,,the ,,romance ,,of ,,science4 ---------------------------------------- ---------- ,,sounding ,,the ,,ocean ,,of ,,air ,,being ,,six ,,lectures ,,delivered ,,before ,,the ,,lowell ,,institute ,,of ,,boston ,,in ,,december #ahih ,,by ,a4 ,,lawrence ,,rotch1 ,s4,b41 ,a4,m41 ,,director ,,of ,,the ,,blue ,,hill ,,meteorological ,,observatory1 ,,massachusetts1 ,u4,s4,a41 ,,and ,,member ,,of ,,the ,,international ,,cloud ,,and ,,aeronautical ,,committees4 ,,published ,,under ,,the ,,direction ,,of ,,the ,,general ,,literature ,,committee4 ,,london3 ,,society ,,for ,,promoting ,,christian ,,knowledge1 ,,northumberland ,,avenue1 ,w4,c42 #dc1 ,,queen ,,victoria ,,street1 ,e4,c4 ,,brighton3 #abi1 ,,north ,,street4 ,,new ,,york3 ,e4 ,j4 ,b4 ,,young ,,co4 #aijj ,this little ,book is gratefully ,dedicated ,,to ,the late ,,augustus ,,lowell1 ,esq4 ,,of ,,boston1 ,u4,s4,a4 ,,who1 ,,as ,,trustee ,,of ,,the ,,lowell ,,institute1 ,,enabled ,,scientific ,,men ,,of ,,two ,,continents ,,to ,,present ,,the ,,results ,,of ,,their ,,investigations ,,to ,,the ,,public ,,corrigenda ,page #ej1 line #aa1 for isolation read insolation4 ,page #ei1 line #ba1 before direction insert opposite4 ,page #aab1 line #b2 page #aae1 lines #b and #ae1 and ,index1 pages #age and #ahc1 for ,violl read ,violle4 ,page #aab1 line #bc2 page #aac1 line #f1 and ,index1 page #aha1 for ,muntz read ,mntz4 ,page #abc1 last line1 for #ahhi read #ahia4 ,index1 page #agg1 for ,cotte 7,t47 read ,cotte 7,l474 ,index1 page #agi1 after ,hann 7,j471 #cf1 add #agc4 ,index1 page #agi1 for ,hellman 7,g47 read ,hellmann 7,g474 ,index1 page #aha1 after ,langley 7,s4 ,p47 insert #bh4 ,transcriber's ,note3 ,these corrections have been applied to the current version ,,contents ,,chap4 ,,page ,i4 ,,the ,,atmosphere--,,ancient ,,and ,,modern ,,knowledge--,,methods ,,of ,,investigation #i ,,ii4 ,,clouds--,,formation ,,and ,,classification--,,measurements ,,at ,,blue ,,hill--,,the ,,international ,,observations #ch ,,iii4 ,,balloons--,,notable ,,ascents ,,and ,,results ,,obtained--,,captive ,,balloons #fh ,,iv4 ,,ballons-,,sondes ,,for ,,great ,,altitudes--,,the ,,international ,,ascents #ih ,v4 ,,kites--,,history ,,and ,,application ,,to ,,meteorological ,,purposes ,,at ,,blue ,,hill ,,and ,,elsewhere #aag ,,vi4 ,,results ,,of ,,the ,,kite-,,flights ,,at ,,blue ,,hill--,,future ,,work #ade ,,index #age ,,list ,,of ,,illustrations ,,page ,,plate ,i4 ,comparative ,altitudes #bb ,,plate ,,ii4 ,optical ,phenomena showing the ,height of the ,atmosphere #bf ,,plate ,,iii4 ,temperature at different ,latitudes and ,altitudes #ca ,,fig4 #a4 ,nephoscope at ,blue ,hill ,observatory4 #eb ,,fig4 #b4 ,cloud ,theodolite at ,blue ,hill ,observatory #ed ,,plate ,,iv4 ,heights and ,velocities of ,clouds #eg ,,plate ,v4 ,atmospheric ,circulation at different ,heights in ,cyclones and ,anti-cyclones #fa ,,fig4 #c4 ,german ,balloon equipped for ,meteorological ,observations #hg ,,plate ,,vi4 ,temperatures observed in ,four ,high ,balloon ,ascents #ia ,,fig4 #d4 ,german ,kite-balloon4 #ie ,,fig4 #e4 ,baro-thermograph of ,richard #ajb ,,fig4 #f4 ,the ,arophile rising #ajc ,,plate ,,vii4 ,heights and ,temperatures recorded in eight ,ascents of the ,cirrus #aji ,,fig4 #g4 ,oriental tailless ,kites4 #aai ,,fig4 #h4 ,eddy tailless ,kite #abi ,,fig4 #i4 ,hargrave ,kite #acj ,,fig4 #aj4 ,modified ,hargrave ,kites at ,blue ,hill #acc ,,fig4 #aa4 ,lamson's ,aero-curve ,kite #ace ,,fig4 #ab4 ,meteorograph lifted by ,kites at ,blue ,hill #ach ,,plate ,,viii4 ,meteorogram from the ,kite-flight of ,oct4 #h1 #ahif1 at ,blue ,hill #adh ,,plate ,,ix4 ,mean ,changes with ,height1 and ,changes during the ,kite-flight of ,oct4 #h1 #ahif #aej ,,plate ,x4 ,changes with ,height recorded by ,kites at ,blue ,hill #aee ,,plate ,,xi4 ,kite ,observations at ,blue ,hill1 ,sept4 #e-aa1 #ahig #afc ,,plate ,,xii4 ,automatic ,records during a ,high ,kite-flight at ,blue ,hill #aff ,,plate ,,xiii4 ,results of ,kite-flights at ,blue ,hill during an ,anti-cyclone and a ,cyclone #afh ,,sounding ,,the ,,ocean ,,of ,,air ---------- ,,chapter ,i ,,the ,,atmosphere--,,ancient ,,and ,,modern ,,knowledge--,,methods ,,of ,,investigation ,concerning this most important element in which we live and move and have our being1 ,pliny1 in the first century of our era1 wrote as follows3 ,it is time to consider the other marvels of the heavens2 thus our fathers called that immense space where flows the vital fluid to which we give the name of air1 and which is not apparent to the senses because of its great rarity4 ,there clouds form1 thunder and lightning also2 it is the region of tempests and of whirlwinds2 from there fall rains1 hail1 and hoar frost2 from there come all those phenomena1 astonishing and often disastrous1 which follow the combat of ,nature with herself4444 ,the sun's rays strike the earth on all sides1 warming and strengthening it2 they are reflected and detach all the particles they can carry away2 vapours descend and rise again2 the winds come empty and return laden with spoil2 animals breathe in from above this vital fluid which animates them1 and the earth sends it back to its source as if she would fill the void by this means4 ,so1 by ,nature acting everywhere and in all directions there results an apparent discord from which is born the harmony of the ,universe2 it is this general movement which puts all things in their places2 some are preserved by the destruction of others2 all move1 all act1 the struggle is continual1 if it ceased an instant everything would fall into chaos4444 ,from the earliest times1 as far back as history extends1 we find mankind interested in meteorological phenomena4 ,this appears natural if we consider the importance of the weather to the ancient pastoral nations1 which1 from the open-air life and keen perceptive faculties of their people1 were well fitted to study natural phenomena4 ,the beauty and grandeur of many of the phenomena occurring in the atmosphere1 and the curiosity excited concerning their causes1 probably contributed to interest people in them4 ,meteorology appears to have been first treated systematically1 as distinct from astronomy and astrology1 by the ,greek philosopher1 ,aristotle1 more than #bjjj years ago4 ,the word meteor1 derived from the ,greek elevated1 was applied to certain phenomena having their origin in the atmosphere4 ,these were classified into arial1 aqueous1 and luminous meteors1 and were all included in the term ,meteorology4 ,in his treatise by this name ,aristotle gave a more detailed account of them than any preceding or contemporary writer1 and ,theophrastus1 his pupil1 wrote two books on the winds and on the signs of rain1 which have been translated into ,latin and ,english4 ,about the same period ,aratus incorporated the current weather proverbs in his poem1 ,diosemeia4 ,the ,greek historians and poets frequently alluded to atmospheric phenomena1 and their example was followed by the ,romans1 of whom ,pliny has been quoted4 ,no doubt the desire to ascend into the air always possessed man1 but owing to the awe with which mountains seem to have inspired the ancients1 there is rarely mention in their writings of climbing mountains1 or of the physiological effects which could hardly have failed to be apparent upon high summits4 ,citing one of the few existing narratives1 ,aristotle relates3 ,those which ascend to the top of the mountain ,olympus could not keep themselves alive without carrying with them wet sponges1 by whose assistance they could respire in that air otherwise too thin for respiration4 ,this mountain of less than #aj1jjj feet was said to be so high that it never rained on its summit1 where1 it was supposed1 the air was always still4 ,a still higher mountain1 easily accessible to the ancient world1 and which we know was ascended1 is ,etna4 ,concerning the progress of meteorology1 from the time of the ancient ,romans to the revival of knowledge in ,europe1 there is little to say except that during the middle ages meteorology1 like other learning1 was confined to the monasteries4 ,speculations were current as to the extent of the atmosphere until1 in the middle of the eleventh century1 ,alhazen1 a learned ,arab1 computed from the duration of twilight that the atmosphere extended nineteen leagues above the earth4 ,the same method was applied with more precision by ,tycho ,brahe1 ,kepler1 and other astronomers of the sixteenth and seventeenth centuries4 ,the earliest weather chronicles were probably noted by monks from time to time in almanacks or missals1 although when this was done first we do not know4 ,the oldest daily chronicles of the weather extant are those kept by ,william ,merle in ,oxford from #accg to #acdd4 ,we owe it to the late ,mr4 ,symons1 the ,english meteorologist and bibliophile1 that this ,,ms4 and many other old records have been brought to light and published4 ,dr4 ,hellmann has done even more in ,germany1 and this historical research is evidence of the growing importance of the science of meteorology4 ,with the advent of the age of geographical discovery it was seen that the climatic features of our globe depend chiefly upon distance from the equator1 proximity to the ocean1 and height above it4 ,in the tropics especially1 the luxuriant vegetation1 which diminishes on mountain slopes and higher up gives place to snow1 must have been visible proof of the decrease of temperature with altitude1 for1 as ,professor ,daniell remarked1 mountains are a gigantic registering thermometer having for the freezing-point the line of perpetual snow4 ,the invention of instruments for measuring temperature and barometric pressure made possible the quantitative observations that have supplied the data for deducing the laws governing the atmosphere4 ,the oldest meteorological instrument is1 no doubt1 the weather or wind-vane1 which had its origin before the ,christian era4 ,the next oldest is the hygrometer1 or instrument for measuring moisture in the air1 the form which acts by absorption dating from the middle of the fifteenth century1 and the condensation hygrometer being a century younger4 ,next in chronological order comes the rain-gauge1 which appears to have been used by ,castelli1 a friend of ,galileo1 in the year #afci4 ,the history of that important instrument1 the thermometer1 is obscure1 but it is certain that ,galileo in ,padua used an air-thermometer in the latter part of the sixteenth century1 which ,rey1 a ,french physician1 filled with liquid in #afca4 ,this thermometer1 as well as other physical instruments1 was perfected by members of the ,accademia del ,cimento at ,florence4 ,these instruments are described in ,saggi di ,naturali ,esperienza1 written in #afff1 and translated into ,latin and ,english4 ,the ,florentine thermometers had one fixed point1 that of freezing water1 and contained either spirits or mercury4 ,in #agbd ,fahrenheit1 in ,danzig1 fixed three points on the scale of the mercurial thermometer1 viz4 the cold produced by ice and sal-ammoniac which he called #j1 freezing water or #cb1 and the heat of the human blood which he assumed to be #if4 ,this thermometric scale1 having #ahj between freezing and boiling water1 and that of ,celsius1 with #ajj1 are the only ones in scientific use to-day4 ,it is a remarkable fact in the history of thermometers that neither of these thermometers remained in the country where it was invented2 thus the thermometer of ,fahrenheit1 a ,german1 came into use exclusively in ,england and her colonies1 while that of ,celsius1 a ,swede1 is now used on the continent of ,europe except in ,germany1 where the thermometer of ,raumur1 a ,frenchman1 is still in popular use4 ,of the four fundamental meteorological instruments1 the barometer was the last invented4 ,aristotle had suspected that air had weight1 but it was not demonstrated until the middle of the seventeenth century1 when the old axiom that ,nature abhors a vacuum was replaced by the rational explanation1 given by ,galileo and ,torricelli1 his pupil1 why water will not rise in a suction pump more than thirty-two feet4 ,in #afdc ,torricelli executed this famous experiment3 he took a glass tube1 sealed at one end1 and filled it with mercury1 then1 closing the open end with his finger1 he inverted it in a basin of mercury4 ,the mercury fell to about thirty inches1 which was recognized to be the weight of a column having the area of the tube and of the height of the atmosphere4 ,the application of the barometer was due to ,blaise ,pascal1 who repeated at ,rouen ,torricelli's experiment with a much longer tube filled with water1 which being thirteen times lighter than mercury1 stood thirteen times higher1 or thirty-two feet1 in the tube4 ,pascal1 being himself at ,paris in #afdh1 got his brother-in-law ,perier to carry a barometric tube filled with mercury to the top of the ,puy de ,dme1 a mountain in ,auvergne rising about #cejj feet above the city of ,clermont4 ,the mercury fell in the tube with the ascent1 and at the top of the mountain it stood some three inches lower than at the base1 showing that the lower layers of the atmosphere are denser than the upper4 ,pascal repeated the experiment on the ,tower of ,st4 ,jacques in ,paris1 and it is interesting to note that more than two hundred years afterwards1 meteorological stations were established both there and on the ,puy de ,dme4 ,it was soon perceived that not only did the level of the mercury in the tube change with height1 but that it oscillated continually at the same place1 and from its observed relation to the state of the weather its name weather-glass is derived4 ,in #afej the weight of the air was demonstrated in another manner by ,otto von ,guericke1 burgomaster of ,magdeburg1 who by means of an air-pump of his invention performed the experiment1 which ,aristotle had tried unsuccessfully1 of weighing a vessel full of air and the same vessel exhausted of air4 ,he also showed the pressure of the air in all directions by the famous experiment of the ,magdeburg hemispheres1 which1 being hollow1 were placed together1 and after the air was exhausted from the sphere so formed sixteen horses were unable to pull them apart4 ,soon afterwards ,robert ,boyle experimented further upon the weight and spring of the air1 as he called it1 and gave the name to the barometer4 ,both ,boyle in ,england and ,mariotte in ,france discovered the law1 bearing indifferently their names1 that the pressure of gases is proportional to their density4 ,halley1 a few years later1 showed that the rate of decrease in pressure differed from the rate of increase in height1 and developed formul for measuring heights by the barometer1 which were afterwards perfected by ,laplace4 ,knowing the heights of the barometer at a high and at a low-level station1 and the mean temperature of the air lying between them1 it is possible to compute accurately the difference of height of the two stations1 or1 conversely1 given this height1 the difference in barometric pressure can be calculated4 ,by the middle of the seventeenth century the most important meteorological instruments had been invented1 and not only can ,italy claim to be their birthplace1 but the ,grand ,duke ,ferdinand ,,ii41 whose brother ,leopold founded the ,accademia del ,cimento1 distributed the new instruments in ,italy and even beyond the ,alps1 so that in #afed observations several times a day were begun at a dozen stations4 ,the observations in ,florence from #afej to #afgj were preserved and constitute the commencement of instrumental meteorology4 ,it was the conquest of ,peru which1 by leading men over the high passes of the ,andes1 first brought them to great heights1 but although we find mention in the history of the expeditions of the so-called mountain sickness1 caused by fatigue as well as by cold and rarefied air1 it does not appear that scientific observations were made4 ,therefore1 while it must be assumed that the atmospheric conditions at considerable altitudes were familiar to travellers1 yet not until the middle of the last century did ,bouguer1 one of three ,french ,academicians sent to ,peru on a geodetic mission1 fix the height of the freezing point in various latitudes1 after observing that the temperature fell below freezing at night upon the mountains near the equator4 ,during the latter part of the century1 ,kirwan1 an ,english chemist1 calculated the temperature for various parallels of latitude1 and in #ahag ,alexander von ,humboldt1 after a voyage around the world1 published his isothermal lines1 or lines of equal temperature on the surface of the globe1 by which he showed that the deviation from the normal1 or calculated1 temperature arose from the distribution of land and water1 and from the geographical relief of the former4 ,this work of von ,humboldt formed the basis of all subsequent studies in comparative climatology4 ,meanwhile chemistry had kept pace with physics1 and in #aggd the old theory1 that air was one of the four elements from which all things originated1 was rendered untenable by ,priestley1 who proved that oxygen gas1 which he discovered1 was a constituent part of air4 ,the other constituent1 nitrogen1 formerly called azote from its destructiveness to life1 was discovered soon afterwards1 and its proportion in the air determined by the ,french chemist1 ,lavoisier4 ,in #aghc man became possessed of the long-sought-for means of rising freely in the air1 and he speedily availed himself of it4 ,the first balloons1 filled with heated air1 were called ,montgolfires from the inventors1 the brothers ,montgolfier1 living in ,annonay1 ,france4 ,after animals had been sent up attached to one1 ,piltre de ,rozier ventured to ascend in the aerostatic machine1 first tethered captive but then set free1 and before the close of the year a balloon1 filled with hydrogen gas1 or inflammable air as it was called1 carried ,m4 ,charles #ijjj feet above ,paris4 ,during more than a century the balloon has been the most important agent for the exploration of the atmosphere1 and yet1 notwithstanding the courage and devotion to science of the early aeronauts1 their ascents with unsuitable instruments furnished much discordant and erroneous data4 ,some of the most remarkable balloon voyages and the modern methods of sounding and dredging the atmosphere1 to borrow terms from the exploration of the ocean1 will be described in two future chapters4 ,perhaps the chief reason for the slow progress of meteorology to the status of a science is the variable character of its phenomena with the place of observation4 ,in this respect it differs from astronomy1 which was more easily cultivated in the restricted ancient world4 ,only after many years of observation at different places had contributed a foundation for climatology was it realized that man1 in his relation to the atmosphere1 resembled marine organisms confined to the bottom of the ocean1 and that in order to discover the true conditions of the atmosphere it was necessary to observe them at considerable heights4 ,in the last century the highest point at which physical observations had been made was the summit of ,mont ,blanc1 less than #af1jjj feet above the sea4 ,the ascent of this mountain was first accomplished in #aghg by ,h4 ,b4 ,de ,saussure and his guides with much difficulty and suffering1 and the observations1 abridged and rendered less accurate by the fatigue and sickness of ,de ,saussure1 were also influenced by the proximity of the mountain itself4 ,in #ahjb von ,humboldt and ,bonpland reached a height of about #ah1jjj feet in the ,andes1 where they made important observations4 ,the ascent of man was rapid during the first years of the nineteenth century1 for in #ahjd ,gay-,lussac rose in a balloon1 without exertion or discomfort1 to the height of #bc1jjj feet1 and there made observations which were assumed to give the true atmospheric conditions4 ,after an active campaign the conquest of the air by balloons was temporarily abandoned1 and the field was left free to the mountaineer4 ,but to-day supremacy rests with the aeronaut1 for no one has succeeded in getting higher than #bd1jjj feet on a mountain1 while the aeronaut has exceeded this altitude by a mile without great hardship1 and lately has sent his unmanned balloons twice as high as the loftiest mountains4 ,plate ,i41 headed ,the ,exploration of the ,atmosphere1 represents a vertical section of the lower portion of our atmosphere4 ,on the right is a scale of miles above the sea1 and on the left is a scale of barometric pressures corresponding to the height4 ,the right-hand half of the diagram shows the eastern hemisphere with the ,himalaya mountains1 the left-hand half the western hemisphere with the ,andes4 ,there are seen the heights of the different kinds of clouds1 measured at ,blue ,hill1 as described in the next chapter2 the highest meteorological stations1 those on ,mont ,blanc and ,el ,misti in ,peru2 the highest permanently inhabited place1 which is a monastery in ,thibet2 and the greatest height to which man has climbed1 namely1 in the ,andes4 ,the heights at which observations have been made in balloons1 carrying observers1 or only recording instruments1 may be compared with the height attained by the ,blue ,hill kites1 to be described hereafter4 ,other altitudes can be noted1 such as the height of the snow-line on various mountains1 and as a thousand-foot measure1 the ,eiffel ,tower in ,paris1 the tallest structure erected by man1 may be used4 ,illustration3 ,,plate ,i4--,,comparative ,,altitudes4 ,the development of meteorological knowledge to the commencement of the present century has now been traced1 but before beginning the consideration of the methods of exploring the atmosphere that form the subject of the book1 let us1 in order to understand this work better1 review the general knowledge which we possess of our atmosphere as regards its origin1 composition1 extent1 and conditions of heat and moisture4 ,first1 then1 regarding the ,origin of the ,atmosphere1 or vapour envelope which the name means4 ,according to the nebular hypothesis of ,laplace1 our earth1 like all existing suns and planets1 was condensed from clouds of nebulous matter and became a highly-heated globular mass rotating1 like every celestial body1 from west to east4 ,as the earth cooled1 a crust was formed1 and many of the substances that now exist in the earth were suspended as clouds in the cooler atmosphere surrounding it4 ,eventually1 these substances were condensed upon the crust2 the oxygen1 especially1 must have been diminished by combining with the rocks1 while the lighter gases1 such as hydrogen1 may have escaped from the earth's atmosphere4 ,no doubt1 when vegetable and animal life began1 the earth's atmosphere was denser than now and much richer in carbonic acid1 which1 during the carboniferous period1 was absorbed by plants1 and is now imprisoned in coal and limestone4 ,within historic times1 however1 there is no evidence of any change in the composition of our atmosphere1 or the climatic conditions as a whole4 ,m4 ,jourdanet1 a distinguished ,french physiologist1 maintained that man appeared on the earth at the close of the tertiary period1 when the barometric pressure at sea-level was1 he supposed1 about forty-three inches1 or nearly a half more than it is to-day1 and owing to the greater density of the air its temperature was also considerably higher4 ,under these circumstances he believed that man first occupied the high regions of ,central ,asia1 and only emigrated to lower levels when the climatic conditions became ameliorated4 ,in other words1 ,m4 ,jourdanet believed in a literal descent of man1 but if this be true1 many of the race have returned to their birthplace1 for to-day millions of people dwell on the great ,asiatic plateau1 and on the ,south ,american ,cordillera1 at an average altitude of #aj1jjj feet1 while a few live throughout the year at extreme heights of #ae1jjj feet4 ,composition of the ,atmosphere4--,dry air is a mixture of about one-fifth of a volume of oxygen to four-fifths of a volume of nitrogen1 besides a very small quantity 7#c_/aj1jjj7 of carbonic acid1 traces of ammonia1 ozone1 argon1 and other recently discovered gases4 ,the oxygen consumed1 and the carbonic acid given off by animal life and by combustion1 are maintained in this fixed proportion in the free air by the absorption of the carbonic acid1 and the setting free of oxygen by vegetation4 ,by diffusion and the mobility of the air1 a thorough mixture is effected1 with the result that the fundamental composition of our atmosphere is everywhere nearly the same4 ,in the lower atmosphere the vapour of water is present in a varying quantity1 in the average about one per cent4 in weight1 with a volume depending on the temperature4 ,dust is always suspended in the atmosphere2 the coarser particles settle1 but the finer ones1 that come from volcanoes1 may float for a long time in the high atmosphere4 ,dust is an important factor in the production of clouds and rain1 and occasions many optical phenomena4 ,illustration3 ,,plate ,,ii4--,,optical ,,phenomena ,,showing ,,the ,,height ,,of ,,the ,,atmosphere4 ,extent of the ,atmosphere4--,if the atmosphere were incompressible and had throughout the density that it has at the earth1 its height would be about five miles only1 but actually it is composed of gases that follow ,boyle's law and vary in volume inversely as the pressure upon them4 ,since the pressure decreases with height in a geometrical progression1 it would be halved for each three and a half miles of ascent were the temperature constant1 but as the temperature also decreases with height1 the successive intervals1 beginning with three and a half miles1 become shorter because the volume of a gas depends on its temperature as well as on the pressure upon it4 ,the decrease of pressure with increasing height above the earth is shown by the left-hand scale of ,plate ,i41 already described1 and the subsequent diminution of density to the limits of our measurable atmosphere is indicated on the right of ,plate ,,ii41 ,optical ,phenomena showing the ,height of the ,atmosphere4 ,the gases composing the atmosphere probably extend to heights proportional to their density2 viz4 oxygen to about thirty miles and nitrogen to thirty-five miles1 although water-vapour nearly disappears at twelve miles4 ,from these considerations it is supposed that the atmosphere1 as measurable by the barometer1 vanishes at about thirty-eight miles1 and this is about the height indicated by twilight1 which is the reflected light of the sun when #ah below the horizon4 ,after the great eruption of the volcano ,krakatoa in the ,south ,seas in #ahhc1 the brilliant sunset glows and the longer twilight showed that the dust emitted by the eruption remained for more than a year suspended at a height of at least sixty miles4 ,the so-called luminous clouds seen at night during the same period1 and which were probably these same dust particles still illumined by the sun1 were found by trigonometrical measurements to have about the same altitude4 ,although it is computed that at a height of seventy miles the air has less than one-millionth of its density at sea-level--which is about the density of the air remaining in the exhausted bulb of an incandescent electric lamp--it is there sufficiently dense to render meteors luminous by friction after they with great velocity enter our atmosphere4 ,the height of these meteors has been found1 from simultaneous trigonometrical measures at two stations1 sometimes to exceed one hundred miles1 and if we suppose the aurora borealis to be an electrical discharge in highly rarefied air1 measures made in the same way indicate as great a height for our atmosphere4 ,the height of the aurora varies enormously1 but the average altitude of it and of the other phenomena described1 with the corresponding computed density of the air1 are shown in the preceding diagram1 in which the depth of the ocean of air may be compared with the deepest seas and the highest mountains4 ,while1 as ,professor ,young says1 it cannot be asserted that the atmosphere has any defined upper limit1 yet the kinetic theory of gases seems to afford evidence that the molecules of oxygen and nitrogen do not escape from the earth's attraction1 and therefore the hypothesis of ,professor ,frster is unwarranted1 that interplanetary space is filled with ,himmelsluft1 or very thin air4 ,temperature of the ,atmosphere4--,the warmth of the atmosphere is derived chiefly from the sun's rays which1 arrested by the earth's surface1 are partly reflected and partly radiated back through the atmosphere4 ,not more than seventy-five per cent4--,professor ,langley says only sixty per cent4--of the heat of the sun1 which is received vertically on the upper surface of the atmosphere1 penetrates to the earth1 and very much less than this when the angle of the sun is low4 ,the reason why temperature diminishes as we ascend1 is partly owing to the greater loss of heat by radiation through the thinner envelope of the upper strata1 and partly owing to the greater absorption of the heat given off from the earth by the lower and denser strata4 ,in general1 it may be said that there is a diminution of #a ,fahrenheit for each three hundred and thirty feet that we rise vertically1 but1 this rate varies greatly at different heights1 places1 and times4 ,for instance1 the decrease is not the same on mountains as it is in the free air1 and in the northern hemisphere it is greater on the south than on the north sides of mountains2 it is usually greatest near the ground1 and is faster in summer than in winter4 ,but in the average1 the temperature falls as much for three hundred and thirty feet of elevation as it does for a change of seventy miles on the earth's surface north or south of the equator4 ,when dry air rises1 because it is heated and thereby is made lighter1 the laws of thermo-dynamics show that1 by reason of its expansion1 its temperature is decreased #a ,fahrenheit for each one hundred and eighty-three feet that it ascends1 and1 by compression1 its temperature is increased as much if it is made to descend the same distance4 ,this is called the adiabatic rate of change of temperature1 because it is produced by an alteration in the density of the air1 due to variation in pressure1 without the addition or loss of heat4 ,in the course of this book there will be occasion frequently to refer to this law of heating and cooling4 ,the adiabatic rate of change is seldom observed on mountains because of their influence upon the currents of air in contact with their flanks1 or even in balloons1 on account of imperfect measurements1 but1 as will be explained in the closing chapter1 the adiabatic change of temperature is confirmed by the observations with kites1 which furnish the best method of obtaining the temperature of the free air up to moderate heights4 ,the adiabatic cooling of rising currents of air is another reason for the rapid decrease of temperature with height up to a mile or more4 ,the upper air alters its temperature from diurnal and seasonal causes much more slowly than the lower air1 and a mile above the earth the daily change of temperature1 apart from the passage of warm and cold waves1 is less than one degree4 ,at a height of six miles above the earth a temperature much below zero constantly prevails1 while1 at ten miles1 #hj below zero has been recorded in a balloon--this is approximately the temperature prevailing winter and summer above pole and equator4 ,these facts are expressed graphically in ,plate ,,iii41 ,temperature at ,different ,latitudes and ,altitudes1 which represents half of a section of the earth1 from the north pole to the equator1 with the superincumbent atmosphere4 ,illustration3 ,,plate ,,iii4--,,temperature ,,at ,,different ,,latitudes ,,and ,,altitudes4 ,perhaps it should be explained1 that whereas the curvature of the earth with respect to the height of the atmosphere in the previous diagram was not exaggerated1 in the present diagram the height of the atmosphere over the radius of the earth is enormously increased4 ,at the north pole the mean annual temperature is about #j ,fahrenheit1 and at the equator it is about #hj4 ,it is seen that the atmospheric layer having a temperature of #ej 7here represented in section by a line7 touches the earth at #de latitude1 but is about two miles above the equator4 ,in the same way the line of freezing 7#cb7 leaves the earth's surface at #eh latitude and rises to about three and a half miles over the equator2 the line of #j rises from the pole to about seven miles at the equator4 ,this is familiarly illustrated by the fact that only the highest mountains in the tropics are snow-capped1 while within the ,arctic circle the snow-line descends nearly to sea-level4 ,the lines in the diagram show the mean annual temperatures1 but the isothermal surfaces rise in summer and sink in winter1 the change of altitude being greatest in northern regions and near the ground4 ,frequently there is an inversion of temperature1 that is to say1 it is warmer above than below4 ,notably1 in ,siberia1 where the winter temperature is #fj below zero1 there can be no immediate decrease of temperature with height1 and it is probable that there is a warmer layer of air interposed between the very cold earth and the still colder upper air1 so that the temperature first rises rapidly with elevation and then falls slowly to the limits of the atmosphere4 ,in temperate latitudes it often happens1 with a high barometric pressure1 in winter that the mountain stations enjoy a long period of still and relatively warm weather1 as compared to that experienced in the valleys4 ,but the subject of inversions of temperature will be discussed at length in considering the results of the balloon and kite observations4 ,the observations from balloons at great heights are neither sufficiently numerous nor accurate to enable us to form an opinion as to what is the temperature of interplanetary space1 which the kinetic theory of gases places at #dfj ,fahrenheit below zero4 ,this temperature is called the absolute zero1 and is calculated from the fact that air under a constant pressure contracts #a_/dij of its volume for each degree ,fahrenheit it is cooled below the temperature of freezing water1 and consequently under no pressure it should have an infinite volume and a temperature of about #dij below freezing1 or #deh below zero4 ,there are other hypotheses regarding the temperature of space1 but since it can never be measured directly1 it will probably remain a matter of speculation4 ,it is certain1 however1 that if the earth were deprived of its atmosphere1 the temperature would fall very low1 and even with our atmosphere as a blanket our earth would be uninhabitable were it not for the aqueous vapour which controls the selective absorption of the solar rays1 transforming them into obscure rays so that they cannot escape from the atmosphere4 ,water-vapour1 then1 is a very important factor in the physics of the atmosphere1 but it can only be considered briefly here4 ,moisture of the ,atmosphere4--,the air is constantly absorbing moisture from the water on the earth1 but the tension of this aqueous vapour decreases with elevation much faster than does the atmospheric pressure4 ,at the height of about a mile and a quarter half the quantity of water-vapour is below1 while we must rise about three and a half miles to reduce the quantity of air one-half1 as may be seen in ,plate ,i4 ,the relative humidity1 or the percentage of moisture in the air1 as compared to the amount which it could contain at that temperature1 is nearly the reverse at low and at high levels4 ,it is found from the kite-observations at ,blue ,hill1 that up to the height of a mile or two the air is drier during winter and at night1 and damper during summer and in the day-time than it is near the ground4 ,at great heights probably the air is always very dry4 ,the condensation of the invisible vapour into a visible form is considered in the next chapter on clouds4 ,it is apparent that our observational knowledge of the atmosphere is gained by two general methods of exploring it1 viz4 observations made from the earth upon clouds and optical phenomena at a distance1 and observations made directly in the air itself4 ,although it was realized at the beginning of this century that meteorological observations were almost all conducted at the very bottom of our atmosphere--in the shoals and shallows of the ocean of air1 von ,humboldt said--yet only within the past thirty years was it thought necessary to replace the occasional observations on mountains by systematic and long-continued ones1 comparable to those so generally carried on at low levels4 ,it is an evidence of the zeal in ,america to advance the young science of meteorology1 that the first mountain-top station in the world was established in #ahga upon ,mount ,washington1 and that both this exposed post of observation1 #fcjj feet above the sea1 and the one more than twice as high on ,pike's ,peak1 which was for a long time the highest in the world1 were maintained for many years by the ,united ,states ,signal ,service4 ,the present highest station in the world is maintained by the ,harvard ,observatory upon ,el ,misti in ,peru1 where1 at a height exceeding #ai1jjj feet1 a combination of self-recording instruments was constructed by my assistant1 ,mr4 ,fergusson1 to operate during three months without attention4 ,it must be admitted1 however1 that the addition to our knowledge of the physics of the atmosphere afforded by the ,american stations has been slight and incommensurate with the expense incurred4 ,more has been gained from the mountain stations in ,europe1 notably from those in the ,austrian ,alps1 which have furnished data for ,dr4 ,hann's splendid discussions of the thermo-dynamics of the atmosphere4 ,while mountain stations present the only means of obtaining continuous observations at a considerable and constant height1 still they have serious drawbacks4 ,not only is the distribution of mountains over our globe irregular1 but since they form part of the earth's crust1 terrestrial influences affect all observations made upon them4 ,in the case of plateaux this was at once admitted1 but by placing the stations on the summits of high and isolated peaks1 it was hoped to approximate to the conditions of the free air4 ,it is now recognized that the equilibrium of the atmosphere is so delicate that for its dynamical study exact and minute measurements of temperature1 moisture1 and currents are required1 and the methods which will be described are intended to give the values of these elements free from terrestrial disturbances4 ,clouds1 balloons1 and kites naturally supplement one another4 ,while clouds indicate the direction and velocity of the air at different heights1 yet the lower clouds often conceal the upper strata1 or there may be no clouds at all1 in which case balloons or kites will aid us to determine the drift of the currents4 ,when there is little wind at the ground1 or to reach heights of several miles1 we must employ balloons1 but otherwise kites are preferable in most cases4 ,the thermal and hygrometric conditions of the free air can be ascertained only by personal observations in balloons1 or by raising self-recording instruments with balloons and kites1 and this latter method it is predicted will be the path of greatest progress4 ,,chapter ,,ii ,,clouds--,,formation ,,and ,,classification--,,measurements ,,at ,,blue ,,hill--,,the ,,international ,,observations ,clouds must have been among the earliest observed natural phenomena1 and they were used from time immemorial as weather signs4 ,yet their every-day occurrence was very likely the reason why their origin was not studied until about a century ago4 ,father ,cotte1 in his classic work on meteorology1 published in #aggd1 devotes only a couple of paragraphs to clouds1 but ,abb ,richard1 in his contemporary ,histoire ,naturelle de l',air1 discusses the appearance and theories of clouds in ten chapters4 ,the cause of evaporation was unknown in the last century1 and it was not until its close that ,dalton1 the ,english chemist1 proved that water-vapour exists independently in the air1 and ,hutton explained that precipitation was produced by the contact of a current of saturated air with a colder one4 ,although there remains much to be learned about cloud formation1 yet it is now pretty well established that its most effective cause is the ascent1 and consequent cooling by expansion of the air1 rather than the mixture of masses of air having different temperatures4 ,the ascent of the air may result from its being forced up a mountain slope by its horizontal movement1 or from its being drawn up in a vortex1 but most commonly the air rises from its lessened specific gravity when warmed4 ,if the temperature of the quiescent air decreases faster than #a for each #ahc feet of height1 which is the adiabatic rate of cooling for dry air1 as explained in the last chapter1 air warmed locally will rise and cool at this rate until the dew-point is reached4 ,then the vapour in the air will be condensed upon particles of dust1 which ,aitken found to be more numerous in clouds than outside them4 ,the most conspicuous of the clouds formed by rising currents is the cumulus1 or rounded summer cloud1 which has been aptly termed the visible capital of an invisible column of air4 ,saturated air cools as it rises more slowly than dry air1 consequently the upward motion is maintained through the cloud mass1 causing the swelling up of the tops of the cumulus clouds1 which reach their highest development in the thunder clouds1 or cumulo-nimbus1 as they are called4 ,the lower limit of the cloud region is determined therefore by the height at which the rising currents reach their dew-point1 and the altitude of the cloud formation depends upon the humidity of the ascending current1 the drier it is1 so much the higher must it rise to have its vapour condensed4 ,in storms the rising current mingles with the stronger horizontal current above1 which carries with it the upper portion of the cloud1 and covers the whole sky with a uniform sheet4 ,the wave1 or ripple cloud1 has been explained by von ,helmholtz and von ,bezold to be due to the undulations in a horizontal current producing alternate rarefaction and condensation of its water-vapour through changes of temperature4 ,still another cause of low-lying clouds is the cooling of the air to its dew-point by contact with a cold surface1 such as the earth when cooled by radiation during a clear night1 or the polar currents of the ocean4 ,fog is often formed in this way1 which we call stratus cloud when it rises above us4 ,the highest clouds consist of ice crystals1 because the temperature of the air where they are is much below that of freezing water4 ,although it is possible to cool drops of water considerably below #cb ,fahrenheit without congelation1 yet it can be told with certainty that the clouds are composed of ice if the sun and moon when seen through them are surrounded by the large rings or halos1 which the theory of optics shows can only result from refraction of light by ice crystals1 whereas water drops in the clouds produce the smaller coloured rings1 which are called coron4 ,the old question1 why clouds float unless their particles are hollow1 is easily answered1 for they do not float1 and always tend to sink if they are not supported by the currents of air4 ,in sinking into warmer air the particles are vapourized and become invisible1 but others rising are condensed and take their places1 so that the cloud persists1 although its particles change4 ,this is illustrated by the cloud banners1 which frequently stream from mountain peaks1 and are caused by the rise of air up the mountain side4 ,even in a strong wind the cloud remains attached to the peak1 showing that its particles are being renewed continually2 but if1 as is often the case1 the wind descends on the leeward side of the mountain1 the cloud particles disappear4 ,lamarck1 the celebrated naturalist1 in the opening year of the present century1 first proposed a classification of cloud forms4 ,two years later ,luke ,howard1 a ,london merchant1 published his epoch-making essay on ,the ,modifications of ,clouds4 ,the theories there advanced and the nomenclature proposed have been accepted generally to our day1 notwithstanding the more complete classifications devised by ,poy1 ,ley1 and others4 ,howard believed that clouds are formed by the aqueous vapour which rises from the earth1 and that the globules which compose them are solid1 and are not filled with hydrogen gas as had been maintained by ,deluc and ,de ,saussure4 ,howard classified the clouds as we do to-day1 according to their appearance1 into three principal types1 viz4 stratus1 cumulus1 and cirrus1 which represented also low1 middle1 and high clouds4 ,stratus is the sheet of low-lying cloud which forms at night1 and commonly rests on the earth2 cumulus is the heaped-up cloud of the day-time2 and cirrus is the curl cloud of the high atmosphere4 ,these three types were further divided into four intermediate types1 viz4 nimbus1 cumulo-stratus1 cirro-stratus1 and cirro-cumulus4 ,howard's nomenclature was used almost exclusively1 until in #ahhi the ,international ,meteorological ,conference that met at ,paris recommended the adoption of another classification1 based on ,howard's1 but modified by two experts1 ,abercromby of ,england and ,hildebrandsson of ,sweden4 ,this classification also disregarded the origin of clouds1 and was based only on their appearance4 ,the next year an atlas1 with coloured pictures of the clouds1 separated according to the new nomenclature1 with descriptive text1 was prepared by ,dr4 ,hildebrandsson1 assisted by ,drs4 ,neumayer and ,kppen of the ,deutsche ,seewarte1 or ,german ,national ,meteorological ,observatory4 ,this atlas was adopted by the principal meteorological institutions on the continent of ,europe for their observers4 ,the preface contained the following statement3 ,the study of the forms of clouds is daily increasing in importance1 both from the standpoints of theory and of weather prediction4 ,observations taken at the bottom of the atmospheric ocean are plainly insufficient to determine its circulation4 ,the clouds1 however1 furnish information about the condition and motion of the air at various levels4 ,but1 a comparison of the observations of different observers is only possible when the same ideas are connected with the same expressions4 ,it is hardly possible to give a sufficient verbal description of such indeterminate and changeable forms as those of the clouds2 graphical representations are therefore necessary1 with the help of a short description1 in order to enable an observer to connect what he sees in the sky with what he finds in the instructions4 ,in order that a cloud picture may be intelligible to non-specialists1 the clouds and the blue sky must1 at least1 be plainly distinguishable from each other4 ,the meeting of the directors of the meteorological institutions in different parts of the world1 which was held at ,munich in #ahia1 decided to adopt the classification of ,abercromby and ,hildebrandsson1 and a committee was appointed to prepare an ,atlas of ,clouds1 which should be cheaper than the preceding one4 ,this committee1 of which the writer has the honour to be the ,american member1 met at ,upsala in #ahid4 ,it defined the various forms of clouds1 selected typical pictures to illustrate them1 and drew up instructions for observing4 ,this atlas1 which was published in #ahif1 is the recognized authority on cloud forms4 ,meanwhile the ,united ,states ,weather ,bureau had issued a plate of clouds1 printed in one colour1 to familiarize its observers with the new system4 ,the ,navy ,department has also an interest in clouds1 for several thousand seamen in various parts of the world send their special logs to the ,united ,states ,hydrographic ,office4 ,the ,hydrographer1 a few years ago1 was ,captain ,sigsbee1 who1 long before he became known to the public as commander of the ill-fated ,maine1 had achieved scientific reputation from his investigations upon the depths and the currents of the ocean4 ,captain ,sigsbee desired to render comparable the observations of clouds which were being made all over the world1 and to this end he resolved to publish a coloured atlas of the international cloud types which should be intelligible to seamen1 and yet not too costly for his office to supply4 ,after two years of experimenting1 during which the writer and his assistant1 ,mr4 ,clayton1 were frequently consulted1 the ,illustrative ,cloud ,forms1 with and without descriptive text1 were issued in #ahig by the ,hydrographic ,office1 and in several respects this atlas is the best4 ,still1 it is impossible for anything but a photograph from the cloud itself to show the extreme delicacy of certain forms4 ,perhaps it should be explained1 however1 that as the blue sky and the white clouds act with almost equal actinic effect upon the sensitized plate1 in order to obtain the proper contrast between sky and cloud it is necessary either to polarize the light from the sky1 or1 as is most commonly done1 to separate the coloured rays by allowing them to pass through a yellow screen1 and to fall upon autochromatic plates4 ,before defining the ten principal types of cloud it should be explained that two general classes of clouds are distinguished1 separate or globular masses1 which are most frequently seen in dry weather1 and forms which are widely extended or completely cover the sky1 which are typical of wet weather4 ,both these classes of clouds are found at all heights4 ,cirrus are thin1 fibrous1 detached1 and feather-like clouds formed of ice-crystals4 ,they are the highest of all the clouds1 and move with the greatest velocity4 ,cirro-stratus form a thin whitish veil1 more or less fibrous1 which often produces halos around the sun and moon and other optical phenomena4 ,cirro-cumulus are flocks of small detached fleecy clouds1 generally white and without shadows4 ,alto-stratus is a grey or bluish veil through which the sun and moon are faintly visible1 occasionally giving rise to coron4 ,its altitude is only about half that of ,cirro-stratus4 ,alto-cumulus are flocks of larger1 more or less rounded1 white or partially shaded masses1 often touching one another1 and frequently arranged in lines in one or more directions4 ,strato-cumulus are large globular masses or rolls of dark cloud1 frequently covering the whole sky1 especially in winter4 ,cumulus are piled clouds with conical or hemispherical tops and flat bases4 ,they are formed by rising currents of heated air1 and are therefore most common in summer and in tropical regions4 ,when broken up by strong winds the detached portions are called ,fracto-cumulus4 ,cumulo-nimbus is the massive thunder shower cloud rising in the form of mountains or turrets1 and generally having above a screen of fibrous appearance 7,false ,cirrus71 and underneath a mass of cloud similar to ,nimbus from which rain falls4 ,nimbus is a dense1 dark sheet of ragged cloud from which continued rain or snow generally falls4 ,broken clouds underneath1 forming the scud of the sailors1 are called ,fracto-nimbus4 ,stratus is a thin uniform layer of cloud at a very low level4 ,when the sheet is broken up into irregular shreds it is called ,fracto-stratus4 ,having described the origin and appearance of the different clouds1 an account will now be given of the measurements made at ,blue ,hill ,observatory and the information which they give about the circulation of the atmosphere4 ,the work there was taken up in #ahhg in consequence of the interest of the meteorologist1 ,mr4 ,clayton1 in the study of clouds2 his discussion of the cloud observations1 published two years ago with the ,blue ,hill observations1 has been termed by far the most thorough study of the kind ever undertaken in ,america if not in the world4 ,most of the conclusions which are stated popularly here have their scientific expression in his work4 ,the first investigation related to the amount of cloud at different hours of the day1 and during the various seasons4 ,it is customary to note the degree of cloudiness on a scale of from #j1 when there are no clouds1 to #aj1 when the whole sky is covered4 ,for twelve years the amount of cloud at each hour of the day has been recorded at ,blue ,hill4 ,the personal observations have been supplemented during the day-time by an automatic instrument called a sunshine-recorder1 for it has been proved that the cloudiness is very nearly the inverse of the bright sunshine4 ,consequently1 if1 as is usual there1 the sun shines forty-six per cent4 of the time when it is above the horizon1 the cloudiness is very nearly fifty-four per cent41 which is the average for the year4 ,the instrument generally used for this purpose is a glass sphere which acts as a burning-glass1 and chars a strip of cardboard placed concentrically around the lower part of the sphere4 ,as the sun moves1 the image on the card moves in the opposite direction over the card1 burning a line as long as it shines1 but leaving the card untouched when it is cloudy4 ,in a similar way a record may be obtained on sensitized blue paper by allowing the sun's rays to enter a dark chamber containing the paper4 ,the maintenance of personal observations at each hour of the night is arduous1 and1 therefore1 during ten years an automatic instrument has been used at ,blue ,hill which deserves to be better known4 ,it is called the pole-star recorder1 and was devised by ,professor ,pickering1 director of the ,harvard ,college ,observatory4 ,the instrument is very simple1 and consists of a telescopic camera focussed on ,polaris4 ,this star is not at the north pole of the heavens but a little more than a degree distant1 and1 consequently1 it describes a small circle in the heavens during twenty-four hours4 ,when the sky is clear around ,polaris its trail upon the photographic plate is continuous1 but when the sky is partly or entirely covered with clouds the trail is broken or obscured4 ,of course the plate is not exposed until after dark1 and a shutter is closed by a clock before dawn4 ,the only hourly records of cloudiness at night in the ,united ,states are obtained by this instrument on ,blue ,hill and at ,cambridge4 ,it will be objected1 perhaps1 that the cloudiness derived from observations of the sun or the pole-star is not the amount over the whole sky1 but only that in the region of the luminary4 ,this is true1 but it is found that the average of the records for a month or a year agrees very closely with the average of estimates of cloudiness over the whole sky during these periods4 ,the use of the pole-star is preferable to that of the sun1 because in our latitude it gives values at a point about half-way between the horizon and the zenith2 while since the sun travels at a variable height across the sky1 when its altitude is low the same mass of cloud may intercept more sunlight than when it shines vertically4 ,from ten years' observations the following deductions have been made concerning the variation in the amount of cloud at ,blue ,hill4 ,for all the months the diurnal amount of cloud is greatest about one o'clock in the afternoon1 on account of the frequency of cumulus clouds near the warmest part of the day1 while the next greatest amount1 due to the frequency of stratus clouds1 occurs near sunrise1 or at the coldest time of day4 ,all over the world the least cloudiness is in the evening1 when the sum of the combined effects of radiation and insolation is least4 ,the annual period in the cloudiness is complex1 because the amount of cloud is connected with changes of humidity at many different levels in the atmosphere1 but in the northern hemisphere there is most cloud during the first half of the year and least during the latter half1 probably because the increasing warmth at the earth's surface produces increased ascending currents until summer1 while the chilling of the earth's surface in the autumn becomes unfavourable for ascending currents4 ,the distribution of cloud over the globe is intimately connected with the general atmospheric circulation1 being greater where there are rising currents and less where there are downward currents4 ,the reason1 naturally1 is that as descending air becomes warmer and therefore relatively drier1 the clouds in it evaporate and disappear4 ,a cloudy belt encircles the earth at the equator1 and on either side are two belts of less cloud1 but in higher latitudes the cloudiness increases4 ,if we could see our earth from outside its atmosphere1 the light reflected from the upper surfaces of the cloud-belts would probably make them appear bright4 ,from the markings on a planet that are known to be caused by condensation1 a ,french meteorologist1 ,m4 ,teisserenc de ,bort1 believes that the circulation of its atmosphere can be inferred1 for wherever on the surface of the planet bright spots are seen1 there the vapour of rising currents should be condensed4 ,if this be true1 there is a resemblance between ,jupiter1 as we see it1 and the earth as it would appear from another planet1 the bright bands being cloud surfaces1 and the dark patches glimpses of the surface of the planet beneath4 ,observations of the direction of motion1 and apparent velocity of clouds at different heights1 have been made at ,blue ,hill several times a day since #ahhf4 ,to measure the motion of clouds the nephoscope 7,fig4 #a7 is used4 ,it consists of a horizontal circular mirror with a concentric circle of azimuths and an eye-piece ,c1 movable in a plane ,,bd at right angles to the mirror and also around it1 through which the image of the cloud is brought to the centre of the mirror ,a4 ,it can be proved by geometry that the motion of the cloud-image is proportional to the movement of the cloud itself1 so by noting in what direction and how far the image is displaced in a given time1 we have the true direction of motion of the cloud itself and also its relative velocity1 comparable with the velocity of all clouds having the same height4 ,if the height is known1 then the relative velocity can be easily converted into absolute velocity1 and thus the velocity of currents at different heights in the atmosphere is accurately ascertained4 ,illustration3 ,,fig4 #a4--,nephoscope at ,blue ,hill ,observatory4 ,the height of clouds seems to have been measured trigonometrically from two stations as early as #afdd by ,riccioli and ,grimaldi1 two ,jesuits of ,bologna1 but notwithstanding these measurements and some conclusions derived from observations on mountains1 and in balloons1 the altitudes of the different clouds were not known with any accuracy until in #ahhd ,ekholm and ,hagstrm made a series of trigonometrical measurements upon the different kinds of clouds at ,upsala1 ,sweden4 ,about the same time attempts were made at ,kew ,observatory to measure clouds by photography1 and in #ahhe probably the first trigonometrical measurements in ,america were made at ,cambridge1 ,mass41 by ,professor ,w4 ,m4 ,davis and ,mr4 ,a4 ,mc,adie4 ,in #ahij-ia the ,swedish methods were employed at ,blue ,hill by ,messrs4 ,clayton and ,fergusson of the ,observatory staff1 and until recently the measurements there and at ,upsala comprised all that was known accurately about the heights and velocities of the various species of clouds4 ,illustration3 ,,fig4 #b4--;,cloud ,theodolite at ,blue ,hill ,observatory4 ,the trigonometrical measurements at ,blue ,hill were made as follows3 at two stations1 one at the ,observatory1 the other at the base of the hill about a mile distant1 two observers determined simultaneously the angular altitude and azimuth of some point on the cloud which was agreed upon by telephonic conversation4 ,if1 as is generally the case1 the lines of sight did not meet1 the trigonometrical formul gave the height of a point midway between the crossing of these lines4 ,such was the accuracy of these measurements that the probable error of the calculated heights of the highest clouds is only a few hundred feet4 ,successive observations at the two stations of the position of the cloud enabled its velocity to be calculated1 or1 as already explained1 this may be got from the relative velocity measured at one station1 if the height of the cloud be known4 ,fig4 #b shows the theodolite on the tower of the ,observatory4 ,five other methods of measuring clouds have been employed at ,blue ,hill3 7#a7 ,the only method of finding the height of lofty and uniform cloud strata is by means of the light thrown on them from below1 and on ,blue ,hill the electrical illumination of the surrounding towns is utilized4 ,the angle which the centre of the illumination makes with the horizon is measured1 and knowing the distance of the town1 the right-angled triangle may be solved4 7#b7 ,an accurate method for low and uniform clouds is to send kites into them1 as will be explained in the closing chapter4 7#c7 ,when the clouds are low enough to cast shadows on the ground1 the angles of the cloud and sun as seen from the ,observatory are measured1 and with the distance of the shadow from the hill-top1 ascertained by a map1 this triangle can be solved4 ,the times of passage of the shadow over known points on the landscape afford another means of calculating its velocity4 7#d7 ,a method that was suggested by ,espy1 the pioneer ,american meteorologist1 for getting the altitude of the bases of clouds lying within a mile of the earth1 is to find the difference in temperature between the air and the dew-point at the ground1 and to compute the height at which this difference should disappear4 ,when the temperature of the rising currents increases1 as on warm days1 and the level of the dew-point rises higher1 the cloud can be seen to ascend1 and1 in fact1 the measurements at ,blue ,hill show that the clouds of moderate altitude are highest during the warmest part of the day4 7#e7 ,finally1 very low stratus or nimbus may be measured by noting the heights of their bases on the sides of the hill4 ,illustration3 ,,plate ,,iv4 ,the identity of cloud-forms all over the world has been established1 and as a result of the measurements at ,blue ,hill1 the heights and speed of all clouds observed there are known4 ,the averages have been plotted in the five levels into which we separate the clouds in ,plate ,,iv41 ,heights and ,velocities of ,clouds1 where ordinates represent heights and absciss velocities1 and1 consequently1 the distances of the various forms of clouds above the horizontal base indicate their heights1 and the distances from the left-hand vertical line their velocities4 ,for comparison1 the velocity of the wind on ,blue ,hill1 a few hundred feet above the general level of the country1 is represented4 ,the mean height of the cirrus is about #bi1jjj feet1 but this cloud sometimes reaches #di1jjj feet4 ,the mean height of the cumulus is about a mile1 but the tops of the cumulo-nimbus1 or thunder-shower cloud1 sometimes penetrate into the cirrus level4 ,generally the base of the nimbus1 or rain cloud1 is only #bcjj feet above the ground1 and it frequently sinks below the top of ,blue ,hill1 which is only #fcj feet above the sea4 ,the poetic saying1 that ,earth wraps her garment closer about her in winter1 has a scientific basis1 for the average height of all the clouds is greatest in summer and least in winter4 ,but the reverse is true of their velocity1 for the entire atmosphere moves twice as fast in winter as it does in summer1 and at the lower levels the seasonal change is even greater4 ,the average velocity of cirriform clouds is ninety miles an hour in winter1 and sixty miles in summer1 but occasionally in winter cirrus have been found to have the enormous velocity of two hundred and thirty miles an hour4 ,in the average1 the velocity of the currents increases1 from the lowest to the highest clouds1 at the rate of about three miles an hour for each #ajjj feet of height1 but near the ground the increase with height is faster4 ,it has been found that the velocity of the lower clouds is less than the velocity of the wind on a mountain of the same height1 which may1 perhaps1 be explained on the supposition that the mountain acts like a dam to accelerate the flow of air over it4 ,the measurements in ,sweden showed that the middle and upper levels of clouds are higher than in ,america1 but that they move less rapidly4 ,this may be because the surfaces of equal temperature in the air are higher in the ,united ,states than in ,sweden1 on account of the direction of the upper currents1 while the greater velocity of our high clouds corresponds with the more rapid movement of areas of low and high barometric pressure over the ,united ,states4 ,these results are suggestive4 ,for instance1 the energy of the upper half of the mass of the atmosphere1 or that portion which lies above #ah1jjj feet1 has been calculated to possess six times the energy of the lower half in which we live1 and as yet1 none of this enormous store of energy is applied to the use of man4 ,while it appears certain that no navigable balloon or flying machine will ever be able to stem the enormous velocity of the upper atmosphere1 rarified though it is1 perhaps in the future arial machines will take advantage of the prevailing currents of the high atmosphere1 as our sailing ships do of the trade winds4 ,the observations of cirrus clouds in various parts of the world show that they always move from a general westerly direction1 while below this primary drift toward the east occur the relatively permanent or transient differences of pressure which cause the deviations from the normal circulation of the atmosphere1 and give rise to the local circulation in storms4 ,in the familiar daily weather map it will be noticed that there is usually some portion marked low1 and another portion marked high4 ,the former is an area of low barometric pressure1 into which the winds at the ground blow spirally inward in the opposite direction that the clock hands turn2 the latter is an area of high barometer1 out of which the winds at the ground blow in the contrary way4 ,the former when well developed are called cyclones1 and are usually accompanied by stormy weather1 and the latter1 called anti-cyclones1 bring fair weather4 ,from the observations of the directions from which the clouds move in cyclones and anti-cyclones1 we have found that above the cumulus level 7at the height of about a mile7 the inward inclination of the wind in a cyclone1 and the outward inclination in an anti-cyclone1 both disappear1 and the general drift from the west prevails4 ,the results of the observations are shown in ,plate ,v41 ,atmospheric ,circulation in ,cyclones and ,anti-cyclones1 representing sections of the atmosphere1 concentric to the earth's surface1 in the five cloud-levels seen from above4 ,the arrows fly with the wind and are proportional in length to its velocity1 the dotted arrows indicating the probable flow of the air through the cyclones and anti-cyclones that are indicated by the circles1 their axes being assumed to be nearly perpendicular to the earth's surface4 ,above the cumulus it will be observed that the wind in the cyclone tends to come from the south-west in front and from the north-west in the rear1 while in the anti-cyclone the contrary is the case1 indicating a deflection of the westerly upper current to the right in cyclones and to the left in anti-cyclones4 ,this sustains the theory that the cyclonic circulation is struggling against a general atmospheric drift from the west which increases with altitude1 and above the height of a mile becomes greater than the cyclonic influence4 ,higher than this1 the atmospheric circulation is controlled primarily by the permanent temperature gradient between equator and pole1 by the seasonal temperature gradient between ocean and continent1 and1 in the ,united ,states1 by the passage of warm and cold waves4 ,mr4 ,clayton's investigations indicate that the motion of the upper clouds is nearly parallel to the lines of equal temperature at the earth's surface4 ,a high temperature1 by expanding the air upward1 causes in the upper air a high pressure2 and a low temperature1 by contracting the air towards the ground1 causes in the upper air a low pressure1 so that the lines of equal pressure in the upper air are parallel to the lower lines of equal temperature1 and since there is little friction in the upper air the motion of the wind is nearly parallel to the lines of equal pressure4 ,below the cumulus level the winds follow the normal cyclonic and anti-cyclonic circulation4 ,there are two theories of the origin of these areas of high and low pressure1 the driven theory which supposes that they derive their energy and drift from the general atmospheric movement from west to east1 and the convectional theory which attributes their formation and progression to the difference of temperature between them and the adjacent air4 ,while the observations on mountains have favoured the driven theory1 yet the inward spiral motion of the cirrus clouds above the anti-cyclone1 indicating a lower pressure than in the surrounding air1 contradicts the hypothesis1 and the recent observations with kites at ,blue ,hill strongly support the convectional theory of cyclones4 ,illustration3 ,,atmospheric ,,circulation ,,at ,,different ,,heights ,,in ,,cyclones ,,anti-,,cyclones ,,plate ,v4 ,the relation of the clouds to weather forecasting has been investigated at ,blue ,hill4 ,for instance1 it is found1 in this region at least1 and contrary to the general opinion1 that cirrus clouds do not indicate rain1 but do foretell a change of temperature that is proportional to the rapidity of motion of the clouds4 ,alto-cumulus is followed by rain within twenty-four hours three times in four4 ,rain follows the appearance of all high and intermediate clouds most frequently when the cloud banks are densest toward some westerly point and when they come from the west4 ,mr4 ,sweetland1 an assistant1 has studied special forms of cloud in their relation to the succeeding weather4 ,he concludes that cirrus plumes precede fair weather1 while dense clots of cirro-cumulus are followed by rain4 ,rounded pendants1 or mammillated clouds1 in the lower levels indicate rain1 but in the upper levels fair weather4 ,of all the forms1 the dark sheet of stratus1 and clouds of lenticular shape1 are most frequently followed by rain4 ,of clouds presaging changes in temperature1 the turreted cumulus1 which is connected with thunder-storms1 precedes the greatest fall in temperature1 and next in order come lenticular clouds1 flaky cirrus1 and alto-cumulus4 ,in general1 flat and flaky clouds1 clouds forming and disappearing rapidly1 and clouds changing to forms at a higher level precede dry and cooler weather4 ,it will be seen that this modern study of clouds as prognostics simply adds to the weather proverbs that have come down to us from the time of ,theophrastus4 ,it does not appear1 however1 that cloud forms alone can usually serve to predict rain for more than twenty-four hours1 but for a few hours in advance the appearance of certain cloud forms frequently furnishes the observer more trustworthy signs of coming rain than does the synoptic weather map4 ,to a forecaster in possession of telegraphic data1 the prevalence of rapidly-moving cirrus over a wide area indicates a rapid storm movement1 with sudden and marked changes of weather and of temperature1 while slowly-moving cirrus indicate slight changes of temperature and dry weather4 ,the direction of the cirrus movements in front and around a storm centre will usually point out the future movement of the storm1 which tends to advance in the same general direction4 ,the work done at ,blue ,hill shows the importance of cloud observations to elucidate the general movements of the atmosphere1 as well as the circulation of the air above barometric maxima and minima1 which can result practically in making accurate weather forecasts possible a day or two in advance4 ,the systematic observation of the upper currents was brought to the attention of the ,international ,meteorological ,committee by ,dr4 ,hildebrandsson in #ahhe1 and at the meeting of the ,international ,cloud ,committee in #ahid1 besides the adoption of the nomenclature of clouds and instructions for observing them1 it was decided that observations of their motion1 as well as measurements of their height1 should be made in various parts of the world4 ,accordingly1 the year commencing ,may #a1 #ahif1 was designated as the ,international ,cloud-,year1 and observations with nephoscopes of the direction of motion and relative velocity of clouds were begun at many stations in ,europe and ,asia1 and at fifteen stations in the ,united ,states4 ,trigonometrical measures of the heights of clouds were undertaken at stations in ,norway and ,sweden1 ,russia1 ,finland1 ,prussia1 and ,france1 as well as at ,toronto1 ,manila1 and ,batavia2 in the ,united ,states the measurements already described were recommenced at ,blue ,hill1 and the ,weather ,bureau equipped a similar station in ,washington4 ,in ,europe it is thought that the determination of heights by photogrammeters1 as the theodolites with attached photographic cameras are called1 possesses advantages over the visual theodolites1 and it is true that not only is the kind of cloud recorded on the plates1 but there are available for calculation as many points on the cloud as can be identified on the two plates exposed simultaneously at both stations4 ,on the other hand1 in the case of nearly uniform or dark cloud-strata1 it is easier to see points for measurement on the cloud than to fix them on the photographic plates4 ,for this reason1 and from the difficulty of manipulating the photogrammeter1 visual instruments were adopted both at ,blue ,hill and at ,washington4 ,the work was successfully carried on until ,may #a1 #ahig1 and the observations and measurements were reduced at ,blue ,hill according to the plan prescribed by the ,committee4 ,already the observations and measurements made at ,upsala1 ,manila1 and ,blue ,hill are published1 and the others will follow4 ,the discussion of the correlated data from the various countries will probably increase our knowledge of the circulation of the atmosphere1 which is certainly one of the most interesting and important questions in the physics of the globe4 ,the result will have been reached by international co-operation1 of which the benefits to science are everywhere manifest to-day4 ,but for the whole problem to be solved1 it is necessary1 not only to know the movement of the air1 but1 as far as possible1 to ascertain its conditions of heat and moisture4 ,this may be accomplished by the use of balloons and kites1 to be described in the remaining chapters4 ,,chapter ,,iii ,,balloons--,,notable ,,ascents ,,and ,,results ,,obtained--,,captive ,,balloons ,in the first chapter the invention of the hot-air and the hydrogen balloon was chronicled1 and it was stated that on ,december #a1 #aghc1 ,charles rose from ,paris to a height of #ijjj feet4 ,public interest in ,france was greatly excited by this wonderful extension of the realm of man1 and numerous ascensions with ,montgolfires and ,charlires1 as the hot-air and hydrogen balloons were respectively called1 took place in ,paris and the provinces4 ,the uses of the balloon seemed innumerable1 and ,lavoisier was instructed by the ,academy of ,sciences to draw up a report on the value of the new discovery4 ,after having described in detail the ascensions which he had witnessed1 the great chemist stopped1 appalled at the multitude of problems which the balloon could solve4 ,history has shown1 however1 that no commercial application of the balloon was possible1 and that aside from its spectacular attractions1 its chief use has been for scientific observations4 ,the first persons in ,england who devoted themselves to arial navigation were foreigners4 ,two of them were ,italians1 the philosopher ,tiberius ,cavallo1 who already in #aghb had showed to a ,london assembly that soap-bubbles filled with hydrogen will rise1 and therefore had almost anticipated the invention of the hydrogen balloon1 and the diplomatist ,vincent ,lunardi1 who made some daring balloon ascents in #aghd4 ,but the honour of making the first scientific balloon voyage is due to a ,bostonian1 ,dr4 ,john ,jeffries4 ,dr4 ,jeffries graduated at ,harvard ,college in #agfc and then practised medicine in ,england1 where he became a loyalist1 and during the ,revolution was with the ,british troops4 ,in ,london he interested himself in aerostation1 and1 aided by the ,royal ,society1 ascended in a balloon because1 he said1 ,i wished to see the following points more clearly determined3 first1 the power of ascending or descending at pleasure1 while suspended and floating in the air2 secondly1 the effect which oars or wings might be made to produce towards the purpose and in directing the course of the balloon2 thirdly1 the state and temperature of the atmosphere at different heights from the earth2 and fourthly1 by observing the varying course of the currents of air1 or winds1 at certain elevations1 to throw some new light on the theory of winds in general4 ,a ,french professional aeronaut named ,blanchard had made three ascents in ,france and one in ,england1 and ,dr4 ,jeffries paid one hundred guineas to accompany ,blanchard on his fifth ascent1 which was made from ,london ,november #cj1 #aghd4 ,he took with him a thermometer1 a barometer1 a hygrometer1 an electrometer1 and a mariner's compass1 also several numbered bottles1 filled with water and provided with glass stoppers1 which were to be emptied and corked up at different heights in the atmosphere4 ,it was arranged to record the observations on ruled paper with a silver pen1 because the doctor would not trust a common pen or pencil as liable to accident4 ,he also had a map of ,england to determine the direction which the balloon took4 ,jeffries' ,english sentiments are shown by this quotation from his narrative3 ,i had provided a handsome ,british flag1 invidiously represented the next day in one of the public papers to have been the flag of the ,american ,states4 ,the barometer and thermometer were observed every few minutes1 and the hygrometer occasionally4 ,the electrometer did not change its indications4 ,samples of air were obtained and sent to the ,royal ,society1 but it does not appear that they were ever analyzed4 ,the balloon rose nearly two miles1 and descended safely in ,kent after an hour and a half4 ,jeffries' observations compare favourably with those made until recently2 indeed1 for nearly a century there was little improvement in the apparatus4 ,the decrease of temperature which ,jeffries found1 viz4 #a for #cfj feet rise1 and the decreasing humidity with height agree very well with later observations4 ,jeffries and ,blanchard undertook a more perilous voyage on ,january #g1 #aghe1 from ,dover across the ,channel1 landing in the province of ,artois1 after1 so runs the announcement1 we were suspended and floating in the atmosphere two hours over the sea and forty-seven minutes over the land of ,france4 ,the voyagers were cordially welcomed1 and were entertained lavishly in ,paris as being1 ,jeffries says1 the first who passed across the sea from ,england into ,france by the route of the air4 ,no instruments but a barometer and a compass were carried1 and the only scientific result worthy of notice was that the balloon seemed to lose buoyancy over the sea1 due to what ,jeffries thought might be the power of attraction over the water4 ,the height of the balloon was measured trigonometrically by ,french officers in ,calais1 who found by angular measures1 when the balloon was midway across the ,channel1 that its height was #dejj feet4 ,jeffries' voyages have been described somewhat at length because the first scientific balloon voyage is generally attributed to the ,belgian physicist1 ,robertson1 who ascended from ,hamburg in #ahjc to the improbable height of #bd1jjj feet4 ,robertson made his third ascent the next year from ,st4 ,petersburg1 accompanied by the ,academician ,sacharoff4 ,this was a scientific voyage1 instituted at the request of the ,russian ,academy1 to ascertain the physical state of the atmosphere and the component parts of it at different heights1 also the difference between the results of vertical ascents and the observations of ,deluc1 ,de ,saussure1 von ,humboldt and others on mountains1 which it was rightly concluded could not be so free from terrestrial influences as those made in the open air4 ,among the experiments which the ,academy proposed were the following3 change of rate of evaporation of fluids1 decrease or increase in the magnetic force1 inclination of the magnetic needle1 increase of heat of the solar rays1 fainter colours in the spectrum1 influence of rarefaction of the air on the human body1 as well as some other chemical and philosophical experiments4 ,a height of about two miles was reached1 and many interesting observations were made1 but since the instruments were not easily used in the basket of the balloon1 the results were unsatisfactory and required repetition to be conclusive4 ,the ,academy of ,sciences of ,paris now took up the investigation with the special object of proving whether the magnetic force decreased as ,robertson in a balloon and ,de ,saussure in the ,alps had supposed4 ,two young physicists1 ,biot and ,gay-,lussac1 were chosen to carry out the investigations4 ,they ascended from ,paris on ,august #bd1 #ahjd1 provided with all necessary instruments1 but the balloon was too small to rise higher than #ac1jjj feet4 ,gay-,lussac ascended alone to a height of #bc1jjj feet on ,september #af1 #ahjd1 in a balloon filled with hydrogen4 ,his observations confirmed those which he had made with ,biot1 that there was no change in the magnetic force1 and from samples of air collected he proved that the chemical constitution of the air is invariable4 ,his observations of temperature seemed to confirm the theory of a decline of temperature of #a in #cjj feet of elevation4 ,the air was found to be very dry1 and ,gay-,lussac noticed that at the highest altitude the clouds were still far above him4 ,passing over several notable ascents in other countries1 it was not until #ahej that scientific ballooning was begun again in the land where the balloon originated4 ,then ,,mm4 ,barral and ,bixio made two ascents from ,paris in rainy weather to the heights of #ai1jjj and #bc1jjj feet respectively1 although they had expected to attain twice these altitudes4 ,their most interesting observations were the great thickness of the cloud mass1 which in one case amounted to #ae1jjj feet1 and the sudden fall of temperature in it from #ae to -#ci4 ,some curious optical phenomena were connected with the floating ice crystals1 and although the light of the sky was found to be strongly polarized1 the light reflected from the clouds was not polarized4 ,the field of operations was now transferred to ,england1 where1 under the auspices of the ,british ,association1 four ascents were made by ,john ,welsh of the ,kew ,observatory in the great ,nassau balloon managed by ,green1 the veteran aeronaut4 ,the special object of these investigations1 like those in ,france1 was the determination of the temperature and hygrometric condition of the air at different elevations4 ,besides this1 samples of air at different heights were collected for analysis and the light reflected from clouds was examined for polarization4 ,recognizing that on account of the calm prevailing in the car of the balloon and the great solar radiation1 the readings of the thermometer would be affected1 ,welsh enclosed the thermometers in polished tubes through which air was forced by bellows4 ,this was the first aspirated thermometer1 which alone gives the true temperature of the air with the conditions prevailing in a balloon4 ,the instrument fell into oblivion until a few years ago1 and to this fact is due the fictitious temperatures generally obtained by aeronauts4 ,welsh reached heights of from #ab1ejj to #bc1jjj feet1 and his observations showed that the temperature of the air decreased uniformly with height until at a certain elevation1 varying on different days1 the decrease is arrested1 and for a space of #bjjj or #cjjj feet the temperature remains nearly constant1 or even increases slightly2 the regular diminution being afterwards resumed and generally maintained at a less rapid rate than in the lower air1 and commencing from a higher temperature than would have existed but for the interruption4 ,the variation of the decrease with the seasons was also demonstrated4 ,the humidity did not change much with height1 and it was nowhere very dry4 ,finally1 the light of the clouds was proved not to be polarized1 and the permanent composition of the atmosphere was confirmed4 ,in #ahfa another grant of money was made by the ,british ,association for balloon experiments to be performed1 under the direction of a ,committee1 by ,mr4 ,james ,glaisher1 then engaged in geodetic and meteorological work in ,england4 ,between #ahfb and #ahfh ,glaisher1 accompanied by the aeronaut ,coxwell1 made thirty ascents4 ,they attained three times a height exceeding #bc1jjj feet1 and once more than #bi1jjj feet1 when they believed that the balloon rose to #cg1jjj feet4 ,the primary objects of ,glaisher's experiments were as follows3 determination of the temperature of the air and its hygrometrical conditions up to five miles1 comparisons of an aneroid barometer with a mercurial one1 determination of the electrical state of the air and of its oxygenic state by means of ozone papers1 time of vibration of a magnet at different distances from the earth4 ,secondary objects of study were the composition of the air1 the form and thickness of clouds1 the atmospheric currents1 acoustical phenomena1 etc4 ,in order to obtain many observations frequent ascents were necessary1 as the insular position of ,england precluded long voyages4 ,during #ahfi ascents in a captive balloon up to #agjj feet supplemented the employment of the free balloon1 which from its rapid rise and fall made observations in it near the earth impossible4 ,glaisher was a good observer2 his instruments were excellent1 and had been previously tested1 but their exposure in the basket of the balloon was bad1 and although the thermometer was provided with an aspirator similar to ,welsh's1 ,glaisher1 noticing that the readings agreed with those of a freely exposed thermometer1 hastily concluded that the use of the aspirator was unnecessary1 and so discarded it4 ,until quite recently ,glaisher's results were accepted as representing the conditions of the free air up to the greatest height which it was possible to reach4 ,these results showed that the temperature did not fall uniformly with height1 but that it fell most rapidly near the earth and much less rapidly at great heights4 ,in cloudy weather up to the height of a mile the mean decrease of temperature in the day-time differed little from the theory of #a per #cjj feet1 but in clear or partly clear weather the decrease was more rapid1 commencing with #a for #afj feet near the ground and diminishing to #a for #ajjj feet at an elevation exceeding six miles4 ,the observations in the captive balloon up to a third of a mile indicated a daily range in the vertical decrease of temperature4 ,the observations of relative humidity agreed with ,welsh's in showing a slight increase up to about half-a-mile1 then a decrease up to above five miles1 where there seemed to be an almost entire absence of water4 ,the other observations were inconclusive1 except that the time of vibration of a magnet was found to be somewhat longer than on the earth1 which was contrary to ,gay-,lussac's experience4 ,the most remarkable of ,glaisher's ascents was made from ,wolverhampton on ,september #e1 #ahfb1 when in less than one hour he had passed the altitude of five miles1 exceeding the greatest height hitherto reached4 ,to quote from ,glaisher's narrative3 ,up to this time ,i had taken observations with comfort and experienced no difficulty in breathing1 whilst ,mr4 ,coxwell1 in consequence of the exertion he had to make1 had breathed with difficulty for some time4 ,having discharged sand1 we ascended still higher2 the aspirator became troublesome to work1 and ,i also found a difficulty in seeing clearly4444 ,about #a hour #eb min41 or later1 ,i read the dry-bulb thermometer as minus #e2 after this ,i could not see the column of mercury in the wet-bulb thermometer1 nor the hands of the watch1 nor the fine divisions of any instrument4 ,i asked ,mr4 ,coxwell to help me to read the instruments4 ,in consequence1 however1 of the rotatory motion of the balloon1 which had continued without ceasing since leaving the earth1 the valve-line had become entangled1 and he had to leave the car and mount into the ring to readjust it4 ,i then looked at the barometer1 and found its reading to be #i-c_/d inches1 still decreasing fast1 and implying a height exceeding #bi1jjj feet4 ,shortly after1 ,i laid my arm upon the table1 possessed of its full vigour1 but on being desirous of using it1 ,i found it powerless4444 ,trying to move the other arm1 ,i found it powerless also4 ,then ,i tried to shake myself and succeeded1 but ,i seemed to have no limbs4444 ,i dimly saw ,mr4 ,coxwell1 and endeavoured to speak1 but could not4 ,in an instant intense darkness overcame me1 so that the optic nerve lost power suddenly1 but ,i was still conscious1 with as active a brain as at the present moment whilst writing this4 ,i thought ,i had been seized with asphyxia1 and believed ,i should experience nothing more1 as death would come unless we speedily descended2 other thoughts were entering my mind1 when ,i suddenly became unconscious4444 ,i cannot tell anything of the sense of hearing1 as no sound reaches the air to break the perfect stillness and silence of the regions between six and seven miles above the earth4 ,my last observation was made at #a hour #ed min41 above #bi1jjj feet4444 ,whilst powerless ,i heard the words1 'temperature' and 'observation1' and ,i knew ,mr4 ,coxwell was in the car speaking to and endeavouring to rouse me4444 ,i then heard him speak more emphatically1 but could not see1 speak1 or move4 ,i heard him again say1 ',do try2 now do6' ,then the instruments became dimly visible1 then ,mr4 ,coxwell1 and very shortly ,i saw clearly4444 ,mr4 ,coxwell told me that while in the ring he felt it piercingly cold1 that hoarfrost was all round the neck of the balloon1 and that on attempting to leave the ring he found his hands frozen4 ,he had1 therefore1 to place his arms on the ring and drop down4444 ,he wished to approach me1 but could not2 and when he felt insensibility coming over him too1 he became anxious to open the valve4 ,but in consequence of having lost the use of his hands he could not do this2 ultimately he succeeded1 by seizing the cord with his teeth1 and dipping his head two or three times1 until the balloon took a decided turn downwards4 ,no inconvenience followed my insensibility2 and when we dropped1 it was in a country where no conveyance of any kind could be obtained1 so ,i had to walk between seven and eight miles4444 ,i have already said that my last observation was made at a height of #bi1jjj feet2 at this time 7#a hour #ed min47 we were ascending at the rate of #ajjj feet per minute2 and when ,i resumed observations we were descending at the rate of #bjjj feet per minute4 ,these two positions must be connected1 taking into account the interval of time between1 viz4 #ac minutes1 and on these considerations the balloon must have attained the altitude of #cf1jjj or #cg1jjj feet4 ,again1 a very delicate minimum thermometer read minus #aa4i1 and this would give a height of #cg1jjj feet4 ,mr4 ,coxwell1 on coming from the ring1 noticed that the centre of the aneroid barometer1 its blue hand1 and a rope attached to the car were all in the same straight line1 and this gave a reading of seven inches and leads to the same result4 ,therefore1 these independent means all lead to about the same elevation1 viz4 fully seven miles4 ,mr4 ,glaisher's circumstantial evidence of the height he reached has been assailed lately1 partly from his assumption that the velocity of the balloon while rising and falling during the thirteen minutes was uniform1 but principally from the supposition that men could have survived in that region of death1 without at least artificial means of respiration4 ,while it is certain that ,berson's observations1 which are described later1 were made at a greater height than ,glaisher's1 yet all credit must be given to this ,nestor of aeronautical and meteorological science in ,great ,britain1 who is still living at the advanced age of ninety4 ,the example of ,glaisher was not followed in ,england1 but it stimulated interest in the balloon again in ,france1 where ,,mm4 ,flammarion1 de ,fonvielle1 and ,tissandier have made many ascents for scientific purposes1 and have presented the results in a popular form to the public4 ,photography in a balloon is generally a failure on account of the intense reflection from the upper cloud surfaces and the haze which masks the earth4 ,consequently1 for scenic effects we must rely upon sketches1 of which those in that interesting1 but now rather rare book1 ,travels in the ,air1 may be referred to4 ,the high atmosphere is often filled with fine ice crystals which1 though invisible from below1 occasion curious optical phenomena1 and some of these have been sketched by ,m4 ,albert ,tissandier1 who has the advantage of being an artist as well as an aeronaut4 ,of the many narratives of balloon voyages1 one of the most thrilling is the tragedy of the ,zenith4 ,in #ahge1 through the co-operation of the ,french ,academy of ,sciences and other scientific bodies1 it was arranged to make two voyages1 one of long duration1 the other to a great height1 in the balloon ,zenith4 ,the long voyage from ,paris to ,bordeaux was successfully accomplished in twenty-four hours1 and on ,april #ae the ,zenith again rose from ,paris1 carrying ,,mm4 ,gaston ,tissandier and ,croc-,spinelli1 with ,sivel as aeronaut4 ,by the advice of ,m4 ,paul ,bert1 the distinguished physiologist1 three small balloons of oxygen were provided to assist respiration4 ,the scientific apparatus was as follows3 a pump was arranged to draw air through tubes filled with potash in which to store the carbonic acid at different heights in the atmosphere1 in order that analysis might determine if its proportion diminished at great heights2 a spectroscope was employed to examine the line of water-vapour in the atmosphere1 and two aneroid barometers were provided1 one giving the pressure corresponding to heights up to #ac1jjj feet1 the other the pressure between #ac1jjj and #cj1jjj feet4 ,there were also two barometric tubes registering the lowest pressure1 as well as thermometers and other scientific instruments4 ,at #ae1jjj feet the voyagers began to breathe oxygen1 which had been used beneficially by ,sivel and ,croc-,spinelli in a high ascent the previous year4 ,at #bd1jjj feet ,tissandier wrote in his notes3 ,my hands are freezing4 ,i am well4 ,we are all right4 ,haze on horizon with small rounded cirrus4 ,we are rising4 ,croc pants4 ,we breathe oxygen4 ,sivel shuts his eyes1 ,croc does the same4 ,five minutes later3 ,sivel throws out ballast1 temperature -#aa ,cent41 barometer #cjj millimeters4 ,after this1 ,tissandier became so weak that he could not turn his head to look at his companions4 ,he tried to seize the oxygen tube1 but was unable to move his arms4 ,his mind was clear1 and he saw the barometer sink below #bhj millimeters1 indicating a height of #bg1jjj feet4 ,then he fainted4 ,after a half-hour of unconsciousness he revived and wrote3 ,we are falling1 temperature -#h1 barometer #cae millimeters4 ,i discharge ballast4 ,croc and ,sivel unconscious in bottom of basket4 ,we fall rapidly4 ,again he fell into a stupor1 from which he was roused by ,croc shaking his arm1 saying1 ,throw out ballast6 which he did1 together with the pump1 wraps1 etc4 ,what happened after this is unknown1 but probably the balloon1 thus lightened and the gas in it being warm1 rose again nearly as high as before4 ,when ,tissandier came to his senses the balloon was falling with frightful speed1 and in the bottom of the basket1 which was oscillating violently from side to side1 were crouched his two companions with black faces and bloody mouths4 ,the shock of striking the ground was terrific1 but the anchor held1 and the balloon soon emptied4 ,from the barometric data it appears probable that the ,zenith attained twice a height of about #bh1jjj feet1 and that asphyxiation from the long deprivation of sufficient oxygen killed the two companions of ,tissandier and nearly proved fatal to him4 ,this disaster discouraged further attempts to reach high altitudes1 and with the exception of the ascent to #bc1jjj feet in ,france by ,,mm4 ,jovis and ,mallet1 no more were made until the past decade4 ,the results of the meteorological observations were seen to be strangely discordant2 for example1 the temperature of #dj below zero1 observed by ,barral and ,bixio at a height of #bc1jjj feet1 and #hj above zero1 noted by the ,american aeronaut ,wise1 at #fjjj feet4 ,the prophecy that the balloon-basket would be the cradle of the young science of meteorology seemed unlikely to be realized1 but1 nevertheless1 observations in balloons continued to be made in ,france1 ,italy1 and ,russia4 ,in the ,united ,states a series of balloon ascents was conducted by the ,signal ,service1 which then included the ,weather ,bureau1 and the height of #ae1ejj feet reached by ,professor ,hazen in #ahhg is probably the greatest at which observations in the free air have been made in ,america4 ,the difficulty of obtaining the true temperature of the air from a balloon is great1 and without special precautions the observations give the conditions of the free air even less well than do observations on mountain summits4 ,during a rapid ascent the air is carried up in the balloon basket like water in a well-bucket1 and since the balloon drifts with the wind it is relatively in a calm1 so that there is no circulation of air2 the thermometers1 even when screened from direct sunshine1 are affected by radiation from the heated gas-bag above1 and moreover they are not sufficiently sensitive to follow the changing temperature of the air strata so quickly traversed by the balloon4 ,the aneroid barometer1 from which the height of the balloon is calculated1 cannot respond to rapid changes of pressure2 consequently there is a double source of error in determining the height at which the temperature is measured4 ,ordinarily1 the temperature of the air may be obtained quite accurately by slinging in a circle a thermometer attached to a cord1 even though this is done in sunshine4 ,during two balloon ascents by the writer1 a sling thermometer was found in extreme cases to read #ad lower than was recorded by automatic instruments1 hung in their usual position from the ring of the balloon4 ,the sling thermometer1 however1 is influenced by intense insolation1 and moreover cannot be swung far enough outside the basket of a balloon to insure good results4 ,the standard instrument for obtaining the temperature of the air under all conditions1 adopted for international use in #ahih1 is a modification of that used by ,welsh forty-five years before4 ,this instrument1 which is the invention of ,dr4 ,assmann of ,berlin1 is called the aspiration thermometer1 and is designed to prevent the casing surrounding the thermometer from being heated by insolation or conduction1 and to insure a flow of air past the thermometer bulbs4 ,illustration3 ,,fig4 #c4--;,german ,balloon equipped for ,meteorological ,observations4 ,the reorganization of balloon observations was accomplished by the ,german ,society for the ,promotion of ,arial ,navigation1 which has been assisted by the ,prussian ,meteorological ,institute1 and by officers of the ,german ,army ,balloon ,corps4 ,the ,german ,emperor takes a personal interest in the work1 and has aided it by the gift of a considerable sum of money4 ,the first voyage under the direction of the ,society was made in #ahhh1 and many notable ones followed4 ,in #ahia1 through the courtesy of the president1 ,dr4 ,assmann1 the writer made an ascent from ,berlin in a balloon equipped for accurate observations1 with the special purpose of comparing the sling with the aspiration thermometer4 ,the car of the balloon is shown in ,fig4 #c4 ,a companion was the now famous ,dr4 ,berson1 who then made his second ascent1 but who has now become an expert aeronaut by reason of more than fifty ascensions1 some of them to great heights4 ,on ,december #d1 #ahid1 he ascended alone from ,stassfurt1 ,prussia1 in the ,phoenix1 to probably the greatest height ever reached by man1 at least in a conscious state4 ,by breathing oxygen he was able to keep his senses and to read the barometer at #ia inches1 indicating approximately an altitude of #cj1jjj feet1 and the aspirated thermometer at #ed below zero4 ,an ordinary thermometer read #aa below zero in the sun1 showing its heat was much diminished in consequence of the haze that prevailed even at this enormous height4 ,the cirriform clouds which surrounded the balloon were found to have the structure of snow-flakes rather than that of ice-crystals4 ,the chief result of this record-breaking ascent was the extraordinarily low temperatures recorded at great heights1 as compared with those observed by ,glaisher1 ,tissandier1 and others4 ,an inversion of temperature--that is an increase of temperature with height--prevailed up to a mile1 but above that the temperature fell at a rapid and accelerated rate which approached the adiabatic fall above #bf1jjj feet4 ,the wind1 which was almost calm at the earth's surface1 increased to a gale in the high atmosphere1 and carried the balloon along at an average speed of thirty-six miles an hour4 ,wishing to demonstrate conclusively whether the insular position of ,england influenced the temperature of the high atmosphere1 as had been suggested1 ,dr4 ,berson determined to execute a high ascension in ,england during the prevalence of a barometric maximum in summer1 when the air column would be abnormally warmed and the upper isothermal surfaces elevated4 ,an opportunity was afforded ,berson to follow in ,glaisher's footsteps on ,september #ad1 #ahih1 when abnormal heat prevailed in ,europe4 ,berson1 with the aeronaut ,spencer1 in the balloon ,excelsior1 rose from the ,crystal ,palace in ,london to the height of #bg1cjj feet1 where he observed a temperature of -#bi4 ,the oxygen inhaled prevented harmful physiological effects except for the discomfort caused by the enormous reduction of temperature from #hj at the ground only thirty-five minutes before4 ,the temperature decreased rapidly at first1 then moderately up to three miles1 and above that it fell almost at the adiabatic rate4 ,even in this hot summer maximum of pressure and notwithstanding the maritime climate and south-westerly currents1 a temperature about #bi below zero reigned at #bg1jjj feet1 being only a few degrees warmer than ,berson had observed in winter at the same height above ,germany4 ,yet ,glaisher1 in all his ascents1 two of which exceeded #bf1jjj feet1 never recorded a temperature of less than #e below zero4 ,these relatively high temperatures1 obtained also by ,welsh1 ,tissandier1 and ,gay-,lussac1 must be attributed to the insufficient protection of the thermometers against insolation1 to the proximity of the instruments to the heated basket and its occupants1 and lastly1 to the sluggishness of the thermometers themselves1 from lack of ventilation1 during the rapid passage through air-strata of different temperatures4 ,plate ,,vi4 indicates the change of temperature with height observed during the four highest balloon ascents in ,europe and in the ,united ,states4 ,dots indicate the observations while ascending1 and crosses the observations while descending2 these are connected by full and broken lines respectively1 an inclination upward to the left showing a decrease of temperature with height and vice vers4 ,the adiabatic lines1 representing a fall of temperature of #a ,fahrenheit per #ahc feet of ascent1 serve for comparison4 ,illustration3 ,,plate ,,vi4--,temperatures observed in ,four ,high ,balloon ,ascents4 ,this account of notable balloon ascents should not be closed without mentioning the most daring and unique of all1 the voyage of ,mr4 ,s4 ,a4 ,andre towards the north pole in #ahig4 ,although his was a voyage of geographical discovery1 and not one for the exploration of the air1 yet meteorological and other observations were to be made1 and ,andre had familiarized himself with the instruments and the management of a balloon during several voyages in ,sweden4 ,the success of the polar voyage depended primarily upon the prevalence of southerly winds1 and the ability of the balloon to keep afloat long enough to profit by them1 even should they be light and variable at times4 ,therefore the impermeability of the balloon to hydrogen gas was of vital importance1 and it was the conviction that the ,eagle1 of #adj1jjj cubic feet1 was neither sufficiently large nor staunch to sustain itself for thirty days1 the time which might be required to reach ,behring ,straits1 that led ,dr4 ,nils ,ekholm1 the meteorologist and physicist1 to withdraw from the expedition4 ,unfortunately1 his fears seem to have been well founded1 and it is probable that we must now abandon hope of the safety of the brave ,andre and his two companions4 ,a less perilous voyage northward across the ,alps was attempted in #ahih by ,professor ,heim1 the ,swiss geologist1 and two associates1 conducted by the ,italian aeronaut1 ,spelterini4 ,with an automatic photographic camera1 similar to one described in the next chapter1 it was hoped to get views of the high ,alps from above1 which would be alike valuable for geologic and topographic study4 ,extensive meteorological observations were made in connection with the sixth international balloon ascent1 but only the ,jura was crossed1 at an altitude of #ac1jjj feet1 because the balloon travelled in a north-westerly direction1 instead of north-east as was expected4 ,many years ago ,wise and ,donaldson1 the ,american aeronauts1 proposed to cross the ,atlantic ,ocean in a balloon4 ,the difficulties which present themselves in such an undertaking are purely technical1 and given a balloon which loses its gas so slowly that its buoyancy can be maintained for several days1 there seems to be no reason why such a balloon1 at a height of four or five miles1 could not pass from ,san ,francisco to ,new ,york1 or from the ,united ,states to ,europe1 since the motion of the upper clouds proves that the high atmosphere moves almost constantly with great velocity from the west to the east4 ,the dirigible balloon has not been realized except in nearly calm weather1 but the aeronaut can often reverse his direction by ascending or descending into a contrary wind to that in which he has been travelling4 ,frequently no clouds separate these opposing currents1 which become apparent only when a balloon enters them4 ,it has been mentioned that in #ahfi ,glaisher made observations in a captive balloon in ,england up to the height of #agjj feet in order to study the conditions of the air within this distance of the earth1 which could not be done in a free and rapidly moving balloon4 ,although captive balloons are frequently used in the ,european cities to lift people who wish to enjoy the view from a height of #ejj or #ajjj feet1 they appear to have been little used by scientific observers since the time of ,glaisher4 ,in #ahij-ia the aeronautical society at ,berlin employed a captive balloon in connection with the observations in free balloons which have been described4 ,this captive balloon had a capacity of only #ejjj cubic feet1 but it sufficed to lift an apparatus weighing sixteen pounds1 designed by ,dr4 ,assmann to record atmospheric pressure1 as well as the temperature and relative humidity of the air4 ,the balloon1 attached to a cable #bfjj feet long1 was drawn down by a steam engine4 ,it was possible in this way to have simultaneous observations at three levels1 viz4 near the ground1 in the free air at a height of about half-a-mile1 and at the highest level attained by a free balloon4 ,but the captive balloon is often at a disadvantage1 for the wind drives it down1 and although the meteorograph mentioned had ingenious devices to neutralize the violent shocks caused by this and by the rebound of the balloon after the gust of wind1 yet these impaired the automatic record4 ,the height to which the balloon rose was so much diminished by the wind that instead of #bfjj feet1 which the balloon attained in calm weather when the cable was vertical1 the average height of the twenty-four ascents was but half this1 and in very windy weather the balloon could not rise at all4 ,illustration3 ,,fig4 #d4--;,german ,kite-balloon4 ,to obviate these difficulties1 a few years ago there was invented by two officers of the ,german army1 ,lieutenants von ,siegsfeld and von ,parseval1 a captive balloon capable of resisting strong winds1 called1 from its action as a kite1 the ,drachen-,ballon or kite-balloon1 and which at the present time is being successfully used in the ,german ,army and ,navy for reconnoitring in all kinds of weather4 ,a smaller kite-balloon1 of #ggjj cubic feet capacity1 filled either with hydrogen or with illuminating gas1 was first used to lift meteorological instruments at ,strassburg in #ahih1 where it remained at a height of several hundred feet during twenty-four hours4 ,as is seen from ,fig4 #d1 the balloon is cylindrical1 with hemispherical ends1 and is attached to its cable like a kite1 so that the wind acts to lift and not to depress it4 ,the cylinder is divided by a diaphragm near its lower end into two chambers1 the upper and larger one being filled with gas1 while the lower chamber1 by means of a valve opening inwards1 receives the pressure of the wind which presses against the diaphragm1 and preserves the sausage-like form of the balloon in spite of leakage of gas4 ,another wind-bag encircling the bottom of the air-chamber serves as a rudder1 and lateral fins or wings give stability to the balloon about its longer axis4 ,the instruments are placed in a basket hung far below the balloon4 ,in cases where there is little or no wind at the ground1 captive balloons can render valuable service for meteorological observations1 but in all other cases kites are preferable4 ,the reasons for this assertion will be given when we consider kites4 ,from what has been said it will be perceived how much the ,germans did to advance scientific ballooning1 yet their constant rivals1 the ,french1 found a way to surpass them in the exploration of the atmosphere4 ,for several years the struggle for supremacy in the attainment of the greatest heights was keen between the scientific men of both countries1 but a truce was declared at ,paris in #ahif1 and since then both nations have worked together harmoniously4 ,the friendly meeting of ,french and ,german physicists at ,strassburg in #ahih to agree upon the details of co-operation1 typified the union of nations through science1 and while it is true that the atmosphere has no boundaries and cannot be pre-empted1 let us hope that the common aims of science will ultimately obliterate even political boundaries4 ,,chapter ,,iv ,,ballons-,,sondes ,,for ,,great ,,altitudes--,,the ,,international ,,ascents ,we have seen that the ascent of human beings to heights of six miles is attended with difficulty and danger1 and even with apparatus for supplying the life-sustaining oxygen1 man can hardly hope to reach much greater altitudes4 ,consequently1 to obtain information about the atmospheric strata lying above six miles1 that is to say1 those facts which require to be ascertained in the medium itself1 we must employ the so-called ballons-sondes1 carrying self-recording instruments but no observers4 ,this method1 which was proposed in ,copenhagen as long ago as #ahji1 was first put into execution by the ,french aeronauts1 ,hermite and ,besanon1 who1 it may be remarked1 suggested attempting to reach the ,north ,pole by balloon some time before ,andre announced his scheme4 ,a balloon is the best of anemometers1 since it takes the direction and speed of the currents in which it floats1 and hence it is customary1 before a manned balloon starts1 to dispatch several small pilot-balloons in order to judge of the direction and strength of the upper winds4 ,even if we do not know the height of the currents in which they float1 though this can be ascertained by measuring the height of the balloon trigonometrically or micrometrically1 we still obtain a general knowledge of the direction and speed of the currents4 ,with this idea1 ,m4 ,bonvallet in #ahia dispatched from ,amiens1 ,france1 ninety-seven paper balloons1 each provided with a postal card asking for the time and place of descent4 ,sixty of these cards were returned1 almost all the balloons having been carried east by the upper current1 ten going beyond one hundred and thirty miles1 and one travelling at a speed of almost one hundred miles an hour4 ,the next year the experiment was continued by ,,mm4 ,hermite and ,besanon with balloons of thirty-five cubic feet contents1 and about half of those dispatched from ,paris were recovered within a radius of one hundred miles4 ,the height to which the balloons could rise is determined by the following considerations3 to ascend #ah1jjj feet1 where the atmospheric pressure is one-half that at the earth 7see ,plate ,i471 the balloon when half full of gas must lift itself from the ground2 to rise #ce1jjj feet1 where the pressure is reduced to one-quarter1 it must be able to start upward when one-quarter filled1 and so on4 ,in practice the ascensional force usually diminishes at first from various causes1 such as the escape of gas1 its cooling1 and the deposit of moisture on the outside of the balloon4 ,to penetrate the clouds1 therefore1 it is necessary to have a considerable excess of ascensional force1 but above the clouds1 since the heating effect of the sun increases greatly with altitude1 the gas in the balloon is warmed much above the surrounding air1 and so the theoretical altitudes are exceeded4 ,having determined that balloons inflated with one hundred and fifty cubic feet of coal-gas would rise to great heights1 simple and light registering instruments1 as well as the postal cards1 were attached to them4 ,as the pressure diminished1 an aneroid barometer traced a line on a smoked glass1 and after the descent was placed under the receiver of an air-pump1 and the pressure required to reproduce the trace was measured by a manometer4 ,from this the height could be computed approximately4 ,the maximum and minimum thermometer was of the well-known ,u-form1 and instructions appended asked that it be read as soon as found4 ,a slow-match was arranged to detach postal cards successively1 so that if they were found and mailed1 the track of the balloon could be determined4 ,these balloons at first were called ballons perdus1 or lost balloons1 but when it was known that most of the fourteen balloons liberated from ,paris were recovered1 the name ballons explorateurs was given1 which was afterwards changed to ballons-sondes1 or sounding balloons4 ,the ,germans call them1 ,registrir-,ballons1 and in ,english they have been designated unmanned balloons also4 ,one of these paper balloons having reached a height of nearly #cj1jjj feet1 ,,mm4 ,hermite and ,besanon proceeded to construct a balloon of gold-beater's skin1 having a capacity of #cifj cubic feet1 in order to carry a better instrumental equipment4 ,the self-recording instruments made by the ,french firm of ,richard ,brothers were well adapted for this purpose1 and a combined barometer and thermometer1 registering in ink on an upright drum that is turned by clockwork inside1 is shown in ,fig4 #e4 ,the exhausted pair of boxes ,b of the barometer actuates the lower pen1 while the curved tube ,c1 which is filled with alcohol1 by its change of shape moves the upper pen and records the temperature4 ,from the indications of the barometer and the temperature of the mass of air1 it is possible by ,laplace's formula to calculate the height at any hour of the registration4 ,the balloon mentioned was the first of the so-called ,arophiles1 and when inflated with coal-gas it could lift seventy-seven pounds besides its own weight of forty pounds4 ,it carried two of the baro-thermographs described1 and a package of information cards arranged to be detached by a slow-match4 ,to mitigate the shock of striking the ground one of the instruments was hung by rubber cords inside a wicker basket that in the first ascent was not screened from the sun4 ,it was decided to liberate these balloons entirely filled with gas 7instead of partly full1 to allow for its expansion71 and to utilize all possible ascensional force at first rather than to weight the balloon with an automatic discharger of ballast 7,fig4 #f74 ,the trial of the ,arophile occurred ,march #ba1 #ahic1 and the next day one of the cards was returned announcing its fall in the department of the ,yonne1 where the balloon and the instruments were recovered injured4 ,from the blurred traces of the latter it was computed that at an altitude of about #di1jjj feet a temperature of -#fj ,fahrenheit had been met with1 both pressure and temperature being the lowest measured in a balloon up to that time4 ,although the data secured by this ascent were somewhat doubtful1 yet the feasibility of exploring the atmosphere by ballons-sondes was proved4 ,it was seen that the enormous velocity of ascent overcame the wind and permitted the path of the balloon to the summit of its trajectory to be followed1 the balloon appearing like a meteor visible in daylight1 and so its height could be calculated by trigonometrical measurements2 while the descent1 caused by the escape and cooling of the gas1 was gentle and regular1 permitting the delicate instruments to be recovered uninjured4 ,illustration3 ,,fig4 #e4--;,baro-thermograph of ,richard4 ,illustration3 ,,fig4 #f4--,the ,arophile rising4 ,the left-hand picture shows the deformation caused by the resistance of the air to its rapid ascent1 and the right-hand one the violent oscillations when first liberated4 ,the second ascent of this ,arophile was its last1 for1 after falling in the ,black ,forest1 it was burned by children4 ,however1 ,m4 ,besanon1 not discouraged1 constructed the ,arophile ,,ii4 of #fcjj cubic feet1 and improved the instruments as experience suggested4 ,the records had often been interrupted by freezing of the ink1 so the pen was replaced by a needle marking with less friction on smoked paper surrounding the record drum4 ,to avoid heating of the thermometers by the sun1 they were placed in a wicker cylinder open at both ends and covered with bright metallic paper4 ,this was hung below the balloon with its axis vertical1 in order that the draught through the cylinder when the balloon was rising or falling should counteract the insolation1 and in the next ascent1 at about the same altitude1 a temperature lower by #cf ,fahrenheit indicated the effect of the protection4 ,to secure an independent record of the lowest temperature an ingenious device was used1 consisting of a thermometer tube filled with alcohol and having black divisions4 ,the lowest point to which the alcohol sank was recorded on photographic paper placed behind the tube1 the whole being enclosed in a metallic box that was automatically closed on striking the ground1 and so was preserved against the meddling of curious persons4 ,up to the middle of #ahih ten voyages had been made by the ,arophiles1 which were now constructed of varnished silk to hold #af1jjj cubic feet of gas4 ,one of the objects sought was the collection of samples of air at great heights1 but this was not accomplished until recently4 ,in the first apparatus for this purpose1 an aneroid barometer at a predetermined pressure turned the cock communicating with an exhausted receiver that filled with air and was then closed4 ,the cock leaked1 so next the ingenious device of generating heat chemically to seal the glass tube was tried4 ,this1 too1 failed1 but finally1 an apparatus of ,m4 ,cailletet solved the problem4 ,it is advisable to control the height deduced from the barometric records by direct observations so long as the balloon remains visible1 and for this purpose micrometric measures were made with a telescope as soon as the balloon left the ground4 ,there was also used a species of registering theodolite which1 when kept pointed at the balloon1 automatically traced on paper its azimuth and angular altitude4 ,these records1 when combined with the barometric height at a known hour1 permitted the horizontal distance traversed1 and hence the velocity1 to be calculated1 or1 with two such instruments at ends of a base line1 the height of the balloon could be found4 ,the first experiments with ballons-sondes in ,france were soon repeated in ,germany1 where a balloon of rubber-fabric holding #hgjj cubic feet was obtained by the ,german ,society for the ,promotion of ,arial ,navigation4 ,when inflated with coal-gas it had a lifting force of about two hundred and ninety pounds1 in excess of its envelope1 etc41 weighing ninety-three pounds1 and the meteorological apparatus weighing six pounds4 ,the ,cirrus1 as it was called1 burst on its first trial1 but in ,july #ahid it made a remarkable voyage from ,berlin to the boundary of ,bosnia1 a distance of seven hundred miles1 at an average speed of sixty-two miles an hour4 ,a maximum height of #ed1jjj feet and a minimum temperature of -#fc ,fahrenheit were recorded4 ,the ,cirrus on its third voyage was accompanied by manned balloons in order to have simultaneous observations at different levels1 and this time it travelled eighty-three miles an hour and rose #fa1jjj feet4 ,the lowest temperature of -#hh ,fahrenheit was supposed to be too high1 for the reason that whereas the ventilation of the thermometers in a rapidly ascending or descending balloon might be sufficient to counteract solar radiation1 this would not be the case when the balloon was approaching its culminating point with a diminishing speed4 ,therefore1 ,dr4 ,assmann1 under whose supervision the ,german experiments were conducted1 employed the thermometer1 which in the captive balloon was aspirated electrically1 but now was driven by a weight1 and later1 because the ink froze1 the registration was made photographic4 ,the efficacy of the aspirator was seen in the ascent referred to1 for1 when its action stopped1 a higher temperature was recorded though the balloon continued to ascend4 ,in ,april #ahie the ,cirrus rose to the extraordinary height of #gb1jjj feet1 or more than thirteen and a quarter miles1 where the barometric pressure was reduced to one and a half inches of mercury4 7,in ,plate ,i4 this extreme and possibly excessive height is not shown as the height of the ballon-sonde1 but the average of the three highest ascents of the ,cirrus is indicated47 ,the comparative warmth 7-#ej ,fahrenheit7 recorded has led ,dr4 ,assmann himself to doubt the accuracy of the usual methods of registering temperature at such extremely low pressures4 ,plate ,,vii4 shows the heights in metres1 and the temperatures in degrees ,centigrade1 during eight voyages from ,berlin prior to ,june #ahig4 ,notwithstanding the rivalry and difference of opinion between the ,germans and ,french as to the methods of exploring the high atmosphere1 there was also a sincere desire to co-operate1 and the ,international ,meteorological ,conference which was held at ,paris in ,september #ahif furnished an opportunity to make the arrangements4 ,resolutions were adopted favouring ascents with manned balloons1 as well as simultaneous ascents of ballons-sondes in the different countries4 ,the successful use of kites at ,blue ,hill to lift self-recording instruments more than a mile into the air led to the wish that similar experiments should be tried elsewhere4 ,an ,international ,committee was appointed to carry out these resolutions1 of which ,professor ,hergesell of ,strassburg is president1 and the veteran ,parisian aeronaut and journalist1 ,wilfrid de ,fonvielle1 is secretary4 ,illustration3 ,,plate ,,vii4--,,heights ,,and ,,temperatures ,,recorded ,,in ,,eight ,,ascents ,,of ,,the ,,cirrus4 ,it was agreed to make a night ascent and to use identical instruments1 in order that the observations might be made everywhere under the same conditions4 ,accordingly1 on the early morning of ,november #ad1 #ahif1 five balloons manned by observers1 and three ballons-sondes with recording instruments1 were liberated in ,france1 ,germany1 and ,russia4 ,by means of the automatic diagrams from the ballons-sondes1 and the direct observations in the manned balloons1 it was sought to determine the decrease of temperature with height in vertical sections of the atmosphere connecting the various centres from which the balloons started4 ,seven such sections were available by connecting ,paris and ,strassburg1 ,berlin and ,st4 ,petersburg1 ,warsaw and ,munich1 etc41 but1 unfortunately1 observations in the highest strata were generally lacking4 ,three more international ascents were made during the year #ahig1 which were participated in less extensively4 ,at this time it was necessary to decide questions that had arisen1 and to make plans for the future1 consequently a meeting of the ,international ,committee was held at ,strassburg in #ahih4 ,many technical questions were settled1 but the chief result accomplished was the dissipation of misunderstandings and prejudices1 not only between ,french and ,germans1 but between the ,german representatives themselves1 for no doubt personal intercourse is the greatest good of such conferences4 ,although it was not a surprise1 nevertheless it was regretted that no one came from ,great ,britain1 where1 since ,glaisher's epoch-making balloon ascensions1 little has been done to explore the air4 ,the beneficial results of the ,conference were apparent at the fifth international ascent1 which occurred in the early morning of ,june #h1 #ahih4 ,austria and ,belgium joined ,germany1 ,france1 and ,russia1 and the field of atmospheric survey was extended over a good part of ,europe4 ,a veritable aeronautic fleet was launched from ,paris1 ,brussels1 ,berlin1 ,warsaw1 ,st4 ,petersburg1 ,strassburg1 ,munich1 and ,vienna1 consisting of twenty-one balloons1 of which thirteen carried observers1 who all used the aspiration thermometers1 and eight were equipped only with self-recording instruments4 ,some of the latter balloons reached altitudes of #ej1jjj feet1 and the former attained extreme heights of one-third this4 ,on the day selected the atmosphere was in a state of repose1 with light variable winds1 except high up1 where they blew1 as is usual1 from the west or south-west4 ,these observations were sufficiently numerous to form a synoptic chart at a considerable height above ,europe for comparison with the usual chart drawn from the surface observations4 ,besides the general work of the ,international ,committee1 special investigations have been undertaken by the ,french1 who formed an ,aerostatic ,commission in ,paris4 ,the services of the eminent physicists1 ,,mm4 ,cailletet and ,violle1 have been enlisted1 while a generous patron has been found in ,prince ,roland ,bonaparte4 ,the apparatus of ,m4 ,cailletet to bring down samples of air from the high regions may now be described4 ,when the balloon has reached its greatest height a cock of special construction1 turned by clockwork1 opens and allows the air to enter a reservoir in which a vacuum exists1 and then the cock is automatically and hermetically closed4 ,as it is known that the balloon reaches its extreme height in about an hour and a quarter1 the time of opening the cock is so regulated1 the closing taking place a little later by its further rotation4 ,in order to protect the moving parts from the extreme cold1 a receptacle filled with fused acetate of soda is placed in the box containing the motor1 so that1 notwithstanding the intense cold of the high regions1 this salt in assuming a crystalline state gives out enough heat during several hours at least4 ,during the ascent of an ,arophile air was collected at #ej1jjj feet1 which when analyzed by ,m4 ,mntz showed what was supposed1 viz4 that at this altitude the composition of the air does not differ much from that of the lower air4 ,the slight excess of carbonic acid found in the upper air might be due to the oxidation of the grease used on the cock1 and the smaller quantity of oxygen1 as compared with normal air1 might be caused by the absorption of this gas by the grease or even the absorption by the tinned sides of the copper reservoir4 ,by eliminating all possible sources of error in future ascensions1 ,m4 ,mntz thinks that it can be proved whether there are real differences in the air at different heights1 for the methods of analysis are to-day accurate enough to show such differences if they exist4 ,but since it is probable that in the regions which can be explored by the ballons-sondes1 the air undergoes the same mixing that renders the lower air nearly uniform1 only the smallest variations in its composition would naturally be found1 requiring minute precautions against errors4 ,this is no doubt why previous measures agreed in showing the invariable composition of the air at lower altitudes4 ,another important contribution of ,m4 ,cailletet is an apparatus for measuring the height of the balloon by photography in order to verify ,laplace's formula connecting the barometric pressure with the altitude4 ,the idea was to replace the observers on the ground1 who sometimes made the trigonometrical measurements of the balloon described1 by a photographic apparatus carried by the balloon itself1 and which at frequent intervals should photograph automatically the ground over which it passed1 at the same time that an aneroid barometer was photographed on the same sheet4 ,the apparatus is hung vertically below the balloon2 in the lower portion of the box is an objective which photographs the ground1 and in the upper portion is a second objective which photographs the face of an aneroid barometer placed at the proper distance above4 ,a clock-movement makes exposures every two minutes1 and a sensitive film unrolled between the objectives receives the images on each side4 ,if there are known1 the focal length of the objective1 the distance of two points on the ground1 and the distance of two points on the photograph1 a simple proportion permits the height of the balloon to be determined at that time1 and consequently1 from the barometric record1 the law connecting the pressure with height can be deduced4 ,the apparatus was successfully used in the voyage of a large balloon with observers1 and the accuracy of the determination of height was found to be within #a_/bej4 ,if the apparatus is to be used at great heights it would be necessary to protect the barometer and the camera from the very low temperatures4 ,besides the use for which it was designed1 this apparatus may serve to trace the route of a balloon and to determine the horizontal velocity at the different points of its path4 ,the exploration of the high atmosphere by ballons-sondes1 which can aid so many investigations1 has been utilized by ,m4 ,violle to obtain actinometric measures1 that is1 to determine the amount of heat given by the sun1 or what is called the solar constant4 ,this has been done on mountains with varying results1 due to the changing amount of atmospheric absorption4 ,in regions traversed by the balloon where the pressure of the air is reduced to a few inches of mercury1 where there is a complete absence of water-vapour1 and at heights to which terrestrial dust does not extend1 the measure of the quantity of heat sent by the sun towards the earth is freed from almost all the errors which we encounter on its surface4 ,the actinometer of ,m4 ,violle is1 in principle1 a sphere of copper1 blackened externally1 and having inside a thermometric apparatus which registers some distance away4 ,under the action of the solar rays the sphere is heated1 and assumes equilibrium when the loss by radiation and by contact with the air compensates for the gain by the absorption of the direct heat4 ,while at low levels the atmosphere also contributes to heat the sphere1 at great heights the sun shines from an almost black sky and alone heats the sphere4 ,since the balloon follows the wind the apparatus is protected from air currents which would otherwise introduce errors4 ,each twenty minutes a screen cuts off the solar rays from the sphere so that it cools to the temperature of the air1 which is also recorded4 ,on account of its weight this apparatus has not yet been carried by a ballon-sonde1 but it has operated successfully in a balloon with observers4 ,m4 ,teisserenc de ,bort1 who is actively engaged in exploring the air from a meteorological standpoint1 has constructed a very sensitive thermometer made of a blade of ,german silver set in a frame of nickel-steel that does not expand with heat4 ,this may be ventilated by a fan1 and1 while extremely sensitive to changes of temperature1 it is not affected by shocks1 and consequently is well adapted for use in ballons-sondes that pass rapidly through air-strata of varying temperature4 ,from this review of the development of the ballons-sondes it is evident that they offer possibilities of obtaining data in the high atmosphere1 perhaps up to fifteen miles or more1 which1 though subject to inaccuracies1 are of great interest to the physicist and astronomer4 ,the meteorologist is chiefly concerned with that portion of the atmosphere which lies within two or three miles of the earth1 and he requires1 moreover1 accurate measurements for his conclusions4 ,the new and most satisfactory way of obtaining these data is by kites1 and the remaining chapters will treat of this method of exploring the atmosphere and the results4 ,,chapter ,v ,,kites--,,history ,,and ,,application ,,to ,,meteorological ,,purposes ,,at ,,blue ,,hill ,,and ,,elsewhere ,kites are supposed to have been invented four hundred years before the ,christian era by ,archytas1 and at ,smyrna the flying of kites remains a national sport to this day4 ,we are told that two hundred years later1 a ,chinese general1 ,han ,sin1 employed kites as a means of communication with the garrison of a besieged town1 and there is a legend about their use in ,japan to dislodge and carry away a golden ornament from a tower4 ,whatever may be the truth of these stories1 we know that kite-flying in the ,malay ,archipelago1 in ,china1 and in ,japan1 has been a pastime for all classes during centuries1 and that the ,asiatic people have always been the expert kite-fliers of the world4 ,kites with tails seem to have been introduced into ,england about two hundred and fifty years ago1 and ,isaac ,newton when a school-boy made some improvements in them4 ,notwithstanding the fact that generations of boys have flown kites and so eminent a mathematician as ,euler investigated their theory1 until recently kites remained toys unsuited for practical purposes4 ,since the tailless kite has become a familiar object1 it has been said facetiously that kites lost their tails by the same process of evolution which deprived man of his caudal appendage2 but as kites without tails have been flown in ,asia for centuries1 the truth is that the tailed kites were the ones first brought to ,europe as playthings4 ,to-day in ,holland we see boys flying the ,english bow-kite and the common kite with crossed sticks1 both of which require tails1 and by the side of them tailless kites imported from the ,dutch colonies in ,java4 ,fig4 #g represents a kite from the east coast of ,java1 drawn from a model in a museum at ,amsterdam1 and also a drawing of a ,chinese bird-kite in the ,national ,museum at ,washington4 ,like most of the oriental kites1 they are made flat1 but when exposed to the wind the extremities of the wings1 which have a frame of split bamboo1 bend backward1 securing in this way the stability which in our common flat kite is gained by the action of the tail in lowering the centre of gravity and in maintaining the inclination to the wind4 ,illustration3 ,,fig4 #g4--,oriental tailless ,kites4 ,from historical researches that have been stimulated by the recent practical applications of kites1 it appears that their first use for scientific purposes was in #agdi1 when ,dr4 ,alexander ,wilson of ,glasgow1 and his pupil1 ,thomas ,melvill1 used kites to lift thermometers4 ,their kites1 from four to seven feet in height1 and covered with paper1 were fastened behind one another1 each kite taking up as much line as could be supported1 thereby allowing its companion to soar to an elevation proportionally higher4 ,it is related that the uppermost one ascended to an amazing height1 disappearing at times among the white summer clouds1 whilst all the rest1 in a series1 formed with it in the air below such a lofty scale1 and that too affected by such regular and conspiring motions1 as at once changed a boyish pastime into a spectacle which greatly interested every beholder4444 ,to obtain the information they wanted they contrived that thermometers1 properly secured1 and having bushy tassels of paper tied to them1 should be let fall at stated periods from some of the higher kites1 which was accomplished by the gradual singeing of a match-line4 ,how the thermometers were prevented from changing their readings while falling to the ground is not explained4 ,the account concludes3 ,when engaged in these experiments1 though now and then they communicated immediately with the clouds1 yet1 as this happened always in fine weather1 no symptoms whatever of an electrical nature came under their observation4 ,the sublime analysis of the thunderbolt1 and of the electricity of the atmosphere1 lay yet entirely undiscovered1 and was reserved two years longer for the sagacity of the celebrated ,dr4 ,franklin4 ,hence it seems that ,franklin's famous experiment of collecting the electricity of a thunder-cloud by means of a kite1 performed at ,philadelphia in #ageb1 was not its first scientific application1 and therefore ,america can claim only the later and most remarkable development of this means of exploring the air4 ,about #ahcg there existed in ,philadelphia an organization called the ,franklin ,kite ,club that flew kites for recreation4 ,espy1 the eminent meteorologist1 was a member1 and he states that on those days when columnar clouds form rapidly and numerously the kite was frequently carried upward nearly perpendicularly by columns of ascending air1 a phenomenon which is often observed to-day4 ,espy calculated the height at which clouds should form by the cooling of the air to its dew-point1 and then employed kites to verify his calculations of the heights of the clouds4 ,it will be remembered that both these methods are utilized in the measurements of cloud-heights at ,blue ,hill4 ,kites were employed to get temperatures a hundred or more feet above the ,arctic ocean early in the present century1 and in #ahdg ,w4 ,r4 ,birt flew a kite at ,kew ,observatory1 with which he hoped to obtain measures of temperature1 humidity1 wind velocity1 etc4 ,this kite1 hexagonal in shape1 required three divergent strings attached to the ground to keep it steady1 and the instruments were to be hoisted up to the kite by a pulley4 ,perhaps the first person to soar aloft on a kite was a lady1 who1 more than fifty years ago1 was lifted some hundred feet by a great kite constructed by ,george ,pocock1 an ,englishman1 to serve as an arial observatory in warfare1 and also to drag carriages along the ground4 ,it was proposed afterwards to make use of kites in shipwrecks to take persons or life-lines ashore1 and in #ahfe ,sir ,george ,nares invented a storm-kite1 so called1 with a tail made up of hollow cones4 ,this form of tail1 subsequently used for both kites and balloons1 is very efficient1 since it offers increasing resistance as the wind becomes stronger4 ,in #ahhb ,mr4 ,douglas ,archibald in ,england revived the use of kites for meteorological observations1 and outlined a comprehensive scheme of exploring the air with kites which included almost all that has been done since1 but his actual work1 performed during the next three years1 was limited to ascertaining the increase of wind velocity with height4 ,to do this1 he attached registering anemometers at four different points on the kite-wire1 but since the total wind movements only were registered from the time the anemometers left the ground until they returned1 it was impossible to obtain simultaneous records near the ground and at the kite1 as is done to-day4 ,still1 ,archibald got differential measurements of the velocity of the wind up to the height of #abjj feet4 ,the kites he employed were diamond-shaped1 covered with silk1 and were flown tandem1 with the hollow cones1 already mentioned1 attached to the tails4 ,although copper and iron wire had been used for flying kites many years before1 yet ,archibald was the first to substitute steel pianoforte wire for the string1 thereby increasing the strength while diminishing the weight1 size1 and cost of the line4 ,mr4 ,archibald in #ahhg took the first photograph from a kite1 a method which ,,mm4 ,batut and ,wenz developed in ,france1 and ,messrs4 ,eddy and ,woglom in the ,united ,states4 ,the subsequent progress of kite-flying for meteorological purposes has taken place in the last-named country1 and may be chronologically stated as follows3 in #ahhe ,mr4 ,alexander ,mc,adie 7later of the ,u4 ,s4 ,weather ,bureau7 repeated ,franklin's kite experiment on ,blue ,hill1 with the addition of an electrometer2 in #ahia1 and again in #ahib1 he measured simultaneously the electric potential at the base of ,blue ,hill1 on the hill1 and with kites as collectors several hundred feet above the hill-top1 about the same time that ,dr4 ,weber1 in ,breslau1 ,germany1 was making a more extensive use of kites for the same purpose4 ,it was no doubt ,william ,a4 ,eddy of ,bayonne1 ,n4 ,j41 who turned the attention of ,american scientific men to kite-flying1 and created the widespread interest in kites which exists to-day4 ,about #ahij ,mr4 ,eddy lifted thermometers with an ordinary kite1 but soon afterwards devised a tailless kite1 resembling the ,java kite except that the horizontal cross-piece is nearer the top of the vertical stick1 and its ends are bent backward in a bow and connected by a cord4 ,this kite starts upward on being held in the wind at the end of a taut line1 and continues to rise until the increasing wind-pressure on the portion above the cross-stick balances the pressure on the larger lower portion4 ,the kite is kept from falling to one side by the looseness of the covering on either side of the backbone1 and if there is more material on one side than on the other1 or if the covering is too tight to form pockets in the wind1 the kite requires a tail4#a #a ,a tail will prevent any kite from turning over1 or diving1 because its weight keeps the lower end down while the pressure of the wind on the tail also pulls the lower end backward and maintains the necessary angle of the kite to the wind1 the most efficient angle being about #bb degrees4 ,bending back the ends of the cross-stick gives stability to a kite because1 when1 on account of the eddies in the wind1 a stronger pressure is exerted on one side of the kite1 this side is driven backward1 thereby presenting less effective surface to the wind1 while as the other side comes forward more nearly at right angles to the wind1 it receives greater pressure than before4 ,in this way the equilibrium about the central stick is automatically maintained1 the required inclination to the wind being secured by the greater surface presented to the wind below the point of attachment of the bridle4 ,in #ahia ,mr4 ,eddy lifted a minimum thermometer by several of these kites flown tandem1 and proposed to obtain in this way data to forecast the weather4 ,in the ,proceedings of the ,aeronautical ,conference1 held in connection with the ,chicago ,exposition1 ,prof4 ,m4 ,w4 ,harrington1 then ,chief of the ,u4 ,s4 ,weather ,bureau1 quoted ,mr4 ,eddy's estimate of the cost of exploring the air by means of kites flown in series1 and advocated their use4 ,up to this time it does not appear that self-recording instruments--that is to say1 those which make continuous graphic records--had been raised by kites4 ,in the days of the early experimenters such instruments were too heavy and cumbersome to be lifted by the more or less unmanageable kites1 but within the past few years ,m4 ,richard of ,paris has made the simple and light recording instruments described in connection with balloons1 which can be attached to kites4 ,in this way it is possible to obtain simultaneous records at the kite and at a station on the ground1 and from them to study the differences of temperature and humidity1 and this seems to have been done first at ,blue ,hill ,observatory4 ,in ,august #ahid ,mr4 ,eddy brought his kites to ,blue ,hill and with them lifted a ,richard thermograph1 which had been partly reconstructed of aluminium by ,mr4 ,fergusson so that it weighed but #a-a_/d lbs41 to the height of #aejj feet1 and so the earliest automatic record of temperature was obtained by a kite4 ,during the next summer1 ,mr4 ,eddy assisted again in the experiments at ,blue ,hill1 and secured photographs of the ,observatory and the hill by a camera carried between his kites to the height of a hundred feet or more4 ,now that the possibility of lifting self-recording meteorological instruments to considerable heights had been demonstrated1 an investigation of the thermal and hygrometric conditions of the free air was undertaken by the staff of the ,blue ,hill ,observatory1 who had already made an investigation of the movements of the clouds by the methods described in the second chapter4 ,the development of the kite and its accessory apparatus1 and the acquisition of the knowledge how to use them1 required much time1 and resulted in the damage or loss of many kites4 ,two meteorographs1 as the combination of two or more self-recording instruments is called1 were dropped from a great height and no trace of them was found4 ,when1 however1 by the breaking of the line both kites and instrument are carried away1 the kites act as a parachute and bear the instrument gently to the ground1 where both are usually recovered uninjured2 to facilitate their return should they fall at a distance1 the name and address are marked on each4 ,it would be tedious to relate the ups and downs of scientific kite-flying at ,blue ,hill before the wind was successfully harnessed to the service of science1 and the kites were prevented from kicking over the traces1 or from breaking away1 so only a brief account of the progress of the work will be given1 and then the methods at present used will be described4 ,at first the ,eddy1 or ,malay kites1 as they are also called1 covered with paper or with varnished cloth1 were coupled tandem to secure greater safety and lifting power4 ,the principle of attaching kites at several points on the line was early adopted at ,blue ,hill1 for although it can be demonstrated theoretically that a greater height is possible by concentrating all the pull at the end of the line1 yet in the case of a line which is not infinitely strong the best results are got by distributing the pull1 and in this way1 too1 kites can be added as the wind conditions aloft warrant4 ,to obviate the frequent breaking of the bowed cross-piece1 ,mr4 ,fergusson made it in two pieces1 each being held in a metal socket on the central stick1 the two pieces forming a dihedral angle towards the wind4 ,it had the advantage also of being readily taken apart for transportation4 ,this kite1 shown in ,fig4 #h1 flew at a high angle above the horizon and through a considerable range of wind velocity1 but it could not be kept permanently in balance1 or made to adjust itself to great variations in wind velocity1 and therefore it was discarded4 ,the first meteorograph1 a combined recording thermometer and barometer 7from which the height can be calculated71 was constructed by ,mr4 ,fergusson in ,august #ahie1 and three months later he united a recording anemometer to the thermometer1 which was probably the first apparatus of this kind to be attached to kites4 ,a meteorograph1 recording the atmospheric pressure1 air temperature1 and relative humidity1 was ordered from ,m4 ,richard of ,paris in #ahie1 like one already carried by ,french aeronauts1 except that1 since for kites lightness is all-essential1 ,m4 ,richard constructed this triple-recorder for the first time of aluminium1 and hereby reduced its weight to #b-d_/e lbs4 ,illustration3 ,,fig4 #h4--;,eddy tailless ,kite4 ,illustration3 ,,fig4 #i4--;,hargrave ,kite4 ,one of these meteorographs was hung to a ring at the point of attachment of the two kite-lines to the main line1 a method which was used until recently4 ,in ,august #ahie1 besides the ,eddy kites1 there was first used the cellular or box kite1 invented by ,lawrence ,hargrave of ,sydney1 ,australia1 which bears no resemblance to the conventional forms of kites and which it would not be supposed could fly4 ,as seen from ,fig4 #i its appearance is that of two light boxes without tops or bottoms1 fastened some distance above each other4 ,the wind exerts its lifting force chiefly upon the front and rear sides of the top box1 the lower box1 which inclines to the rear1 and so receives less pressure1 preserving the balance4 ,the ends of the boxes1 being in line with the wind1 keep the kite steady and serve the purpose of the dihedral angle in the ,malay kite4 ,the ,japanese are said to fly a single box1 which is the prototype of the ,hargrave double cell4 ,at the present time some form of the ,hargrave kite is generally employed for scientific purposes4 ,on account of the weight of the large cord necessary to control these kites1 and the surface which it presented to the wind1 a height of #bjjj feet could not be reached1 so1 during the winter of #ahie-f1 following ,archibald's example and the methods of deep-sea sounding employed by ,captain ,sigsbee1 ,u4 ,s4 ,n41 steel pianoforte wire was substituted for the cord4 ,this wire is less than half as heavy1 and less than one-fourth the size of cord having the same strength1 and1 moreover1 its surface is polished1 which reduces the friction of the wind blowing past it4 ,with the wire the height of a mile was reached in ,july1 and a mile and two-thirds above ,blue ,hill in ,october #ahif4 ,up to this time a reel turned by two men sufficed to draw down the kites1 but the increasing pull and length of wire made recourse to steam-power necessary4 ,in ,january #ahig a grant of money was allotted from the ,hodgkins ,fund of the ,smithsonian ,institution for the purpose of obtaining meteorological records at heights exceeding ten thousand feet1 and no doubt the first application of steam to kite-flying was the winch built by ,mr4 ,fergusson with ingenious devices for distributing1 oiling1 and measuring the length of wire4 ,the cumulative pressure of the successive coils of wire finally crushed the drum1 and the next apparatus applied the principle of ,sir ,william ,thomson's deep-sea sounding apparatus1 in which there is no accumulation of pressure4 ,in ,october #ahig records were brought down from eleven thousand feet1 or a thousand feet above the prescribed height4 ,the kites and apparatus at present employed at ,blue ,hill will now be described4 ,the kites are all of the multiplane type1 and mostly of ,hargrave's construction with two rectangular cells4 ,these cells are covered with cloth or silk1 except at their tops and bottoms1 and one is secured above the other by four or more sticks4 ,the wooden frames are as light as possible1 but are made rigid by guys of steel wire that bind them in all directions4 ,the average weight is about two ounces a square foot of lifting surface1 which is about the same weight a square foot as the ,eddy kites when all the surface is included in the estimate4 ,the largest of the ,hargrave kites stands nine feet high1 weighs eleven pounds1 and contains ninety square feet of lifting surface1 which in the recent kites is arched1 resembling the curvature of a bird's wings1 a construction that was proposed many years ago by ,phillips 7,fig4 #aj74 ,these curved surfaces increase the lift1 or upward pull1 more than the drift1 or motion to leeward1 and so the angular elevation is augmented without materially adding to the total pull on the wire1 which should not exceed one-half its breaking strength4 ,illustration3 ,,fig4 #aj4--,modified ,hargrave ,kite at ,blue ,hill4 ,perhaps the most important factor in the success of the ,blue ,hill work was the invention by ,mr4 ,clayton of the regulating bridle which is applied to every kite4 ,an elastic cord is inserted in the lower part of the bridle1 to which the flying-line is attached1 and when the wind-pressure increases this cord stretches1 and causes the kite to diminish its angle of incidence to the wind until the gust subsides4 ,a kite can be set to pull only a fixed amount in the strongest wind1 when the kite will fly nearly horizontal4 ,we are therefore able to calculate the greatest pull which can be exerted on the wire by all the kites4 ,with this device the kites have flown through gales of fifty or sixty miles an hour without breaking loose or injuring themselves4 ,another efficient kite which has been used at ,blue ,hill is the so-called aero-curve kite made by ,mr4 ,c4 ,h4 ,lamson of ,portland1 ,maine4 ,as is seen from ,fig4 #aa1 this kite resembles a soaring bird1 and it can be taken apart and folded up for storage or transportation4 ,in general1 the angle of the flying lines of the ,blue ,hill kites is #ej or #fj above the horizon1 and in winds of twenty miles an hour the pull on the line is about one pound for each square foot of lifting surface in the kite4 ,kites can be raised in a wind that blows more than twelve miles an hour at the ground1 and as the average velocity of the wind for the year on ,blue ,hill is eighteen miles an hour1 the days are few when kites will not fly there4 ,illustration3 ,,fig4 #aa4--,lamson's ,aero-curve ,kite4 ,the wire to which the kites are attached is steel music-wire1 #cb_/ajjj of an inch in diameter1 weighing fifteen pounds a mile1 and capable of withstanding a pull of three hundred pounds4 ,the wire is spliced in lengths of more than a mile with the greatest care1 special pains being taken that no sharp bends or rust-spots occur which would cause it to break4 ,to lift the increasing weight of wire1 kites are attached at intervals of a few thousand feet1 so that the angle may be maintained as high as is consistent with a safe pull1 and this is done by screwing on the wire aluminium clamps1 to which the kite-lines are fastened4 ,on account of the greater stability and strength of the new kites1 the meteorograph is suspended directly from the top kite4 ,the ,richard meteorograph1 contained in an aluminium cage of about a foot cube1 weighs less than three pounds1 and it is only necessary to screen the thermometer from the sun's rays to obtain the true temperature of the air1 since the wind insures a circulation of air around the thermometer4 ,another meteorograph1 constructed by ,mr4 ,fergusson1 records the velocity of the wind in addition to the three other elements1 and it weighs no more than the ,french instrument4 ,the reeling apparatus is an example of how the same apparatus may serve diametrically opposite purposes4 ,in sounding the deep sea the wire must be pulled upwards1 whereas in sounding the heights of the atmosphere the wire must be pulled in the reverse direction4 ,therefore the deep-sea sounding apparatus has been altered by ,mr4 ,fergusson to pull obliquely downwards1 the wire passing over a swivelling pulley which follows its direction and registers on a dial the exact length unreeled4 ,next the wire bears against a pulley carried by a strong spiral spring1 by which the pull upon it at all times is recorded on a paper-covered drum turned by clockwork4 ,the wire passes now several times around a strain-pulley1 and finally is coiled under slight tension upon a large storage-drum4 ,when the kites are to be pulled down1 the strain-pulley is connected with a two-horse-power steam-engine1 and the wire is drawn in at a speed of from three to six miles an hour2 but when the kites are rising the belt is removed1 and the pull of the kites unreels the wire4 ,illustration3 ,,fig4 #ab4--,meteorograph lifted by ,kites at ,blue ,hill4 ,the method of making a kite-flight for meteorological purposes at ,blue ,hill is as follows3 a kite1 fastened by a long wire to the ring in the main wire1 being in the air1 and the meteorograph suspended1 another kite is attached to the ring by a shorter cord 7,fig4 #ab74 ,they are then allowed to rise1 and to unreel the wire1 until its angle with the horizon becomes low1 when1 by means of the clamps described1 other kites are added1 the number depending on the size of the kites and the strength of the wind4 ,after a pause at the highest attainable altitude1 the winch is connected with the steam-engine and the kites are drawn down4 ,the pauses at the highest point1 and when kites are attached or detached1 are necessary to allow the recording instruments to acquire the conditions of the surrounding air2 and because at these times the meteorograph is nearly stationary1 measurements of its angular elevation are made with a surveyor's transit1 while observations of azimuth give the direction of the wind at the different heights4 ,the time of making each angular measurement is noted1 so that the corresponding point on the trace of the meteorograph may be found4 ,from the length of the wire and its vertical angle1 the height of the meteorograph can be calculated1 it having been found that the sag of the wire1 or its deviation either in a vertical or a horizontal plane from the straight line joining the kite and the reel1 does not cause an error exceeding three per cent4 in the height so computed4 ,when the meteorograph is hidden by clouds1 the height above the last point trigonometrically determined is computed from the barometer record by ,laplace's formula4 ,at night there is only the barometer from which to determine the height2 for although an attempt was made to use a lantern to sight upon1 yet it soon became invisible1 or1 when seen1 was confounded with the stars4 ,before and after the flight the meteorograph is hung upon a tripod in the free air1 in order that its thermometer and hygrometer may be compared with the standards4 ,,heights ,,above ,,sea-,,level ,,of ,,kite-,,flights4 7,blue ,hill is #fcj feet above the sea7 ---------------------------------------- --------------------------- ,no4,heights in ,feet ,percentages of ,records above ,year of ---------------------------------------- -------------- ,rec-,mean of,absolute #ejj m4 #ajjj m4 #aejj m4 #bjjj m4 #cjjj m4 ords,maximum,maximum 7#afdj 7#cbhj 7#dibj 7#fefj 7#ihdj ft47 ft47 ft47 ft47 ft47 ---------------------------------------- ---------------------- #ahid #b #a1hfj #b1jgj #ej #j #j #j #j #ahie #bh #a1fgc #b1dij #ei #j #j #j #j #ahif #hf #b1ggb #i1cbg #gh #bh #i #d #j #ahig #ch #d1eeg #aa1gaf #ie #fh #de #ba #e #ahih #ce #g1cej #ab1jgj #ajj #ib #hj #ff #bj ---------------------------------------- ---------------------- ,since the use of wire and more efficient kites1 the heights have been greatly increased4 ,thus the average height above the hill attained by the meteorograph in thirty-five flights made during #ahih was more than a mile and a quarter1 whereas the average height of all the ascents prior to #ahig was about a quarter of a mile 7see ,table74 ,the average height of the meteorograph above the hill1 in all the flights during ,august #ahih1 was nearly a mile and a half1 and on ,august #bf the meteorograph was raised #cfj feet higher than ever before1 its altitude1 determined trigonometrically1 being #aa1ddj feet above ,blue ,hill1 or #ab1jgj feet above the neighbouring ocean4 ,the meteorograph was suspended from the topmost kite1 one of the ,lamson pattern1 having #ga square feet of lifting surface1 and this was increased to a total of #adi square feet by four kites of the modified ,hargrave type1 that were attached at intervals to the wire4 ,the five miles of wire in the air weighed #ge lbs41 and the total weight including kites and apparatus was #aab lbs4 ,the meteorograph left the ground at #aj3dj a4m41 attained its greatest height at #d3ae p4m41 and returned to the ground at #h3dj p4m41 a feat which it would be difficult for a man to equal on a mountain4 ,the cumulus clouds were traversed three-quarters of a mile from the earth1 and above them the air was found to be very dry4 ,on the hill the air temperature was #gb1 when it was #ch in the free air #aa1ddj feet above1 and the wind velocity increased from twenty-two to forty miles an hour4 ,these figures give an idea of the change of atmospheric conditions which occurs1 but the conclusions deduced from the ,blue ,hill kite-flights will be discussed in the next chapter4 ,however1 the phenomena of atmospheric electricity1 which have become noticeable since the use of wire1 may be described here4 ,generally1 whenever the kites rise above seventeen hundred feet1 the wire becomes strongly charged with electricity1 and when the great heights are reached the electricity is discharged in long and brilliant sparks at the reel1 often to the inconvenience of the attendants4 ,usually1 the electrical potential increases with altitude1 and it is greatest during snow-storms or when the conditions favour thunder-storms4 ,notwithstanding its intensity1 the quantity of electricity in the atmosphere is probably insufficient to make its collection and storage for practical purposes worth while4 ,it must not be imagined that kite-flying for meteorological purposes is a sinecure4 ,at ,blue ,hill about two hundred flights have been made in all seasons and in all weathers1 with temperatures varying from -#e to #ij1 in gales1 in rain1 and in snow-storms1 though not in thunder-storms4 ,sometimes the kites are invisible from almost the time they leave the earth until their return1 but when the upper kites are visible it is necessary to observe them with theodolites every few minutes4 ,remembering that a high flight occupies ten or twelve hours1 and frequently terminates late at night1 or even continues until morning1 it will be obvious that the work requires skill1 energy1 and perseverance1 which have been shown by my assistants at the ,blue ,hill ,observatory who have conducted the flights4 ,occasionally1 for lack of wind or from breakage of the line1 the kites fall to the ground1 usually intact4 ,if they were visible1 trigonometrical measurements on the hill enable the place of descent to be located1 and then the kites and meteorograph are sent for and the wire is reeled up4 ,but at night1 or when clouds hide the kites1 the direction in which they fall is not known1 because the azimuth of the wire at the reel often differs from that of the kites2 so last autumn several hundred miles of road1 path1 wood1 and swamp were traversed before the arial apparatus1 which had been lost during a flight at night1 was found comparatively close at hand4 ,from what has been said it will be evident that a former toy has been proved to be of the greatest importance for meteorological investigation at the ,blue ,hill ,observatory4 ,on account of the success there attained it is coming into use elsewhere for meteorological observations4 ,in #ahih the ,united ,states ,weather ,bureau created seventeen kite stations1 chiefly in the ,mississippi ,valley1 with the intention of obtaining data every day1 at the height of a mile or more1 with which to plot a synoptic weather map similar to the map that is now drawn from the data at the ground4 ,from a knowledge of the weather conditions prevailing simultaneously in the upper and lower air1 it was expected that the weather forecasts could be improved1 but unfortunately1 on account of the light winds during the summer1 it was impossible to make enough simultaneous kite-flights to construct the upper-air map1 and therefore the scheme was abandoned4 ,however1 the data obtained will no doubt furnish valuable information about the vertical temperature gradient1 etc41 in various conditions of weather4 ,the chief meteorological bureaus of ,germany and ,russia are equipping stations with kites and balloons1 and ,m4 ,teisserenc de ,bort1 who has provided his private observatory near ,paris with kite apparatus of the ,blue ,hill type1 has already reached high altitudes4 ,in ,scotland too1 which was the birthplace of scientific kite-flying1 experiments have been resumed by a ,scotchman and an ,american--a happy union of forces4 ,from these preparations it appears that the resolution of the ,international ,aeronautical ,conference1 recommending that all central observatories should employ this method of investigation as being of prime importance for the advancement of meteorological knowledge1 is being carried out1 and seems likely to produce important results4 ,,chapter ,,vi ,,results ,,of ,,the ,,kite-,,flights ,,at ,,blue ,,hill--,,future ,,work ,kites possess several advantages over other methods of exploring the air up to heights of at least #ab1jjj feet whenever there is wind1 but their chief merit is1 that with them the true conditions of the air may be ascertained4 ,the disadvantages of other methods of exploring the air1 as compared with kites1 are these3 #a4 ,mountains not only affect by contact the adjacent air1 but by deflecting the air-currents cause mixture and ascent1 which give conditions differing widely from those of the free air4 #b4 ,free ,balloons are more or less surrounded by heated or stagnant air1 because they drift with the wind1 and on account of the sluggishness of the thermometers1 the temperatures observed at a given height in a balloon are generally higher during the ascent1 i4e4 when passing from warm to cold air1 than during the descent1 when the conditions are reversed4 ,again1 it is not possible to study the progressive changes in the atmospheric conditions at one place1 because observations in a drifting balloon are not comparable with simultaneous ones made at a station on the ground below4 ,with kites1 however1 the possibility of making frequent and nearly vertical ascents and descents permits observations to be obtained almost simultaneously in superincumbent strata of air4 ,the height of the kite can usually be determined with an accuracy not attainable by the barometer in a balloon4 #c4 ,captive ,balloons1 although constructed so as not to be driven down by wind1 cannot rise nearly so high as kites on account of the weight and resistance of the cable necessary to control them1 and even the ,german kite-balloon1 on account of its large surface1 would hardly withstand the strong winds in which kites can fly4 #d4 ,the ,cost of installing and operating either mountain stations or balloons is much greater than for kites4 ,the exploration of the lower two miles of air with kites flown from ,blue ,hill is no doubt the most complete ever made at one place4 ,nearly two hundred records have been obtained in all kinds of weather conditions1 and the progressive attainment of greater and greater heights is shown in the table in the preceding chapter4 ,the records from the flights have been discussed by ,mr4 ,clayton2 those until ,february #ahig1 with the ,blue ,hill ,observations1 in ,vol4 xlii41 ,part ,i41 of the ,annals of the ,astronomical ,observatory of ,harvard ,college1 and later records in two ,bulletins of the ,blue ,hill ,observatory1 in which the changes of temperature and humidity with height1 and their relation to the positions of cyclones and anti-cyclones1 are investigated4 ,the use of kites for weather predicting1 as was said1 has been tried by the ,united ,states ,weather ,bureau1 but it is certain that further studies1 such as have been made on ,blue ,hill1 are necessary before the sequence of the conditions at the earth's surface to the phenomena observed in the upper air is definitely known1 so that the latter can be utilized in forecasting4 ,some of the deductions from the observations with kites at ,blue ,hill follow4 ,plate ,,viii4 is a facsimile of the record of the baro-thermo-hygrograph during two flights on ,october #h1 #ahif1 when for the first time the height of a mile and a half was attained4 ,the record-sheet1 it may be said1 is wrapped around a cylinder that turns on its axis in twelve hours1 and the curved lines in each of the three horizontal sections divide them into quarter hours4 ,the lower section contains the trace of the barometer1 the horizontal lines being the heights in metres and feet that correspond to the barometric pressure with a temperature of #cb ,fahrenheit2 in the middle section is the trace of the hygrometer on a scale of relative humidity in percentages1 and in the upper section is the trace of the thermometer on a scale of temperatures in ,fahrenheit and ,centigrade degrees4 ,it will be observed that the record of the barometer is reversed1 i4e4 the trace rises for falling pressure1 and in the second flight when the unexpected height of #hfig feet above ,blue ,hill was reached1 the limit of the altitude scale was exceeded4 ,illustration3 ,,plate ,,viii4--,,meteorogram ,,from ,,the ,,kite-,,flight ,,of ,,oct4 #h1 #ahif1 ,,at ,,blue ,,hill4 ,in order to study the changes of these elements with height during the higher flight1 in ,plate ,,ix41 ,figs4 #d and #e1 the temperature and humidity of the automatic record are plotted as absciss1 with the heights above sea-level in metres as ordinates4 ,for those not familiar with this unit of length1 it may be said that #ajj metres are about #ccj feet1 and that #afjj metres equal one mile approximately4 ,when the meteorograph was ascending1 dots indicate the recorded temperatures and humidities1 which are each connected respectively by continuous lines2 when the meteorograph was descending1 crosses indicate the observations1 which are connected by broken lines4 ,lines inclining upwards to the left indicate decreasing temperature and humidity with increase of height1 and lines inclining to the right increasing temperature and humidity with height4 ,the straight dotted lines show the adiabatic decrease of temperature for ascending dry air4 ,the ascent was made during the warmest part of the day1 and the descent for the most part after sunset4 ,the two branches of the temperature-lines typify the temperature change with height which usually occurs in fair weather during the day and the night respectively4 ,the continuous line1 representing the day observations1 shows a uniform fall of temperature at the adiabatic rate to the cloud level4 ,during the night1 the lower part of the broken line bends decidedly to the left1 showing a body of relatively cold air near the ground1 caused by radiation4 ,there is a rise of temperature with increasing altitude above the ground up to a certain height1 and afterwards a comparatively uniform fall as high as the clouds1 if they exist2 but the rate of fall with increasing altitude1 shown by the upper part of the diagram1 is slower at night than during the day4 ,it appears that the diurnal change of temperature is very small at great altitudes1 compared with the change near the earth's surface4 ,the relative humidity 7,fig4 #e7 up to #bjjj metres varies inversely with the temperature1 and in the present case there was only a slight change in the direction of the wind 7,fig4 #f74 ,illustration3 ,,plate ,,ix4--,,mean ,,changes ,,with ,,height1 ,,and ,,changes ,,during ,,the ,,kite-,,flight ,,of ,,oct4 #h1 #ahif4 ,diurnal ,changes of ,temperature at ,different ,altitudes4--,the curve representing the diurnal change in the air at some distance above the ground is probably similar to one representing the change near the ground1 except that its amplitude is less4 ,if this be true1 then the diurnal rate of fall for a given time at any two levels will be proportional to the daily ranges of temperature at the two levels4 ,it is impossible in practice to keep a kite at exactly the same level for twenty-four hours2 hence the daily ranges for the different levels must be found by comparing the rates of rise or fall of temperature for given times with the rates found from records near the ground1 made simultaneously with those above4 ,in ,plate ,,ix41 ,fig4 #a1 the results for six stations1 i4e4 the kite at #ajjj and #ejj metres1 the ,eiffel ,tower in ,paris 7#cjj metres71 the summit of ,blue ,hill1 its base1 and the valley 7#bjj1 #ej1 and #ae metres respectively71 are connected1 and a smooth curve is drawn through them4 ,the curve passes approximately through every one of the observed and the computed ranges1 except the one at the summit of ,blue ,hill1 which is too great4 ,this evidently is because insolation and radiation1 acting through the soil of the hill1 heat and cool the air to a greater extent than the free air is heated and cooled at the same altitude1 and this must be true at every mountain station4 ,the smoothed curve passes also very slightly to the left of the data for the ,eiffel ,tower1 indicating that the range there is about #a greater than the true range on account of the heating and cooling of the ,tower4 ,from this it appears that the diurnal range of temperature diminishes rapidly with increasing altitude in the free air1 and almost disappears in the average at a height of #ajjj metres4 ,the records of the anemometer show that1 as a rule1 the wind increases steadily as the kites rise1 but the increase is greatest between ,boston and the top of ,blue ,hill1 due probably to the retarding of the lower winds by contact with the ground4 ,the results are plotted in ,plate ,,ix41 ,fig4 #c1 together with the mean wind velocity on ,blue ,hill 7#bji metres71 and the velocity on a tower in ,boston 7#fj metres74 ,single records of the kite-anemometer differ much1 for sometimes the wind velocity diminished with altitude1 and at other times it increased so rapidly that the kites were unable to rise higher4 ,on several occasions when the kites passed from one current into another1 having a different direction and a different temperature1 the wind suddenly increased1 and was stronger between the two currents than above or below that plane4 ,diurnal ,changes of ,humidity at ,different ,altitudes4--,it is found that as night approaches the humidity at the altitude of #ajjj metres diminishes1 while at the earth it increases4 ,this agrees with the evidence furnished by the cumulus clouds that form during the day between #ajjj and #bjjj metres1 and disappear at night1 thus visibly indicating an increase of humidity by day and a decrease by night4 ,if the trend of the humidity-curve at a height of #ajjj metres is assumed to be the reverse of its trend at the ground1 then the results from the kite-meteorograph show the minimum humidity to be at the coldest and the maximum humidity at the warmest part of the day4 ,the mean daily ranges for different altitudes are plotted in ,plate ,,ix41 ,fig4 #b4 ,the part of the curve at the left of the zero line shows the range at different altitudes1 with the minimum humidity near the warmest time of day1 while the part at the right of the zero shows the ranges at different altitudes1 with the minimum humidity at the coldest time of day4 ,types of ,change of ,temperature with ,altitude4--,when the records of temperature and humidity made aloft by the kite-meteorograph and at the stations near the ground are plotted in relation to altitude1 they are found to be easily divisible into a few types4 ,in ,plate ,x41 ,type #a represents the decrease of temperature on most fair days from the ground to altitudes of a mile or more1 when no clouds are met4 ,the continuous line1 plotted from the records of the ascent1 represents the day conditions1 and the broken line1 plotted from the records of the descent1 represents the night conditions4 ,this curve shows that with increasing altitude the temperature falls uniformly during the day and approximately at the adiabatic rate represented by the dotted lines4 ,the fall of temperature with increasing altitude during the night is slower than during the day1 and in fact1 from the earth's surface to an altitude of a few hundred metres1 there is often a rise of temperature with height1 so that the air at altitudes of from #cjj to #ejj metres may be considerably warmer than it is at the ground4 ,this was shown in the descent on ,october #h1 #ahif1 and is found in ,type #c4 ,illustration3 ,,plate ,x4--,,changes ,,with ,,height ,,recorded ,,by ,,kites ,,at ,,blue ,,hill4 ,when clouds are traversed during the flight1 the temperature curve assumes the form of ,type #b4 ,the continuous curve is plotted from the records of an ascent2 the broken curve from the records of the descent1 both occurring in the day-time4 ,the temperature falls at the adiabatic rate in unsaturated air till the base of the cumulus cloud is reached4 ,it falls at a slower rate in the cloud1 the rate probably being that computed by physicists as the adiabatic rate for air in which condensation is taking place4 ,above the clouds1 the fall of temperature appears to be very slow4 ,type #c is a condition which persists throughout the day and night1 and it resembles the night form of ,type #a4 ,the temperature rises very rapidly for a short distance above the ground and then falls1 with increase of height1 somewhat slower than the adiabatic rate4 ,the rise of temperature near the ground with increasing height is more marked after sunset than during the day-time4 ,type #d was illustrated by the ascent of ,october #h4 ,this distribution of temperature is caused by a warmer current overflowing colder air1 which is very commonly found at low altitudes in the atmosphere and probably exists usually at some altitude1 great or small4 ,recent observations indicate that this type represents the normal condition of the atmosphere in all sorts of weather4 ,frequently there are two or more sudden rises of temperature at different heights1 so that the plotted data resemble inverted stair-steps4 ,during the day there is a decrease of temperature at the adiabatic rate 7#ah in #ajj metres7 from the ground to the height of several hundred metres1 then a sudden rise of temperature in the next one or two hundred metres1 and above this a slow fall of temperature with increasing altitude1 usually much less than the adiabatic rate4 ,generally1 clouds are found near the plane of meeting of the warm and cold current4 ,the reverse of ,type #d1 that is1 a sudden fall of temperature1 due to a colder current overlying a warmer one1 is probably impossible1 because the colder air1 on account of its greater weight1 would immediately begin to sink and the warmer air would rise4 ,this should cause a fall of temperature at the adiabatic rate from the ground to the top of the colder current1 and is probably the origin of the cold wave shown in ,type #e4 ,both the continuous and broken curves 7representing an ascent and a descent7 show a fall of temperature at the adiabatic rate of unsaturated air1 from about #ejj metres to the highest point reached4 ,up to #ejj metres the decrease of temperature is more rapid than the adiabatic rate1 due to the rapid moving in of colder air above1 whereby air rising from the ground is cooled by contact as well as by its expansion1 and also because the air is heated more than usual by contact with the ground1 which under these conditions is abnormally warmer4 ,this is the special characteristic of the cold wave type of curve during the day hours4 ,the night form of ,type #e1 notwithstanding the excessive radiation from the ground through the dry air1 shows a rapid decrease of temperature with increase of altitude from the ground upward4 ,type #f shows a less common1 but an interesting form1 of vertical distribution of temperature1 in which the temperature is about the same from #djj metres to #adjj metres or more4 ,up to #djj metres there is a fall of temperature with increasing altitude during the day1 and a rise with increasing altitude at night4 ,these last conditions can be readily traced to the effects of insolation and radiation near the ground4 ,in the morning1 if the temperature of the air be the same from the ground up to #ajjj metres or more1 the heating of the ground by the sun will cause ascending currents1 until the warmest part of the day4 ,this air1 cooling by expansion at the adiabatic rate1 will rise to about #ddj metres before it assumes the mean temperature of the upper air column4 ,at night cooling takes place next the ground by radiation and is gradually transferred upward a few hundred metres by conduction1 thus producing an increasing temperature with increasing altitude1 until sunrise4 ,as a result of the conditions described1 it is evident that on certain days the diurnal range of temperature is but little felt above #ejj metres4 ,types of ,change of ,relative ,humidity with ,altitude4--,as in the temperature types1 the continuous lines represent the records of the ascent1 and the broken lines the records of the descent1 generally under changing conditions4 ,lines inclining upward to the left show a decreasing humidity1 and to the right an increasing humidity4 ,type #a may be called a normal type of curve when there are clouds4 ,a variation of this type was met with in the ascent on ,october #h1 #ahif1 and it differed from that now illustrated in indicating in its upper part a fall of humidity rather than a rise4 ,these two types can be taken as the normal change of humidity with change of altitude in cloudy or partly cloudy weather4 ,the humidity increases steadily to the base of the cloud1 then there is complete saturation in the cloud1 and above it is a sudden fall of humidity1 on entering the dry air above the cloud1 into which the ascending currents from the ground have not penetrated4 ,type #c is a clear-weather form of curve in which the humidity increases until a certain altitude is reached1 probably at the upper limits of the currents rising from the ground4 ,above this altitude the humidity decreases rapidly4 ,type #e is also a clear-weather form and accompanies the cold wave type of temperature1 also numbered #e4 ,the very dry descending air mingles with air rendered damp by ascent1 and the result is a nearly uniform relative humidity at different altitudes1 although the absolute humidity diminishes on account of decreasing pressure and temperature4 ,in ,type #f both the relative and the absolute humidity decrease rapidly1 this type coinciding with the temperature1 ,type #f4 ,during the week of ,september #e to #aa1 #ahig1 kite-flights were made daily on ,blue ,hill4 ,twice the kites were maintained in the air1 and continuous records were obtained during most of twenty-four hours4 ,these records furnish an example of the small diurnal changes of temperature in the free air at short distances above the ground1 which were deduced from the average changes at different hours and at different heights4 ,from #b p4m4 of the fifth to #b p4m4 of the sixth1 the altitude of the self-recording instruments varied between #ejj and #ajjj metres above sea-level1 averaging about #gjj metres and varying little from this height during much of the night4 ,the times when the kite-meteorograph crossed the #gjj-metre level in ascending and descending were determined from its barograph trace1 and the synchronous temperatures and humidities were read from the records of its thermograph and hygrograph4 ,the results have been plotted in ,plate ,,xi41 ,figs4 #a and #b1 together with the temperatures recorded simultaneously at the summit and valley stations of the ,observatory and the humidities at the summit4 ,fig4 #a shows that the diurnal variation of temperature1 well marked at the lower levels1 is very slight or has entirely disappeared at #gjj metres4 ,fig4 #b shows that the course of the relative humidity at #gjj metres is exactly opposite in phase to that recorded at lower levels1 for at #gjj metres the minimum humidity was recorded at night and the maximum during the day1 while the opposite conditions prevailed on the hill4 ,repeated kite-flights indicate that these are the normal conditions at the two levels4 ,in ,plate ,,xi41 ,fig4 #c1 is plotted a curve from the hourly readings of the thermograph at the ,blue ,hill valley station 7fifteen metres7 during the week1 and also a curve connecting temperatures recorded by the kite-meteorograph once or twice each day during the same week at a level of #ejj metres1 obtained in the way described or computed from the adiabatic change4 ,all the night records show that it was decidedly warmer at the height of #ejj metres during the night than it was at the ground1 except during the cool wave on the seventh and eighth4 ,furthermore1 the curves in ,fig4 #c indicate a control of the surface temperatures during the day by those above4 ,for instance1 on the seventh there was a distinct flattening of the day curve1 evidently because1 as the temperature on the ground rose #aj above that at #ejj metres1 the air was in unstable equilibrium1 and colder air descended to take the place of the surface air so that its temperature could rise no higher4 ,on the tenth1 the temperature at #ejj metres was considerably greater than the mean of the day at the ground1 and the air at the ground did not acquire the unstable condition in any volume until the warmest part of the day1 so that the diurnal curve at the lower station forms a sharp peak4 ,illustration3 ,,plate ,,xi4--,,kite ,,observations ,,at ,,blue ,,hill1 ,,sept4 #e-aa1 #ahig4 ,since there appears to be no appreciable diurnal period in the temperature at and above #ejj metres1 a better comparison of the relative changes aloft and below during the passage of warm and cold waves is obtained by smoothing out the diurnal period below4 ,this has been done in ,plate ,,xi41 ,fig4 #d1 with the data given by the kites at #ejj and #ajjj metres plotted in curves1 which it was necessary to complete by extrapolation4 ,it is seen that there is a much greater range in the temperature from the crest of a warm to the crest of a cold wave at a height of #ejj metres than at the ground4 ,at #ajjj metres the range appears to be slightly greater than at #ejj metres1 and the crests of the warm and cold waves occur successively earlier than they do at the ground4 ,on the approach1 and until the passage of the crest of the cold wave the air is colder aloft than at the ground1 the difference being apparently that of the adiabatic cooling of ascending air4 ,after the passage of the crest of the cold wave1 the temperature aloft rises much more rapidly than at the ground1 and at the crest of the warm wave the air at #ejj metres is some #aj warmer than the mean daily temperature at the ground4 ,in many kite-flights the difference was found to be even greater than this4 ,taking the mean temperature of twenty-four-hours1 it is seen that the average temperature at the ground during a week or more is about the same as it is at #ejj metres4 ,fig4 #e shows the change in the vertical distribution of temperature during the oncoming of the warm wave on the eighth and early morning of the ninth1 as determined by four ascents1 culminating at #aa a4m41 #i p4m41 #aa p4m41 and #d a4m4 ,the lines of #ei1 #fb1 #fe1 and #fh show that there was a gradual rise of temperature aloft1 which extended downwards to #bjj metres1 or to the top of ,blue ,hill4 ,clouds formed at the level of lowest temperature1 and these sank also until they covered the top of the hill4 ,plate ,,xii4 is a facsimile of the meteorogram during the kite-flight of ,october #ae1 #ahig1 the lower part showing the trace of the barometer on a scale of heights in metres1 the middle section the trace of the hygrometer1 and the upper one the trace of the thermometer on a scale of ,centigrade degrees4 ,the temperature followed the normal change1 which is as follows3 during the day1 up to a certain height1 which varies under different conditions1 there is a decrease nearly at the adiabatic rate of #ah ,f4 per hundred metres4 ,above that height the air suddenly becomes warmer1 and then cools with ascent at a rate somewhat less than the adiabatic rate4 ,during the night there is a marked inversion of temperature between the ground and #bjj or #cjj metres4 ,illustration3 ,,plate ,,xii4--,,automatic ,,records ,,during ,a ,,high ,,kite-,,flight ,,at ,,blue ,,hill4 ,higher than this1 the temperature decreases at a fairly uniform rate1 but more slowly than the adiabatic rate4 ,although no clouds were visible1 yet the relative humidity increased greatly1 both during the ascent and descent1 near #aejj and #bgjj metres1 these being about the heights at which cumulus and alto-cumulus clouds usually form4 ,during ,september #ahih four kite-flights were made on four successive days when an anti-cyclone and a cyclone passed nearly over ,blue ,hill4 ,this is a rare occurrence1 and the mechanism of these phenomena was accordingly studied by ,mr4 ,clayton1 some of whose deductions will now be given1 illustrated by ,plate ,,xiii4 ,figs4 #a and #b give the temperature plotted according to height on ,september #ba in the anti-cyclone1 and on ,september #bb1 when the barometric pressure was falling1 the full lines1 as in previous diagrams1 indicating observations during the ascents1 and the broken lines observations during the descents4 ,it is seen that from the ground the lines all incline upward to the left1 indicating a fall of temperature1 to a certain height when the lines bend to the right sharply1 showing a sudden rise of temperature4 ,above this1 the temperature again falls1 but more slowly than at lower levels4 ,the general prevalence of this phenomenon was noted by ,welsh in his balloon ascents in ,england in #ahed1 and the high kite-flights at ,blue ,hill show it to be very frequent below #bjjj metres4 ,the plane of increased temperature usually determines the height of the tops of cumulus and strato-cumulus clouds4 ,above #bjjj metres other sudden rises of temperature are found during the highest kite-flights4 ,illustration3 ,,plate ,,xiii4--,,results ,,of ,,kite-,,flights ,,at ,,blue ,,hill ,,during ,,an ,,anti-,,cyclone ,,and ,a ,,cyclone4 ,figs4 #c to #f show the changes in the various elements during the four days at some of the following levels1 viz4 near sea-level1 #bjj1 #ajjj1 #bjjj1 and #cjjj metres4 ,fig4 #c shows the changes in the barometer at the four levels1 from which it is evident that the fall of pressure was greatest near sea-level4 ,fig4 #d shows temperature changes at the different levels1 and indicates that the changes were of the same nature up to #cjjj metres4 ,the greatest non-diurnal range of temperature is seen to be at #ajjj metres1 and it diminishes both at higher and at lower levels4 ,fig4 #e shows changes in relative humidity at #bjj1 #ajjj1 and #bjjj metres4 ,the curves show that the greatest range of humidity was at #bjjj metres4 ,there the relative humidity rose from almost zero1 in the anti-cyclone on the twenty-first1 to saturation at the same level in the cyclone4 ,at #bjj metres the change is similar to that at #bjjj1 but is less in amount4 ,at #ajjj metres the relative humidity fell until the twenty-second1 but then rose rapidly1 showing the very dry air at #bjjj metres on the twenty-first had descended as low as #ajjj metres on the twenty-second4 ,fig4 #f gives the change in wind velocity at the different levels4 ,there was an increase of wind at all the levels from the time of the passage of the anti-cyclone to the passage of the cyclone4 ,the minimum of wind at #bjj metres was in the anti-cyclone1 with a secondary minimum during the passage of the centre of the cyclone4 ,figs4 #g to #aj show the changes in height from day to day of the equal conditions at the different levels4 ,fig4 #g shows the change in level of the isobars1 which1 although very small1 is largest at the lower levels4 ,the light broken lines in ,fig4 #g and subsequent figures indicate the axes of the anti-cyclone and cyclone4 ,that the axis of the cyclone was inclined backward1 and that the high pressure occurred later at high than at low levels1 was confirmed by the wind observations on the twenty-first4 ,fig4 #h shows the heights at which the same temperatures were found on successive days4 ,since the isotherms rose until the twenty-third1 the temperature of the air up to #cjjj metres was higher on the day of the cyclone than on the day of the anti-cyclone4 ,previous high flights indicate that this is the normal condition in the moving cyclones and anti-cyclones of the eastern ,united ,states4 ,as the light broken lines represent the axes of the anti-cyclone and cyclone up to #cjjj metres1 it is seen that at this level the temperature at the place of maximum pressure is probably higher than at the place of minimum pressure1 although this is not true for a vertical column of air above the earth4 ,fig4 #i gives the positions of equal humidities on successive days1 saturated and cloudy areas being indicated by crossed shading1 and less humidity by single ruling4 ,from the laws of thermo-dynamics the unshaded curves should represent descending currents1 and the shaded portions ascending ones4 ,in the first case1 increased warmth and a lower relative humidity are produced in the descent to a lower altitude2 in the last case1 cooling1 increasing relative humidity1 and condensation are produced by expansion in the ascent to a higher altitude4 ,consequently1 two regions of descending air are indicated1 one in the centre of the anti-cyclone1 the other in the centre of the cyclone4 ,fig4 #aj shows the change in height of the lines of equal wind velocity4 ,with ascending currents and precipitation1 high wind velocities were found at low levels1 because of increased barometric gradient1 while with the descending currents in the anti-cyclone and centre of the cyclone1 the high velocities were found only at great altitudes4 ,the study of these data indicate that the cyclonic and anti-cyclonic circulations observed in this latitude do not embrace any air-movements at greater altitudes than #bjjj metres1 except in front of the cyclone1 when the air appears to be carried upward to a great height4 ,above #bjjj metres there are probably other weak cyclones and anti-cyclones1 or secondary ones1 with their centres at different places from those at the earth's surface and producing a different circulation of wind4 ,the observations of the cirrus clouds at ,blue ,hill indicate that at their level exists a cyclonic circulation above the anti-cyclone apparent at the earth's surface4 ,the shallowness of our anti-cyclones would be inferred from the great differences in speed of the general atmospheric drift1 for since the velocity of the general drift from the west is more than thirty times greater at #aj1jjj metres than it is at #bjj metres1 a circulation of great depth could not endure long4 ,cyclones and anti-cyclones appear to be but secondary phenomena in the great waves of warm and cold air which sweep across the ,united ,states from periodic causes4 ,the origin of cyclones and anti-cyclones is perhaps the most important problem remaining for meteorological study4 ,the theory that they are produced by differences of temperature in adjacent masses of air1 or1 as it is called1 the convectional theory of the ,american meteorologists1 ,espy and ,ferrel1 is opposed by the observations on mountains in ,europe which were collected by ,dr4 ,hann of ,vienna4 ,if the question can be solved by the use of kites1 as seems to be foreshadowed by the results just stated1 another foundation-stone will be laid in the science of meteorology and the status of the kite established as an instrument of research4 ,the kite fails when there is little or no wind at the ground1 but it seems possible in such cases to lift the kite into the upper air1 where there usually is wind1 by attaching it to a small balloon that1 after the kite can support itself1 shall be detached automatically4 ,while the height to which kites can rise is limited1 and the limit is probably being approached1 judging from the less gain of altitude in recent flights1 yet it seems reasonable to expect that1 with favourable conditions1 a height of at least three miles will be reached4 ,besides lifting the meteorological instruments described1 kites can carry apparatus for other investigations in the free air1 such as the measurement of atmospheric electricity1 and the collection of samples of air1 to be examined for cosmic dust and bacteria4 ,cameras have been lifted by kites1 as already said1 and for the purpose of photographing the upper surfaces of clouds there is being constructed for the ,blue ,hill ,observatory a very light automatic camera1 similar in principle to ,m4 ,cailletet's apparatus for photographing the ground from a balloon4 ,the use of the kite as an aeroplane can only be alluded to in this book1 and it may be sufficient to say that if a motor attached to a kite can1 by wings or screws1 propel it against the wind1 the sustaining string is unnecessary1 and we shall have the flying machine which ,professor ,langley tells us will soon be realized4 ,the surface of our globe has been tolerably well explored2 the exploration of the atmosphere by balloons and kites will continue to make great progress during the last year of the century1 and at the end of the twentieth century we may confidently expect that as the seas now are a medium for transportation1 so the ocean of air will have been brought likewise into man's domain4 ,,index ,a ,abercromby 7,r471 classification of clouds1 #db ,academy of ,sciences1 ,french1 #ah1 #gb-c ,academy of ,sciences1 ,russian1 balloon ascent1 #gb ,accademia del ,cimento1 #ad ,actinometer1 ,violl's1 #aae ,adiabatic rate of change of temperature1 #bi ,aeronautical ,conference at ,chicago1 #abe ---- ,conference at ,strassburg1 #ig1 #aaj ---- ,committee2 ,international1 #ajh ,arophile balloons1 #ajb1 #ajd ,aerostatic ,commission1 ,french1 #aaa ,air1 collection and analysis of1 #gj1 #gc1 #ge1 #hb1 #aab ---- weight of1 #af ,aitken 7,j471 dust particles1 #ci ,alhazen 7,b4 ,a471 height of atmosphere1 #ab ,altitudes1 comparative1 #bj ,andre 7,s4 ,a471 balloon voyage to ,north ,pole1 #ij ,anti-cyclones1 #ei1 #agj ,aratus1 ,diosemeia1 #aa ,archibald 7,d471 kites for meteorological observations1 #abb ,archytas1 supposed inventor of kite1 #aag ,aristotle1 #aj1 #aa1 #ae ,assmann 7,r471 #hf1 #id1 #ajh ,atmosphere1 composition of1 #bd ---- energy of upper portion1 #eh ---- extent of1 #bh ---- methods of exploring same1 #ce et seq41 #ade ---- moisture of1 #cd ---- origin of1 #bc ---- phenomena showing height of1 #bf ---- ,pliny on1 #i ---- temperature of1 #bh ,atmospheric circulation in cyclones and anti-cyclones1 #fj ---- electricity1 #gj1 #gf1 #aba1 #ada ,b ,balloon ascents1 international1 #ajh et seq4 ---- crossing the ,atlantic by1 #ib ---- invention of hot-air1 #ai ---- kite1 #id ,balloons1 #ai1 #bj1 #ba1 #cg1 #fh1 et seq4 ---- captive1 #gf1 #ic1 #adf ---- changes of temperature observed in1 #ga1 #gc1 #ge1 #gg1 #hd1 #hh1 #ij ---- changing the direction of1 #ic ,ballons-sondes1 #ih et seq4 ,barometer1 #ae1 #af1 #he1 #aac ,baro-thermograph of ,richard1 #ajb ,barral1 balloon ascent1 #gc1 #hd ,batavia1 ,java1 international cloud measurements1 #fe ,batut 7,a471 photography from kites1 #abc ,berson 7,a471 balloon ascents1 #ha1 #hg et seq4 ,bert 7,p471 respiration of oxygen1 #hb ,besanon 7,g471 #ih1 #ii1 #aja1 #ajd ,bezold 7,w4 von71 wave-cloud1 #dj ,biot 7,j4 ,b471 balloon ascent1 #gc ,birt 7,w4 ,r471 kite at ,kew ,observatory1 #abb ,bixio1 balloon ascent1 #gc1 #hd ,blanc1 ,mont1 #bj1 #ba ,blanchard1 balloon ascent with ,jeffries1 #gj1 #ga ,blue ,hill ,observatory1 #dg1 #ea1 #ec1 #fd1 #ajh1 #abf et seq4 ,bonaparte 7,prince ,roland71 patron of aeronautics1 #aab ,bonpland 7,a471 ascent in ,andes1 #bj ,bonvallet 7,l471 exploring balloons1 #ii ,bouguer 7,p471 height of freezing-point1 #ah ,boyle 7,r471 #af ,c ,cailletet 7,l471 #aab1 #aac ,cambridge1 ,mass41 clouds measured at1 #ec ,castelli 7,b471 invented rain-gauge1 #ac ,cavallo 7,t471 showed lightness of hydrogen1 #fi ,celsius 7,a471 thermometer1 #ad ,charles 7,j4 ,a4 ,c471 ascent in hydrogen balloon1 #ai1 #fh ,cimento1 ,accademia del1 #ad ,cirrus balloon1 #ajf ,clayton 7,h4 ,h471 #de1 #dg1 #ec1 #fb1 #acc1 #adg1 #afg ,cloud1 amount of1 #dg et seq4 ---- atlases1 #db1 #dc1 #dd ---- ,committee1 ,international1 #dd1 #fe ---- -year1 international1 #fe ,clouds1 classification of1 #da et seq4 ---- definitions of1 #de ---- formation of1 #ci ---- observations of direction and relative velocity1 #ea1 #fe ---- measurements of height and velocity1 #eb1 #ec et seq41 #fe1 #aba ---- on ,jupiter1 #ea ---- relation to forecasting1 #fc-d ,cotte 7,l471 on clouds1 #ch ,coxwell 7,h471 aeronaut for ,glaisher1 #ge et seq4 ,croc-,spinelli 7,j471 ascent in ,zenith1 #hb ,cyclones1 #ei1 #agj ,d ,dalton 7,j471 water-vapour in the air1 #ch ,daniell 7,j4 ,f471 mountains a registering thermometer1 #ac ,davis 7,w4 ,m471 cloud measurements1 #ec ,deluc 7,j4 ,a471 theory of clouds1 #db ,de ,saussure 7,h4 ,b471 #bj1 #db1 #gc ---- 7,h4 ,b471 ascent of ,mont ,blanc1 #bj ,deutsche-,seewarte1 ,hamburg1 #dc ,donaldson 7,w4 ,h471 proposed crossing ,atlantic in a balloon1 #ib ,e ,eddy 7,w4 ,a471 #abc1 #abd et seq4 ,eiffel ,tower1 ,paris1 #bc1 #aeb ,ekholm 7,n471 #ec1 #ib ,electricity1 atmospheric1 #gj1 #gf1 #aba1 #ada ,espy 7,j4 ,p471 kites to verify calculated height of clouds1 #aba ,etna1 ascended by ancients1 #ab ,euler 7,l471 theory of kites1 #aah ,exploring the atmosphere1 methods of1 #ce et seq41 #ade-f ,f ,fahrenheit 7,d4 ,g471 thermometer1 #ad ,ferdinand ,,ii4 7,grand ,duke71 distributed meteorological instruments1 #ag ,fergusson 7,s4 ,p471 #ce1 #ec1 #abf1 #abh1 #aca1 #acf ,ferrel 7,w471 theory of cyclones1 #agc ,flammarion 7,c471 balloon ascents1 #ha ,flying machines1 future1 #ei1 #agd ,fonvielle 7,w4 de71 #ha1 #ajh ,frster 7,w471 hypothesis of ,himmelsluft1 #bh ,forecasting by kites1 #adc1 #adg ,franklin 7,b471 experiment with kites1 #aba1 #abc ,franklin ,kite ,club1 #aba ,g ,galileo 7,g471 #ad1 #ae ,gay-,lussac 7,j4 ,l471 balloon ascent1 #bj1 #gc ,german ,emperor 7,william ,,ii471 patron of aeronautics1 #hf ---- ,society for ,promotion of ,arial ,navigation1 #hf1 #ic1 #ajf ,glaisher 7,j471 balloon ascents1 #ge et seq41 #ic ,green 7,c471 aeronaut for ,welsh1 #gd ,grimaldi 7,f4 ,m471 first measured clouds trigonometrically1 #eb ,guericke 7,o4 von71 experiment of ,magdeburg hemispheres1 #af ,h ,hagstrm 7,k471 measured clouds1 #ec ,halley 7,e471 measured heights by barometer1 #ag ,hann 7,j471 #cf1 #agc ,han ,sin1 employed kites in warfare1 #aag ,hargrave 7,l471 invented cellular kite1 #abi ,harrington 7,m4 ,w471 advocated exploring air with kites1 #abe ,harvard ,college ,observatory1 #ce1 #dh ,hazen 7,h4 ,a471 highest balloon ascent in ,america1 #he ,height of balloon1 ,cailletet's apparatus for obtaining1 #aac ,heights of kite-flights at ,blue ,hill1 #ba1 #adj ---- how measured by barometer1 #ag1 #aja ,heim 7,a471 voyage across the ,alps1 #ib ,hellmann 7,g471 historical researches1 #ab ,helmholtz 7,h4 von71 wave-cloud1 #dj ,hergesell 7,h471 ,president of ,aeronautical ,committee1 #ajh ,hermite 7,g471 #ih1 #ii1 #aja ,hildebrandsson 7,h4 ,h471 #db1 #fe ,hodgkins' ,fund of ,smithsonian ,institution1 grant from1 #aca ,howard 7,l471 cloud nomenclature1 #da ,humboldt 7,a4 von71 #ah1 #bj1 #ce ,humidity1 changes with altitudes1 #cd1 #ga1 #gc1 #gg1 #aea1 #afi1 #aga ---- diurnal changes at different altitudes1 #aec ---- types of change with altitudes1 #aei et seq4 ,hutton 7,j471 cause of precipitation1 #ch ,hygrometer1 invention of1 #ac ,j ,jeffries 7,j471 first scientific balloon ascent1 #fi ---- first to cross the ,english ,channel1 #ga ,jourdanet 7,d471 hypothesis of descent of man1 #bd ,jovis1 balloon ascent1 #hd ,jupiter1 analogy between cloudiness on earth and on1 #ea ,k ,kepler 7,j471 height of atmosphere1 #ab ,kew ,observatory1 #ec1 #gd1 #abb ,kppen 7,w471 cloud atlas1 #dc ,kirwan 7,r471 temperature at different latitudes1 #ah ,kite1 antiquity of the1 #aag ---- ,eddy or ,malay1 #abd1 #abi ---- flights at ,blue ,hill1 #ba1 #acg1 #adj1 #adb ---- ,hargrave1 #abi1 #acb ---- ,lamson's aero-curve1 #acd ---- photography1 #abc1 #abf1 #agc ---- theory of1 #aah1 #abd1 #acj ,kites1 first scientific use of1 #abj ---- first self-recording instruments raised by1 #abf ---- oriental tailless1 #aah ---- scientific uses of1 #agc ,kite-winch at ,blue ,hill1 steam1 #aca1 #acf ,krakatoa1 eruption of volcano1 #bg ,l ,lamarck 7,j4 ,b471 first to classify cloud forms1 #da ,lamson 7,c4 ,h471 aero-curve kite1 #acd ,langley 7,s4 ,p471 #bh1 #agd ,laplace 7,p4 ,s4 de71 #ag1 #bc1 #aja ,lavoisier 7,a4 ,l471 #ai1 #fh ,ley 7,w4 ,c471 classification of clouds1 #db ,lunardi 7,v471 balloon ascent1 #fi ,m ,m',adie 7,a471 #ec1 #abc ,magnetism1 variation with height1 #gc1 #gg ,mallet 7,m471 balloon ascent1 #hd ,manila1 ,philippine ,islands1 cloud measurements at1 #fe-f ,mariotte 7,e471 law of gases1 #af ,melvill 7,t471 aided in first scientific use of kites1 #abj ,merle 7,w471 oldest weather chronicles1 #ab ,meteorograph for kites1 #abh1 #acf ,meteorological conferences1 international1 #db1 #dd1 #ajh ,meteorology1 first treated by ,aristotle1 #aj ---- origin of1 #aj ,misti1 ,el1 highest station1 #ce ,montgolfier brothers1 invented hot-air balloon1 #ai ,mntz 7,a471 analysis of air1 #aab-ac ,n ,nares 7,sir ,g471 storm-kite1 #abb ,nebular hypothesis of ,laplace1 #bc ,neumayer 7,g471 cloud-atlas1 #db ,newton 7,i471 improved kites1 #aah ,o ,olympus1 mountain ascended by ancients1 #aa ,oxford1 oldest weather chronicles1 #ab ,p ,parseval 7,a4 von71 kite-balloon1 #id ,pascal 7,b471 experiment with barometer1 #ae1 #af ,perier 7,f471 idem1 #ae ,photography from balloons1 #ha1 #aac ---- from kites1 #abc1 #abf1 #agc ,pickering 7,e4 ,c471 pole-star recorder1 #dh ,pike's ,peak1 meteorological station1 #ce ,piltre de ,rozier 7,j4 ,f471 first to ascend in balloon1 #ai ,pliny1 the atmosphere1 #i ,pocock 7,g471 great kite1 #abb ,poy 7,a471 classification of clouds1 #db ,priestley 7,j471 oxygen in the air1 #ah ,r ,rain-gauge1 invention of1 #ac ,raumur 7,r4 ,a4 ,f4 de71 thermometer1 #ad ,rey 7,j471 first thermometer filled with liquid1 #ad ,riccioli 7,g4 ,b471 first to measure clouds trigonometrically1 #eb ,richard 7,abb71 clouds1 #ch ---- 7,j471 self-recording instruments1 #aja1 #abe1 #abh1 #acf ,robertson 7,e4 ,g471 #gb1 #gc ---- balloon ascent1 #gb ,rotch 7,a4 ,l471 balloon ascents1 #he1 #hf ,s ,sacharoff1 balloon ascent1 #gb ,siegsfeld 7,h4 ,b4 von71 kite-balloon1 #id ,sigsbee 7,c4 ,d471 #dd1 #aca ,sivel 7,t471 ascent in ,zenith1 #hb ,spelterini 7,e471 balloon voyage with ,heim1 #ib ,spencer 7,s471 aeronaut for ,berson1 #hi ,sweetland 7,a4 ,e471 prognostics from clouds1 #fc ,symons 7,g4 ,j471 meteorologist and bibliophile1 #ab ,t ,teisserenc de ,bort 7,l471 #ea1 #aaf1 #add ,temperature1 change with height1 #ah1 #bi1 #ga1 #gc1 #ge1 #gg1 #hi1 #ij1 #ajd1 #ajg1 #abj1 #aba1 #abf1 #ada1 #aea1 #afg ---- diurnal changes at different altitudes1 #aeb1 #afa-b ---- types of change with altitude1 #aed et seq4 ,theodolite1 registering1 #ajf ,theophrastus1 weather prognostics1 #aa ,thermometer1 aspiration1 #gd1 #hf ---- metallic1 #aaf ---- sling1 #he ,thermometers1 early1 #ad ,tissandier 7,a471 sketches of optical phenomena1 #ha ---- 7,g471 ascent in ,zenith1 #ha1 #hb ,toronto1 ,canada1 international cloud measurements1 #fe ,torricelli 7,e471 invented barometer1 #ae ,tycho ,brahe1 height of atmosphere1 #ab ,u ,united ,states hydrographic office1 #dd ---- weather bureau1 #dd1 #fe1 #adc ,upsala1 ,sweden1 clouds measured at1 #ec1 #eh1 #ff ,v ,violle 7,j471 #aab1 #aae ,w ,washington 7,mount71 meteorological station1 #ce ,weather chronicles1 first1 #ab ---- forecasting by means of clouds1 #fc ---- prognostics of ,aristotle and ,theophrastus1 #aa ---- vane1 oldest meteorological instrument1 #ac ,weber 7,l471 measured electric potential with kites1 #abd ,welsh 7,j471 balloon ascents1 #gd ,wenz 7,e471 photography from kites1 #abc ,wilson 7,a471 first scientific use of kites1 #abj ,wind at different heights1 #eg et seq41 #ih1 #aec1 #agj1 #aga ,wire for kite-lines1 #abc1 #aca1 #acd ,wise 7,j471 #hd1 #ib ,woglom 7,j4 ,t471 photography from kites1 #abc ,y ,young 7,c4 ,a471 limit of atmosphere1 #bh ,z ,zenith1 catastrophe of balloon1 #hb ,zero1 absolute1 #cc ,richard ,clay ,sons1 ,limited1 ,london ,bungay4 ,transcriber's ,notes ,the text presented here is essentially that in the original printed volume4 ,the list of corrections 7,,corrigenda7 which accompanied the original has been applied4 ,one additional typo 7see below7 has also been made4 ,there may have been some minor corrections 7missing period1 commas1 etc4 added7 which are not detailed here4 ,in the original publication1 several figures and plates were placed in the middle of paragrahs4 ,here most were moved between paragraphs4 ,the ,list of ,illustrations and any other page references still indicate the page number of the original location4 ,on page #hh1 the oe ligature was replaced with the individual letters4 ,typographical ,correction ,page ,correction #abh all-assential all-essential