing that neither ,langley1 nor any of the scientists1 in treating of the matter of flight1 have taken into consideration this quality of momentum1 in their calculations of the elements of flight4 ,fig4 #b ,horizontal ,flight ,all have treated the subject as though the whole problem rested on the angle at which the planes were placed4 ,at #de degrees the lift and drift are assumed to be equal4 ,,lift ,,and ,,drift4--,the terms should be explained1 in view of the frequent allusion which will be made to the terms hereinafter4 ,lift is the word employed to indicate the amount which a plane surface will support while in flight4 ,drift is the term used to indicate the resistance which is offered to a plane moving forwardly against the atmosphere4 ,fig4 #c4 ,lift and ,drift ,in ,fig4 #c the plane ,a is assumed to be moving forwardly in the direction of the arrow ,b4 ,this indicates the resistance4 ,the vertical arrow ,c shows the direction of lift1 which is the weight held up by the plane4 ,,normal ,,pressure4--,now there is another term much used which needs explanation1 and that is normal pressure4 ,a pressure of this kind against a plane is where the wind strikes it at right angles4 ,this is illustrated in ,fig4 #d1 in which the plane is shown with the wind striking it squarely4 ,it is obvious that the wind will exert a greater force against a plane when at its normal4 ,on the other hand1 the least pressure against a plane is when it is in a horizontal position1 because then the wind has no force against the surfaces1 and the only effect on the drift is that which takes place when the wind strikes its forward edge4 ,fig4 #d4 ,normal ,air ,pressure ,fig4 #e4 ,edge ,resistance ,,head ,,resistance4--,fig4 #e shows such a plane1 the only resistance being the thickness of the plane as at ,a4 ,this is called head resistance1 and on this subject there has been much controversy1 and many theories1 which will be considered under the proper headings4 ,if a plane is placed at an angle of #de degrees the lift and the drift are the same1 assumedly1 because1 if we were to measure the power required to drive it forwardly1 it would be found to equal the weight necessary to lift it4 ,that is1 suppose we should hold a plane at that angle with a heavy wind blowing against it1 and attach two pairs of scales to the plane1 both would show the same pull4 ,fig4 #f4 ,measuring ,lift and ,drift ,,measuring ,,lift ,,and ,,drift4--,in ,fig4 #f1 ,a is the plane1 ,b the horizontal line which attaches the plane to a scale ,c1 and ,d the line attaching it to the scale ,e4 ,when the wind is of sufficient force to hold up the plane1 the scales will show the same pull1 neglecting1 of course1 the weight of the plane itself4 ,,pressure ,,at ,,different ,,angles4--,what every one wants to know1 and a subject on which a great deal of experiment and time have been expended1 is to determine what the pressures are at the different angles between the horizontal1 and laws have been formulated which enable the pressures to be calculated4 ,,difference ,,between ,,lift ,,and ,,drift ,,in ,,motion4--,the first observation is directed to the differences that exist between the lift and drift1 when the plane is placed at an angle of less than #de degrees4 ,a machine weighing #ajjj pounds has always the same lift4 ,its mass does not change4 ,remember1 now1 we allude to its mass1 or density4 ,we are not now referring to weight1 because that must be taken into consideration1 in the problem4 ,as heretofore stated1 when an object moves horizontally1 it has less weight than when at rest4 ,if it had the same weight it would not move forwardly1 but come to rest4 ,when in motion1 therefore1 while the lift1 so far as its mass is concerned1 does not change1 the drift does decrease1 or the forward pull is less than when at #de degrees1 and the decrease is less and less until the plane assumes a horizontal position1 where it is absolutely nil1 if we do not consider head resistance4 ,,tables ,,of ,,lift ,,and ,,drift4--,all tables of ,lift and ,drift consider only the air pressures4 ,they do not take into account the fact that momentum takes an important part in the translation of an object1 like a flying machine4 ,a mass of material1 weighing #ajjj pounds while at rest1 sets up an enormous energy when moving through the air at fifty1 seventy-five1 or one hundred miles an hour4 ,at the latter speed the movement is about #afj feet per second1 a motion which is nearly sufficient to maintain it in horizontal flight1 independently of any plane surface4 ,such being the case1 why take into account only the angle of the plane8 ,it is no wonder that aviators have not been able to make the theoretical considerations and the practical demonstrations agree4 ,,why ,,tables ,,of ,,lift ,,and ,,drift ,,are ,,wrong4-- ,a little reflection will show why such tables are wrong4 ,they were prepared by using a plane surface at rest1 and forcing a blast of air against the plane placed at different angles2 and for determining air pressures1 this is1 no doubt1 correct4 ,but it does not represent actual flying conditions4 ,it does not show the conditions existing in an aeroplane while in flight4 ,to determine this1 short of actual experiments with a machine in horizontal translation1 is impossible1 unless it is done by taking into account the factor due to momentum and the element attributable to the lift of the plane itself due to its impact against the atmosphere4 ,,langley',s ,,law4--,the law enunciated by ,langley is1 that the greater the speed the less the power required to propel it4 ,water as a propelling medium has over seven hundred times more force than air4 ,a vessel having1 for instance1 twenty horse power1 and a speed of ten miles per hour1 would require four times that power to drive it through the water at double the speed4 ,the power is as the square of the speed4 ,with air the conditions are entirely different4 ,the boat submergence in the water is practically the same1 whether going ten or twenty miles an hour4 ,the head resistance is the same1 substantially1 at all times in the case of the boat2 with the flying machine the resistance of its sustaining surfaces decreases4 ,without going into a too technical description of the reasoning which led to the discovery of the law of air pressures1 let us try and understand it by examining the diagram1 ,fig4 #g4 ,a represents a plane at an angle of #de degrees1 moving forwardly into the atmosphere in the direction of the arrows ,b4 ,the measurement across the plane vertically1 along the line ,b1 which is called the sine of the angle1 represents the surface impact of air against the plane4 ,in ,fig4 #h the plane is at an angle of #bg degrees1 which makes the distance in height across the line ,c just one-half the length of the line ,b of ,fig4 #g1 hence the surface impact of the air is one-half that of ,fig4 #g1 and the drift is correspondingly decreased4 ,fig4 #g4 ,equal ,lift and ,drift in ,flight4 ,fig4 #h4 ,unequal ,lift and ,drift4 ,,moving ,,planes ,,vs4 ,,winds4--,in this way ,boisset1 ,duchemin1 ,langley1 and others1 determined the comparative drift1 and those results have been largely relied upon by aviators1 and assumed to be correct when applied to flying machines4 ,that they are not correct has been proven by the ,wrights and others1 the only explanation being that some errors had been made in the calculations1 or that aviators were liable to commit errors in observing the true angle of the planes while in flight4 ,,momentum ,,not ,,considered4--,the great factor of momentum has been entirely ignored1 and it is our desire to press the important point on those who begin to study the question of flying machines4 ,,the ,,flight ,,of ,,birds4--,volumes have been written concerning observations on the flight of birds4 ,the marvel has been why do soaring birds maintain themselves in space without flapping their wings4 ,in fact1 it is a much more remarkable thing to contemplate why birds which depend on flapping wings can fly4 ,,the ,,downward ,,beat4--,it is argued that the downward beat of the wings is so much more rapid than the upward motion1 that it gets an action on the air so as to force the body upwardly4 ,this is disposed of by the wing motion of many birds1 notoriously the crow1 whose lazily-flapping wings can be readily followed by the eye1 and the difference in movement1 if any1 is not perceptible4 ,,the ,,concaved ,,wing4--,it is also urged that the concave on the under side of the wing gives the quality of lift4 ,certain kinds of beetles1 and particularly the common house fly1 disprove that theory1 as their wings are perfectly flat4 ,,feather ,,structure ,,considered4--,then the feather argument is advanced1 which seeks to show that as each wing is made up of a plurality of feathers1 overlapping each other1 they form a sort of a valved surface1 opening so as to permit air to pass through them during the period of their upward movement1 and closing up as the wing descends4 ,it is difficult to perform this experiment with wings1 so as to show such an individual feather movement4 ,it is certain that there is nothing in the structure of the wing bone and the feather connection which points to any individual feather movement1 and our observation is1 that each feather is entirely too rigid to permit of such an opening up between them4 ,it is obvious that the wing is built up in that way for an entirely different reason4 ,soaring birds1 which do not depend on the flapping motion1 have the same overlapping feather formation4 ,,webbed ,,wings4--,furthermore1 there are numerous flying creatures which do not have feathered wings1 but web-like structures1 or like the house fly1 in one continuous and unbroken plane4 ,that birds which fly with flapping wings derive their support from the air1 is undoubtedly true1 and that the lift produced is due1 not to the form1 or shape1 or area of the wing1 is also beyond question4 ,the records show that every conceivable type of outlined structure is used by nature2 the material and texture of the wings themselves differ to such a degree that there is absolutely no similarity2 some have concaved under surfaces1 and others have not2 some fly with rapidly beating wings1 and others with slow and measured movements2 many of them fly with equal facility without flapping movements2 and the proportions of weight to wing surface vary to such an extent that it is utterly impossible to use such data as a guide in calculating what the proper surface should be for a correct flying machine4 ,,the ,,angle ,,of ,,movement4--,how1 then1 it may be asked1 do they get their support8 ,there must be something1 in all this variety and diversity of form1 of motion1 and of characteristics1 which supplies the true answer4 ,the answer lies in the angle of movement of every wing motion1 which is at the control of the bird1 and if this is examined it will be found that it supplies the correct answer to every type of wing which nature has made4 ,,an ,,initial ,,impulse ,,or ,,movement ,,necessary4-- ,let ,a1 ,fig4 #i1 represent the section of a bird's wing4 ,all birds1 whether of the soaring or the flapping kind1 must have an initial forward movement in order to attain flight4 ,this impulse is acquired either by running along the ground1 or by a leap1 or in dropping from a perch4 ,soaring birds cannot1 by any possibility1 begin flight1 unless there is such a movement to change from a position of rest to one of motion4 ,fig4 #i4 ,wing ,movement in ,flight4 ,in the diagram1 therefore1 the bird1 in moving forwardly1 while raising the wing upwardly1 depresses the rear edge of the wing1 as in position #a1 and when the wing beats downwardly the rear margin is raised1 in relation to its front margin1 as shown in position #b4 ,a ,,wedging ,,motion4--,thus the bird1 by a wedge-like motion1 gives a forwardly-propelling action1 and as the rear margin has more or less flexure1 its action against the air is less during its upward beat1 and this also adds to the upward lift of the body of the bird4 ,,no ,,mystery ,,in ,,the ,,wave ,,motion4--,there is no mystery in the effect of such a wave-like motion1 and it must be obvious that the humming bird1 and like flyers1 which poise at one spot1 are able to do so because1 instead of moving forwardly1 or changing the position of its body horizontally1 in performing the undulatory motion of the wing1 it causes the body to rock1 so that at the point where the wing joins the body1 an elliptical motion is produced4 ,fig4 #aj4 ,evolution of ,humming-,bird's ,wing4 ,,how ,,birds ,,poise ,,with ,,flapping ,,wings4--,this is shown in ,fig4 #aj1 in which eight successive positions of the wing are shown1 and wherein four of the position1 namely1 #a1 #b1 #c1 and #d1 represent the downward movement1 and #f1 #g1 #h1 and #i1 the upward beat4 ,all the wing angles are such that whether the suspension point of each wing is moving downwardly1 or upwardly1 a support is found in some part of the wing4 ,,narrow-,,winged ,,birds4--,birds with rapid flapping motions have comparatively narrow wings1 fore and aft4 ,those which flap slowly1 and are not swift flyers1 have correspondingly broader wings4 ,the broad wing is also typical of the soaring birds4 ,but how do the latter overcome gravitation without exercising some sort of wing movement8 ,,initial ,,movement ,,of ,,soaring ,,birds4--,acute observations show that during the early stages of flight1 before speed is acquired1 they depend on the undulating movement of the wings1 and some of them acquire the initial motion by flapping4 ,when speed is finally attained it is difficult for the eye to note the motion of the wings4 ,,soaring ,,birds ,,move ,,swiftly4--,now1 the first observation is1 that soaring birds are swiftly- moving creatures4 ,as they sail overhead majestically they seem to be moving slowly4 ,but distance is deceptive4 ,the soaring bird travels at great speeds1 and this in itself should be sufficient to enable us to cease wondering1 when it is remembered that swift translation decreases weight1 so that this factor does not1 under those conditions1 operate against flight4 ,,muscular ,,energy ,,exerted ,,by ,,soaring ,,birds4 --,it is not conceivable that the mere will of the bird would impel it forwardly1 without it exerted some muscular energy to keep up its speed4 ,the distance at which the bird performs this wonderful evolution is at such heights from the observer that the eye cannot detect a movement4 ,,wings ,,not ,,motionless4--,while the wings appear to be absolutely motionless1 it is more reasonable to assume that a slight sinuous movement1 or a rocking motion is constantly kept up1 which wedges forwardly with sufficient speed to compel momentum to maintain it in flight4 ,to do so requires but a small amount of energy4 ,the head resistance of the bird formation is reduced to a minimum1 and at such high speeds the angle of incidence of the wings is very small1 requiring but little aid to maintain it in horizontal flight4 ,,chapter ,,ii ,,principles ,,of ,,aeroplane ,,flight ,,from the foregoing chapter1 while it may be rightly inferred that power is the true secret of aeroplane flight1 it is desirable to point out certain other things which must be considered4 ,,speed ,,as ,,one ,,of ,,the ,,elements--,every boy1 probably1 has at some time or other thrown small flat stones1 called skippers4 ,he has noticed that if they are particularly thin1 and large in diameter1 that there is a peculiar sailing motion1 and that they move through the air in an undulating or wave-like path4 ,two things contribute to this motion2 one is the size of the skipper1 relative to its weight1 and the other is its speed4 ,if the speed is slow it will quickly wend its way to the earth in a gradual curve4 ,this curved line is called its trajectory4 ,if it is not very large diametrically1 in proportion to its weight1 it will also make a gradual curve in descending1 without skimming up and down in its flight4 ,,shape ,,and ,,speed4--,it has been observed1 also1 that a round ball1 or an object not flattened out1 will make a regular curved path1 whatever the speed may be4 ,it may be assumed1 therefore1 that the shape alone does not account for this sinuous motion2 but that speed is the element which accounts for it4 ,such being the case it may be well to inquire into the peculiar action which causes a skipper to dart up and down1 and why the path thus formed grows more and more accentuated as the speed increases4 ,as will be more fully described in a later chapter1 the impact of air against a moving body does not increase in proportion to its speed1 but in the ratio of the square of the speed4 ,,what ,,square ,,of ,,the ,,speed ,,means4--,in mathematics a figure is squared when it is multiplied by itself4 ,thus1 #d ,x #d #af2 #e ,x #e #be2 and so on1 so that #af is the square of #d1 and #be the square of #e4 ,it has been found that a wind moving at the speed of #bj miles an hour has a striking or pushing force of #b pounds on every square foot of surface4 ,if the wind travels twice as fast1 or #dj miles an hour1 the pushing force is not #d pounds1 but #h pounds4 ,if the speed is #fj miles an hour the pushing force increases to #ah pounds4 ,,action ,,of ,a ,,skipper4--,when the skipper leaves the hands of the thrower it goes through the air in such a way that its fiat surface is absolutely on a line with the direction in which it is projected4 ,at first it moves through the air solely by force of the power which impels it1 and does not in any way depend on the air to hold it up4 ,see ,fig4 #a1 in which ,a represents the line of projection1 and ,b the disk in its flight4 ,fig4 #aa4 ,a ,skipper in ,flight4 ,after it has traveled a certain distance1 and the force decreases1 it begins to descend1 thus describing the line ,c1 ,fig4 #a1 the disk ,b1 in this case descending1 without changing its position1 which might be described by saying that it merely settles down to the earth without changing its plane4 ,the skipper still remains horizontal1 so that as it moves toward the earth its flat surface1 which is now exposed to the action of the air1 meets with a resistance1 and this changes the angle of the disk1 so that it will not be horizontal4 ,instead it assumes the position as indicated at ,d1 and this impinging effect against the air causes the skipper to move upwardly along the line ,e1 and having reached a certain limit1 as at1 say ,e1 it automatically again changes its angle and moves downwardly along the path ,f1 and thus continues to undulate1 more or less1 dependent on the combined action of the power and weight1 or momentum1 until it reaches the earth4 ,it is1 therefore1 clear that the atmosphere has an action on a plane surface1 and that the extent of the action1 to sustain it in flight1 depends on two things1 surface and speed4 ,furthermore1 the greater the speed the less the necessity for surface1 and that for gliding purposes speed may be sacrificed1 in a large measure1 where there is a large surface4 ,this very action of the skipper is utilized by the aviator in volplaning1--that is1 where the power of the engine is cut off1 either by accident1 or designedly1 and the machine descends to the earth1 whether in a long straight glide1 or in a great circle4 ,as the machine nears the earth it is caused to change the angle of flight by the control mechanism so that it will dart upwardly at an angle1 or downwardly1 and thus enable the pilot to sail to another point beyond where he may safely land4 ,this changing the course of the machine so that it will glide upwardly1 means that the incidence of the planes has been changed to a positive angle4 ,,angle ,,of ,,incidence4--,in aviation this is a term given to the position of a plane1 relative to the air against which it impinges4 ,if1 for instance1 an aeroplane is moving through the air with the front margin of the planes higher than their rear margins1 it is said to have the planes at a positive angle of incidence4 ,if the rear margins are higher than the front1 then the planes have a negative angle of incidence4 ,the word incidence really means1 a falling upon1 or against2 and it will be seen1 therefore1 that the angle of incidence means the tilt of the planes in relation to the air which strikes it4 ,having in view1 therefore1 that the two qualities1 namely1 speed and surface1 bear an intimate relation with each other1 it may be understood wherein mechanical flight is supposed to be analogous to bird flight4 ,,speed ,,and ,,surface4--,birds which poise in the air1 like the humming bird1 do so because they beat their wings with great rapidity4 ,those which soar1 as stated1 can do so only by moving through the atmosphere rapidly1 or by having a large wing spread relative to the weight4 ,it will thus be seen that speed and surface become the controlling factors in flight1 and that while the latter may be entirely eliminated from the problem1 speed is absolutely necessary under any and all conditions4 ,by speed in this connection is not meant high velocity1 but that a movement1 produced by power expressed in some form1 is the sole and most necessary requisite to movement through the air with all heavier-than-air machines4 ,if sufficient power can be applied to an aeroplane1 surface is of no consequence2 shape need not be considered1 and any sort of contrivance will move through the air horizontally4 ,,control ,,of ,,the ,,direction ,,of ,,flight4--,but the control of such a body1 when propelled through space by force alone1 is a different matter4 ,to change the machine from a straight path to a curved one1 means that it must be acted upon by some external force4 ,we have explained that power is something which is inherent in the thing itself4 ,now1 in order that there may be a change imparted to a moving mass1 advantage must be taken of the medium through which it moves1--the atmosphere4 ,,vertical ,,control ,,planes4--,if vertically-arranged planes are provided1 either fore or aft of the machine1 or at both ends1 the angles of incidence may be such as to cause the machine to turn from its straight course4 ,in practice1 therefore1 since it is difficult to supply sufficient power to a machine to keep it in motion horizontally1 at all times1 aeroplanes are provided with supporting surfaces1 and this aid in holding it up grows less and less as its speed increases4 ,but1 however strong the power1 or great the speed1 its control from side to side is not dependent on the power of the engine1 or the speed at which it travels through the air4 ,here the size of the vertical planes1 and their angles1 are the only factors to be considered1 and these questions will be considered in their proper places4 ,,chapter ,,iii ,,the ,,form ,,or ,,shape ,,of ,,flying ,,machines ,,every investigator1 experimenter1 and scientist1 who has given the subject of flight study1 proceeds on the theory that in order to fly man must copy nature1 and make the machine similar to the type so provided4 ,,the ,,theory ,,of ,,copying ,,nature4--,if such is the case then it is pertinent to inquire which bird is the proper example to use for mechanical flight4 ,we have shown that they differ so radically in every essential1 that what would be correct in one thing would be entirely wrong in another4 ,the bi-plane is certainly not a true copy4 ,the only thing in the ,wright machine which in any way resembles the bird's wing1 is the rounded end of the planes1 and judging from other machines1 which have square ends1 this slight similarity does not contribute to its stability or otherwise help the structure4 ,the monoplane1 which is much nearer the bird type1 has also sounded wing ends1 made not so much for the purpose of imitating the wing of the bird1 as for structural reasons4 ,,hulls ,,of ,,vessels4--,if some marine architect should come forward and assert that he intended to follow nature by making a boat with a hull of the shape or outline of a duck1 or other swimming fowl1 he would be laughed at1 and justly so1 because the lines of vessels which are most efficient are not made like those of a duck or other swimming creatures4 ,,man ,,does ,,not ,,copy ,,nature4--,look about you1 and see how many mechanical devices follow the forms laid down by nature1 or in what respect man uses the types which nature provides in devising the many inventions which ingenuity has brought forth4 ,,principles ,,essential1 ,,not ,,forms4--,it is essential that man shall follow nature's laws4 ,he cannot evade the principles on which the operations of mechanism depend2 but in doing so he has1 in nearly every instance1 departed from the form which nature has suggested1 and made the machine irrespective of nature's type4 ,let us consider some of these striking differences to illustrate this fact4 ,originally pins were stuck upon a paper web by hand1 and placed in rows1 equidistant from each other4 ,this necessitates the cooperative function of the fingers and the eye4 ,an expert pin sticker could thus assemble from four to five thousand pins a day4 ,the first mechanical pinsticker placed over #ejj1jjj pins a day on the web1 rejecting every bent or headless pin1 and did the work with greater accuracy than it was possible to do it by hand4 ,there was not the suggestion of an eye1 or a finger in the entire machine1 to show that nature furnished the type4 ,,nature ,,not ,,the ,,guide ,,as ,,to ,,forms4--,nature does not furnish a wheel in any of its mechanical expressions4 ,if man followed nature's form in the building of the locomotive1 it would move along on four legs like an elephant4 ,curiously enough1 one of the first road wagons had push legs1--an instance where the mechanic tried to copy nature1--and failed4 ,,the ,,propeller ,,type4--,the well known propeller is a type of wheel which has no prototype in nature4 ,it is maintained that the tail of a fish in its movement suggested the propeller1 but the latter is a long departure from it4 ,the ,venetian rower1 who stands at the stern1 and with a long-bladed oar1 fulcrumed to the boat's extremity1 in making his graceful lateral oscillations1 simulates the propelling motion of the tail in an absolutely perfect manner1 but it is not a propeller1 by any means comparable to the kind mounted on a shaft1 and revoluble4 ,how much more efficient are the spirally-formed blades of the propeller than any wing or fin movement1 in air or sea4 ,there is no comparison between the two forms in utility or value4 ,again1 the connecting points of the arms and legs with the trunk of a human body afford the most perfect types of universal joints which nature has produced4 ,the man-made universal joint has a wider range of movement1 possesses greater strength1 and is more perfect mechanically4 ,a universal joint is a piece of mechanism between two elements1 which enables them to be turned1 or moved1 at any angle relative to each other4 ,but why multiply these instances4 ,like samples will be found on every hand1 and in all directions1 and man1 the greatest of all of nature's products1 while imperfect in himself1 is improving and adapting the things he sees about him4 ,,why ,,specially-,,designed ,,forms ,,improve ,,natural ,,structures4--,the reason for this is1 primarily1 that the inventor must design the article for its special work1 and in doing so makes it better adapted to do that particular thing4 ,the hands and fingers can do a multiplicity of things1 but it cannot do any particular work with the facility or the degree of perfection that is possible with the machine made for that purpose4 ,the hands and fingers will bind a sheaf of wheat1 but it cannot compete with the special machine made for that purpose4 ,on the other hand the binder has no capacity to do anything else than what it was specially made for4 ,in applying the same sort of reasoning to the building of flying machines we must be led to the conclusion that the inventor can1 and will1 eventually1 bring out a form which is as far superior to the form which nature has taught us to use as the wonderful machines we see all about us are superior to carry out the special work they were designed to do4 ,on land1 man has shown this superiority over matter1 and so on the sea4 ,singularly1 the submarines1 which go beneath the sea1 are very far from that perfected state which have been attained by vessels sailing on the surface2 and while the means of transportation on land are arriving at points where the developments are swift and remarkable1 the space above the earth has not yet been conquered1 but is going through that same period of development which precedes the production of the true form itself4 ,,mechanism ,,devoid ,,of ,,intelligence4--,the great error1 however1 in seeking to copy nature's form in a flying machine is1 that we cannot invest the mechanism with that which the bird has1 namely1 a guiding intelligence to direct it instinctively1 as the flying creature does4 ,a ,,machine ,,must ,,have ,a ,,substitute ,,for ,,intelligence4 --,such being the case it must be endowed with something which is a substitute4 ,a bird is a supple1 pliant organism2 a machine is a rigid structure4 ,one is capable of being directed by a mind which is a part of the thing itself2 while the other must depend on an intelligence which is separate from it1 and not responsive in feeling or movement4 ,for the foregoing reasons success can never be attained until some structural form is devised which will consider the flying machine independently of the prototypes pointed out as the correct things to follow4 ,it does not1 necessarily1 have to be unlike the bird form1 but we do know that the present structures have been made and insisted upon blindly1 because of this wrong insistence on forms4 ,,study ,,of ,,bird ,,flight ,,useless4--,the study of the flight of birds has never been of any special value to the art4 ,volumes have been written on the subject4 ,the ,seventh ,duke of ,argyle1 and later1 ,pettigrew1 an ,englishman1 contributed a vast amount of written matter on the subject of bird flight1 in which it was sought to show that soaring birds did not exert any power in flying4 ,writers and experimenters do not agree on the question of the propulsive power1 or on the form or shape of the wing which is most effective1 or in the matter of the relation of surface to weight1 nor do they agree in any particular as to the effect and action of matter in the soaring principle4 ,only a small percentage of flying creatures use motionless wings as in soaring4 ,by far1 the greater majority use beating wings1 a method of translation in air which has not met with success in any attempts on the part of the inventor4 ,nevertheless1 experimenting has proceeded on lines which seek to recognize nature's form only1 while avoiding the best known and most persistent type4 ,,shape ,,of ,,supporting ,,surfaces4--,when we examine the prevailing type of supporting surfaces we cannot fail to be impressed with one feature1 namely1 the determination to insist on a broad spread of plane surface1 in imitation of the bird with outstretched wings4 ,,the ,,trouble ,,arising ,,from ,,outstretched ,,wings4--,this form of construction is what brings all the troubles in its train4 ,the literature on aviation is full of arguments on this subject1 all declaring that a wide spread is essential1 because1 --birds fly that way4 ,these assertions are made notwithstanding the fact that only a few years ago1 in the great exhibit of aeroplanes in ,paris1 many unique forms of machines were shown1 all of them capable of flying1 as proven by numerous experiments1 and among them were a half dozen types whose length fore and aft were much greater than transversely1 and it was particularly noted that they had most wonderful stability4 ,,density ,,of ,,the ,,atmosphere4--,experts declare that the density of the atmosphere varies throughout1 --that it has spots here and there which are1 apparently1 like holes1 so that one side or the other of the machine will1 unaccountably1 tilt1 and sometimes the entire machine will suddenly drop for many feet1 while in flight4 ,,elasticity ,,of ,,the ,,air4--,air is the most elastic substance known4 ,the particles constituting it are constantly in motion4 ,when heat or cold penetrate the mass it does so1 in a general way1 so as to permeate the entire body1 but the conductivity of the atmospheric gases is such that the heat does not reach all parts at the same time4 ,,air ,,holes4--,the result is that varying strata of heat and cold seem to be superposed1 and also distributed along the route taken by a machine1 causing air currents which vary in direction and intensity4 ,when1 therefore1 a rapidly-moving machine passes through an atmosphere so disturbed1 the surfaces of the planes strike a mass of air moving1 we may say1 first toward the plane1 and the next instant the current is reversed1 and the machine drops1 because its support is temporarily gone1 and the aviator experiences the sensation of going into a hole4 ,,responsibility ,,for ,,accidents4--,these so-called holes are responsible for many accidents4 ,the outstretched wings1 many of them over forty feet from tip to tip1 offer opportunities for a tilt at one end or the other1 which has sent so many machines to destruction4 ,the high center of gravity in all machines makes the weight useless to counterbalance the rising end or to hold up the depressed wing4 ,all aviators agree that these unequal areas of density extend over small spaces1 and it is1 therefore1 obvious that a machine which is of such a structure that it moves through the air broadside on1 will be more liable to meet these inequalities than one which is narrow and does not take in such a wide path4 ,why1 therefore1 persist in making a form which1 by its very nature1 invites danger8 ,because birds fly that way6 ,,the ,,turning ,,movement4--,this structural arrangement accentuates the difficulty when the machine turns4 ,the air pressure against the wing surface is dependent on the speed4 ,the broad outstretched surfaces compel the wing at the outer side of the circle to travel faster than the inner one4 ,as a result1 the outer end of the aeroplane is elevated4 ,,centrifugal ,,action4--,at the same time the running gear1 and the frame which carries it and supports the machine while at rest1 being below the planes1 a centrifugal force is exerted1 when turning a circle1 which tends to swing the wheels and frame outwardly1 and thereby still further elevating the outer end of the plane4 ,,the ,,warping ,,planes4--,the only remedy to meet this condition is expressed in the mechanism which wraps or twists the outer ends of the planes1 as constructed in the ,wright machine1 or the ailerons1 or small wings at the rear margins of the planes1 as illustrated by the ,farman machine4 ,the object of this arrangement is to decrease the angle of incidence at the rising end1 and increase the angle at the depressed end1 and thus1 by manually- operated means keep the machine on an even keel4 ,,chapter ,,iv ,,fore ,,and ,,aft ,,control ,,there is no phase of the art of flying more important than the fore and aft control of an airship4 ,lateral stability is secondary to this feature1 for reasons which will appear as we develop the subject4 ,,the ,,bird ,,type ,,of ,,fore ,,and ,,aft ,,control4-- ,every aeroplane follows the type set by nature in the particular that the body is caused to oscillate on a vertical fore and aft plane while in flight4 ,the bird has one important advantage1 however1 in structure4 ,its wing has a flexure at the joint1 so that its body can so oscillate independently of the angle of the wings4 ,the aeroplane has the wing firmly fixed to the body1 hence the only way in which it is possible to effect a change in the angle of the wing is by changing the angle of the body4 ,to be consistent the aeroplane should be so constructed that the angle of the supporting surfaces should be movable1 and not controllable by the body4 ,the bird1 in initiating flight from a perch1 darts downwardly1 and changes the angle of the body to correspond with the direction of the flying start4 ,when it alights the body is thrown so that its breast banks against the air1 but in ordinary flight its wings only are used to change the angle of flight4 ,,angle ,,and ,,direction ,,of ,,flight4--,in order to become familiar with terms which will be frequently used throughout the book1 care should be taken to distinguish between the terms angle and direction of flight4 ,the former has reference to the up and down movement of an aeroplane1 whereas the latter is used to designate a turning movement to the right or to the left4 ,,why ,,should ,,the ,,angle ,,of ,,the ,,body ,,change8 --,the first question that presents itself is1 why should the angle of the aeroplane body change8 ,why should it be made to dart up and down and produce a sinuous motion8 ,why should its nose tilt toward the earth1 when it is descending1 and raise the forward part of the structure while ascending8 ,the ready answer on the part of the bird-form advocate is1 that nature has so designed a flying structure4 ,the argument is not consistent1 because in this respect1 as in every other1 it is not made to conform to the structure which they seek to copy4 ,,changing ,,angle ,,of ,,body ,,not ,,safe4--,furthermore1 there is not a single argument which can be advanced in behalf of that method of building1 which proves it to be correct4 ,contrariwise1 an analysis of the flying movement will show that it is the one feature which has militated against safety1 and that machines will never be safe so long as the angle of the body must be depended upon to control the angle of flying4 ,fig4 #aa;a ,monoplane in ,flight4 ,in ,fig4 #aa;a three positions of a monoplane are shown1 each in horizontal flight4 ,let us say that the first figure ,a is going at #dj miles per hour1 the second1 ,b1 at #ej1 and the third1 ,c1 at #fj miles4 ,the body in ,a is nearly horizontal1 the angle of the plane ,d being such that1 with the tail ,e also horizontal1 an even flight is maintained4 ,when the speed increases to #ej miles an hour1 the angle of incidence in the plane ,d must be decreased1 so that the rear end of the frame must be raised1 which is done by giving the tail an angle of incidence1 otherwise1 as the upper side of the tail should meet the air it would drive the rear end of the frame down1 and thus defeat the attempt to elevate that part4 ,fig4 #ab4 ,angles of ,flight4 ,as the speed increases ten miles more1 the tail is swung down still further and the rear end of the frame is now actually above the plane of flight4 ,in order1 now1 to change the angle of flight1 without altering the speed of the machine1 the tail is used to effect the control4 ,examine the first diagram in ,fig4 #ab4 ,this shows the tail ,e still further depressed1 and the air striking its lower side1 causes an upward movement of the frame at that end1 which so much decreases the angle of incidence that the aeroplane darts downwardly4 ,in order to ascend1 the tail1 as shown in the second diagram1 is elevated so as to depress the rear end1 and now the sustaining surface shoots upwardly4 ,suppose that in either of the positions #a or #b1 thus described1 the aviator should lose control of the mechanism1 or it should become deranged or stick1 conditions which have existed in the history of the art1 what is there to prevent an accident8 ,in the first case1 if there is room1 the machine will loop the loop1 and in the second case the machine will move upwardly until it is vertical1 and then1 in all probability1 as its propelling power is not sufficient to hold it in that position1 like a helicopter1 and having absolutely no wing supporting surface when in that position1 it will dart down tail foremost4 ,a ,,non-,,changing ,,body4--,we may contrast the foregoing instances of flight with a machine having the sustaining planes hinged to the body in such a manner as to make the disposition of its angles synchronous with the tail4 ,in other words1 see how a machine acts that has the angle of flight controllable by both planes1--that is1 the sustaining planes1 as well as the tail4 ,fig4 #ac4 ,planes on ,non-changing ,body4 ,in ,fig4 #ac let the body of the aeroplane be horizontal1 and the sustaining planes ,b disposed at the same angle1 which we will assume to be #ae degrees1 this being the imaginary angle for illustrative purposes1 with the power of the machine to drive it along horizontally1 as shown in position #a4 ,in position #b the angles of both planes are now at #aj degrees1 and the speed #fj miles an hour1 which still drives the machine forward horizontally4 ,in position #c the angle is still less1 being now only #e degrees but the speed is increased to #hj miles per hour1 but in each instance the body of the machine is horizontal4 ,now it is obvious that in order to ascend1 in either case1 the changing of the planes to a greater angle would raise the machine1 but at the same time keep the body on an even keel4 ,fig4 #ad4 ,descent with ,non-changing ,body4 ,,descending ,,positions ,,by ,,power ,,control4--,in ,fig4 #ad the planes are the same angles in the three positions respectively1 as in ,fig4 #ac1 but now the power has been reduced1 and the speeds are #cj1 #be1 and #bj miles per hour1 in positions ,a1 ,b and ,c4 ,suppose that in either position the power should cease1 and the control broken1 so that it would be impossible to move the planes4 ,when the machine begins to lose its momentum it will descend on a curve shown1 for instance1 in ,fig4 #ae1 where position #a of ,fig4 #ad is taken as the speed and angles of the plane when the power ceased4 ,fig4 #ae4 ,utilizing ,momentum4 ,,cutting ,,off ,,the ,,power4--,this curve1 ,a1 may reach that point where momentum has ceased as a forwardly-propelling factor1 and the machine now begins to travel rearwardly4 7,fig4 #af47 ,it has still the entire supporting surfaces of the planes4 ,it cannot loop-the-loop1 as in the instance where the planes are fixed immovably to the body4 ,carefully study the foregoing arrangement1 and it will be seen that it is more nearly in accord with the true flying principle as given by nature than the vaunted theories and practices now indulged in and so persistently adhered to4 ,the body of a flying machine should not be oscillated like a lever4 ,the support of the aeroplane should never be taken from it4 ,while it may be impossible to prevent a machine from coming down1 it can be prevented from overturning1 and this can be done without in the least detracting from it structurally4 ,fig4 #af4 ,reversing ,motion4 ,the plan suggested has one great fault1 however4 ,it will be impossible with such a structure to cause it to fly upside down4 ,it does not present any means whereby dare-devil stunts can be performed to edify the grandstand4 ,in this respect it is not in the same class with the present types4 ,,the ,,starting ,,movement4--,examine this plan from the position of starting1 and see the advantages it possesses4 ,in these illustrations we have used1 for convenience only1 the monoplane type1 and it is obvious that the same remarks apply to the bi-plane4 ,fig4 #ag shows the starting position of the stock monoplane1 in position #a1 while it is being initially run over the ground1 preparatory to launching4 ,position #b represents the negative angle at which the tail is thrown1 which movement depresses the rear end of the frame and thus gives the supporting planes the proper angle to raise the machine1 through a positive angle of incidence1 of the plane4 ,fig4 #ag4 ,showing changing angle of body4 ,,the ,,suggested ,,type4--,in ,fig4 #ah the suggested type is shown with the body normally in a horizontal position1 and the planes in a neutral position1 as represented in position #a4 ,when sufficient speed had been attained both planes are turned to the same angle1 as in position #b1 and flight is initiated without the abnormal oscillating motion of the body4 ,but now let us see what takes place the moment the present type is launched4 ,if1 by any error on the part of the aviator1 he should fail to readjust the tail to a neutral or to a proper angle of incidence1 after leaving the ground1 the machine would try to perform an over-head loop4 ,the suggested plan does not require this caution4 ,the machine may rise too rapidly1 or its planes may be at too great an angle for the power or the speed1 or the planes may be at too small an angle1 but in either case1 neglect would not turn the machine to a dangerous position4 ,these suggestions are offered to the novice1 because they go to the very foundation of a correct understanding of the principles involved in the building and in the manipulation of flying machines and while they are counter to the beliefs of aviators1 as is shown by the persistency in adhering to the old methods1 are believed to be mechanically correct1 and worthy of consideration4 ,,the ,,low ,,center ,,of ,,gravity4--,but we have still to examine another feature which shows the wrong principle in the fixed planes4 ,the question is often asked1 why do the builders of aeroplanes place most of the weight up close to the planes8 ,it must be obvious to the novice that the lower the weight the less liability of overturning4 ,,fore ,,and ,,aft ,,oscillations4--,the answer is1 that when the weight is placed below the planes it acts like a pendulum4 ,when the machine is traveling forward1 and the propeller ceases its motion1 as it usually does instantaneously1 the weight1 being below1 and having a certain momentum1 continues to move on1 and the plane surface meeting the resistance just the same1 and having no means to push it forward1 a greater angle of resistance is formed4 ,in ,fig4 #ai this action of the two forces is illustrated4 ,the plane at the speed of #cj miles is at an angle of #ae degrees1 the body ,b of the machine being horizontal1 and the weight ,c suspended directly below the supporting surfaces4 ,the moment the power ceases the weight continues moving forwardly1 and it swings the forward end of the frame upwardly1 ,fig4 #bj1 and we now have1 as in the second figure1 a new angle of incidence1 which is #cj degrees1 instead of #ab4 ,it will be understood that in order to effect a change in the position of the machine1 the forward end ascends1 as shown by the dotted line ,a4 ,fig4 #bj4 ,action when ,propeller ceases to pull4 ,the weight a having now ascended as far as possible forward in its swing1 and its motion checked by the banking action of the plan it will again swing back1 and again carry with it the frame1 thus setting up an oscillation1 which is extremely dangerous4 ,the tail ,e1 with its unchanged angle1 does not1 in any degree1 aid in maintaining the frame on an even keel4 ,being nearly horizontal while in flight1 if not at a negative angle1 it actually assists the forward end of the frame to ascend4 ,,application ,,of ,,the ,,new ,,principle4--,extending the application of the suggested form1 let us see wherein it will prevent this pendulous motion at the moment the power ceases to exert a forwardly- propelling force4 ,fig4 #ba4 ,synchronously moving ,planes4 ,in ,fig4 #ba the body ,a is shown to be equipped with the supporting plane ,b and the tail a1 so they are adjustable simultaneously at the same angle1 and the weight ,d is placed below1 similar to the other structure4 ,at every moment during the forward movement of this type of structure1 the rear end of the machine has a tendency to move upwardly1 the same as the forward end1 hence1 when the weight seeks1 in this case to go on1 it acts on the rear plane1 or tail1 and causes that end to raise1 and thus by mutual action1 prevents any pendulous swing4 ,,low ,,weight ,,not ,,necessary ,,with ,,synchronously-,,moving ,,wings4 --,a little reflection will convince any one that if the two wings move in harmony1 the weight does not have to be placed low1 and thus still further aid in making a compact machine4 ,by increasing the area of the tail1 and making that a true supporting surface1 instead of a mere idler1 the weight can be moved further back1 the distance transversely across the planes may be shortened1 and in that way still further increase the lateral stability4 ,,chapter ,v ,,different ,,machine ,,types ,,and ,,their ,,characteristics ,,there are three distinct types of heavier-than- air machines1 which are widely separated in all their characteristics1 so that there is scarcely a single feature in common4 ,two of them1 the aeroplane1 and the orthopter1 have prototypes in nature1 and are distinguished by their respective similarities to the soaring birds1 and those with flapping wings4 ,the ,helicopter1 on the other hand1 has no antecedent type1 but is dependent for its raising powers on the pull of a propeller1 or a plurality of them1 constructed1 as will be pointed out hereinafter4 ,,aeroplanes4--,the only form which has met with any success is the aeroplane1 which1 in practice1 is made in two distinct forms1 one with a single set of supporting planes1 in imitation of birds1 and called a monoplane2 and the other having two wings1 one above the other1 and called the bi-plane1 or two-planes4 ,all machines now on the market which do not depend on wing oscillations come under those types4 ,,the ,,monoplane4--,the single plane type has some strong claims for support4 ,first of these is the comparatively small head resistance1 due to the entire absence of vertical supporting posts1 which latter are necessary with the biplane type4 ,the bracing supports which hold the outer ends of the planes are composed of wires1 which offer but little resistance1 comparatively1 in flight4 ,,its ,,advantages4--,then the vertical height of the machine is much less than in the biplane4 ,as a result the weight1 which is farther below the supporting surface than in the biplane1 aids in maintaining the lateral stability1 particularly since the supporting frame is higher4 ,usually1 for the same wing spread1 the monoplane is narrower1 laterally1 which is a further aid to prevent tilting4 ,,its ,,disadvantages4--,but it also has disadvantages which must be apparent from its structure4 ,as all the supporting surface is concentrated in half the number of planes1 they must be made of greater width fore and aft1 and this1 as we shall see1 later on1 proves to be a disadvantage4 ,it is also doubted whether the monoplane can be made as strong structurally as the other form1 owing to the lack of the truss formation which is the strong point with the superposed frame4 ,a truss is a form of construction where braces can be used from one member to the next1 so as to brace and stiffen the whole4 ,,the ,,biplane4--,nature does not furnish a type of creature which has superposed wings4 ,in this particular the inventor surely did not follow nature4 ,the reasons which led man to employ this type may be summarized as follows3 ,in experimenting with planes it is found that a broad fore and aft surface will not lift as much as a narrow plane4 ,this subject is fully explained in the chapter on ,the ,lifting ,surfaces of ,planes4 ,in view of that the technical descriptions of the operation will not be touched upon at this place1 except so far as it may be necessary to set forth the present subject4 ,this peculiarity is due to the accumulation of a mass of moving air at the rear end of the plane1 which detracts from its lifting power4 ,as it would be a point of structural weakness to make the wings narrow and very long1 ,wenham many years ago suggested the idea of placing one plane above the other1 and later on ,chanute1 an engineer1 used that form almost exclusively1 in experimenting with his gliders4 ,it was due to his influence that the ,wrights adopted that form in their gliding experiments1 and later on constructed their successful flyers in that manner4 ,originally the monoplane was the type generally employed by experimenters1 such as ,lilienthal1 and others4 ,,stability ,,in ,,biplanes4--,biplanes are not naturally as stable laterally as the monoplane4 ,the reason is1 that a downward tilt has the benefit of only a narrow surface1 comparable with the monoplane1 which has broadness of wing4 ,to illustrate this1 let us assume that we have a biplane with planes five feet from front to rear1 and thirty-six feet in length4 ,this would give two planes with a sustaining surface of #cfj square feet4 ,the monoplane would1 probably1 divide this area into one plane eight and a half feet from front to rear1 and #db feet in length4 ,in the monoplane each wing would project out about three feet more on each side1 but it would have eight and a half feet fore and aft spread to the biplane's five feet1 and thus act as a greater support4 ,,the ,,orthopter4--,the term orthopter1 or ornithopter1 meaning bird wing1 is applied to such flying machines as depend on wing motion to support them in the air4 ,unquestionably1 a support can be obtained by beating on the air but to do so it is necessary to adopt the principle employed by nature to secure an upward propulsion4 ,as pointed out elsewhere1 it cannot be the concaved type of wing1 or its shape1 or relative size to the weight it must carry4 ,as nature has furnished such a variety of data on these points1 all varying to such a remarkable degree1 we must look elsewhere to find the secret4 ,only one other direction offers any opportunity1 and that is in the individual wing movement4 ,,nature',s ,,type ,,not ,,uniform4--,when this is examined1 the same obscurity surrounds the issue4 ,even the speeds vary to such an extent that when it is tried to differentiate them1 in comparison with form1 shape1 and construction1 the experimenter finds himself wrapt in doubt and perplexity4 ,but birds do fly1 notwithstanding this wonderful array of contradictory exhibitions4 ,observation has not enabled us to learn why these things are so4 ,high authorities1 and men who are expert aviators1 tell us that the bird flies because it is able to pick out ascending air currents4 ,,theories ,,about ,,flight ,,of ,,birds4--,then we are offered the theory that the bird has an instinct which tells it just how to balance in the air when its wings are once set in motion4 ,frequently1 what is taken for instinct1 is something entirely different4 ,it has been assumed1 for instance1 that a cyclist making a turn at a rapid speed1 and a bird flying around a circle will throw the upper part of the body inwardly to counteract the centrifugal force which tends to throw it outwardly4 ,experiments with the monorail car1 which is equipped with a gyroscope to hold it in a vertical position1 show that when the car approaches a curve the car will lean inwardly1 exactly the same as a bird1 or a cyclist1 and when a straight stretch is reached1 it will again straighten up4 ,,instinct4--,now1 either the car1 so equipped possesses instinct1 or there must be a principle in the laws of nature which produces the similarity of action4 ,in like manner there must be some principle that is entirely independent of the form of matter1 or its arrangement1 which enables the bird to perform its evolutions4 ,we are led to believe from all the foregoing considerations that it is the manner or the form of the motion4 ,,mode ,,of ,,motion4--,in this respect it seems to be comparable in every respect to the great and universal law of the motions in the universe4 ,thus1 light1 heat and electricity are the same1 the manifestations being unlike only because they have different modes of motion4 ,everything in nature manifests itself by motion4 ,it is the only way in which nature acts4 ,every transformation from one thing to another1 is by way of a movement which is characteristic in itself4 ,why1 then1 should this great mystery of nature1 act unlike the other portions of which it is a part8 ,,the ,,wing ,,structure4--,the wing structure of every flying creature that man has examined1 has one universal point of similarity1 and that is the manner of its connection with the body4 ,it is a sort of universal joint1 which permits the wing to swing up and down1 perform a gyratory movement while doing so1 and folds to the rear when at rest4 ,some have these movements in a greater or less degree1 or capable of a greater range2 but the joint is the same1 with scarcely an exception4 ,when the stroke of the wing is downwardly the rear margin is higher than the front edge1 so that the downward beat not only raises the body upwardly1 but also propels it forwardly4 ,,the ,,wing ,,movement4--,the moment the wing starts to swing upwardly the rear end is depressed1 and now1 as the bird is moving forwardly1 the wing surface has a positive angle of incidence1 and as the wing rises while the forward motion is taking place1 there is no resistance which is effective enough to counteract the momentum which has been set up4 ,the great problem is to put this motion into a mechanical form4 ,the trouble is not ascribable to the inability of the mechanic to describe this movement4 ,it is an exceedingly simple one4 ,the first difficulty is in the material that must be used4 ,lightness and strength for the wing itself are the first requirements4 ,then rigidity in the joint and in the main rib of the wing1 are the next considerations4 ,in these respects the ability of man is limited4 ,the wing ligatures of flying creatures is exceedingly strong1 and flexible2 the hollow bone formation and the feathers are extremely light1 compared with their sustaining powers4 ,,the ,,helicopter ,,motion4--,the helicopter1 or helix-wing1 is a form of flying machine which depends on revolving screws to maintain it in the air4 ,many propellers are now made1 six feet in length1 which have a pull of from #djj to #ejj pounds4 ,if these are placed on vertically-disposed shafts they would exert a like power to raise a machine from the earth4 ,obviously1 it is difficult to equip such a machine with planes for sustaining it in flight1 after it is once in the air1 and unless such means are provided the propellers themselves must be the mechanism to propel it horizontally4 ,this means a change of direction of the shafts which support the propellers1 and the construction is necessarily more complicated than if they were held within non-changeable bearings4 ,this principle1 however1 affords a safer means of navigating than the orthopter type1 because the blades of such an instrument can be forced through the air with infinitely greater speed than beating wings1 and it devolves on the inventor to devise some form of apparatus which will permit the change of pull from a vertical to a horizontal direction while in flight4 ,,chapter ,,vi ,,the ,,lifting ,,surfaces ,,of ,,aeroplanes ,,this subject includes the form1 shape and angle of planes1 used in flight4 ,it is the direction in which most of the energy has been expended in developing machines1 and the true form is still involved in doubt and uncertainty4 ,,relative ,,speed ,,and ,,angle4--,the relative speed and angle1 and the camber1 or the curved formation of the plane1 have been considered in all their aspects1 so that the art in this respect has advanced with rapid strides4 ,,narrow ,,plates ,,most ,,effective4--,it was learned1 in the early stages of the development by practical experiments1 that a narrow plane1 fore and aft1 produces a greater lift than a wide one1 so that1 assuming the plane has #ajj square feet of sustaining surface1 it is far better to make the shape five feet by twenty than ten by ten4 ,however1 it must be observed1 that to use the narrow blade effectively1 it must be projected through the air with the long margin forwardly4 ,its sustaining power per square foot of surface is much less if forced through the air lengthwise4 ,experiments have shown why a narrow blade has proportionally a greater lift1 and this may be more clearly understood by examining the illustrations which show the movement of planes through the air at appropriate angles4 ,fig4 #bb4 ,stream lines along a plane4 ,,stream ,,lines ,,along ,a ,,plane4--,in ,fig4 #bb1 ,a is a flat plane1 which we will assume is #aj feet from the front to the rear margin4 ,for convenience seven stream lines of air are shown1 which contact with this inclined surface4 ,the first line #a1 after the contact at the forward end1 is driven downwardly along the surface1 so that it forms what we might term a moving film4 ,the second air stream #b1 strikes the first stream1 followed successively by the other streams1 #c1 #d1 and so on1 each succeeding stream being compelled to ride over1 or along on the preceding mass of cushioned air1 the last lines1 near the lower end1 being1 therefore1 at such angles1 and contacting with such a rapidly-moving column1 that it produces but little lift in comparison with the #ast1 #b;d and #c;d stream lines4 ,these stream lines are taken by imagining that the air approaches and contacts with the plane only along the lines indicated in the sketch1 although they also in practice are active against every part of the plane4 ,,the ,,center ,,of ,,pressure4--,in such a plane the center of pressure is near its upper end1 probably near the line #c1 so that the greater portion of the lift is exerted by that part of the plane above line #c4 ,,air ,,lines ,,on ,,the ,,upper ,,side ,,of ,,the ,,plane4-- ,now1 another factor must be considered1 namely1 the effect produced on the upper side of the plane1 over which a rarefied area is formed at certain points1 and1 in practice1 this also produces1 or should be utilized to effect a lift4 ,,rarefied ,,area4--,what is called a rarefied area1 has reference to a state or condition of the atmosphere which has less than the normal pressure or quantity of air4 ,thus1 the pressure at sea level1 is about #ad #c_/d per square inch ,as we ascend the pressure grows less1 and the air is thus rarer1 or1 there is less of it4 ,this is a condition which is normally found in the atmosphere4 ,several things tend to make a rarefied condition4 ,one is altitude1 to which we have just referred4 ,then heat will expand air1 making it less dense1 or lighter1 so that it will move upwardly1 to be replaced by a colder body of air4 ,in aeronautics neither of these conditions is of any importance in considering the lifting power of aeroplane surfaces4 ,,rarefaction ,,produced ,,by ,,motion4--,the third rarefied condition is produced by motion1 and generally the area is very limited when brought about by this means4 ,if1 for instance1 a plane is held horizontally and allowed to fall toward the earth1 it will be retarded by two forces1 namely1 compression and rarefaction1 the former acting on the under side of the plane1 and the latter on the upper side4 ,of the two rarefaction is the most effectual1 and produces a greater effect than compression4 ,this may be proven by compressing air in a long pipe1 and noting the difference in gauge pressure between the ends1 and then using a suction pump on the same pipe4 ,when a plane is forced through the air at any angle1 a rarefied area is formed on the side which is opposite the one having the positive angle of incidence4 ,if the plane can be so formed as to make a large and effective area it will add greatly to the value of the sustaining surface4 ,unfortunately1 the long fiat plane does not lend any aid in this particular1 as the stream line flows down along the top1 as shown in ,fig4 #bc1 without being of any service4 ,fig4 #bc4 ,air lines on the upper side of a ,plane4 ,,the ,,concaved ,,plane4--,these considerations led to the adoption of the concaved plane formation1 and for purposes of comparison the diagram1 ,fig4 #bd1 shows the plane ,b of the same length and angle as the straight planes4 ,in examining the successive stream lines it will be found that while the #ast1 #b;d and #c;d lines have a little less angle of impact than the corresponding lines in the straight plane1 the last lines1 #e1 #f and #g1 have much greater angles1 so that only line #d strikes the plane at the same angle4 ,such a plane structure would1 therefore1 have its center of pressure somewhere between the lines #c and #d1 and the lift being thus1 practically1 uniform over the surface1 would be more effective4 ,,the ,,center ,,of ,,pressure4--,this is a term used to indicate the place on the plane where the air acts with the greatest force4 ,it has reference to a point between the front and rear margins only of the plane4 ,fig4 #bd4 ,air lines below a concaved ,plane4 ,,utilizing ,,the ,,rarefied ,,area4--,this structure1 however1 has another important advantage1 as it utilizes the rarefied area which is produced1 and which may be understood by reference to ,fig4 #be4 ,the plane ,b1 with its upward curve1 and at the same angle as the straight plane1 has its lower end so curved1 with relation to the forward movement1 that the air1 in rushing past the upper end1 cannot follow the curve rapidly enough to maintain the same density along ,c1 hence this exerts an upward pull1 due to the rarefied area1 which serves as a lifting force1 as well as the compressed mass beneath the plane4 ,,changing ,,center ,,of ,,pressure4--,the center of pressure is not constant4 ,it changes with the angle of the plane1 but the range is considerably less on a concave surface than on a flat plane4 ,fig4 #be4 ,air lines above a convex ,plane4 ,in a plane disposed at a small angle1 ,a1 as in ,fig4 #bf1 the center of pressure is nearer the forward end of the plane than with a greater positive angle of incidence1 as in ,fig4 #bg1 and when the plane is in a normal flying angle1 it is at the center1 or at a point midway between the margins4 ,,plane ,,monstrosities4--,growing out of the idea that the wing in nature must be faithfully copied1 it is believed by many that a plane with a pronounced thickness at its forward margin is one of the secrets of bird flight4 ,accordingly certain inventors have designed types of wings which are shown in ,figs4 #bh and #bi4 ,fig4 #bh ,changing centers of ,pressures4 ,fig #bi4 ,bird-wing structures4 ,both of these types have pronounced bulges1 designed to split the air1 forgetting1 apparently1 that in other parts of the machine every effort is made to prevent head resistance4 ,,the ,,bird ,,wing ,,structure4--,the advocates of such construction maintain that the forward edge of the plane must forcibly drive the air column apart1 because the bird wing is so made1 and that while it may not appear exactly logical1 still there is something about it which seems to do the work1 and for that reason it is largely adopted4 ,,why ,,the ,,bird',s ,,wing ,,has ,a ,,pronounced ,,bulge4--,let us examine this claim4 ,the bone which supports the entire wing surface1 called the 7pectoral71 has a heavy duty to perform4 ,it is so constructed that it must withstand an extraordinary torsional strain1 being located at the forward portion of the wing surface4 ,torsion has reference to a twisting motion4 ,in some cases1 as in the bat1 this primary bone has an attachment to the rear of the main joint1 where the rear margin of the wing is attached to the leg of the animal1 thus giving it a support and the main bone is1 therefore1 relieved of this torsional stress4 ,,the ,,bat',s ,,wing4--,an examination of the bat's wing shows that the pectoral bone is very small and thin1 thus proving that when the entire wing support is thrown upon the primary bone it must be large enough to enable it to carry out its functions4 ,it is certainly not so made because it is a necessary shape which best adapts it for flying4 ,if such were the case then nature erred in the case of the bat1 and it made a mistake in the housefly's wing which has no such anterior enlargement to assist 787 it in flying4 ,,an ,,abnormal ,,shape4--,another illustration is shown in ,fig4 #cj1 which has a deep concave directly behind the forward margin1 as at ,a1 so that when the plane is at an angle of about #bb degrees1 a horizontal line1 as ,b1 passing back from the nose1 touches the incurved surface of the plane at a point about one-third of its measurement back across the plane4 ,fig4 #cj4 ,one of the ,monstrosities ,this form is an exact copy of the wing of an actual bird1 but it belongs1 not to the soaring1 but to the class which depends on flapping wings1 and as such it cannot be understood why it should be used for soaring machines1 as all aeroplanes are4 ,the foregoing instances of construction are cited to show how wildly the imagination will roam when it follows wrong ideals4 ,,the ,,tail ,,as ,a ,,monitor4--,the tendency of the center of pressure to change necessitates a correctional means1 which is supplied in the tail of the machine1 just as the tail of a kite serves to hold it at a correct angle with respect to the wind and the pull of the supporting string4 ,,chapter ,,vii ,,abnormal ,,flying ,,stunts ,,and ,,speeds ,,pequod1 a ,frenchman1 yesterday repeatedly performed the remarkable feat of flying with the machine upside down4 ,this exhibition shows that the age of perfection has arrived in flying machines1 and that stability is an accomplished fact4--,news item4 ,this is quoted to show how little the general public knows of the subject of aviation4 ,it correctly represents the achievement of the aviator1 and it probably voiced the sentiment of many scientific men1 as well as of the great majority of aviators4 ,a few days afterwards1 the same newspaper published the following3 ,lieutenant ----1 while experimenting yesterday morning1 met his death by the overturning of his machine at an altitude of #cjj meters4 ,death was instantaneous1 and the machine was completely destroyed4 ,the machines used by the two men were of the same manufacture1 as ,pequod used a stock machine which was strongly braced to support the inverted weight1 but otherwise it was not unlike the well known type of monoplane4 ,beachy has since repeated the experiment with a bi-plane1 and it is a feat which has many imitators1 and while those remarkable exhibitions are going on1 one catastrophe follows the other with the same regularity as in the past4 ,let us consider this phase of flying4 ,are they of any value1 and wherein do they teach anything that may be utilized1 ,,lack ,,of ,,improvements ,,in ,,machines4--,it is remarkable that not one single forward step has been taken to improve the type of flying machines for the past five years4 ,they possess the same shape1 their stabilizing qualities and mechanism for assuring stability are still the same4 ,,men ,,expedited1 ,,and ,,not ,,the ,,machine4--,the fact is1 that during this period the man has been exploited and not the machine4 ,men have learned1 some few of them1 to perform peculiar stunts1 such as looping the loop1 the side glide1 the drop1 and other features1 which look1 and are1 hazardous1 all of which pander to the sentiments of the spectators4 ,,abnormal ,,flying ,,of ,,no ,,value4--,it would be too broad an assertion to say that it has absolutely no value1 because everything has its use in a certain sense1 but if we are to judge from the progress of inventions in other directions1 such exhibitions will not improve the art of building the device1 or make a fool-proof machine4 ,indeed1 it is the very thing which serves as a deterrent1 rather than an incentive4 ,if machines can be handled in such a remarkable manner1 they must be1 indeed1 perfect6 ,nothing more is needed6 ,they must represent the highest structural type of mechanism6 ,that is the idea sought to be conveyed in the first paragraph quoted4 ,it is pernicious1 instead of praiseworthy1 because it gives a false impression1 and it is remarkable that even certain scientific journals have gravely discussed the perfected 787 type of flying machine as demonstrated by the experiments alluded to4 ,,the ,,art ,,of ,,juggling4--,we may1 occasionally1 see a cyclist who understands the art of balancing so well that he can1 with ease1 ride a machine which has only a single wheel2 or he can1 with a stock bicycle1 ride it in every conceivable attitude1 and make it perform all sorts of feats4 ,it merely shows that man has become an expert at juggling with a machine1 the same as he manipulates balls1 and wheels1 and other artifices1 by his dexterity4 ,,practical ,,uses ,,the ,,best ,,test4--,the bicycle did not require such displays to bring it to perfection4 ,it has been the history of every invention that improvements were brought about1 not by abnormal experiments1 but by practical uses and by normal developments4 ,the ability of an aviator to fly with the machine in an inverted position is no test of the machine's stability1 nor does it in any manner prove that it is correctly built4 ,it is simply and solely a juggling feat--something in the capacity of a certain man to perform1 and attract attention because they are out of the ordinary4 ,,concaved ,,and ,,coxvex ,,planes3--,they were performed as exhibition features1 and intended as such1 and none of the exponents of that kind of flying have the effrontery to claim that they prove anything of value in the machine itself1 except that it incidentally has destroyed the largely vaunted claim that concaved wings for supporting surfaces are necessary4 ,,how ,,momentum ,,is ,a ,,factor ,,in ,,inverted ,,flying4-- ,when flying upside down1 the convex side of the plane takes the pressure of the air1 and maintains1 so it is asserted1 the weight of the machine4 ,this is true during that period when the loop is being made4 ,the evolution is made by first darting down1 as shown in ,fig4 #ca1 from the horizontal position1 #a1 to the position #b1 where the turn begins4 ,fig4 #ca4 ,flying upside down4 ,,turning ,,movement4--,now note the characteristic angles of the tail1 which is the controlling factor4 ,in position #a the tail is practically horizontal4 ,in fact1 in all machines1 at high flight1 the tail is elevated so as to give little positive angle of incidence to the supporting planes4 ,in position ,no4 #b1 the tail is turned to an angle of incidence to make the downward plunge1 and when the machine has assumed the vertical1 as in position #c1 the tail is again reversed to assume the angle1 as in #a1 when flying horizontally4 ,at the lower turn1 position #d1 the tail is turned similar to the angle of position #b1 which throws the rear end of the machine down1 and as the horizontal line of flight is resumed1 in an inverted position1 as in position #d1 the tail has the same angle1 with relation to the frame1 as the supporting planes4 ,during this evolution the engine is running1 and the downward plunge develops a tremendous speed1 and the great momentum thus acquired1 together with the pulling power of the propeller while thus in flight1 is sufficient to propel it along horizontally1 whatever the plane surface curve1 or formation may be4 ,it is the momentum which sustains it in space1 not the air pressure beneath the wings1 for reasons which we have heretofore explained4 ,flights of sufficient duration have thus been made to prove that convex1 as well as concave surfaces are efficient2 nevertheless1 in its proper place we have given an exposition of the reasoning which led to the adoption of the concaved supporting surfaces4 ,,when ,,concaved ,,planes ,,are ,,desirable4-- ,unquestionably1 for slow speeds the concaved wing is desirable1 as will be explained1 but for high speeds1 surface formation has no value4 ,that is shown by ,pequod's feat4 ,,the ,,speed ,,mania4--,this is a type of mania which pervades every field of activity in the building of aeroplanes4 ,speed contests are of more importance to the spectators on exhibition grounds than stability or durability4 ,builders pander to this1 hence machines are built on lines which disregard every consideration of safety while at normal flight4 ,,uses ,,of ,,flying ,,machines4--,the machine as now constructed is of little use commercially4 ,within certain limitations it is valuable for scouting purposes1 and attempts have been made to use it commercially4 ,but the unreliable character of its performances1 due to the many elements which are necessary to its proper working1 have operated against it4 ,,perfection ,,in ,,machines ,,must ,,come ,,before ,,speed4--,contrary to every precept in the building of a new article1 the attempt is made to make a machine with high speed1 which1 in the very nature of things1 operates against its improvement4 ,the opposite lack of speed--is of far greater utility at this stage of its development4 ,,the ,,range ,,of ,,its ,,use4--,the subject might be illustrated by assuming that we have a line running from ,a to ,z1 which indicates the range of speeds in aeroplanes4 ,the limits of speeds are fairly stated as being within thirty and eighty- five miles per hour4 ,less than thirty miles are impossible with any type of plane1 and while some have made higher speeds than eighty-five miles it may be safe to assume that such flights took place under conditions where the wind contributed to the movement4 ,fig4 #cb4 ,chart showing ,range of ,uses ,,commercial ,,utility4--,before machines can be used successfully they must be able to attain slower speeds4 ,alighting is the danger factor4 ,speed machines are dangerous1 not in flight or at high speeds1 but when attempting to land4 ,a large plane surface is incompatible with speed1 which is another illustration that at high velocities supporting surfaces are not necessary4 ,commercial uses require safety as the first element1 and reliability as the next essential4 ,for passenger service there must be an assurance that it will not overturn1 or that in landing danger is not ever-present4 ,for the carrying of freight interrupted service will militate against it4 ,how few are the attempts to solve the problem of decreased speed1 and what an eager1 restless campaign is being waged to go faster and faster1 and the addition of every mile above the record is hailed as another illustration of the perfection 787 of the flying machine4 ,to be able to navigate a machine at ten1 or fifteen miles an hour1 would scarcely be interesting enough to merit a paragraph2 but such an accomplishment would be of far more value than all of ,pequod's feats1 and be more far-reaching in its effects than a flight of two hundred miles per hour4 ,,chapter ,,viii ,,kites ,,and ,,gliders ,,kites are of very ancient origin1 and in ,china1 ,japan1 and the ,malayan ,peninsula1 they have been used for many years as toys1 and for the purposes of exhibiting forms of men1 animals1 and particularly dragons1 in their periodical displays4 ,,the ,,dragon ,,kite4--,the most noted of all are the dragon kites1 many of them over a hundred feet in length1 are adapted to sail along majestically1 their sinuous or snake-like motions lending an idea of reality to their gorgeously-colored appearance in flight4 ,,its ,,construction4--,it is very curiously wrought1 and as it must be extremely light1 bamboo and rattan are almost wholly used1 together with rice paper1 in its construction4 ,fig4 #cc shows one form of the arrangement1 in which the bamboo rib1 ,a1 in which only two sections are shown1 as ,b1 ,b1 form the backbone1 and these sections are secured together with pivot pins ,c4 ,each section has attached thereto a hoop1 or circularly-formed rib1 ,d1 the rib passing through the section ,b1 and these ribs are connected together loosely by cords ,e1 which run from one to the other1 as shown4 ,these circular ribs1 ,d1 are designed to carry a plurality of light paper disks1 ,f1 which are attached at intervals1 and they are placed at such angles that they serve as small wing surfaces or aeroplanes to hold the structure in flight4 ,fig4 #cc4 ,ribs of ,dragon ,kite ,,the ,,malay ,,kite4--,the ,malay kite1 of which ,fig4 #cd shows the structure1 is merely made up of two cross sticks1 ,a1 ,b1 the vertical strip1 ,a1 being bent and rigid1 whereas the cross stick1 ,b1 is light and yielding1 so that when in flight it will bend1 as shown1 and as a result it has wonderful stability due to the dihedral angles of the two surfaces4 ,this kite requires no tail to give it stability4 ,fig4 #cd4 ,the ,malay ,kite4 ,,dihedral ,,angles4--,this is a term to designate a form of disposing of the wings which has been found of great service in the single plane machines4 ,a plane which is disposed at a rising angle1 as ,a1 ,a1 ,fig4 #ce1 above the horizontal line1 is called dihedral1 or diedral4 ,fig4 #ce4 ,dihedral ,angle4 ,this arrangement in monoplanes does away with the necessity of warping the planes1 or changing them while in flight4 ,if1 however1 the angle is too great1 the wind from either quarter is liable to raise the side that is exposed4 ,,the ,,common ,,kite4--,while the ,malay kite has only two points of cord attachment1 both along the vertical rib1 the common kite1 as shown in ,fig4 #cf1 has a four-point connection1 to which the flying cord is attached4 ,since this form has no dihedral angle1 it is necessary to supply a tail1 which thus serves to keep it in equilibrium1 while in flight4 ,fig4 #cf4 ,common ,kite4 ,various modifications have grown out of the ,malay kite4 ,one of these forms1 designed by ,eddy1 is exactly like the ,malay structure1 but instead of having a light flexible cross piece1 it is bent to resemble a bow1 so that it is rigidly held in a bent position1 instead of permitting the wind to give it the dihedral angle4 ,,the ,,bow ,,kite4--,among the different types are the bow kite1 ,fig4 #cg1 and the sexagonal structure1 ,fig4 #ch1 the latter form affording an especially large surface4 ,fig4 #cg4 ,bow ,kite4- ,fig4 #ch4 ,hexagonal ,kite4 ,,the ,,box ,,kite4--,the most marked improvement in the form of kites was made by ,hargreaves1 in #ahhe1 and called the box kite4 ,it has wonderful stability1 and its use1 with certain modifications1 in ,weather ,bureau experiments1 have proven its value4 ,it is made in the form of two boxes1 ,a1 ,b1 open at the ends1 which are secured together by means of longitudinal bars1 ,c1 that extends from one to the other1 so that they are held apart a distance1 approximately1 equal to the length of one of the boxes4 ,fig4 #ci4 ,hargreave ,kite4 ,their fore and aft stability is so perfect that the flying cord ,d is attached at one point only1 and the sides of the boxes provide lateral stability to a marked degree4 ,,the ,,voison ,,biplane4--,this kind of kite furnished the suggestion for the ,voison biplane1 which was one of the earlier productions in flying machines4 ,fig4 #dj shows a perspective of the ,voison plane1 which has vertical planes ,a1 ,a1 at the ends1 and also intermediate curtains ,b1 ,b4 ,this was found to be remarkably stable1 but during its turning movements1 or in high winds1 was not satisfactory1 and for that reason was finally abandoned4 ,,lateral ,,stability ,,in ,,kites ,,not ,,conclusive ,,as ,,to ,,planes4--,this is instanced to show that while such a form is admirably adapted for kite purposes1 where vertical curtains are always in line with the wind movement1 and the structure is held taut by a cord1 the lateral effect1 when used on a machine which does not at all times move in line with the moving air current4 ,a condition is thus set up which destroys the usefulness of the box kite formation4 ,fig4 #dj4 ,voison ,biplane4 ,,the ,,spear ,,kite4--,this is a novel kite1 with remarkable steadiness and is usually made with the wings on the rear end larger than those on the forward end 7,fig4 #da71 as thereby the cord ,a can be attached to the spear midway between the two sets of wings4 ,fig4 #da4 ,spear ,kite4 ,,the ,,cellular ,,kite4--,following out the suggestion of the ,hargreaves kite1 numerous forms embodying the principle of the box structure were made and put on the market before the aeroplane became a reality4 ,fig4 #db4 ,cellular ,kite4 ,a structure of this form is illustrated in ,fig4 #db4 ,each box1 as ,a1 ,b1 has therein a plurality of vertical and horizontal partitions1 so that a number of cells are provided1 the two cell-like boxes being held apart by a bar ,c1 axially arranged4 ,this type is remarkably stable1 due to the small cells1 and kites of this kind are largely used for making scientific experiments4 ,,the ,,tetrahedral ,,kite4--,prof4 ,bell1 inventor of the telephone1 gave a great deal of study to kites1 which resulted in the tetrahedral formation1 as shown in ,fig4 #dc4 ,fig4 #dc4 ,tetrahedral ,kite4 ,the structure1 apparently1 is somewhat complicated1 but an examination of a single pair of blades1 as shown at ,a1 shows that it is built up of triangularly-formed pieces1 and that the openings between the pieces are equal to the latter1 thereby providing a form of kite which possesses equilibrium to a great degree4 ,it has never been tried with power1 and it is doubtful whether it would be successful as a sustaining surface for flying machines1 for the same reasons that caused failure with the box-like formation of the ,voison ,machine4 ,,the ,,deltoid4--,the deltoid is the simplest1 and the most easily constructed of all the kites4 ,it is usually made from stiff cardboard1 ,a-shaped in outline1 as shown in ,figs4 #dd and #de1 and bent along a central line1 as at ,a1 forming two wings1 each of which is a right-angled triangle4 ,fig4 #dd4 and #de4 ,deltoid ,formation4 ,the peculiarity of this formation is1 that it has remarkable stability when used as a kite1 with either end foremost4 ,if a small weight is placed at the pointed end1 and it is projected through the air1 it will fly straight1 and is but little affected by cross currents4 ,,the ,,dunne ,,flying ,,machine4--,a top view of this biplane is shown in ,fig4 #df4 ,the ,a-shaped disposition of the planes1 gives it good lateral stability1 but it has the disadvantage under which all aeroplanes labor1 that the entire body of the machine must move on a fore and aft vertical plan in order to ascend or descend4 ,fig4 #df4 ,the ,dunne ,bi-plane4 ,this is a true deltoid formation1 as the angle of incidence of the planes is so disposed that when the planes are horizontal from end to end1 the inclination is such as to make it similar to the deltoid kite referred to4 ,,rotating ,,kite4--,a type of kite unlike the others illustrated is a rotating structure1 which gives great stability1 due to the gyroscopic action on the supporting surfaces4 ,fig4 #dg shows a side view with the top in section4 ,the supporting surface is umbrella-shaped4 ,in fact1 the ordinary umbrella will answer if not dished too much4 ,an angularly-bent piece of wire ,a1 provided with loops ,b1 ,b1 at the ends1 serve as bearings for the handle of the umbrella4 ,at the bend of the wire loop ,c1 the cord ,d is attached4 ,the lower side of the umbrella top has cup-shaped pockets ,e1 near the margin1 so arranged that their open ends project in the same direction1 and the wind catching them rotates the circular plane4 ,fig4 #dg4 ,rotable ,umbrella ,kite4 ,,kite ,,principles4--,a careful study of the examples here given1 will impress the novice with one important fact1 which1 in its effect has a more important bearing on successful flight1 than all the bird study and speculations concerning its mysteries4 ,this fact1 in essence1 is1 that the angle of the kite is the great factor in flight next to the power necessary to hold it4 ,aside from this1 the comparison between kites and aeroplanes is of no practical value4 ,disregarding the element of momentum1 the drift of a machine against a wind1 is the same1 dynamically1 as a plane at rest with the wind moving past it4 ,but there is this pronounced difference3 ,the cord which supports the kite holds it so that the power is in one direction only4 ,when a side gust of wind strikes the kite it is moved laterally1 in sympathy with the kite1 hence the problem of lateral displacement is not the same as with the aeroplane4 ,,lateral ,,stability ,,in ,,kites4--,in the latter the power is definitely fixed with relation to the machine itself1 and if we should assume that a plane with a power on it sufficient to maintain a flight of #dj miles an hour1 should meet a wind moving at the same speed1 the machine would be stationary in space4 ,such a condition would be the same1 so far as the angles of the planes are concerned1 with a kite held by a string1 but there all similarity in action ends4 ,the stabilizing quality of the kite may be perfect1 as the wind varies from side to side1 but the aeroplane1 being free1 moves to the right or to the left1 and does not adjust itself by means of a fixed point1 but by a movable one4 ,,similarity ,,of ,,fore ,,and ,,aft ,,control4--,fore and aft1 however1 the kite and aeroplane act the same4 ,fig4 #dh shows a diagram which illustrates the forces which act on the kite1 and by means of which it adjusts its angle automatically4 ,let us assume that the kite ,a is flown from a cord ,b1 so that its angle is #bb #a_/b degrees1 the wind being #ae miles per hour to maintain the cord ,b at that angle4 ,when the wind increases to #bj miles an hour there is a correspondingly greater lift against the kite4 ,fig4 #dh4 ,action of ,wind forces on ,kite4 ,as its angle is fixed by means of the loop ,c1 it cannot change its angle with reference to the cord1 or independently of it1 and its only course is to move up higher and assume the position shown by the figure at ,d1 and the angle of incidence of the kite is therefore changed to #ae degrees1 or even to #aj degrees4 ,in the case of the aeroplane the effect is similar from the standpoint of power and disposition of the planes4 ,if it has sufficient power1 and the angle of the planes is not changed1 it will ascend2 if the planes are changed to #ae degrees to correspond with the kite angle it will remain stationary4 ,,gliding ,,flight4--,the earliest attempt to fly by gliding is attributed to ,oliver1 a ,monk of ,malmesbury who1 in #ajfe prepared artificial wings1 and with them jumped from a tower1 being injured in the experiment4 ,nearly #gjj years later1 in #ahja1 ,resnier1 a ,frenchman1 conducted experiments with varying results1 followed by ,berblinger1 in #ahdb1 and ,le,bris1 a ,french sailor1 in #ahef4 ,in #ahhd1 ,j4 ,j4 ,montgomery1 of ,california1 designed a successful glider1 and in #ahhi ,otto and ,gustav ,lilienthal made the most extended tests1 in ,germany1 and became experts in handling gliders4 ,pilcher1 in ,england1 was the next to take up the subject1 and in #ahic made many successful glides1 all of the foregoing machines being single plane surfaces1 similar to the monoplane4 ,long prior to #ahif ,octave ,chanute1 an engineer1 gave the subject much study1 and in that year made many remarkable flights1 developing the double plane1 now known as the biplane4 ,he was an ardent believer in the ability of man to fly by soaring means1 and without using power for the purpose4 ,it is doubtful whether gliders contributed much to the art in the direction of laterally stabilizing aeroplanes4 ,they taught useful lessons with respect to area and fore and aft control4 ,the kite gave the first impulse to seek out a means for giving equilibrium to planes1 and ,montgomery made a kite with warping wings as early as #ahhd4 ,penaud1 a ,frenchman1 in #ahgb1 made a model aeroplane which had the stabilizing means in the tail4 ,all these grew out of kite experiments2 and all gliders followed the kite construction1 or the principles involved in them1 so that1 really1 there is but one intervening step between the kite and the flying machine1 as we know it1 the latter being merely kites with power attached1 as substitutes for the cords4 ,,one ,,of ,,the ,,uses ,,of ,,glider ,,experiments4-- ,there is one direction in which gliders are valuable to the boy and to the novice who are interested in aviation4 ,he may spend a lifetime in gliding and not advance in the art4 ,it is questionable whether in a scientific way it will be of any service to him2 but experiments of this character give confidence1 the ability to quickly grasp a situation1 and it will thus teach self reliance in emergencies4 ,when in a glider quick thinking is necessary4 ,the ability to shift from one position to another2 to apply the weight where required instantaneously2 to be able during the brief exciting moment of flight to know just what to do1 requires alertness4 ,some are so wedded to the earth that slight elevation disturbs them4 ,the sensation in a glider while in flight is unlike any other experience4 ,it is like riding a lot of tense springs1 and the exhilaration in gliding down the side of a hill1 with the feet free and body suspended1 is quite different from riding in an aeroplane with power attached4 ,,hints ,,in ,,gliding4--,it seems to be a difficult matter to give any advice in the art of gliding4 ,it is a feat which seems to necessitate experiment from first to last4 ,during the hundreds of tests personally made1 and after witnessing thousands of attempts1 there seems to be only a few suggestions or possible directions in which caution might be offered4 ,first1 in respect to the position of the body at the moment of launching4 ,the glider is usually so made that in carrying it1 preparatory to making the run and the leap required to glide1 it is held so that it balances in the hands4 ,now the center of air pressure in gliding may not be at the same point as its sustaining weight when held by the hand1 and furthermore1 as the arm-pits1 by which the body of the experimenter are held while gliding1 are not at the same point1 but to the rear of the hands1 the moment the glider is launched too great a weight is brought to the rear margin of the planes1 hence its forward end lifts up4 ,this condition will soon manifest itself1 and be corrected by the experimenter2 but there is another difficulty which is not so easy to discover and so quick to remedy1 and that is the swing of the legs the moment the operator leaves the ground4 ,the experimenter learns1 after many attempts1 that gliding is a matter of a few feet only1 and he anticipates landing too soon1 and the moment he leaps from the ground the legs are swung forwardly ready to alight4 ,this is done unconsciously1 just as a jumper swings his legs forwardly in the act of alighting4 ,such a motion naturally disturbs the fore and aft stability of the gliding machine1 by tilting up the forward margin1 and it banks against the air1 instead of gliding4 ,the constant fear of all gliders is1 that the machine will point downwardly1 and his motion1 as well as the position of the body1 tend to shoot it upwardly1 instead4 ,,chapter ,,ix ,,aeroplane ,,construction ,as may be inferred from the foregoing statements1 there are no definite rules for the construction of either type of flying machine1 as the flying models vary to such an extent that it is difficult to take either of them as a model to represent the preferred type of construction4 ,,lateral1 ,,and ,,fore ,,and ,,aft4--,the term lateral should be understood1 as applied to aeroplanes4 ,it is always used to designate the direction at right angles to the movement of the machine4 ,fore and aft is a marine term meaning lengthwise1 or from front to rear1 hence is always at right angles to the lateral direction4 ,the term transverse is equivalent to lateral1 in flying machine parlance1 but there is this distinction3 ,transverse has reference to a machine or object which1 like the main planes of an aeroplane1 are broader1 7that is1--from end to end7 than their length1 7from front to rear74 ,on the other hand1 lateral has reference to side branches1 as1 for instance1 the monoplane wings1 which branch out from the sides of the fore and aft body4 ,,stability ,,and ,,stabilization4--,these terms constantly appear in describing machines and their operations4 ,if the flying structure1 whatever it may be1 has means whereby it is kept from rocking from side to side1 it has stability1 which is usually designated as lateral stability4 ,the mechanism for doing this is called a stabilizer4 ,,the ,,wright ,,system4--,the ,wright machine has reference solely to the matter of laterally controlling the flying structure1 and does not pertain to the form or shape of the planes4 ,in ,fig4 #di ,a designates the upper and lower planes of a ,wright machine1 with the peculiar rounded ends4 ,the ends of the planes are so arranged that the rear margins may be raised or lowered1 independently of the other portions of the planes1 which are rigid4 ,this movement is indicated in sketch #a1 where the movable part ,b is1 as we might say1 hinged along the line ,c4 ,the dotted line ,d on the right hand end1 shows how the section is depressed1 while the dotted lines ,e at the left hand end shows the section raised4 ,it is obvious that the downturned ends1 as at ,d1 will give a positive angle at one end of the planes1 and the upturned wings ,e at the other end will give a negative angle1 and thus cause the right hand end to raise1 and the other end to move downwardly1 as the machine moves forwardly through the air4 ,,controlling ,,the ,,warping ,,ends4--,originally the ,wrights controlled these warping sections by means of a cradle occupied by the aviator1 so that the cradle would move or rock1 dependent on the tilt of the machine4 ,this was what was termed automatic control4 ,this was found to be unsatisfactory1 and the control has now been placed so that it connects with a lever and is operated by the aviator1 and is called ,manually-operated control4 ,in all forms of control the wings on one side are depressed on one side and correspondingly elevated on the other4 ,,the ,,curtis ,,wings4--,curtis has small wings1 or ailerons1 intermediate the supporting surfaces1 and at their extremities1 as shown in sketch #b4 ,these are controlled by a shoulder rack or swinging frame operated by the driver1 so that the body in swinging laterally will change the two wings at the same time1 but with angles in different directions4 ,,the ,,farman ,,ailerons4--,farman's disposition is somewhat different1 as shown in sketch #c4 ,the wings are hinged to the upper planes at their rear edges1 and near the extremities of the planes4 ,operating wires lead to a lever within reach of the aviator1 and1 by this means1 the wings are held at any desired angle1 or changed at will4 ,the difficulty of using any particular model1 is true1 also1 of the arrangement of the fore and aft control1 as well as the means for laterally stabilizing it4 ,in view of this we shall submit a general form1 which may be departed from at will4 ,,features ,,well ,,developed4--,certain features are fairly well developed1 however4 ,one is the angle of the supporting plane1 with reference to the frame itself2 and the other is the height at which the tail and rudder should be placed above the surface of the ground when the machine is at rest4 ,,depressing ,,the ,,rear ,,end4--,this latter is a matter which must be taken into consideration1 because in initiating flight the rear end of the frame is depressed in order to give a sufficient angle to the supporting planes so as to be able to inaugurate flight4 ,in order to commence building we should have some definite idea with respect to the power1 as this will1 in a measure1 determine the area of the supporting surfaces1 as a whole1 and from this the sizes of the different planes may be determined4 ,,determining ,,the ,,size4--,suppose we decide on #cjj square feet of sustaining surface4 ,this may require a #cj1 a #dj or a #ej horse power motor1 dependent on the speed required1 and much higher power has been used on that area4 ,however1 let us assume that a forty horse power motor is available1 our #cjj square feet of surface may be put into two planes1 each having #aej square feet of surface1 which would make each #e' by #cj' in size2 or1 it may be decided to make the planes narrower1 and proportionally longer4 ,this is immaterial4 ,the shorter the planes transversely1 the greater will be the stability1 and the wider the planes the less will be the lift1 comparatively4 ,,rule ,,for ,,placing ,,the ,,planes4--,the rule for placing the planes is to place them apart a distance equal to the width of the planes themselves1 so that if we decide on making them five feet wide1 they should be placed at least five feet apart4 ,this rule1 while it is an admirable one for slow movements or when starting flight1 is not of any advantage while in rapid flight4 ,if the machine is made with front and rear horizontally-disposed rudders1 or elevators1 they also serve as sustaining surfaces1 which1 for the present will be disregarded4 ,lay off a square ,a1 ,fig4 #di;a1 in which the vertical lines ,b1 ,b1 and the horizontal lines ,c1 ,c1 are #e' long1 and draw a cross ,d within this1 the lines running diagonally from the corners4 ,now step off from the center cross line ,d1 three spaces1 each five feet long1 to a point ,e1 and join this point by means of upper and lower bars ,f1 ,g1 with the upper and lower planes1 so as to form the tail frame4 ,fig4 #di;a4 ,rule for spacing ,planes4 ,as shown in ,fig4 #ej1 the planes should now be indicated1 and placed at an angle of about #h degrees angle1 which are illustrated1 ,h being the upper and ,i the lower plane4 ,midway between the forward edges of the two planes1 is a horizontal line ,j1 extending forwardly1 and by stepping off the width of two planes1 a point ,k is made1 which forms the apex of a frame ,l1 the rear ends of the bars being attached to the respective planes ,h1 ,i1 at their forward edges4 ,fig4 #ej4 ,frame of ,control ,planes4 ,fig4 #ea4 and ,fig4 #eb4 ,,elevating ,,planes4--,we must now have the general side elevation of the frame1 the planes1 their angles1 the tail and the rudder support1 and the frame for the forward elevator4 ,to this may be added the forward elevating plane ,l1 the rear elevator1 or tail ,m1 and the vertical steering rudder ,n4 ,the frame which supports the structure thus described1 may be made in a variety of ways1 the object being to provide a resilient connection for the rear wheel ,o4 ,fig4 #eb shows a frame which is simple in construction and easily attached4 ,the lower fore and aft side bars ,p have the single front wheel axle at the forward end1 and the aft double wheels at the rear end1 a flexible bar ,q1 running from the rear wheel axle to the forward end of the lower plane4 ,a compression spring ,r is also mounted between the bar and rear end of the lower plane to take the shock of landing4 ,the forward end of the bar ,p has a brace ,s extending up to the front edge of the lower plane1 and another brace ,t connects the bars ,p1 ,s1 with the end of the forwardly- projecting frame4 ,fig4 #ec4 ,plan view4 ,the full page view1 ,fig4 #ec1 represents a plan view1 with one of the wings cut away1 showing the general arrangement of the frame1 and the three wheels required for support1 together with the brace bars referred to4 ,the necessity of the rear end elevation will now be referred to4 ,the tail need not1 necessarily1 be located at a point on a horizontal line between the planes4 ,it may be higher1 or lower than the planes1 but it should not be in a position to touch the ground when the machine is about to ascend4 ,fig4 #ed4 ,alighting4 ,the angle of ascension in the planes need not exceed #be degrees so the frame does not require an angle of more than #ag degrees4 ,this is shown in ,fig4 #ed1 where the machine is in a position ready to take the air at that angle1 leaving ample room for the steering rudder4 ,,action ,,in ,,alighting4--,also1 in alighting1 the machine is banked1 practically in the same position thus shown1 so that it alights on the rear wheels ,o4 ,the motor ,u is usually mounted so its shaft is midway between the planes1 the propeller ,v being connected directly with the shaft1 and being behind the planes1 is on a medial line with the machine4 ,the control planes ,l1 ,m1 ,n1 are all connected up by means of flexible wires with the aviator at the set ,w1 the attachments being of such a character that their arrangement will readily suggest themselves to the novice4 ,,the ,,monoplane4--,from a spectacular standpoint a monoplane is the ideal flying machine4 ,it is graceful in outline1 and from the fact that it closely approaches the form of the natural flyer1 seems to be best adapted as a type1 compared with the biplane4 ,,the ,,common ,,fly4--,so many birds have been cited in support of the various flying theories that the house fly1 as an example has been disregarded4 ,we are prone to overlook the small insect1 but it is1 nevertheless1 a sample which is just as potent to show the efficiency of wing surface as the condor or the vulture4 ,the fly has greater mobility than any other flying creature4 ,by the combined action of its legs and wings it can spring eighteen inches in the tenth of a second2 and when in flight can change its course instantaneously4 ,if a sparrow had the same dexterity1 proportionally1 it could make a flight of #hjj feet in the same time4 ,the posterior legs of the fly are the same length as its body1 which enable it to spring from its perch with amazing facility4 ,fig4 #ee4 ,common ,fly4 ,outstretched ,wings4 ,the wing surface1 proportioned to its body and weight1 is no less a matter for wonder and consideration4 ,in ,fig4 #ee is shown the outlines of the fly with outstretched wings4 ,fig4 #ef represents it with the wing folded1 and ,fig4 #eg is a view of a wing with the relative size of the top of the body shown in dotted lines4 ,fig4 #ef4 ,common ,fly4 ,folded ,wings4 ,the first thing that must attract attention1 after a careful study is the relative size of the body and wing surface4 ,each wing is slightly smaller than the upper surface of the body1 and the thickness of the body is equal to each wing spread4 ,fig4 #eg4 ,relative size of wing and body4 ,the weight1 compared with sustaining surface1 if expressed in understandable terms1 would be equal to sixty pounds for every square foot of surface4 ,,stream ,,lines4--,the next observation is1 that what are called stream lines do not exist in the fly4 ,its head is as large in cross section as its body1 with the slightest suggestion only1 of a pointed end4 ,its wings are perfectly flat1 forming a true plane1 not dished1 or provided with a cambre1 even1 that upward curve1 or bulge on the top of the aeroplane surface1 which seems to possess such a fascination for many bird flight advocates4 ,it will also be observed that the wing connection with the body is forward of the line ,a1 which represents the point at which the body will balance itself1 and this line passes through the wings so that there is an equal amount of supporting surface fore and aft of the line4 ,again1 the wing attachment is at the upper side of the body1 and the vertical dimension of the body1 or its thickness1 is equal to four-fifths of the length of he wing4 ,the wing socket permits a motion similar to a universal joint1 ,fig4 #ee showing how the inner end of the wing has a downward bend where it joins the back1 as at ,b4 ,,the ,,monoplane ,,form4--,for the purpose of making comparisons the illustrations of the monoplane show a machine of #cjj square feet of surface1 which necessitates a wing spread of forty feet from tip to tip1 so that the general dimensions of each should be #ah #a_/b feet by #h #a_/b feet at its widest point4 ,first draw a square forty feet each way1 as in ,fig4 #eh1 and through this make a horizontal line #a1 and four intermediate vertical lines are then drawn1 as #b1 #c1 #d1 #e1 thus providing five divisions1 each eight feet wide4 ,in the first division the planes ,a1 ,b1 are placed1 and the tail1 or elevator ,c1 is one-half the width of the last division4 ,fig4 #eh4 ,plan of ,monoplane4 ,the frame is #c #a_/b feet wide at its forward end1 and tapers down to a point at its rear end1 where the vertical control plane ,d is hinged1 and the cross struts ,e1 ,e1 are placed at the division lines #c1 #d1 #e4 ,the angles of the planes1 with relation to the frame1 are usually greater than in the biplane1 for the reason that the long tail plane requires a greater angle to be given to the planes when arising2 or1 instead of this1 the planes ,a1 ,b1 are mounted high enough to permit of sufficient angle for initiating flight without injuring the tail ,d4 ,some monoplanes are built so they have a support on wheels placed fore and aft4 ,in others the tail is supported by curved skids1 as shown at ,a1 ,fig4 #ei1 in which case the forward supporting wheels are located directly beneath the planes4 ,as the planes are at about eighteen degrees angle1 relative to the frame1 and the tail plane ,b is at a slight negative angle of incidence1 as shown at the time when the engine is started1 the air rushing back from the propeller1 elevates the tail1 and as the machine moves forwardly over the ground1 the tail raises still higher1 so as to give a less angle of incidence to the planes while skimming along the surface of the ground4 ,fig4 #ei4 ,side ,elevation1 ,monoplane4 ,in order to mount1 the tail is suddenly turned to assume a sharp negative angle1 thus swinging the tail downwardly1 and this increases the angle of planes to such an extent that the machine leaves the ground1 after which the tail is brought to the proper angle to assure horizontal flight4 ,the drawing shows a skid at the forward end1 attached to the frame which carries the wheels4 ,the wheels are mounted beneath springs so that when the machine alights the springs yield sufficiently to permit the skids to strike the ground1 and they1 therefore1 act as brakes1 to prevent the machine from traveling too far4 ,,chapter ,x ,,power ,,and ,,its ,,application ,,this is a phase of the flying machine which has the greatest interest to the boy4 ,he instinctively sees the direction in which the machine has its life1--its moving principle4 ,planes have their fascination1 and propellers their mysterious elements1 but power is the great and absorbing question with him4 ,we shall try to make its application plain in the following pages4 ,we have nothing to do here with the construction and operation of the motor itself1 as1 to do that justice1 would require pages4 ,,features ,,in ,,power ,,application4--,it will be more directly to the point to consider the following features of the power and its application3 #a4 ,the amount of power necessary4 #b4 ,how to calculate the power applied4 #c4 ,its mounting4 ,,what ,,amount ,,of ,,power ,,is ,,necessary4--,in the consideration of any power plant certain calculations must be made to determine what is required4 ,a horse power means the lifting of a certain weight1 a definite distance1 within a specified time4 ,if the weight of the vehicle1 with its load1 are known1 and its resistance1 or the character of the roadway is understood1 it is a comparatively easy matter to calculate just how much power must be exerted to overcome that resistance1 and move the vehicle a certain speed4 ,in a flying machine the same thing is true1 but while these problems may be known in a general way1 the aviator has several unknown elements ever present1 which make estimates difficult to solve4 ,,the ,,pull ,,of ,,the ,,propeller4--,two such factors are ever present4 ,the first is the propeller pull4 ,the energy of a motor1 when put into a propeller1 gives a pull of less than eight pounds for every horse power exerted4 ,,foot ,,pounds4--,the work produced by a motor is calculated in ,foot ,pounds4 ,if #eej pounds should be lifted1 or pulled1 one foot in one second of time1 it would be equal to one horse power4 ,but here we have a case where one horse power pulls only eight pounds1 a distance of one foot within one second of time1 and we have utilized less than one sixty-fifth of the actual energy produced4 ,,small ,,amount ,,of ,,power ,,available4--,this is due to two things3 ,first1 the exceeding lightness of the air1 and its great elasticity2 and1 second1 the difficulty of making a surface which1 when it strikes the air1 will get a sufficient grip to effect a proper pull4 ,now it must be obvious1 that where only such a small amount of energy can be made available1 in a medium as elusive as air1 the least change1 or form1 of the propeller1 must have an important bearing in the general results4 ,,high ,,propeller ,,speed ,,important4--,furthermore1 all things considered1 high speed is important in the rotation of the propeller1 up to a certain point1 beyond which the pull decreases in proportion to the speed4 ,high speed makes a vacuum behind the blade and thus decreases the effective pull of the succeeding blade4 ,,width ,,and ,,pitch ,,of ,,blades4--,if the blade is too wide the speed of the engine is cut down to a point where it cannot exert the proper energy2 if the pitch is very small then it must turn further to get the same thrust1 so that the relation of diameter1 pitch and speed1 are three problems far from being solved4 ,it may be a question whether the propeller form1 as we now know it1 is anything like the true or ultimate shape1 which will some day be discovered4 ,,effect ,,of ,,increasing ,,propeller ,,pull4--,if the present pull could be doubled what a wonderful revolution would take place in aerial navigation1 and if it were possible to get only a quarter of the effective pull of an engine1 the results would be so stupendous that the present method of flying would seem like child's play in comparison4 ,it is in this very matter1--the application of the power1 that the bird1 and other flying creatures so far excel what man has done4 ,calculations made with birds as samples1 show that many of them are able to fly with such a small amount of power that1 if the same energy should be applied to a flying machine1 it would scarcely drive it along the ground4 ,,disposition ,,of ,,the ,,planes4--,the second factor is the disposition or arrangement of the planes with relation to the weight4 ,let us illustrate this with a concrete example3 ,we have an aeroplane with a sustaining surface of #cjj square feet which weighs #ijj pounds1 or #cj pounds per square foot of surface4 ,,different ,,speeds ,,with ,,same ,,power4--,now1 we may be able to do two things with an airship under those conditions4 ,it may be propelled through the air thirty miles an hour1 or sixty miles1 with the expenditure of the same power4 ,an automobile1 if propelled at sixty1 instead of thirty miles an hour1 would require an additional power in doing so1 but an airship acts differently1 within certain limitations4 ,when it is first set in motion its effective pull may not be equal to four pounds for each horse power1 due to the slow speed of the propeller1 and also owing to the great angle of incidence which resists the forward movement of the ship4 ,,increase ,,of ,,speed ,,adds ,,to ,,resistance4--,finally1 as speed increases1 the angle of the planes decrease1 resistance is less1 and up to a certain point the pull of the propeller increases2 but beyond that the vacuum behind the blades becomes so great as to bring down the pull1 and there is thus a balance1--a sort of mutual governing motion which1 together1 determine the ultimate speed of the aeroplane4 ,,how ,,power ,,decreases ,,with ,,speed4--,if now1 with the same propeller1 the speed should be doubled1 the ship would go no faster1 because the bite of the propeller on the air would be ineffective1 hence it will be seen that it is not the amount of power in itself1 that determines the speed1 but the shape of the propeller1 which must be so made that it will be most effective at the speed required for the ship4 ,while that is true when speed is the matter of greatest importance1 it is not the case where it is desired to effect a launching4 ,in that case the propeller must be made so that its greatest pull will be at a slow speed4 ,this means a wider blade1 and a greater pitch1 and a comparatively greater pull at a slow speed4 ,no such consideration need be given to an automobile4 ,the constant accretion of power adds to its speed4 ,in flying machines the aviator must always consider some companion factor which must be consulted4 ,,how ,,to ,,calculate ,,the ,,power ,,applied4--,in a previous chapter reference was made to a plane at an angle of forty-five degrees1 to which two scales were attached1 one to get its horizontal pull1 or drift1 and the other its vertical pull1 or lift4 ,,pulling ,,against ,,an ,,angle4--,let us take the same example in our aeroplane4 ,assuming that it weighs #ijj pounds1 and that the angle of the planes is forty-five degrees4 ,if we suppose that the air beneath the plane is a solid1 and frictionless1 and a pair of scales should draw it up the incline1 the pull in doing so would be one-half of its weight1 or #dej pounds4 ,it must be obvious1 therefore1 that its force1 in moving downwardly1 along the surface ,a1 ,fig4 #fj1 would be #dej pounds4 ,the incline thus shown has thereon a weight ,b1 mounted on wheels a1 and the forwardly-projecting cord represents the power1 or propeller pull1 which must1 therefore1 exert a force of #dej pounds to keep it in a stationary position against the surface ,a4 ,in such a case the thrust along the diagonal line ,e would be #ijj pounds1 being the composition of the two forces pulling along the lines ,d1 ,f4 ,,the ,,horizontal ,,and ,,vertical ,,pull4--,now it must be obvious1 that if the incline takes half of the weight while it is being drawn forwardly1 in the line of ,d1 if we had a propeller drawing along that line1 which has a pull of #dej pounds1 it would maintain the plane in flight1 or1 at any rate hold it in space1 assuming that the air should be moving past the plane4 ,fig4 #fj4 ,horizontal and ,vertical pull4 ,the table of lift and drift gives a fairly accurate method of determining this factor1 and we refer to the chapter on that subject which will show the manner of making the calculations4 ,,the ,,power ,,mounting4--,more time and labor has been wasted1 in airship experiments1 in poor motor mounting1 than in any other direction4 ,this is especially true where two propellers are used1 or where the construction is such that the propeller is mounted some distance from the motor4 ,,securing ,,the ,,propeller ,,to ,,the ,,shaft4--,but even where the propeller is mounted on the engine shaft1 too little care is exercised to fix it securely4 ,the vibratory character of the mounting makes this a matter of first importance4 ,if there is a solid base a poorly fixed propeller will hold much longer1 but it is the extreme vibration that causes the propeller fastening to give way4 ,,vibrations4--,if experimenters realized that an insecure1 shaking1 or weaving bed would cause a loss of from ten to fifteen per cent4 in the pull of the propeller1 more care and attention would be given to this part of the structure4 ,,weaknesses ,,in ,,mounting4--,the general weaknesses to which attention should be directed are1 first1 the insecure attachment of the propeller to the shaft2 second1 the liability of the base to weave2 or permit of a torsional movement2 third1 improper bracing of the base to the main body of the aeroplane4 ,if the power is transferred from the cylinder to the engine shaft where it could deliver its output without the use of a propeller1 it would not be so important to consider the matter of vibration2 but the propeller1 if permitted to vibrate1 or dance about1 absorbs a vast amount of energy1 while at the same time cutting down its effective pull4 ,aside from this it is dangerous to permit the slightest displacement while the engine is running4 ,any looseness is sure to grow worse1 instead of better1 and many accidents have been registered by bolts which have come loose from excessive vibration4 ,it is well1 therefore1 to have each individual nut secured1 or properly locked1 which is a matter easily done1 and when so secured there is but little trouble in going over the machine to notice just how much more the nut must be taken up to again make it secure4 ,,the ,,gasoline ,,tank4--,what horrid details have been told of the pilots who have been burned to death with the escaping gasoline after an accident1 before help arrived4 ,there is no excuse for such dangers4 ,most of such accidents were due to the old practice of making the tanks of exceedingly light or thin material1 so that the least undue jar would tear a hole at the fastening points1 and thus permit the gasoline to escape4 ,a thick copper tank is by far the safest1 as this metal will not readily rupture by the wrench which is likely in landing4 ,,where ,,to ,,locate ,,the ,,tank4--,there has been considerable discussion as to the proper place to locate the tank4 ,those who advocate its placement overhead argue that in case of an accident the aeroplane is likely to overturn1 and the tank will1 therefore1 be below the pilot4 ,those who believe it should be placed below1 claim that in case of overturning it is safer to have the tank afire above than below4 ,,danger ,,to ,,the ,,pilot4--,the great danger to the pilot1 in all cases of accidents1 lies in the overturning of the machine4 ,many have had accidents where the machine landed right side up1 even where the fall was from a great height1 and the only damage to the aviator was bruises4 ,few1 if any1 pilots have escaped where the machine has overturned4 ,it is far better1 in case the tank is light1 to have it detached from its position1 when the ship strikes the earth1 because in doing so1 it will not be so likely to burn the imprisoned aviator4 ,in all cases the tank should be kept as far away from the engine as possible4 ,there is no reason why it cannot be placed toward the tail end of the machine1 a place of safety for two reasons3 ,first1 it is out of the reach of any possible danger from fire2 and1 second1 the accidents in the past show that the tail frame is the least likely to be injured4 ,in looking over the illustrations taken from the accidents1 notice how few of the tails are even disarranged1 and in many of them1 while the entire fore body and planes were crushed to atoms1 the tail still remained as a relic1 to show its comparative freedom from the accident4 ,in all monoplanes the tail really forms part of the supporting surface of the machine1 and the adding of the weight of the gasoline would be placing but little additional duty on the tail1 and it could be readily provided for by a larger tail surface1 if required4 ,,the ,,closed-,,in ,,body4--,the closed-in body is a vast improvement1 which has had the effect of giving greater security to the pilot1 but even this is useless in case of overturning4 ,,starting ,,the ,,machine4--,the direction in which improvements have been slow is in the starting of the machine4 ,the power is usually so mounted that the pilot has no control over the starting1 as he is not in a position to crank it4 ,the propeller being mounted directly on the shaft1 without the intervention of a clutch1 makes it necessary1 while on the ground1 for the propeller to be started by some one outside1 while others hold the machine until it attains the proper speed4 ,this could be readily remedied by using a clutch1 but in the past this has been regarded as one of the weight luxuries that all have been trying to avoid4 ,self starters are readily provided1 and this with the provision that the propeller can be thrown in or out at will1 would be a vast improvement in all machines4 ,,propellers ,,with ,,varying ,,pitch4--,it is growing more apparent each day1 that a new type of propeller must be devised which will enable the pilot to change the pitch1 as the speed increases1 and to give a greater pitch1 when alighting1 so as to make the power output conform to the conditions4 ,such propellers1 while they may be dangerous1 and much heavier than the rigid type1 will1 no doubt1 appear in time1 and the real improvement would be in the direction of having the blades capable of automatic adjustment1 dependent on the wind pressure1 or the turning speed1 and thus not impose this additional duty on the pilot4 ,,chapter ,,xi ,,flying ,,machine ,,accessories ,,the ,,anemometer4--,it requires an expert to judge the force or the speed of a wind1 and even they will go astray in their calculations4 ,it is an easy matter to make a little apparatus which will accurately indicate the speed4 ,a device of this kind is called an ,anemometer4 ,two other instruments have grown out of this1 one to indicate the pressure1 and the other the direction of the moving air current4 ,,the ,,anemograph4--,while these instruments indicate1 they are also made so they will record the speed1 the pressure and the direction1 and the device for recording the speed and pressure is called a ,anemograph4 ,all these instruments may be attached to the same case1 and thus make a handy little device1 which will give all the information at a glance4 ,,the ,,anemometrograph4--,this device for recording1 as well as indicating the speed1 pressure and direction1 is called an ,anemometrograph1 ,the two important parts of the combined apparatus1 for the speed and pressure1 are illustrated1 to show the principle involved4 ,while the speed will give the pressure1 it is necessary to make a calculation to get the result while the machine does this for you4 ,fig4 #fa4 ,speed ,indicator4 ,,the ,,speed ,,indicator4--,four hemispherical cups ,a are mounted on four radiating arms ,b1 which are secured to a vertical stem ,c1 and adapted to rotate in suitable bearings in a case1 which1 for convenience in explaining1 is not shown4 ,on the lower end of the stem ,c1 is a small bevel pinion1 which meshes with a smaller bevel pinion within the base4 ,this latter is on a shaft which carries a small gear on its other end1 to mesh with a larger gear on a shaft which carries a pointer ,d that thus turns at a greatly reduced speed1 so that it can be easily timed4 ,fig4 #fb4 ,air ,pressure ,indicator4 ,,air ,,pressure ,,indicator4--,this little apparatus is readily made of a base ,a which is provided with two uprights ,b1 ,c1 through the upper ends of which are holes to receive a horizontally-disposed bar ,d4 ,one end of the bar is a flat plane surface ,e1 which is disposed at right angles to the bar1 and firmly fixed thereto4 ,the other end of the bar has a lateral pin to serve as a pivot for the end of a link ,f1 its other end being hinged to the upper end of a lever ,g1 which is pivoted to the post ,c1 a short distance below the hinged attachment of the link ,f1 so that the long end of the pointer which is constituted by the lever ,g is below its pivot1 and has1 therefore1 a long range of movement4 ,a spring ,i between the upper end of the pointer ,g and the other post ,b1 serves to hold the pointer at a zero position4 ,a graduated scale plate ,j1 within range of the pointer will show at a glance the pressure in pounds of the moving wind1 and for this purpose it would be convenient to make the plane ,e exactly one foot square4 ,,determining ,,the ,,pressure ,,from ,,the ,,speed4-- ,these two instruments can be made to check each other and thus pretty accurately enable you to determine the proper places to mark the pressure indicator1 as well as to make the wheels in the anemometer the proper size to turn the pointer in seconds when the wind is blowing at a certain speed1 say ten miles per hour4 ,suppose the air pressure indicator has the scale divided into quarter pound marks4 ,this will make it accurate enough for all purposes4 ,,calculating ,,pressures ,,from ,,speed4--,the following table will give the pressures from #e to #ajj miles per hour3 ,velocity of wind in ,pressure ,velocity of wind in ,pressure miles per hour per sq4 ft4 miles per hour per sq ft #e 4#aab #ee #ae4abe #aj 4#ejj #fj #ah4jjj #ae #a4abe #fe #ba4abe #bj #b4jjj #gj #bb4ejj #be #c4abe #ge #bh4abe #cj #d4fjj #hj #cb4jjj #ce #f4abf #hf #cf4abf #dj #h4jjj #ij #dj4ejj #de #aj4abe #ie #de4abe #ej #ab4e #ajj #ej4jjj ,,how ,,the ,,figures ,,are ,,determined4--,the foregoing figures are determined in the following manner3 ,as an example let us assume that the velocity of the wind is forty-five miles per hour4 ,if this is squared1 or #de multiplied by #de1 the product is #bjbe4 ,in many calculations the mathematician employs what is called a constant1 a figure that never varies1 and which is used to multiply or divide certain factors4 ,in this case the constant is #e_/ajjj1 or1 as usually written1 4#jje4 ,this is the same as one two hundredths of the squared figure4 ,that would make the problem as follows3 #de ,x #de #bjbe _/ #bjj #aj4abe2 or1 #de ,x #de - #bjbe ,x 4#jje #aj4abe4 ,again1 twenty-five miles per hour would be #be ,x #be #fbe2 and this multiplied by 4#jje equals #b pounds pressure4 ,,converting ,,hours ,,into ,,minutes4--,it is sometimes confusing to think of miles per hour1 when you wish to express it in minutes or seconds4 ,a simple rule1 which is not absolutely accurate1 but is correct within a few feet1 in order to express the speed in feet per minute1 is to multiply the figure indicating the miles per hour1 by #h #c_/d4 ,to illustrate3 ,if the wind is moving at the rate of twenty miles an hour1 it will travel in that time #aje1fjj feet 7#ebhj ,x #bj74 ,as there are sixty minutes in an hour1 #aje1fjj divided by #fj1 equals #agfj feet per minute4 ,instead of going through all this process of calculating the speed per minute1 remember to multiply the speed in miles per hour by #ij1 which will give #ahjj feet4 ,this is a little more then two per cent4 above the correct figure4 ,again2 #dj ,x #ij equals #cfjj4 ,as the correct figure is #cebj1 a little mental calculation will enable you to correct the figures so as to get it within a few feet4 ,,changing ,,speed ,,hours ,,to ,,seconds4--,as one- sixtieth of the speed per minute will represent the rate of movement per second1 it is a comparatively easy matter to convert the time from speed in miles per hour to fraction of a mile traveled in a second1 by merely taking one-half of the speed in miles1 and adding it1 which will very nearly express the true number of feet4 ,as examples1 take the following3 ,if the wind is traveling #bj miles an hour1 it is easy to take one-half of #bj1 which is #aj1 and add it to #bj1 making #cj1 as the number of feet per second4 ,if the wind travels #ej miles per hour1 add #be1 making #ge1 as the speed per second4 ,the correct speed per second of a wind traveling #bj miles an hour is a little over #bi feet4 ,at #ej miles per hour1 the correct figure is #gc #a_/c feet1 which show that the figures under this rule are within about one per cent4 of being correct4 ,with the table before you it will be an easy matter1 by observing the air pressure indicator1 to determine the proper speed for the anemometer4 ,suppose it shows a pressure of two pounds1 which will indicate a speed of twenty miles an hour4 ,you have thus a fixed point to start from4 ,,pressure ,,as ,,the ,,square ,,of ,,the ,,speed4--,now it must not be assumed that if the pressure at twenty miles an hour is two pounds1 that forty miles an hour it is four pounds4 ,the pressure is as the square of the speed4 ,this may be explained as follows3 ,as the speed of the wind increases1 it has a more effective push against an object than its rate of speed indicates1 and this is most simply expressed by saying that each time the speed is doubled the pressure is four times greater4 ,as an example of this1 let us take a speed of ten miles an hour1 which means a pressure of one- half pound4 ,double this speed1 and we have #bj miles4 ,multiplying one-half pound by #d1 the result is #b pounds4 ,again1 double #bj1 which means #dj miles1 and multiplying #b by #d1 the result is #h4 ,doubling forty is eighty miles an hour1 and again multiplying #h by #d1 we have #cb as the pounds pressure at a speed of #hj miles an hour4 ,the anemometer1 however1 is constant in its speed4 ,if the pointer should turn once a second at #aj miles an hour1 it would turn twice at #bj miles an hour1 and four times a second at #dj miles an hour4 ,,gyroscopic ,,balance4--,some advance has been made in the use of the gyroscope for the purpose of giving lateral stability to an aeroplane4 ,while the best of such devices is at best a makeshift1 it is well to understand the principle on which they operate1 and to get an understanding how they are applied4 ,,the ,,principle ,,involved4--,the only thing known about the gyroscope is1 that it objects to changing the plane of its rotation4 ,this statement must be taken with some allowance1 however1 as1 when left free to move1 it will change in one direction4 ,to explain this without being too technical1 examine ,fig4 #fc1 which shows a gyroscopic top1 one end of the rim ,a1 which supports the rotating wheel ,b1 having a projecting finger ,c1 that is mounted on a pin-point on the upper end of the pedestal ,d4 ,fig4 #fc4 ,the ,gyroscope4 ,when the wheel ,b is set in rotation it will maintain itself so that its axis ,e is horizontal1 or at any other angle that the top is placed in when the wheel is spun4 ,if it is set so the axis is horizontal the wheel ,b will rotate on a vertical plane1 and it forcibly objects to any attempt to make it turn except in the direction indicated by the curved arrows ,f4 ,the wheel ,b will cause the axis ,e to swing around on a horizontal plane1 and this turning movement is always in a certain direction in relation to the turn of the wheel ,b1 and it is obvious1 therefore1 that to make a gyroscope that will not move1 or swing around an axis1 the placing of two such wheels side by side1 and rotated in opposite directions1 will maintain them in a fixed position2 this can also be accomplished by so mounting the two that one rotates on a plane at right angles to the other4 ,fig4 #fd4 ,application of the ,gyroscope4 ,,the ,,application ,,of ,,the ,,gyroscope4--,without in any manner showing the structural details of the device1 in its application to a flying machine1 except in so far as it may be necessary to explain its operation1 we refer to ,fig4 #fd1 which assumes that ,a represents the frame of the aeroplane1 and ,b a frame for holding the gyroscopic wheel ,c1 the latter being mounted so it rotates on a horizontal plane1 and the frame ,b being hinged fore and aft1 so that it is free to swing to the right or to the left4 ,for convenience in explaining the action1 the planes ,e are placed at right angles to their regular positions1 ,f being the forward margin of the plane1 and ,g the rear edge4 ,wires ,h connect the ends of the frame ,b with the respective planes1 or ailerons1 ,e1 and another wire ,i joins the downwardly-projecting arms of the two ailerons1 so that motion is transmitted to both at the same time1 and by a positive motion in either direction4 ,fig4 #fe4 ,action of the ,gyroscope4 ,in the second figure1 #fe1 the frame of the aeroplane is shown tilted at an angle1 so that its right side is elevated4 ,as the gyroscopic wheel remains level it causes the aileron on the right side to change to a negative angle1 while at the same time giving a positive angle to the aileron on the left side1 which would1 as a result1 depress the right side1 and bring the frame of the machine back to a horizontal position4 ,,fore ,,and ,,aft ,,gyroscopic ,,control4--,it is obvious that the same application of this force may be applied to control the ship fore and aft1 although it is doubtful whether such a plan would have any advantages1 since this should be wholly within the control of the pilot4 ,laterally the ship should not be out of balance2 fore and aft this is a necessity1 and as the great trouble with all aeroplanes is to control them laterally1 it may well be doubted whether it would add anything of value to the machine by having an automatic fore and aft control1 which might1 in emergencies1 counteract the personal control of the operator4 ,,angle ,,indicator4--,in flight it is an exceedingly difficult matter for the pilot to give an accurate idea of the angle of the planes4 ,if the air is calm and he is moving over a certain course1 and knows1 from experience1 what his speed is1 he may be able to judge of this factor1 but he cannot tell what changes take place under certain conditions during the flight4 ,for this purpose a simple little indicator may be provided1 shown in ,fig4 #ff1 which is merely a vertical board ,a1 with a pendulum ,b1 swinging fore and aft from a pin a which projects out from the board a short distance above its center4 ,the upper end of the pendulum has a heart- shaped wire structure ,d1 that carries a sliding weight ,e4 ,normally1 when the aeroplane is on an even keel1 or is even at an angle1 the weight ,e rests within the bottom of the loop ,d1 but should there be a sudden downward lurch or a quick upward inclination1 which would cause the pendulum below to rapidly swing in either direction1 the sliding weight ,e would at once move forward in the same direction that the pendulum had moved1 and thus counteract1 for the instant only1 the swing1 when it would again drop back into its central position4 ,fig4 #ff4 ,angle ,indicator4 ,with such an arrangement1 the pendulum would hang vertically at all times1 and the pointer below1 being in range of a circle with degrees indicated thereon1 and the base attached to the frame of the machine1 can always be observed1 and the conditions noted at the time the changes take place4 ,,pendulum ,,stabilizer4--,in many respects the use of a pendulum has advantages over the gyroscope4 ,the latter requires power to keep it in motion4 ,the pendulum is always in condition for service4 ,while it may be more difficult to adjust the pendulum1 so that it does not affect the planes by too rapid a swing1 or an oscillation which is beyond the true angle desired1 still1 these are matters which1 in time1 will make the pendulum a strong factor in lateral stability4 ,fig4 #fg4 ,simple ,pendulum ,stabilizer4 ,it is an exceedingly simple matter to attach the lead wires from an aileron to the pendulum4 ,in ,fig4 #fg one plan is illustrated4 ,the pendulum ,a swings from the frame ,b of the machine1 the ailerons a being in this case also shown at right angles to their true positions4 ,the other1 ,fig4 #fh1 assumes that the machine is exactly horizontal1 and as the pendulum is in a vertical position1 the forward edges of both ailerons are elevated1 but when the pendulum swings both ailerons will be swung with their forward margins up or down in unison1 and thus the proper angles are made to right the machine4 ,,steering ,,and ,,controlling ,,wheel4--,for the purpose of concentrating the control in a single wheel1 which has not alone a turning motion1 but is also mounted in such a manner that it will oscillate to and fro1 is very desirable1 and is adapted for any kind of machine4 ,fig4 #fh4 ,pendulum ,stabilizers4 ,fig4 #fi shows such a structure1 in which ,a represents the frame of the machine1 and ,b a segment for the stem of the wheel1 the segment being made of two parts1 so as to form a guideway for the stem a to travel between1 and the segment is placed so that the stem will travel in a fore and aft direction4 ,the lower end of the stem is mounted in a socket1 at ,d1 so that while it may be turned1 it will also permit this oscillating motion4 ,near its lower end is a cross bar ,e from which the wires run to the vertical control plane1 and also to the ailerons1 if the machine is equipped with them1 or to the warping ends of the planes4 ,fig4 #fi4 ,steering and ,control ,wheel4 ,above the cross arms is a loose collar ,f to which the fore and aft cords are attached that go to the elevators1 or horizontal planes4 ,the upper end of the stem has a wheel ,g1 which may also be equipped with the throttle and spark levers4 ,,automatic ,,stabilizing ,,wings4--,unquestionably1 the best stabilizer is one which will act on its own initiative4 ,the difficulty with automatic devices is1 that they act too late1 as a general thing1 to be effective4 ,the device represented in ,fig4 #gj is very simple1 and in practice is found to be most efficient4 ,in this ,fig4 #gj ,a and ,b represent the upper and the lower planes1 respectively4 ,near the end vertical standards a1 ,d1 are narrow wings ,e ,e1 ,f ,f1 hinged on a fore and aft line close below each of the planes1 the wings being at such distances from the standards ,c ,d that when they swing outwardly they will touch the standards1 and when in that position will be at an angle of about #ce degrees from the planes ,a ,b4 ,fig4 #gj4 ,automatic ,stabilizing ,wings4 ,fig4 #ga4 ,action of ,stabilizing ,wings4 ,inwardly they are permitted to swing up and lie parallel with the planes1 as shown in ,fig4 #ga where the planes are at an angle4 ,in turning1 all machines skid1--that is they travel obliquely across the field1 and this is also true when the ship is sailing at right angles to the course of the wind4 ,this will be made clear by reference to ,fig4 #gb1 in which the dart ,a represents the direction of the movement of the aeroplane1 and ,b the direction of the wind1 the vertical rudder a being almost at right angles to the course of the wind4 ,fig4 #gb4 ,into the ,wind at an ,angle4 ,in turning a circle the same thing takes place as shown in ,fig4 #gc1 with the tail at a different angle1 so as to give a turning movement to the plane4 ,it will be seen that in the circling movement the tendency of the aeroplane is to fly out at a tangent1 shown by the line ,d1 so that the planes of the machine are not radially-disposed with reference to the center of the circle1 the line ,e showing the true radial line4 ,referring now to ,fig4 #ga1 it will be seen that this skidding motion of the machine swings the wings ,e ,f inwardly1 so that they offer no resistance to the oblique movement1 but the wings ,e ,e1 at the other end of the planes are swung outwardly1 to provide an angle1 which tends to raise up the inner end of the planes1 and thereby seek to keep the planes horizontal4 ,fig4 #gc4 ,turning a ,circle4 ,,barometers4--,these instruments are used for registering heights4 ,a barometer is a device for measuring the weight or pressure of the air4 ,the air is supposed to extend to a height of #dj miles from the surface of the sea4 ,a column of air one inch square1 and forty miles high1 weighs the same as a column of mercury one inch square and #cj inches high4 ,such a column of air1 or of mercury1 weighs #ad #c_/d pounds4 ,if the air column should be weighed at the top of the mountain1 that part above would weigh less than if measured at the sea level1 hence1 as we ascend or descend the pressure becomes less or more1 dependent on the altitude4 ,mercury is also used to indicate temperature1 but this is brought about by the expansive quality of the mercury1 and not by its weight4 ,fig4 #gd4 ,aneroid ,barometer4 ,,aneroid ,,barometer4--,the term ,aneroid barometer is frequently used in connection with air- ship experiments4 ,the word aneroid means not wet1 or not a fluid1 like mercury1 so that1 while aneroid barometers are being made which do use mercury1 they are generally made without4 ,one such form is illustrated in ,fig4 #gd1 which represents a cylindrical shell ,a1 which has at each end a head of concentrically formed corrugations4 ,these heads are securely fixed to the ends of the shell ,a4 ,within1 one of the disk heads has a short stem ,c1 which is attached to the short end of a lever ,d1 this lever being pivoted at ,e4 ,the outer end of this lever is hinged to the short end of another lever ,f1 and so by compounding the levers1 it will be seen that a very slight movement of the head ,b will cause a considerable movement in the long end of the lever ,f4 ,this end of the lever ,f connects with one limb of a bell-crank lever ,g1 and its other limb has a toothed rack connection with a gear ,h1 which turns the shaft to which the pointer ,i is attached4 ,air is withdrawn from the interior of the shell1 so that any change in the pressure1 or weight of the atmosphere1 is at once felt by the disk heads1 and the finger turns to indicate the amount of pressure4 ,,hydroplanes4--,hydro means water1 hence the term hydroplane has been given to machines which have suitable pontoons or boats1 so they may alight or initiate flight from water4 ,there is no particular form which has been adopted to attach to aeroplanes1 the object generally being to so make them that they will sustain the greatest amount of weight with the least submergence1 and also offer the least resistance while the motor is drawing the machine along the surface of the water1 preparatory to launching it4 ,,sustaining ,,weight ,,of ,,pontoons4--,a pontoon having within nothing but air1 is merely a measuring device which determines the difference between the weight of water and the amount placed on the pontoon4 ,water weighs #fb #a_/b pounds per cubic foot4 ,ordinary wood1 an average of #cb pounds1 and steel #ejj pounds4 ,it is1 therefore1 an easy matter to determine how much of solid matter will be sustained by a pontoon of a given size1 or what the dimensions of a pontoon should be to hold up an aeroplane which weighs1 with the pilot1 say1 #aajj pounds4 ,as we must calculate for a sufficient excess to prevent the pontoons from being too much immersed1 and also allow a sufficient difference in weight so that they will keep on the surface when the aeroplane strikes the surface in alighting1 we will take the figure of #aejj pounds to make the calculations from4 ,if this figure is divided by #fb #a_/b we shall find the cubical contents of the pontoons1 not considering1 of course1 the weight of the material of which they are composed4 ,this calculation shows that we must have #bd cubic feet in the pontoons4 ,as there should be two main pontoons1 and a smaller one for the rear1 each of the main ones might have ten cubic feet1 and the smaller one four cubic feet4 ,,shapes ,,of ,,the ,,pontoons4--,we are now ready to design the shapes4 ,fig4 #ge shows three general types1 ,a being made rectangular in form1 with a tapering forward end1 so constructed as to ride up on the water4 ,the type ,b has a rounded under body1 the forward end being also skiff-shaped to decrease as much as possible the resistance of the water impact4 ,fig4 #ge4 ,hydroplane ,floats4 ,the third type ,c is made in the form of a closed boat1 with both ends pointed1 and the bottom rounded1 or provided with a keel4 ,or1 as in some cases the body may be made triangular in cross section so that as it is submerged its sustaining weight will increase at a greater degree as it is pressed down than its vertical measurement indicates4 ,all this1 however1 is a matter left to the judgment of the designer1 and is1 in a great degree1 dependent on the character of the craft to which it is to be applied4 ,,chapter ,,xii ,,experimental ,,work ,,in ,,flying ,,the novice about to take his first trial trip in an automobile will soon learn that the great task in his mind is to properly start the machine4 ,he is conscious of one thing1 that it will be an easy matter to stop it by cutting off the fuel supply and applying the brakes4 ,,certain ,,conditions ,,in ,,flying4--,in an aeroplane conditions are reversed4 ,shutting off the fuel supply and applying the brakes only bring on the main difficulty4 ,he must learn to stop the machine after all this is done1 and this is the great test of flying4 ,it is not the launching1-- the ability to get into the air1 but the landing1 that gives the pupil his first shock4 ,man is so accustomed to the little swirls of air all about him1 that he does not appreciate what they mean to a machine which is once free to glide along in the little currents which are so unnoticeable to him as a pedestrian4 ,the contour of the earth1 the fences1 trees1 little elevations and other natural surroundings1 all have their effect on a slight moving air current1 and these inequalities affect the air and disturb it to a still greater extent as the wind increases4 ,even in a still air1 with the sun shining1 there are air eddies1 caused by the uneven heating of the air in space4 ,,heat ,,in ,,air4--,heat is transmitted through the air by what is called convection1 that is1 the particles of the air transmit it from one point to the next4 ,if a room is closed up tight1 and a little aperture provided so as to let in a streak of sunlight1 it will give some idea of the unrest of the atmosphere4 ,this may be exhibited by smoke along the line of the sun's rays1 which indicates that the particles of air are constantly in motion1 although there may be absolutely nothing in the room to disturb it4 ,,motion ,,when ,,in ,,flight4--,if you can imagine a small airship floating in that space1 you can readily conceive that it will be hurled hither and thither by the motion which is thus apparent to the eye4 ,this motion is greatly accentuated by the surface of the earth1 independently of its uneven contour4 ,if a ball is thrown through the air1 its dynamic force is measured by its impact4 ,so with light1 and heat4 ,in the space between the planets it is very cold4 ,the sunlight1 or the rays from the sun are there1 just the same as on the earth4 ,unless the rays come into contact with something1 they produce no effect4 ,when the beams from the sun come into contact with the atmosphere a dynamic force is exerted1 just the same as when the ball struck an object4 ,when the rays reach the earth1 reflection takes place1 and these reflected beams act on the air under different conditions4 ,,changing ,,atmosphere4--,if the air is full of moisture1 as it may be at some places1 while comparatively dry at other points1 the reflection throughout the moist area is much greater than in the dry places1 hence evaporation will take place and whenever a liquid vaporizes it means heat4 ,on the other hand1 when the vapor is turning to a liquid1 condensation takes place1 and that means cooling4 ,if the air should be of the same degree of saturation throughout1--that is1 have the same amount of moisture everywhere1 there would be few winds4 ,these remarks apply to conditions which exist over low altitudes all over the earth4 ,but at high altitudes the conditions are entirely different4 ,as we ascend the air becomes rarer4 ,it has less moisture1 because a wet atmosphere1 being heavier1 lies nearer the surface of the earth4 ,being rarer the action of sunlight on the particles is less intense4 ,reflection and refraction of the rays acting on the light atmosphere do not produce such a powerful effect as on the air near the ground4 ,all these conditions--the contour of the earth2 the uneven character of the moisture in the air2 the inequalities of the convection currents2 and the unstable1 tenuous1 elastic nature of the atmosphere1 make the trials of the aviator a hazardous one1 and it has brought out numerous theories connected with bird flight4 ,one of these assumes that the bird1 by means of its finely organized sense1 is able to detect rising air currents1 and it selects them in its flight1 and by that means is enabled to continue in flight indefinitely1 by soaring1 or by flapping its wings4 ,,ascending ,,currents4--,it has not been explained how it happens that these particular ascending currents always appear directly in the line of the bird flight2 or why it is that when1 for instance1 a flock of wild geese which always fly through space in an ,a-shaped formation1 are able to get ascending air currents over the wide scope of space they cover4 ,,aspirate ,,currents4--,some years ago1 in making experiments with the outstretched wings of one of the large soaring birds1 a ,french sailor was surprised to experience a peculiar pulling motion1 when the bird's wings were held at a certain angle1 so that the air actually seemed to draw it into the teeth of the current4 ,it is known that if a ball is suspended by a string1 and a jet of air is directed against it1 in a particular way1 the ball will move toward the jet1 instead of being driven away from it4 ,a well known spraying device1 called the ball nozzle1 is simply a ball on the end of a nozzle1 and the stream of water issuing is not effectual to drive the ball away4 ,from the bird incident alluded to1 a new theory was propounded1 namely1 that birds flew because of the aspirated action of the air1 and the wings and body were so made as to cause the moving air current to act on it1 and draw it forwardly4 ,,outstretched ,,wings4--,this only added to the bird wing theory a new argument that all flying things must have outstretched wings1 in order to fly1 forgetting that the ball1 which has no outstretched wings1 has also the same aspirate movement attributed to the wings of the bird4 ,the foregoing remarks are made in order to impress on the novice that theories do not make flying machines1 and that speculations1 or analogies of what we see all about us1 will not make an aviator4 ,a flying machine is a question of dynamics1 just as surely as the action of the sun on the air1 and the movements of the currents1 and the knowledge of applying those forces in the flying machine makes the aviator4 ,,the ,,starting ,,point4--,before the uninitiated should attempt to even mount a machine he should know what it is composed of1 and how it is made4 ,his investigation should take in every part of the mechanism2 he should understand about the plane surface1 what the stresses are upon its surface1 what is the duty of each strut1 or brace or wire and be able to make the proper repairs4 ,,the ,,vital ,,part ,,of ,,the ,,machine4--,the motor1 the life of the machine itself1 should be like a book to him4 ,it is not required that he should know all the theories which is necessary in the building1 as to the many features which go to make up a scientifically-designed motor2 but he must know how and why it works4 ,he should understand the cam action1 whereby the valves are lifted at the proper time2 what the effect of the spark advance means2 the throttling of the engine2 air admission and supply2 the regulation of the carbureter2 its mechanism and construction2 the propeller should be studied1 and its action at various speeds4 ,,studying ,,the ,,action ,,of ,,the ,,machine4--,then comes the study on the seat of the machine itself4 ,it will be a novel sensation4 ,before him is the steering wheel1 if it should be so equipped4 ,turning it to the right1 swings the vertical tail plane so the machine will turn to the right4 ,certainly1 he knows that2 but how far must he turn the wheel to give it a certain angle4 ,it is not enough to know that a lever or a wheel when moved a certain way will move a plane a definite direction4 ,he should learn to know instinctively1 how ,,far a movement to make to get a certain result in the plane itself1 and under running conditions1 as well4 ,suppose we have an automobile1 running at the rate of ten miles an hour1 and the chauffeur turns the steering wheel ten degrees4 ,he can do so with perfect safety2 but let the machine be going forty miles an hour1 and turn the wheel ten degrees1 and it may mean an accident4 ,in one case the machine is moving #ad #a_/b feet a second1 and in the other instance #eh feet4 ,if the airship has a lever for controlling the angle of flight1 he must study its arrangement1 and note how far it must be moved to assume the proper elevating angle4 ,then come the means for controlling the lateral stability of the machine4 ,all these features should be considered and studied over and over1 until you have made them your friends4 ,while thus engaged1 you are perfectly sure that you can remember and act on a set of complicated movements4 ,you imagine that you are skimming over the ground1 and your sense tells you that you have sufficient speed to effect a launching4 ,in your mind the critical time has come4 ,,elevating ,,the ,,machine4--,simply give the elevator lever the proper angle1 sharp and quick and up you go4 ,as the machine responds1 and you can feel the cushioning motion1 which follows1 as it begins to ride the air1 you are aware of a sensation as though the machine were about to turn over to one side2 you think of the lateral control at once1 but in doing so forget that the elevator must be changed1 or you will go too high4 ,you forget about the earth2 you are too busy thinking about several things which seem to need your attention4 ,yes1 there are a variety of matters which will crowd upon you1 each of which require two things2 the first being to get the proper lever1 and the second1 to move it just so far4 ,in the early days of aeroplaning1 when accidents came thick and fast1 the most usual explanation which came from the pilot1 when he recovered1 was3 ,i pushed the lever too far4 ,hundreds of trial machines were built1 when man learned that he could fly1 and in every instance1 it is safe to say1 the experimenter made the most strenuous exertion to get up in the air the first time the machine was put on the trial ground4 ,it is a wonder that accidents were not recorded by the hundreds1 instead of by the comparatively few that were heard from4 ,it was very discouraging1 no doubt1 that the machines would not fly1 but that all of them1 if they had sufficient power1 would fly1 there can be no doubt4 ,,how ,,to ,,practice4--,absolute familiarity with every part of the machine and conditions is the first thing4 ,the machine is brought out1 and the engine tested1 the machine being held in leash while this is done4 ,it is then throttled down so that the power of the engine will be less than is necessary to raise the machine from the ground4 ,,the ,,first ,,stage4--,usually it will require over #be miles an hour to raise the machine4 ,the engine is set in motion1 and now1 for the first time a new sensation takes possession of you1 for the reason that you are cut off from communication with those around you as absolutely as though they were a hundred miles away4 ,this new dependence on yourself is1 in itself1 one of the best teachers you could have1 because it begins to instill confidence and control4 ,as the machine darts forward1 going ten or fifteen miles an hour1 with the din of the engine behind you1 and feeling the rumbling motion of the wheels over the uneven surface of the earth1 you have the sensation of going forty miles an hour4 ,the newness of the first sensation1 which is always under those conditions very much augmented in the mind1 wears away as the machine goes back and forth4 ,there is only one control that requires your care1 namely1 to keep it on a straight course4 ,this is easy work1 but you are learning to make your control a reflex action1--to do it without exercising a distinct will power4 ,,patience ,,the ,,most ,,difficult ,,thing4--,if you have the patience1 as you should1 to continue this running practice1 until you absolutely eliminate the right and left control1 as a matter of thought1 occasionally1 if the air is still turning the machine1 and eventually1 bringing it back1 by turning it completely around1 while skimming the ground1 you will be ready for the second stage in the trials4 ,,the ,,second ,,stage4--,the engine is now arranged so that it will barely lift1 when running at its best4 ,after the engine is at full speed1 and you are sure the machine is going fast enough1 the elevator control is turned to point the machine in the air4 ,it is a tense moment4 ,you are on the alert4 ,the elevator is turned1 and the forward end changes its relation with the ground before you4 ,there was a slight lift1 but your caution induces you to return the planes to their normal running angle4 ,you try it again4 ,you are now certain that the machine made a leap and left the ground4 ,this is the exhilarating moment4 ,with a calm air the machine is turned while running1 by means of the vertical rudders4 ,this is an easy matter1 because while going at twenty miles an hour1 the weight of the machine on the surface of the ground is less than one-tenth of its weight when at rest4 ,thus the trial spins1 half the time in the air1 in little glides of fifty to a hundred feet1 increasing in length1 give practice1 practice1 ,,practice1 each turn of the field making the sport less exciting and fixing the controls more perfectly in the mind4 ,,the ,,third ,,stage4--,thus far you have been turning on the ground4 ,you want to turn in the air4 ,only the tail control was required while on the ground4 ,now two things are required after you leave the ground in trying to make a turn3 namely1 putting the tail at the proper angle1 and taking charge of the stabilizers1 because in making the turn in the air1 the first thing which will arrest the attention will be the tendency of the machine to turn over in the direction that you are turning4 ,after going back and forth in straight-away glides1 until you have perfect confidence and full control1 comes the period when the turns should be practiced on4 ,these should be long1 and tried only on that portion of the field where you have plenty of room4 ,,observations ,,while ,,in ,,flight4--,if there are any bad spots1 or trees1 or dangerous places1 they should be spotted out1 and mentally noted before attempting to make any flight4 ,when in the air during these trials you will have enough to occupy your mind without looking out for the hazardous regions at the same time4 ,make the first turns in a still air4 ,if you should attempt to make the first attempts with a wind blowing you will find a compound motion that will very likely give you a surprise4 ,in making the first turn you will get the sensation of trying to fly against a wind4 ,assuming that you are turning to the left1 it will have the sensation of a wind coming to you from the right4 ,,flying ,,in ,a ,,wind4--,suppose you are flying directly in the face of a wind1 the moment you begin to turn the action1 or bite of the wind1 will cause the ends of the planes to the right to be unduly elevated1 much more so than if the air should be calm4 ,this raising action will be liable to startle you1 because up to this time you have been accustomed to flying along in a straight line4 ,while flying around at the part of the circle where the wind strikes you directly on the right side the machine has a tendency to climb1 and you try to depress the forward end1 but as soon as you reach that part of the circle where the winds begin to strike on your back1 an entirely new thing occurs4 ,as the machine is now traveling with the wind1 its grip on the air is less1 and since the planes were set to lower the machine1 at the first part of the turn1 the descent will be pretty rapid unless the angle is corrected4 ,,first ,,trials ,,in ,,quiet ,,atmosphere4--,all this would be avoided if the first trials were made in a quiet atmosphere4 ,furthermore1 you will be told that in making a turn the machine should be pointed downwardly1 as though about to make a glide4 ,this can be done with safety1 in a still air1 although you may be flying low1 but it would be exceedingly dangerous with a wind blowing4 ,,making ,,turns4--,when making a turn1 under no circumstances try to make a landing4 ,this should never be done except when flying straight1 and then safety demands that the landing should be made against the wind and not with it4 ,there are two reasons for this3 ,first1 when flying with the wind the speed must be greater than when flying against it4 ,by greater speed is meant relative to the earth4 ,if the machine has a speed of thirty miles an hour1 in still air1 the speed would be forty miles an hour going with the wind1 but only twenty miles against the wind4 ,second1 the banking of the planes against the air is more effective when going into the wind than when traveling with it1 and1 therefore1 the speed at which you contact with the earth is lessened to such an extent that a comparatively easy landing is effected4 ,,the ,,fourth ,,stage4--,after sufficient time has been devoted to the long turns shorter turns may be made1 and these also require the same care1 and will give an opportunity to use the lateral controls to a greater extent4 ,begin the turns1 not by an abrupt throw of the turning rudder1 but bring it around gently1 correcting the turning movement to a straight course1 if you find the machine inclined to tilt too much1 until you get used to the sensation of keeling over4 ,constant practice at this will soon give confidence1 and assure you that you have full control of the machine4 ,,the ,,figure #h4--,you are now to increase the height of flying1 and this involves also the ability to turn in the opposite direction1 so that you may be able to experience the sensation of using the stabilizers in the opposite direction4 ,you will find in this practice that the senses must take in the course of the wind from two quarters now1 as you attempt to describe the figure #h4 ,this is a test which is required in order to obtain a pilot's license4 ,it means that you shall be able to show the ability to turn in either direction with equal facility4 ,to keep an even flying altitude while describing this figure in a wind1 is the severest test that can be exacted4 ,,the ,,volplane4--,this is the technical term for a glide4 ,many accidents have been recorded owing to the stopping of the motor1 which in the past might have been avoided if the character of the glide had been understood4 ,the only thing that now troubles the pilot when the engine goes dead1 is to select a landing place4 ,the proper course in such a case is to urge the machine to descend as rapidly as possible1 in order to get a headway1 for the time being4 ,as there is now no propelling force the glide is depended upon to act as a substitute4 ,the experienced pilot will not make a straight-away glide1 but like the vulture1 or the condor1 and birds of that class1 soar in a circle1 and thus1 by passing over and over the same surfaces of the earth1 enable him to select a proper landing place4 ,,the ,,landing4--,the pilot who can make a good landing is generally a good flyer4 ,it requires nicety of judgment to come down properly4 ,one thing which will appear novel after the first altitude flights are attempted is the peculiar sensation of the apparently increased speed as the earth comes close up to the machine4 ,at a height of one hundred feet1 flying thirty miles an hour1 does not seem fast1 because the surface of the earth is such a distance away that particular objects remain in view for some moments2 but when within ten feet of the surface the same object is in the eye for an instant only4 ,this lends a sort of terror to the novice4 ,he imagines a great many things1 but forgets some things which are very important to do at this time4 ,one is1 that the front of the machine must be thrown up so as to bank the planes against the wind4 ,the next is to shut off the power1 which is to be done the moment the wheels strike the ground1 or a little before4 ,upon his judgment of the time of first touching the earth depends the success of safely alighting4 ,he may bank too high1 and come down on the tail with disastrous results4 ,if there is plenty of field room it is better to come down at a less angle1 or even keep the machine at an even keel1 and the elevator can then depress the tail while running over the ground1 and thus bring the machine to rest4 ,frequently1 when about to land the machine will rock from side to side4 ,in such a case it is far safer to go up into the air than to make the land1 because1 unless the utmost care is exercised1 one of the wing tips will strike the earth and wreck the machine4 ,another danger point is losing headway1 as the earth is neared1 due to flying at too flat an angle1 or against a wind that happens to be blowing particularly hard at the landing place4 ,if the motor is still going this does not make so much difference1 but in a volplane it means that the descent must be so steep1 at the last moment of flight1 that the chassis is liable to be crushed by the impact4 ,,flying ,,altitude4--,it is doubtful whether the disturbed condition of the atmosphere1 due to the contour of the earth's surface1 reaches higher than #ejj feet4 ,over a level area it is certain that it is much less1 but in some sections of the country1 where the hill ranges extend for many miles1 at altitudes of three and four hundred feet1 the upper atmosphere may be affected for a thousand feet above4 ,prof4 ,lowe1 in making a flight with a balloon1 from ,cincinnati to ,north ,carolina1 which lasted a day and all of one night1 found that during the early morning the balloon1 for some reason1 began to ascend1 and climbed nearly five thousand feet in a few hours1 and as unaccountably began to descend several hours before he landed4 ,before it began to ascend1 he was on the western side of the great mountain range which extends south from ,pennsylvania and terminates in ,georgia4 ,he was actually climbing the mountain in a drift of air which was moving eastwardly1 and at no time was he within four thousand feet of the earth during that period1 which shows that air movements are of such a character as to exert their influence vertically to great heights4 ,for cross country flying the safest altitude is #ajjj feet1 a distance which gives ample opportunity to volplane1 if necessary1 and it is a height which enables the pilot to make observations of the surface so as to be able to judge of its character4 ,but explanations and statements1 and the experiences of pilots might be detailed in pages1 and still it would be ineffectual to teach the art of flying4 ,the only sure course is to do the work on an actual machine4 ,many of the experiences are valuable to the learner1 some are merely in the nature of cautions1 and it is advisable for the beginner to learn what the experiences of others have been1 although they may never be called upon to duplicate them4 ,all agree that at great elevations the flying conditions are entirely different from those met with near the surface of the ground1 and the history of accidents show that in every case where a mishap was had at high altitude it came about through defect in the machine1 and not from gusts or bad air condition4 ,on the other hand1 the uptilting of machines1 the accidents due to the so-called ,holes in the air1 which have dotted the historic pages with accidents1 were brought about at low altitudes4 ,at from two to five thousand feet the air may be moving at speeds of from twenty to forty miles an hour1--great masses of winds1 like the trade stream1 which are uniform over vast areas4 ,to the aviator flying in such a field1 with the earth hidden from him1 there would be no wind to indicate that he was moving in any particular direction4 ,he would fly in that medium1 in any direction1 without the slightest sense that he was in a gale4 ,it would not affect the control of the machine1 because the air1 though moving as a mass1 would be the same as flying in still air4 ,it is only when he sees fixed objects that he is conscious of the movement of the wind4 ,,chapter ,,xiii ,,the ,,propeller ,,by far the most difficult problem connected with aviation is the propeller4 ,it is the one great vital element in the science and art pertaining to this subject which has not advanced in the slightest degree since the first machine was launched4 ,the engine has come in for a far greater share of expert experimental work1 and has advanced most rapidly during the past ten years4 ,but1 strange to say1 the propeller is1 essentially1 the same with the exception of a few small changes4 ,,propeller ,,changes4--,the changes which have been made pertaining to the form of structure1 principally1 and in the use of new materials4 ,the kind of wood most suitable has been discovered1 but the lines are the same1 and nothing has been done to fill the requirement which grows out of the difference in speed when a machine is in the act of launching and when it is in full flight4 ,,propeller ,,shape4--,it cannot be possible that the present shape of the propeller will be its ultimate form4 ,it is inconceivable that the propeller is so inefficient that only one sixty-fifth of the power of the engine is available4 ,the improvement in propeller efficiency is a direction which calls for experimental work on the part of inventors everywhere4 ,the making of a propeller1 although it appears a difficult task1 is not as complicated as would appear1 and with the object in view of making the subject readily understood1 an explanation will be given of the terms ,diameter1 and ,pitch1 as used in the art4 ,the ,diameter has reference to the length of the propeller1 from end to end4 ,in calculating propeller pull1 the diameter is that which indicates the speed of travel1 and for this reason is a necessary element4 ,thus1 for instance1 a propeller three feet in diameter1 rotating #ejj times a minute1 has a tip speed of #aejj feet1 whereas a six foot propeller1 rotating at the same speed1 moves #cjjj feet at the tips4 ,,pitch4--,this is the term which is most confusing1 and is that which causes the most frequent trouble in the mind of the novice4 ,the term will be made clear by carefully examining the accompanying illustration and the following description3 ,in ,fig4 #gf is shown a side view of a propeller ,a1 mounted on a shaft ,b1 which is free to move longitudinally4 ,suppose we turn the shaft so the tip will move along on the line indicated by the arrow ,c4 ,now the pitch of the blade at ,d is such that it will be exactly in line with the spirally-formed course ,e1 for one complete turn4 ,as the propeller shaft has now advanced1 along the line ,e1 and stopped after one turn1 at ,f1 the measure between the points ,f and ,g represents the pitch of the propeller4 ,another way to express it would be to call the angle of the blade a five1 or six1 or a seven foot pitch1 as the pitches are measured in feet4 ,fig4 #gf4 ,describing the ,pitch ,line4 ,in the illustration thus given the propeller shaft1 having advanced six feet1 we have what is called a six foot pitch4 ,now1 to lay out such a pitch is an easy matter4 ,assume1 as in ,fig4 #gg1 that ,a represents the end of the blank from which the propeller is to be cut1 and that the diameter of this blank1 or its length from end to end is seven feet4 ,the problem now is to cut the blades at such an angle that we shall have a six foot pitch4 ,fig4 #gg4 ,laying out the ,pitch4 ,,laying ,,out ,,the ,,pitch4--,first1 we must get the circumference of the propeller1 that is1 the distance the tip of the propeller will travel in making one complete turn4 ,this is done by multiplying #g by #c4adaf4 ,this equals #ba4ii1 or1 practically1 #bb feet4 ,a line ,b is drawn1 extending out horizontally along one side of the blank ,a1 this line being made on a scale1 to represent #bb feet4 ,secondly1 at the end of this line drawn a perpendicular line ,c1 #f feet long4 ,a perpendicular line is always one which is at right angles to a base line4 ,in this case ,b is the base line4 ,line ,c is made #f feet long1 because we are trying to find the angle of a #f foot pitch4 ,if1 now1 a line ,d is drawn from the ends of the two lines ,b1 ,c1 it will represent the pitch which1 marked across the end of the blank ,a1 will indicate the line to cut the blade4 ,,pitch ,,rule4--,the rule may1 therefore1 be stated as follows3 ,multiply the diameter 7in feet7 of the propeller by #c4adaf1 and draw a line the length indicated by the product4 ,at one end of this line draw a perpendicular line the length of the pitch requirement 7in feet71 and join the ends of the two lines by a diagonal line1 and this line will represent the pitch angle4 ,propellers may be made of wood or metal1 the former being preferred for the reason that this material makes a lighter article1 and is stronger1 in some respects1 than any metal yet suggested4 ,,laminated ,,construction4--,all propellers should be laminated1--that is1 built up of layers of wood1 glued together and thoroughly dried1 from which the propeller is cut4 ,a product thus made is much more serviceable than if made of one piece1 even though the laminated parts are of the same wood1 because the different strips used will have their fibers overlapping each other1 and thus greatly augment the strength of the whole4 ,generally the alternate strips are of different materials1 black walnut1 mahogany1 birch1 spruce1 and maple being the most largely used1 but mahogany and birch seem to be mostly favored4 ,,laying ,,up ,a ,,propeller ,,form4--,the first step necessary is to prepare thin strips1 each1 say1 seven feet long1 and five inches wide1 and three- eighths of an inch thick4 ,if seven such pieces are put together1 as in ,fig4 #gh1 it will make an assemblage of two and five-eighth inches high4 ,fig4 #gh4 ,a ,laminated ,blank4 ,bore a hole centrally through the assemblage1 and place therein a pin ,b4 ,the contact faces of these strips should be previously well painted over with hot glue liberally applied4 ,when they are then placed in position and the pin is in place1 the ends of the separate pieces are offset1 one beyond the other1 a half inch1 as shown1 for instance1 in ,fig4 #gi4 ,this will provide ends which are eight and a half inches broad1 and thus furnish sufficient material for the blades4 ,the mass is then subjected to heavy pressure1 and allowed to dry before the blades are pared down4 ,fig4 #gi4 ,arranging the ,strips4 ,,making ,,wide ,,blades4--,if a wider blade is desired1 a greater number of steps may be made by adding the requisite number of strips2 or1 the strips may be made thicker4 ,in many propellers1 not to exceed four different strips are thus glued together4 ,the number is optional with the maker4 ,an end view of such an assemblage of strips is illustrated in ,fig4 #hj4 ,the next step is to lay off the pitch1 the method of obtaining which has been explained4 ,fig4 #hj4 ,end view of ,blank4 ,before starting work the sides1 as well as the ends1 should be marked1 and care observed to place a distinctive mark on the front side of the propeller4 ,around the pin ,b1 ,fig4 #ha1 make ,s-shaped marks ,c1 to indicate where the cuts on the faces of the blades are to begin4 ,then on the ends of the block2 scribe the pitch angle1 which is indicated by the diagonal line ,d1 ,fig4 #hj4 ,fig4 #ha4 ,marking the ,side4 ,this line is on the rear side of the propeller1 and is perfectly straight4 ,along the front of this line is a bowline ,e1 which indicates the front surface of the propeller blade4 ,,propeller ,,outline4--,while the marks thus given show the angles1 and are designed to indicate the two faces of the blades1 there is still another important element to be considered1 and that is the final outline of the blades4 ,fig4 #hb4 ,outlining4 ,it is obvious that the outline may be varied so that the entire width at #a1 ,fig4 #hb1 may be used1 or it may have an outline1 as represented by the line #b1 in this figure1 so that the widest part will be at or near the dotted line #c1 say two-thirds of the distance from the center of the blade4 ,this is the practice with most of the manufacturers at the present time1 and some of them claim that this form produces the best results4 ,,for ,,higher ,,speeds4--,fig4 #hc shows a propeller cut from a blank1 #d x #f in cross section1 not laminated4 ,fig4 #hc4 ,cut from a #d x #f ,single ,blank4 ,it should be borne in mind that for high speeds the blades must be narrow4 ,a propeller seven feet in diameter with a six foot pitch1 turning #iej revolutions per minute1 will produce a pull of #cej pounds1 if properly made4 ,such a propeller can be readily handled by a forty horse power motor1 such as are specially constructed for flying machine purposes4 ,,increasing ,,propeller ,,efficiency4--,some experiments have been made lately1 which1 it is claimed1 largely increase the efficiency of propellers4 ,the improvement is directed to the outline shape of the blade4 ,the typical propeller1 such as we have illustrated1 is one with the wide part of the blade at the extremity4 ,the new type1 as suggested1 reverses this1 and makes the wide part of the blade near the hub1 so that it gradually tapers down to a narrow tip4 ,such a form of construction is shown in ,fig4 #hd4 ,this outline has some advantages from one standpoint1 namely1 that it utilizes that part of the blade near the hub1 to produce a pull1 and does not relegate all the duty to the extreme ends or tips4 ,fig4 #hd4 ,a ,suggested ,form4 ,to understand this more fully1 let us take a propeller six feet in diameter1 and measure the pull or thrust at the tips1 and also at a point half way between the tip and the hub4 ,in such a propeller1 if the blade is the same width and pitch at the two points named1 the pull at the tips will be four times greater than at the intermediate point4 ,,chapter ,,xiv ,,experimental ,,gliders ,,and ,,model ,,aeroplanes ,,an amusing and very instructive pastime is afforded by constructing and flying gliding machines1 and operating model aeroplanes1 the latter being equipped with their own power4 ,abroad this work has been very successful as a means of interesting boys1 and1 indeed1 men who have taken up the science of aviation are giving this sport serious thought and study4 ,when a machine of small dimensions is made the boy wonders why a large machine does not bear the same relation in weight as a small machine4 ,this is one of the first lessons to learn4 ,,the ,,relation ,,of ,,models ,,to ,,flying ,,machines4 --,a model aeroplane1 say two feet in length1 which has1 we will assume1 #ej square inches of supporting surface1 seems to be a very rigid structure1 in proportion to its weight4 ,it may be dropped from a considerable height without injuring it1 since the weight is only between two and three ounces4 ,an aeroplane twenty times the length of this model1 however strongly it may be made1 if dropped the same distance1 would be crushed1 and probably broken into fragments4 ,if the large machine is twenty times the dimensions of the small one1 it would be forty feet in length1 and1 proportionally1 would have only seven square feet of sustaining surface4 ,but an operative machine of that size1 to be at all rigid1 would require more than twenty times the material in weight to be equal in strength4 ,it would weigh about #hjj pounds1 that is1 #dhjj times the weight of the model1 and instead of having twenty times the plane surface would require one thousand times the spread4 ,it is this peculiarity between models and the actual flyers that for years made the question of flying a problem which1 on the basis of pure calculation alone1 seemed to offer a negative2 and many scientific men declared that practical flying was an impossibility4 ,,lessons ,,from ,,models4--,men1 and boys1 too1 can learn a useful lesson from the model aeroplanes in other directions1 however1 and the principal thing is the one of stability4 ,when everything is considered the form or shape of a flying model will serve to make a large flyer4 ,the manner of balancing one will be a good criterion for the other in practice1 and experimenting with these small devices is1 therefore1 most instructive4 ,the difference between gliders and model aeroplanes is1 that gliders must be made much lighter because they are designed to be projected through the air by a kick of some kind4 ,,flying ,,model ,,aeroplanes4--,model aeroplanes contain their own power and propellers which1 while they may run for a few seconds only1 serve the purpose of indicating how the propeller will act1 and in what respect the sustaining surfaces are efficient and properly arranged4 ,it is not our purpose to give a treatise on this subject but to confine this chapter to an exposition of a few of the gliders and model forms which are found to be most efficient for experimental work4 ,,an ,,efficient ,,glider4--,probably the simplest and most efficient glider1 and one which can be made in a few moments1 is to make a copy of the deltoid kite1 previously referred to4 ,this is merely a triangularly-shaped piece of paper1 or stiff cardboard ,a1 ,fig4 #hd1 creased in the middle1 along the dotted line ,b1 the side wings ,c1 ,c1 being bent up so as to form1 what are called diedral angles4 ,this may be shot through the air by a flick of the finger1 with the pointed end foremost1 when used as a glider4 ,fig4 #he4 ,deltoid ,glider4 ,,the ,,deltoid ,,formation4--,this same form may be advantageously used as a model aeroplane1 but in that case the broad end should be foremost4 ,fig4 #hf4 ,the ,deltoid ,racer4 ,fig4 #hf shows the deltoid glider1 or aeroplane1 with three cross braces1 ,a1 ,b1 ,c1 in the two forward braces of which are journaled the propeller shaft ,d1 so that the propeller ,e is at the broad end of the glider4 ,a short stem ,f through the rear brace ,c1 provided with a crank1 has its inner end connected with the rear end of the shaft ,d by a rubber band ,g1 by which the propeller is driven4 ,a tail may be attached to the rear end1 or at the apex of the planes1 so it can be set for the purpose of directing the angle of flight1 but it will be found that this form has remarkable stability in flight1 and will move forwardly in a straight line1 always making a graceful downward movement when the power is exhausted4 ,it seems to be a form which has equal stabilizing powers whether at slow or at high speeds1 thus differing essentially from many forms which require a certain speed in order to get the best results4 ,,racing ,,models4--,here and in ,england many racing models have been made1 generally of the ,a-shaped type1 which will be explained hereinafter4 ,such models are also strong1 and able to withstand the torsional strain required by the rubber which is used for exerting the power4 ,it is unfortunate that there is not some type of cheap motor which is light1 and adapted to run for several minutes1 which would be of great value in work of this kind1 but in the absence of such mechanism rubber bands are found to be most serviceable1 giving better results than springs or bows1 since the latter are both too heavy to be available1 in proportion to the amount of power developed4 ,unlike the large aeroplanes1 the supporting surfaces1 in the models1 are at the rear end of the frames1 the pointed ends being in front4 ,fig4 #hg4 ,a-,shaped ,racing ,glider4 ,fig4 #hg shows the general design of the ,a- shaped gliding plane or aeroplane4 ,this is composed of main frame pieces ,a1 ,a1 running fore and aft1 joined at their rear ends by a cross bar ,b1 the ends of which project out slightly beyond their juncture with the side bars ,a1 ,a4 ,these projecting ends have holes drilled therein to receive the shafts a1 a1 of the propeller ,d1 ,d4 ,a main plane ,e is mounted transversely across this frame at its rear end1 while at its forward end is a small plane1 called the elevator4 ,the pointed end of the frame has on each side a turnbuckle ,g1 for the purpose of winding up the shaft1 and thus twisting the propeller1 although this is usually dispensed with1 and the propeller itself is turned to give sufficient twist to the rubber for this purpose4 ,,the ,,power ,,for ,,model ,,aeroplanes4--,one end of the rubber is attached to the hook of the shaft ,c1 and the other end to the hook or to the turnbuckle ,g1 if it should be so equipped4 ,the rubbers are twisted in opposite directions1 to correspond with the twist of the propeller blades1 and when the propellers are permitted to turn1 their grip on the air will cause the model to shoot forwardly1 until the rubbers are untwisted1 when the machine will gradually glide to the ground4 ,,making ,,the ,,propeller4--,these should have the pitch uniform on both ends1 and a simple little device can be made to hold the twisted blade after it has been steamed and bent4 ,birch and holly are good woods for the blades4 ,the strips should be made thin and then boiled1 or1 what is better still1 should be placed in a deep pan1 and held on a grid above the water1 so they will be thoroughly steamed4 ,they are then taken out and bent by hand1 or secured between a form specially prepared for the purpose4 ,the device shown in ,fig4 #hh shows a base board which has in the center a pair of parallel pins ,a1 ,a1 slightly separated from each other4 ,fig4 #hh4 ,making the ,propeller4 ,at each end of the base board is a pair of holes ,c1 ,d1 drilled in at an angle1 the angles being the pitch desired for the ends of the propeller4 ,in one of these holes a pin ,e is placed1 so the pins at the opposite ends project in different directions1 and the tips of the propeller are held against the ends of these pins1 while the middle of the propeller is held between the parallel pins ,a1 ,a4 ,the two holes1 at the two angles at the ends of the board1 are for the purpose of making right and left hand propellers1 as it is desirable to use two propellers with the ,a-shaped model4 ,two propellers with the deltoid model are not so necessary4 ,after the twist is made and the blade properly secured in position it should be allowed to thoroughly dry1 and afterwards1 if it is coated with shellac1 will not untwist1 as it is the changing character of the atmosphere which usually causes the twisted strips to change their positions4 ,shellac prevents the moist atmosphere from affecting them4 ,,material ,,for ,,propellers4--,very light propellers can also be made of thin1 annealed aluminum sheets1 and the pins in that case will serve as guides to enable you to get the desired pitch4 ,fiber board may also be used1 but this is more difficult to handle4 ,another good material is celluloid sheets1 which1 when cut into proper strips1 is dipped in hot water1 for bending purposes1 and it readily retains its shape when cooled4 ,,rubber--,suitable rubber for the strips are readily obtainable in the market4 ,experiment will soon show what size and lengths are best adapted for the particular type of propellers which you succeed in making4 ,,propeller ,,shape ,,and ,,size4--,a good proportion of propeller is shown in ,fig4 #hi4 ,this also shows the form and manner of connecting the shaft4 ,the latter ,a has a hook ,b on one end to which the rubber may be attached1 and its other end is flattened1 as at ,c1 and secured to the blade by two-pointed brads ,d1 clinched on the other side4 ,fig4 #hi4 ,shape and ,size4 ,the collar ,e is soldered on the shaft1 and in practice the shaft is placed through the bearing hole at the end of the frame before the hook is bent4 ,,supporting ,,surfaces4--,the supporting surfaces may be made perfectly flat1 although in this particular it would be well to observe the rules with respect to the camber of large machines4 ,,chapter ,,xv ,,the ,,aeroplane ,,in ,,the ,,great ,,war ,,during the civil war the ,federal forces used captive balloons for the purpose of discovering the positions of the enemy4 ,they were of great service at that time1 although they were stationed far within the lines to prevent hostile guns from reaching them4 ,,balloon ,,observations4--,necessarily1 observations from balloons were and are imperfect4 ,it was found to be very unsatisfactory during the ,russian-,japanese war1 because the angle of vision is very low1 and1 furthermore1 at such distances the movements1 or even the location of troops is not observable1 except under the most favorable conditions4 ,balloon observation during the progress of a battle is absolutely useless1 because the smoke from the firing line is1 necessarily1 between the balloon and the enemy1 so that the aerial scout has no opportunity to make any observations1 even in detached portions of the fighting zone1 which are of any value to the commanders4 ,,changed ,,conditions ,,of ,,warfare4--,since our great war1 conditions pertaining to guns have been revolutionized4 ,now the ranges are so great that captive balloons would have to be located far in the rear1 and at such a great distance from the firing line that even the best field glasses would be useless4 ,the science of war has also evolved another condition4 ,soldiers are no longer exposed during artillery attacks4 ,uniforms are made to imitate natural objects4 ,the khaki suits were designed to imitate the yellow veldts of ,south ,africa2 the gray-green garments of the ,german forces are designed to simulate the green fields of the north4 ,,the ,,effort ,,to ,,conceal ,,combatants4--,the ,french have discarded the historic red trousers1 and the elimination of lace1 white gloves1 and other telltale insignias of the officers1 have been dispensed with by special orders4 ,in the great ,european war armies have burrowed in the earth along battle lines hundreds of miles in length2 made covered trenches2 prepared artificial groves to conceal batteries1 and in many ingenious ways endeavored to make the battlefield an imitation field of nature4 ,,smokeless ,,powder4--,while smokeless powder has been utilized to still further hide a fighting force1 it has1 in a measure1 uncovered itself1 as the battlefield is not now1 as in olden times1 overspread with masses of rolling smoke4 ,nevertheless1 over every battlefield there is a haze which can be penetrated only from above1 hence the possibilities of utilizing the aeroplane in war became the most important study with all nations1 as soon as flying became an accomplished fact4 ,,inventions ,,to ,,attack ,,aerial ,,craft4--,before any nation had the opportunity to make an actual test on the battlefield1 inventors were at work to devise a means whereby an aerial foe could be met4 ,in a measure the aerial gun has been successful1 but months of war has shown that the aeroplane is one of the strongest arms of the service in actual warfare4 ,it was assumed prior to the ,european war that the chief function of the aeroplane would be the dropping of bombs1--that is for service in attacking a foe4 ,actual practice has not justified this theory4 ,in some places the appearance of the aeroplane has caused terror1 but it has been found the great value is its scouting advantages4 ,,function ,,of ,,the ,,aeroplane ,,in ,,war4--,while bomb throwing may in the future be perfected1 it is not at all an easy problem for an aviator to do work which is commensurate with the risk involved4 ,the range is generally too great2 the necessity of swift movement in the machine too speedy to assure accuracy1 and to attack a foe at haphazard points can never be effectual4 ,even the slowly-moving gas fields1 like the ,zeppelin1 cannot deliver bombs with any degree of precision or accuracy4 ,,bomb-,,throwing ,,tests4--,it is interesting1 however1 to understand how an aviator knows where or when to drop the bomb from a swiftly-moving machine4 ,several things must be taken into consideration1 such as the height of the machine from the earth2 its speed1 and the parabolic curve that the bomb will take on its flight to the earth4 ,when an object is released from a moving machine it will follow the machine from which it is dropped1 gradually receding from it1 as it descends1 so that the machine is actually beyond the place where the bomb strikes the earth1 due to the retarding motion of the atmosphere against the missile4 ,the diagram ,fig4 #ij will aid the boy in grasping the situation4 ,a is the airship2 ,b the path of its flight2 a the course of the bomb after it leaves the airship2 and ,d the earth4 ,the question is how to determine the proper movement when to release the bomb4 ,,method ,,for ,,determining ,,movement ,,of ,a ,,bomb4--,lieut4 ,scott1 ,u4 ,s4 ,a41 of the ,coast ,survey ,artillery1 suggested a method for determining these questions4 ,it was necessary to ascertain1 first1 the altitude and speed4 ,while the barometer is used to determine altitudes1 it is obvious that speed is a matter much more difficult to ascertain1 owing to the wind movements1 which in all cases make it difficult for a flier to determine1 even with instruments which have been devised for the purpose4 ,fig4 #ij4 ,course of a ,bomb4 ,instead1 therefore1 of relying on the barometer1 the ship is equipped with a telescope which may be instantly set at an angle of #de degrees1 or vertically4 ,thus1 ,fig #ia shows a ship ,a1 on which is mounted a telescope ,b1 at an angle of #de degrees4 ,the observer first notes the object along the line of #de degrees1 and starts the time of this observation by a stop watch4 ,the telescope is then turned so it is vertical1 as at ,c1 and the observer watches through the telescope until the machine passes directly over the object1 when the watch is stopped1 to indicate the time between the two observations4 ,fig4 #ia4 ,determining ,altitude and ,speed4 ,the height of the machine along the line ,d is thus equal to the line ,e from ,b to ,c1 and the time of the flight from ,b to a being thus known1 as well as the height of the machine1 the observer consults specially-prepared tables which show just what kind of a curve the bomb will make at that height and speed4 ,all that is necessary now is to set the sighter of the telescope at the angle given in the tables1 and when the object to be hit appears at the sight1 the bomb is dropped4 ,,the ,,great ,,extent ,,of ,,modern ,,battle ,,lines4-- ,the great war brought into the field such stupendous masses of men that the battle lines have extended over an unbroken front of over #bjj miles4 ,in the battle of ,waterloo1 about #adj1jjj men were engaged on both sides1 and the battle front was less than six miles4 ,there were1 thus massed1 along the front1 over #bj1jjj men every mile of the way1 or #aj1jjj on each side4 ,in the conflict between the ,allies and the ,germans it is estimated that there were less than #gejj along each mile4 ,it was predicted in the earlier stages of the war that it would be an easy matter for either side to suddenly mass such an overwhelming force at one point as to enable the attacking party to go through the opposing force like a wedge4 ,such tactics were often employed by ,napoleon and other great masters of war2 but in every effort where it has been attempted in the present conflict1 it was foiled4 ,the opposing force was ready to meet the attack with equal or superior numbers4 ,the eye of the army1 the aeroplane1 detected the movements in every instance4 ,,the ,,aeroplane ,,detecting ,,the ,,movements ,,of ,,armies4--,in the early stages of the war1 when the ,germans drove the left of the ,french army towards ,paris1 the world expected an investment of that city4 ,suddenly1 and for no apparent reason1 the ,german right was forced back and commenced to retreat4 ,it was not known until weeks afterwards that the ,french had assembled a large army to the west and northwest of ,paris1 ready to take the ,germans in flank the moment an attempt should be made to encircle the ,paris forts4 ,the ,german aviators1 flying over ,paris1 discovered the hidden army1 and it is well they did so1 for it is certain if they had surrounded the outlying forts1 it would have been an easy matter for the concealed forces to destroy their communications1 and probably have forced the surrender of a large part of the besiegers4 ,the aeroplane in warfare1 therefore1 has constantly noted every disposition of troops1 located the positions and judged the destination of convoys2 the battery emplacements2 and the direction in which large forces have been moved from one part of the line to the other1 thus keeping the commanders so well informed that few surprises were possible4 ,,the ,,effective ,,height ,,for ,,scouting4--,it has been shown that aeroplane scouting is not effective at high altitudes4 ,it is not difficult for aviators to reach and maintain altitudes of five thousand feet and over1 but at that elevation it is impossible to distinguish anything but the movement of large forces4 ,,sizes ,,of ,,objects ,,at ,,great ,,distances4--,at a distance of one mile an automobile1 twenty feet in length1 is about as large as a piece of pencil one inch long1 viewed at a distance of thirty-five feet4 ,a company of one hundred men1 which in marching order1 say four abreast1 occupies a space of eight by one hundred feet1 looks to the aviator about as large as an object one inch in length1 four and a half feet from the eye4 ,the march of such a body of men1 viewed at that distance1 is so small as almost to be imperceptible to the eye of an observer at rest4 ,how much more difficult it is to distinguish a movement if the observer is in a rapidly-moving machine4 ,for these reasons observations must be made at altitudes of less than a mile1 and the hazard of these enterprises is1 therefore1 very great1 since the successful scout must bring himself within range of specially designed guns1 which are effective at a range of #cjjj yards or more1 knowing that his only hope of safety lies in the chance that the rapidly-moving machine will avoid the rain of bullets that try to seek him out4 ,,some ,,daring ,,feats ,,in ,,war4--,it would be impossible to recount the many remarkable aerial fights which have taken place in the great war4 ,some of them seem to be unreal1 so startling are the tales that have been told4 ,we may well imagine the bravery that will nerve men to fight thousands of feet above the earth4 ,one of the most thrilling combats took place between a ,russian aeroplane and a ,zeppelin1 over ,russian ,poland1 at the time of the first ,german invasion4 ,the ,zeppelin was soaring over the ,russian position1 at an altitude of about a mile4 ,a ,russian aviator ascended and after circling about1 so as to gain a position higher than the airship1 darted down1 and crashed into the great gas field4 ,the aviator knew that it meant death to him1 but his devotion led him to make the sacrifice4 ,the ,zeppelin1 broken in two1 and robbed of its gas1 slowly moved toward the earth1 then gradually increased the speed of its descent1 as the aeroplane clung to its shattered hulk1 and by the time it neared the earth its velocity was great enough to assure the destruction of all on board1 while the ship itself was crushed to atoms4 ,one of the most spectacular fights of the war occurred outside ,paris1 when one of the ,german ,taubes attempted to make its periodical tour of observation4 ,one of the ,french aeroplanes1 which had the advantage of greater speed1 mounted to a greater altitude1 and circled about the ,taube4 ,the latter with its machine gun made a furious attack1 during these maneuvers1 but the ,french ship did not reply until it was at such an elevation that it could deliver the attack from above4 ,then its machine gun was brought into play4 ,as was afterwards discovered1 the wings and body of the ,taube were completely riddled1 and it was a marvel how it was possible for the ,german aviator to remain afloat as long as he did4 ,soon the ,taube was noticed to lurch from side to side1 and then dart downwardly4 ,the monoplane1 in the pursuit1 gradually descended1 but it was not able to follow the destroyed ,taube to the earth1 as the latter finally turned over1 and went swirling to destruction4 ,the observer1 as well as the aviator1 had both been killed by the fire from the monoplane4 ,in the trenches on the ,marne1 to the northeast of ,paris1 where the most stubborn conflict raged for over a week1 the air was never clear of aeroplanes4 ,they could be seen in all directions1 and almost all types of machines were represented4 ,the principal ones1 however1 were monoplanes4 ,,the ,,german ,,taube4--,the ,german ,taube is a monoplane1 its main supporting surfaces1 as well as the tail planes1 are so constructed that they represent a bird4 ,taube means dove4 ,it would have been more appropriate to call it a hawk4 ,on the other hand1 the ,french monoplane1 of which the ,bleriot is the best known example1 has wings with well rounded extremities1 and flaring tail1 so that the two can be readily distinguished4 ,on one occasion1 during the lull in the battle1 two of the ,taubes approached the area above the ,french lines1 and after ascending to a great height1 began the volplane toward their own lines4 ,such a maneuver was found to be the most advantageous1 as it gave the scouting aeroplane the advantage of being able to discover the positions and movements with greater ease1 and at the same time1 in case of accident to the machine1 the impetus of the flight would be to their own lines4 ,three of the ,french aeroplanes at once began their circling flight1 mounting higher and higher1 but without attempting to go near the ,taubes4 ,when the ,french ships had gained the proper altitude1 they closed in toward the ,german ships1 before the latter could reach their own lines in their volplaning act4 ,this meant that they must retreat or fight1 and the crack of the guns showed that it meant a struggle4 ,the monoplanes circled about with incredible skill1 pouring forth shot after shot4 ,soon one of the ,taubes was seen to flutter4 ,this was the signal for a more concentrated attack on her4 ,the army in the trenches1 and on the fields below1 witnessed the novel combat4 ,the flying ships were now approaching the earth1 but the gunners below dared not use their guns1 because in the maneuvers they would be as likely to strike friend as foe4 ,the wounded ,taube was now shooting to the earth1 and the two monoplanes began to give their attention to the other ship1 which was attempting to escape to the north4 ,the flash of the guns of all the fliers could be plainly seen1 but the sounds were drowned by the roar of the great conflict all about them4 ,the ,taube could not escape the net around her4 ,she1 too1 was doomed4 ,a shot seemed to strike the gasoline tank1 and the framework was soon enveloped in flames4 ,then she turned sidewise1 as the material on one side burned away1 and skidding to the left she darted to the earth1 a shapeless mass4 ,it was found that the aviator was not hurt by the shot1 but was1 undoubtedly1 killed by the impact with the earth4 ,the observer was riddled with bullets1 and was likely dead before the ship reached the earth4 ,in the western confines of ,belgium1 near ,ypres1 the ,british employed numerous aircraft1 many of them biplanes1 and at all times they were in the air1 reporting observations4 ,many of the flying fights have been recorded1 and the reports when published will be most thrilling reading4 ,,how ,,aeroplanes ,,report ,,observations4--,it may be of some interest to know how aeroplanes are able to report observations to the commanders in the field1 from the airship itself4 ,many ingenious devices have been devised for this purpose4 ,,signal ,,flags4--,the best known and most universally used method is by the use of signaling flags4 ,suppose the commander of a force is desirous of getting the range of a hidden battery1 or a massed force in his front4 ,the observer in the aeroplane will sail over the area at an understood altitude1 say one mile in height4 ,the officer in charge of the battery1 knowing the height of the airship1 is able1 by means of the angle thus given him1 to get the distance between his battery and the concealed point beneath the airship4 ,the observer in the airship1 of course1 signals the engineer officer1 the exact point or time when the airship is directly above1 and this gives him the correct angle4 ,the guns of the battery are then directed and fired so as to reach the concealed point4 ,it is now important to be able to send intelligible signals to the officer in charge of the battery4 ,if the shot goes beyond the mark1 the observer in the airship raises the flag above his head1 which indicates that it was too high4 ,,how ,,used4--,if the shot fell short he would lower the flag4 ,if the shot landed too far to the right1 this would be indicated by the flag1 and if too far to the left1 the signal would1 in like manner1 be sufficient to enable the gunners to correct the guns4 ,when the exact range is obtained the observer in the ship waves the flag about his head1 in token of approval4 ,all this work of noting the effect of the shots must be taken while the airship is under fire1 and while circling about within visual range of the concealed object below4 ,the officer in charge of the battery1 as well as the observer on the flying craft1 must be equipped with powerful glasses1 so the effect of the shots may be noted on the one hand1 and the signals properly read by the officer on the other hand4 ,it may be said1 however1 that air battles have not been frequent and that they have been merely incidents of the conditions under which they were operated4 ,the mission of the aeroplane is now conceded to be purely one of observation1 such as we have described4 ,both ,french and ,german reports are full of incidents showing the value of observations1 and also concerning the effects of bombs4 ,extracts from the diaries of prisoners gave many interesting features of the results of aeroplane work4 ,,casualties ,,due ,,to ,,aeroplanes4--,in the diary of one was found the remark3 ,i was lucky to escape the bomb thrown by a ,french aviator at ,conrobet1 which killed eight of my companions4 ,another says3 ,the ,seventh ,company of the ,third ,regiment of the ,guard had eight killed and twenty-two wounded by bomb from a ,french aeroplane4 ,another3 ,an officer showed us a torn coat taken from one of sixty soldiers wounded by a bomb from an aeroplane4 ,a prisoner says3 ,near ,neuville an aeroplane bomb dropped on a supply train1 killed four men1 wounded six1 and killed a considerable number of horses4 ,the ,belgians1 after their defeat and the capture of ,antwerp1 were forced to the west along the coast4 ,in some way they learned that the ,kaiser was about to occupy a chateau near ,dixmunde4 ,several aviators flew above the position and dropped a number of bombs on the building1 completely wrecking it1 and it was fortunate that the ,emperor left the building only twenty minutes before1 as several of his aides and soldiers on duty were killed4 ,on numerous occasions the headquarters of the different commanders have been discovered and had to be moved to safer places4 ,during all these wonderful exploits which will live in history because men had the opportunity during the war to use them for the first time in actual conflict1 the official reports have not mentioned the aviators by name4 ,the deaths of the brave men have brought forth the acknowledgments of their services4 ,during the first three months of the war it is estimated that over sixty aviators and aides had lost their lives in the conflict on the two great battle lines4 ,this does not take into account those who met death on the ,zeppelins1 of which five had been destroyed during that time4 ,,the ,,end ,,glossary ,,of ,,words ,,used ,,in ,,text ,,of ,,this ,,volume ,where a word has various meanings1 that definition is given which will express the terms used by the author in explaining the mechanism or subject to which it refers4 ,aviation4 ,the art of flying4 ,altitude4 ,height2 a vertical distance above any point4 ,attraction4 ,the art or process of drawing towards4 ,allusion4 ,referring to a certain thing4 ,assume4 ,taking it for granted4 ,accentuated4 ,to lay great stress upon a thing4 ,angle of ,movement4 ,any direction which is upwardly or downwardly1 as distinguished from the direction of movement which is either to the right or to the left4 ,acquire4 ,to obtain2 to recover2 to procure4 ,analogous4 ,corresponding to or resembling some other thing or object4 ,air ,hole4 ,a term used to express a condition in flying where the machine while in horizontal flight takes a sudden drop1 due to counter currents4 ,ailerons4 ,literally1 small planes4 ,used to designate the small planes which are designed to stabilize a machine4 ,angle4 ,a figure1 or two straight lines which start at the same point4 ,the sides of these lines are termed the angle4 ,analysis4 ,to separate2 to take apart and examine the various parts or elements of a thing4 ,aeroplane4 ,any form of machine which has planes1 and is heavier than air4 ,usually a flying structure which is propelled by some motive power4 ,accumulation4 ,adding to2 bringing together the same or unlike articles4 ,ascribable4 ,a reference to some antecedent source4 ,aeronautics4 ,the science of flying4 ,anterior4 ,meaning the front or forward margin or portion of a body4 ,artifices4 ,any artificial product1 or workmanship4 ,axially4 ,through the central portion4 ,thus1 the shaft which goes through a cylinder is axially arranged4 ,automatic4 ,a thing which operates by its own mechanism2 a contrivance which is made in such a manner that it will run without manual operation or care4 ,alertness4 ,quick2 being active4 ,apex4 ,the point at which two lines meet2 also the extreme pointed end of a conical figure4 ,ascension4 ,moving upwardly4 ,accessories4 ,the parts of a machine1 or artielee which may ha used in connection therewith4 ,anemometer4 ,an instrument for measuring the force or the velocity of wind4 ,anemograph4 ,an instrument that usually traces a curved line ,,oh paper to make a record of the force or direction1 or velocity of the wind4 ,anemometrograph4 ,a device which determines the force1 velocity and direction of the wind4 ,accretion4 ,adding to little by little4 ,accelerated4 ,quiekening2 hurrying the process4 ,abridged4 ,partly taken away from2 shortened4 ,abrogate4 ,to dispense with2 to set aside4 ,abnormal ,not in the usual manner2 not in a regular way4 ,alternate4 ,first one and then another2 going from one side to the other4 ,ancient ,lights4 ,an old ,english law which prevents a neighbor from shutting off sunlight4 ,angularly4 ,a line which runs out from another so that the two are not parallel4 ,aneroid4 ,not wet4 ,applied to the type of barometer where the medium for determ1ining the pressure is not made of mercury4 ,aspirate4 ,a term given by the ,french to that peculiar action of wing1 or other body1 which1 when placed in certain positions1 relative to a current of air1 will cause it to be drawn into the current4 ,assemblage4 ,the bringing together of the parts or elements of a machine4 ,augment4 ,to aid2 to add to or increase4 ,banked4 ,the term used in aviation which indicates that the machine is turned up so that its supporting surfaces rest against the air1 as in alighting4 ,barometer4 ,an instrument for determining the air pressure1 and thereby indicating altitudes4 ,bevel ,pinion4 ,a toothed wheel driven by a larger wheel4 ,bi-,plane4 ,two planes4 ,in aviation that type which has two planes1 similar in size1 usually1 and generally placed one above the other so they are separated the same distance from each other1 as the width of each of the planes4 ,bulge4 ,a hump2 an enlargement beyond the normal at any point4 ,camber1 also ,cambre4 ,the upward curve in a plane4 ,catapult4 ,a piece of mechanism for projecting or throwing a missile4 ,carbureter4 ,the device which breaks up the fuel oil1 and mixes the proper quantity of air with it before it is drawn into the engine4 ,catastrophe4 ,a calamity2 a sad ending2 loss of life or of property4 ,cellular4 ,made up of small hollows1 or compartments2 filled with holes4 ,celestial4 ,pertaining to the heavens4 ,centrifugal4 ,that force which throws outwardly from a rotating body4 ,centripetal4 ,that force1 like the attraction of gravity1 which draws a body to the center4 ,characteristic4 ,striking2 that which is peculiar to some thing or object4 ,commensurate4 ,sufficient2 in proper proportion2 sufficient for the occasion4 ,commercially4 ,pertaining to the nature of trade2 the making of money4 ,complicated4 ,not easily explainable2 not easy to separate4 ,comparatively4 ,judged by something else2 taken with reference to another object or thing4 ,compression4 ,the drawing together2 forcing into a smaller compass1 or space4 ,composition4 ,made up of different elements1 or things4 ,conceivable4 ,made up from the imagination4 ,concaved4 ,hollowed3 ,in aviation it has reference to the underside of the plane1 which is usually provided1 structurally1 with a hollow or trough formation4 ,conforming4 ,to make alike in form2 to bring into harmony4 ,conjunction4 ,in eonneetion with2 joining together4 ,convex4 ,a rounded surface2 a bulging out4 ,conclusion4 ,the end2 a finding in law2 a reasoning from a certain condition4 ,conductivity4 ,the property of materials whereby they will transmit heat along from one part to another1 also electricity4 ,concentrated4 ,brought together2 assembled in a smaller space4 ,conclusive4 ,a positive ending2 decisive of the matter at issue4 ,concentrically4 ,a line which is at all points at the same distance from one point4 ,condensation4 ,the act or process of making denser1 or being brought together4 ,contemplate4 ,to consider2 to judge4 ,convoys4 ,a protecting force which aeeompanies the transfer of property4 ,convection4 ,the diffusion of heat through a liquid or gas4 ,consistent4 ,a state of harmony2 the same at #aa times4 ,constant4 ,in mathematics1 a figure which never changes2 or a figure used as a fixed valuation in a problem4 ,controllable4 ,held within bounds2 that which can be within the power to accomplish4 ,correctional4 ,the means whereby a fault may be made right4 ,consequence4 ,the result2 that which flows from a preceding action4 ,counterforce4 ,an action contrary or opposite to the main force4 ,counter-balance4 ,any power equally opposing another4 ,counteract4 ,a force acting in opposition to another4 ,countercurrent4 ,an air current which sets up in an opposite direction in the path of a moving aeroplane4 ,cushioned4 ,an action which takes place against a moving aeroplane1 by a sudden gust of air or countercurrent4 ,dedicated4 ,to set apart for some special purpose4 ,degree4 ,an interval2 a grade2 a stage2 a certain proportion4 ,deltoid4 ,shaped like the ,greek letter delta4 ,density4 ,closeness of parts4 ,demonstration4 ,making clear2 showing up2 an exhibition or expression4 ,deceptive4 ,the power or tendency to give a false impression4 ,deterrent4 ,to hold back2 to prevent action4 ,detracting4 ,the tendency to take away2 to belittle4 ,depressed4 ,to move downwardly4 ,destination4 ,the place set for the end of the journey4 ,despoiling4 ,to take away from2 robbing or taking from another by force or by stealth4 ,dependant4 ,hanging below2 projecting from the lower side4 ,dexterity4 ,agility2 smartness in action4 ,deranged4 ,put out of order2 wrongly arranged4 ,develop4 ,brought out2 to put into a correct shape or form4 ,deferred4 ,put over to another time4 ,designedly4 ,with a direct purpose4 ,diagonal4 ,across an object at an angle to one or more aides4 ,diametrically4 ,across an object through or near the center thereof4 ,diagram4 ,a mechanical plan or outline of an object4 ,dimension4 ,the distance across an object4 ,the measurement1 for instance1 of a propeller from tip to tip4 ,dynamically4 ,pertaining to motion as a result of force4 ,dispossessed4 ,a term used to indicate the act which removes a person from the possession of property4 ,diameter4 ,the measurement across an object4 ,divest4 ,taken away from2 removed out of4 ,disregard4 ,deliberate lack of attention4 ,diversity4 ,the state wherein one is unlike another2 dissimilarity4 ,drift4 ,the term used to indicate the horizontal motion1 or the pull of an aeroplane4 ,dragon4 ,a fabulous monster1 usually in the form of a serpent4 ,duplicate4 ,two2 made in exact imitation of an original4 ,easement4 ,a legal phrase to designate that right which man possesses1 irrespective of any law1 to gain access to his property4 ,effrontery4 ,boldness with insolence2 rashness without propriety4 ,effective4 ,to be efficient4 ,element4 ,one part of a whole4 ,elasticity4 ,material which will go back to its original form after being distorted1 is said to be elastic4 ,eliminate4 ,to take away from2 to remove a part1 or the whole4 ,elliptical4 ,oblong with rounded ends4 ,elusive4 ,capable of escaping from2 hard to hold4 ,elevator4 ,the horizontal planes in front or rear1 or in both front and rear of the supporting surfaces of an aeroplane4 ,emergency4 ,a sudden occurrence calling for immediate action4 ,emplacement4 ,a spot designed to hold heavy field pieces in intrenchments4 ,enactment4 ,the formulation of a law2 the doing of a special thing4 ,enunciated4 ,announced2 setting forth of an act or a condition4 ,energy4 ,that quality by reason of which anything tends to move or act4 ,equidistant4 ,two points or objects at equal distance from a common point4 ,equilibrinm4 ,a balance produced by the action of two or more forces4 ,equalizing1 ,one made equal to the other2 one side the same as the other4 ,equipped4 ,armed2 provided with the proper material1 or in the same condition4 ,essential4 ,the important part or element4 ,essence ,the real charaeter or element of the thing itself4 ,external4 ,the outermost portion4 ,evolution4 ,a gradual change or building up2 from a lower to a higher order4 ,evolved4 ,brought out from a crude condition to a better form4 ,expression4 ,the art of explaining or setting forth4 ,expansion4 ,growing larger2 to occupy a greater space4 ,exerted4 ,to work to the utmost2 to put forth in action4 ,exhilaratiorn4 ,a lively1 pleasing or happy sensation4 ,exploited4 ,to fully examine and consider1 as well as carry out4 ,extremity4 ,the end2 as far as ean be considered4 ,facility4 ,ease of management2 to do things without difficulty4 ,factor4 ,one of the elements in a problem1 or in mechanical action4 ,fascination1 ,attraetiveness that is pleasing4 ,flexure4 ,the capacity to bend and yield1 and return to its original position4 ,flexible1 ,that which will yield2 springy4 ,fore and ,aft4 ,lengthwise1 as from stem to stern of a ship4 ,formation4 ,the shape or arrangement of an article or thing4 ,formulated4 ,put into some eonerete form1 or so arranged that it may be understood4 ,frictionless4 ,being without a grinding or retarding aotion4 ,fulcrumed4 ,a resting place for a lever4 ,function4 ,the duty or sphere of action in a person1 or object4 ,glider4 ,an aeroplane1 without power1 adapted to be operated by an aviator4 ,governing4 ,an element which is designed to control a machine in a regular manner4 ,graduated4 ,a marked portion1 which is regularly laid off to indicate measurements or quantities4 ,gravity4 ,the attraction of mass for mass4 ,the tendency of bodies to move toward the earth4 ,gravitatior ,the force with which all bodies attract each other4 ,gyratory4 ,having a circular and wheeling as well as a rotary motion4 ,gyroscope4 ,a wheel1 designed to illustrate the laws of motion1 which freely revolves in gimbals within a ring1 and when set into motion1 objects to change its plane of rotation4 ,hemispherical4 ,the half of a sphere4 ,the half of an apple would be hemispherical4 ,hazardous4 ,that which is doubtful2 accompanied by danger4 ,helicopter4 ,a type of flying machine which has a large propeller1 or more than one1 revolubly fixed on vertical shafts1 by means of which the machine is launched and projected through the air4 ,horizontal4 ,level1 like water4 ,hydroplane4 ,a term used to designate an aeroplane which is provided with pontoons1 whereby it may alight on the water1 and be launched from the surface4 ,the term hydroaeroplane is most generally used to indicate this type of machine4 ,impact4 ,the striking against2 the striking force of one body against another4 ,immersed4 ,placed under water below the surface4 ,impinge4 ,to strike against2 usually applied where air strikes a plane or a surface at an angle4 ,imitation4 ,similarity2 the same in appearance4 ,incompatible4 ,without harmony2 incapable of existing together4 ,incurved4 ,applied to a surface formation where there is a depression1 or hollow4 ,inequalities4 ,not smooth1 or regular2 uneven4 ,infinitely1 ,boundless2 in great number1 or quality2 without measure4 ,initial4 ,the first2 that which is at the beginning4 ,indestructibility4 ,not capable of being injured or destroyed4 ,influenced4 ,swayed2 to be induced to change4 ,inherent4 ,that which is in or belongs to itself4 ,initiating4 ,to teach2 to instill2 to give an insight4 ,indicator4 ,a term applied to mechanism which shows the results of certain operations and enables the user to read the measure1 quantity1 or quality shown4 ,inconceivable4 ,not capable of understanding2 that which cannot be understood by the human mind4 ,institute4 ,to start2 to bring into operation4 ,insignias4 ,things which are significant of any particular calling or profession4 ,instinct4 ,that quality in man or animals which prompts the doing of things independently of any direct knowledge or understanding4 ,intermediate4 ,between2 that which may be within or inside the scope of the mind1 or of certain areas4 ,intervening4 ,the time between2 also applied to the action of a person who may take part in an affair between two or more persons4 ,interval4 ,a time between4 ,investigator4 ,one who undertakes to find out certain things4 ,incidence4 ,in physics this is a term to indicate the line which falls upon or strikes another at an angle4 ,inverted4 ,upside down4 ,invest4 ,to give to another thing something that it lacked before4 ,kinetic4 ,consisting in or depending upon motion4 ,laminated4 ,made up of a plurality of parts4 ,when wooden strips1 of different or of the same kinds are glued and then laid together and put under heavy pressure until thoroughly dried1 the mass makes a far more rigid structure than if cut out of a single piece4 ,launchiug4 ,the term applied to the raising1 or starting of a boat1 or of a flying object4 ,lateral4 ,in mining this is a term to indicate the drifts or tunnels which branch out from the main tunnel4 ,generally it has reference to a transverse position or direction1--that is1 at right angles to a fore and aft direction4 ,lift4 ,the vertical motion1 or direction in an airship2 thus the lift may be the load1 or the term used to designate what the ship is capable of raising up4 ,ligament4 ,the exceedingly strong tendons or muscles of birds and animals1 usually of firm1 compact tissues4 ,limitations4 ,within certain bounds2 in a prescribed scope4 ,longitudinally4 ,usually that direction across the longest part4 ,majestically4 ,grand2 exalted dignity2 the quality which inspires reverence or fear4 ,manipulate4 ,to handle2 to conduct so that it will result in a certain way4 ,maneuver4 ,a methodical movement or change in troops4 ,manually4 ,to perform by hand4 ,manifestations4 ,the act of making plain to the eye or to the understanding4 ,manually-operated4 ,with the hands2 a term applied to such machines as have the control planes operated by hand4 ,maintained4 ,kept up2 to provide for2 to sustain4 ,material4 ,the substance1 or the matter from which an article is made2 also the important thing1 or element4 ,mass4 ,in physics it is that which in an article is always the same4 ,it differs from weight in the particular that the mass of an article is the same1 however far it may be from the center of the earth1 whereas weight changes1 and becomes less and less as it recedes from the center of the earth4 ,margin4 ,the edge2 the principal differecee between this word and edge1 is1 that margin has reference also to a border1 or narrow strip along the edge1 as1 for instance1 the blank spaces at the edges of a printed page4 ,medievral4 ,belonging to the ,middle ,ages4 ,mercury4 ,a silver-white liquid metal1 usually called quicksilver1 and rather heavy4 ,it dissolves most metals1 and this process is called amalgamation4 ,militate4 ,in determining a question1 to have weight1 or to influence a decision4 ,mobility4 ,being freely movable2 capable of quick change4 ,modifieation4 ,a change2 making a difference4 ,monitor4 ,advising or reproving4 ,advising or approving by way of caution4 ,monstrosities4 ,anything which is huge1 or distorted1 or wrong in structure4 ,monorail4 ,a railway with a single track1 designed to be used by a bicycle form of carriage1 with two wheels1 fore and aft of each other1 and depending for its stability upon gyroscopes1 mounted on the carriage4 ,momentum4 ,that which makes a moving body difficult to stop4 ,it is the weight of a moving body1 multiplied by its speed4 ,monoplane4 ,the literal meaning is one plane4 ,as monoplane machines are all provided with a fore and aft body1 and each has a wing or plane projecting out from each side of this body1 it is obvious that it has two planes instead of one4 ,the term1 however1 has reference to the fact that it has only one supporting surface on the same plane4 ,biplanes have two supporting surfaces1 one above the other4 ,multiplicity4 ,frequently confounded with plurality4 ,the latter means more than one1 whereas multiplicity has reference to a great number1 or to a great variety4 ,muscular4 ,being strong2 well developed4 ,negative4 ,the opposite of positive2 not decisive4 ,neutralize4 ,from the word neuter1 which means neither1 hence the term may be defined as one which is not a part of either1 or does not take up with either side4 ,normal ,pressure4 ,normal means the natural or usual1 and when applied to air it would have reference to the condition of the atmosphere at that particular place4 ,if the pressure could change from its usual condition1 it would be an abnormal pressure4 ,notoriously4 ,generally known1 but not favorably so2 the subject of general remark2 or unfavorably known4 ,obscurity4 ,not well known2 in the background2 without clear vision2 hidden from view4 ,obliquely4 ,that which differs from a right angle2 neither obtuse nor acute2 deviating from a line by any angle except a right angle4 ,obvious4 ,that which is readily observed and understood4 ,orthopter4 ,that type of flying machine which depends on flapping wings to hold it in space1 and to transport it1 in imitation of the motion of the wings of birds in flying4 ,oscillate4 ,moving to and fro2 the piston of a steam engine has an oscillating motion4 ,outline4 ,describing a marginal line on a drawing2 setting forth the principal features of an argument1 or the details of a story1 or the like4 ,overlapping4 ,one placed over the other4 ,parabolic4 ,a form of curve somewhat similar to an ellipse4 ,pedestal4 ,a standard or support2 an upright to hold machinery4 ,pertinent4 ,appropriate2 pertaining to the subject4 ,pectoral4 ,the bone which forms the main rib or support at the forward edge of a bird's wing4 ,persistent4 ,keeping at it2 determination to proceed4 ,perpendicular4 ,at right angles to a surface4 ,this term is sometimes wrongly applied in referring to an object1 particularly to an object which is vertical1 meaning up and down4 ,the blade of a square is perpendieular to the handle at all times1 but the blade is vertical only when it points to the center of the earth4 ,pernicious4 ,bad2 not having good features or possessing wrong attributes4 ,pendulum4 ,a bar or body suspended at a point and adapted to swing to and fro4 ,perpetual4 ,for all time2 unending or unlimited time4 ,phenomena4 ,some peculiar happening1 or event1 or object4 ,pitch4 ,in aviation this applies to the angle at which the blades of a propeller are cut4 ,if a propeller is turned1 and it moves forwardly in the exact path made by the angle1 for one complete turn1 the distance traveled by the propeller axially indicates the pitch in feet4 ,placement4 ,when an object is located at any particular point1 so that it is operative the location is called the placement4 ,plane4 ,a flat surface for supporting a flying machine in the air4 ,plane of movement pertains to the imaginary surface described by a moving body4 ,a bicycle wheel1 for instance1 when moving forwardly in a straight line1 has a plane of movement which is vertical2 but when the machine turns in a circle the upper end of the wheel is turned inwardly1 and the plane of rhovement is at an angle4 ,pliant4 ,easily yielding2 capable of being bent2 liable to be put out of shape4 ,plurality4 ,see multiplicity4 ,more than one4 ,poise4 ,held in suspension2 disposed in a particular way4 ,pontoon4 ,applied to a series of boats ranged side by side to support a walk laid thereon4 ,in aviation it has reference to a float for supporting an aeroplane4 ,ponderous4 ,large2 heavy2 difficult to handle4 ,posterior4 ,the rear end2 the opposite of anterior4 ,principles4 ,the very nature or essence of a thing2 the source or cause from which a thing springs4 ,proportion4 ,the relation that exists between different parts or things4 ,propounded4 ,questioned2 stated2 to state formally for consideration ,proprietary4 ,a right2 the ownership of certain property4 ,primitive4 ,the beginning or early times2 long ago4 ,prelude4 ,a statement or action which precedes the main feature to be presented4 ,proximity4 ,close to2 near at hand4 ,prototype4 ,that which is used as the sample from1 which something is made or judged4 ,propeller4 ,the piece of meebanism1 with screw shaped blade1 designed to be rapidly rotated in order to drive a vessel forwardly4 ,it is claimed by some that the word ,impeller would be the more proper term4 ,primarily4 ,at the first2 the commencement4 ,precedes4 ,goes ahead2 forward of all4 ,propulsive4 ,the force which gives motion to an object4 ,projected4 ,thrown forward2 caused to fly through the air4 ,radially4 ,out from the center2 projecting like the spokes of a wheel4 ,ratio4 ,the relation of degree1 number1 amount2 one with another4 ,reaction4 ,a counterforce2 acting against4 ,recognize4 ,to know2 seeing1 hearing1 or feeling1 and having knowledge therefrom4 ,reflection4 ,considering2 judging one thing by the examination of another4 ,a beam of light1 or an object1 leaving a surface4 ,refraction4 ,that peculiarity in a beam of light1 which1 in passing through water at an angle1 bends out of its course and again assumes a direct line after passing through4 ,reflex4 ,turned back on itself1 or in the direction from which it came4 ,requisite4 ,enough2 suffieient for all purposes4 ,relegate4 ,to put back or away4 ,rectangular4 ,having one or more right angles4 ,reservations4 ,land which is held by the ,government for various purposes4 ,resistance4 ,that which holds back2 preventing movement4 ,retarding4 ,preventing a free movement4 ,revoluble4 ,the turning or swinging motion of a body like the earth in its movement around the sun4 ,see ,rotative4 ,to cause to move as in an orbit or circle4 ,resilient4 ,springy2 having the quality of elasticity4 ,reversed4 ,changed about2 turned front side to the rear4 ,rotative4 ,that which turns1 like a shaft4 ,the movement of the earth on its axis is rotative4 ,saturation4 ,putting one substance into another until it will hold no more4 ,for instance1 adding salt to water until the water cannot take up any more4 ,security4 ,safety1 assuredness that there will be no danger4 ,segment4 ,a part eut off from a circle4 ,distinguished from a sector1 which might be likened to the form of one of the sections of an orange4 ,sexagonal4 ,six-sided4 ,sine of the ,angle4 ,the line dropped from the highest point of an angle to the line which runs out horizontally4 ,sinuous4 ,wavelike2 moving up and down like the waves of the ocean4 ,simulates4 ,to pattern or copy after2 the making of the like4 ,skipper4 ,a thin flat stone4 ,spirally-formed4 ,made like an auger2 twisted4 ,stability4 ,in airships that quality which holds the ship on an even and unswerving course1 and prevents plunging and side motions4 ,structural4 ,belonging to the features of eonstruetion4 ,strata4 ,two or more layers2 one over or below the other4 ,stream line4 ,in expressing the action of moving air1 or an aeroplane transported through air1 every part is acted upon by the air4 ,stream lines are imaginary lines which act upon the planes at all points1 and all in the same direction1 or angle4 ,stupendous4 ,great2 important2 above the ordinary4 ,substitute4 ,one taken for another2 replacing one thing by something else4 ,supporting4 ,giving aid2 helping another4 ,synchronous4 ,acting at the same time1 and to the same extent4 ,thus if two wheels1 separated from each other at great distances1 are so arranged that they turn at exactly the same speed1 they are said to turn synchronously4 ,tactics4 ,the art of handling troops in the presence of an enemy4 ,it differs from strategy in the particular that the latter word is used to explain the movements or arrangement of forces before they arrive at the battle line4 ,tandem4 ,one before the other2 one after the other4 ,tangent4 ,a line drawn from a circle at an angle1 instead of radially4 ,technically4 ,pertaining to some particular trade1 science or art4 ,tenuous4 ,thin1 slender1 willowy1 slight4 ,tetrahedral4 ,this has reference to a form which is made up of a multiplicity of triangularly shaped thin blades1 so as to form numerous cells1 and thus make a large number of supporting surfaces4 ,used as a kite4 ,theories4 ,views based upon certain consideration4 ,theoretical4 ,where opinions are founded on certain information1 and expressed1 not from the standpoint of actual knowledge1 but upon conclusions derived from such examinations4 ,torsion4 ,a twist2 a circular motion around a body4 ,transmitted4 ,sent out2 conveyed from one point to another4 ,transformed4 ,changed2 entirely made over from one thing to another4 ,transverse4 ,when a body is shorter from front to rear than from side to side its longest dimension is transversely4 ,distinguish from lateral1 which has reference only to the distance at right angles from the main body4 ,translation4 ,the transportation of a body through the air4 ,trajectory4 ,the path made by a body projected through the air4 ,triangular4 ,a form or body having three sides and three angles4 ,typical4 ,in the form of2 a likeness to4 ,ultimate4 ,the end2 the finality2 the last that can be said4 ,uninitiated4 ,not having full knowledge2 withont information4 ,unique4 ,peculiar2 something that on account of its peculiar construction or arrangements stands out beyond the others4 ,universal4 ,everywhere2 all over the world4 ,undulate4 ,to move up and down2 a wave-like motion4 ,utility4 ,of use2 to take advantageous use of4 ,unstable4 ,not having anything permanent2 in a ship in flight one that will not ride on an even keel1 and is liable to pitch about4 ,vacuum4 ,where air is partly taken away1 or rendered rarer4 ,valved4 ,a surface which has a multiplicity of openings with valves therein1 or1 through which air can move in one direction4 ,vaunted4 ,to boast concerning2 to give a high opinion4 ,velocity4 ,speed2 the rate at which an object can move from place to place4 ,vertical4 ,a line running directly to the center of the earth2 a line at right angles to the surface of water4 ,vibratory4 ,moving from side to side2 a regular motion4 ,volplane4 ,the glide of a machine without the use of power4 ,warping4 ,the twist given to certain portions of planes1 so as to cause the air to aet against the warped portions4 ,weight4 ,the measure of the force which gravity exerts on all objects4