,,shilling ,,scientific ,,series ,illustration3 ,,dr4 ,,aitken',s ,,dust-,,counter4 ,r is the test-receiver2 ,p the air-pump2 ,m the measuring apparatus2 ,l the illuminating arrangements2 ,g the ,gasometer2 ,a the pipe through which the tested air is drawn4 ,,meteorology2 ,,or1 ,,weather ,,explained4 ,,by ,j4 ,g4 ,m',,pherson1 ,ph4,d41 ,f4,r4,s4,e41 ,,graduate ,,with ,,first-,,class ,,honours1 ,,and ,,for ,,nine ,,years ,,extension ,,lecturer ,,on ,,meteorology ,,and ,,mathematical ,,examiner ,,in ,,the ,,university ,,of ,,st4 ,,andrews2 ,,author ,,of ,,tales ,,of ,,science1 ,,etc4 ,,london3 ,t4 ,c4 ,e4 ,c4 ,,jack1 #cd ,,henrietta ,,street1 ,w4,c4 ,,and ,,edinburgh4 #aije4 ,,the ,,shilling ,,scientific ,,series ,the following ,vols4 are now ready or in the ,press3-- ,,balloons1 ,,airships1 ,,and ,,flying ,,machines4 ,by ,,gertrude ,,bacon4 ,,motors ,,and ,,motoring4 ,by ,professor ,,harry ,,spooner4 ,,radium4 ,by ,dr4 ,,hampson4 ,,telegraphy ,,with ,,and ,,without ,,wires4 ,by ,w4 ,j4 ,,white4 ,,electric ,,lighting4 ,by ,s4 ,f4 ,,walker1 ,r4,n41 ,m4,i4,e4,e4 ,,local ,,government4 ,by ,,percy ,,ashley1 ,m4,a4 ,others in ,preparation ,printed by ,,ballantyne1 ,,hanson ,,co4 ,at the ,ballantyne ,press ,,contents ,,chap4 ,,page ,i4 ,,introduction #i ,,ii4 ,,the ,,formation ,,of ,,dew #ac ,,iii4 ,,true ,,and ,,false ,,dew #ag ,,iv4 ,,hoar-,,frost #bj ,v4 ,,fog #bc ,,vi4 ,,the ,,numbering ,,of ,,the ,,dust #bf ,,vii4 ,,dust ,,and ,,atmospheric ,,phenomena #bi ,,viii4 ,a ,,fog-,,counter #ca ,,ix4 ,,formation ,,of ,,clouds #cd ,x4 ,,decay ,,of ,,clouds #cg ,,xi4 ,,it ,,always ,,rains #dj ,,xii4 ,,haze #dc ,,xiii4 ,,hazing ,,effects ,,of ,,atmospheric ,,dust #dg ,,xiv4 ,,thunder ,,clears ,,the ,,air #di ,,xv4 ,,disease ,,germs ,,in ,,the ,,air #ec ,,xvi4 ,a ,,change ,,of ,,air #ee ,,xvii4 ,,the ,,old ,,moon ,,in ,,the ,,new ,,moon',s ,,arms #eh ,,xviii4 ,,an ,,autumn ,,afterglow #fb ,,xix4 ,a ,,winter ,,foreglow #fe ,,xx4 ,,the ,,rainbow #fh ,,xxi4 ,,the ,,aurora ,,borealis #ga ,,xxii4 ,,the ,,blue ,,sky #gd ,,xxiii4 ,a ,,sanitary ,,detective #gh ,,xxiv4 ,,fog ,,and ,,smoke #hj ,,xxv4 ,,electrical ,,deposition ,,of ,,smoke #hc ,,xxvi4 ,,radiation ,,from ,,snow #hf ,,xxvii4 ,,mountain ,,giants #hh ,,xxviii4 ,,the ,,wind #ib ,,xxix4 ,,cyclones ,,and ,,anti-,,cyclones #ie ,,xxx4 ,,rain ,,phenomena #ih ,,xxxi4 ,,the ,,meteorology ,,of ,,ben ,,nevis #ajb ,,xxxii4 ,,the ,,weather ,,and ,,influenza #ajg ,,xxxiii4 ,,climate #aaj ,,xxxiv4 ,,the ,,challenger ,,weather ,,reports #aad ,,xxxv4 ,,weather-,,forecasting #aaf ,,index #abd ,,prefatory ,,note ,i am very much indebted to ,dr4 ,john ,aitken1 ,f4,r4,s41 for his great kindness in carefully revising the proof sheets1 and giving me most valuable suggestions4 ,this is a sufficient guarantee that accuracy has not been sacrificed to popular explanation4 ,j4 ,g4 ,m',p4 ,,ruthven ,,manse1 ,june #aj1 #aije4 ,,meteorology ,,chapter ,i ,,introduction ,though by familiarity made commonplace1 the weather is one of the most important topics of conversation1 and has constant bearings upon the work and prospects of business-men and men of pleasure4 ,the state of the weather is the password when people meet on the country road3 we could not do without the humble talisman4 ,a fine day comes spontaneously to the lips1 whatever be the state of the atmosphere1 unless it is peculiarly and strikingly repulsive2 then ,a bitter day would take the place of the expression4 ,yet ,i have heard ,terrible guid wither as often as ,terrible bad day among country people4 ,scarcely a friendly letter is penned without a reference to the weather1 as to what has been1 is1 or may be4 ,it is a new stimulus to a lagging conversation at any dinner-table4 ,all are so dependent on the weather1 especially those getting up in years or of delicate health4 ,i remember1 when at ,strathpeffer1 the great health-resort in the ,north of ,scotland1 in #ahhe1 an anxious invalid at ,the ,pump asking a weather-beaten1 rheumatic old gamekeeper what sort of a day it was to be1 considering that it had been wet for some time4 ,the keeper crippled to the barometer outside the doorway1 and returned with the matter-of-fact answer3 ,she's faurer doon ta tay nur she wass up yestreen4 ,the barometer had evidently fallen during the night4 ,and what are we to expect8 sadly inquired the invalid4 ,it'll pe aither ferry wat1 or mohr rain--a poor consolation6 ,most men who are bent on business or pleasure1 and all dwellers in the country who have the instruments1 make a first call at the barometer in the lobby1 or the aneroid in the breakfast-parlour1 to see what she says4 ,a good rise of the black needle 7that is1 to the right7 above the yellow needle is a source of rejoicing1 as it will likely be clear1 dry1 and hard weather4 ,a slight fall 7that is1 to the left7 causes anxiety as to coming rain1 and a big depression forebodes much rain or a violent storm of wind4 ,in either case of fall1 the shutters come over the eyes of the observer4 ,next1 even before breakfast1 a move is made to the self-registering thermometer 7set the night before7 on a stone1 a couple of feet above the grass4 ,a good reading1 above the freezing-point in winter and much above it in summer1 indicates the absence of killing rimes1 that are generally followed by rain4 ,a very low register accounts for the feeling of cold during the night1 though the fires were not out2 and predicts precarious weather4 ,ordinarily careful observers--as ,i1 who have been in one place for more than thirty years--can1 with the morning indications of these two instruments1 come pretty sure of their prognostics of the day's weather4 ,of course1 the morning newspaper is carefully scanned as to the weather-forecasts from the ,london ,meteorological ,office--direction of wind2 warm1 mild1 or cold2 rain or fair1 and so on--and in general these indications are wonderfully accurate for twenty-four hours2 though the three days' prognostics seem to stretch a point4 ,we are hardly up to that yet4 ,the lower animals are very sensitive as to the state of approaching extremes of weather4 ,thae sea beass1 referring to sea-gulls over the inland leas during ploughing1 are ordinary indicators of stormy weather4 ,wind is sure to follow violent wheelings of crows4 ,beware of rain when the sheep are restive1 rubbing themselves on tree stumps4 ,but all are familiar with ,jenner's prognostics of rain4 ,science has come to the aid of ordinary weather-lore during the last twenty years1 by leaps and bounds4 ,time-honoured notions and revered fictions1 around which the hallowed associations of our early training fondly and firmly cling1 must now yield to the exact handling of modern science2 and with reluctance we have to part with them4 ,yet there is in all a fascination to account for certain ordinary phenomena4 ,the man in the street1 as well as the strong reading man1 wishes to know the why and the how of weather-forecasting4 ,they are anxious to have weather-phenomena explained in a plain1 interesting1 but accurate way4 ,the freshness of the marvellous results has an irresistible charm for the open mind1 keen for useful information4 ,the discoveries often seem so simple that one wonders why they were not made before4 ,until about twenty years ago1 ,meteorology was comparatively far back as a science2 and in one important branch of it1 no one has done more to put weather-lore on a scientific basis than ,dr4 ,john ,aitken1 ,f4,r4,s41 who has very kindly given me his full permission to popularise what ,i like of his numerous and very valuable scientific papers in the ,transactions of the ,royal ,society of ,edinburgh4 ,this ,i have done my best to carry out in the following pages4 ,the way of putting it is my only claim4 ,many scientific men are decoyed on in the search for truth with a spell unknown to others3 the anticipation of the results sometimes amounts to a passion4 ,many wrong tracks do they take1 yet they start afresh1 just as the detective has to take several courses before he hits upon the correct scent4 ,when they succeed1 they experience a pleasure which is indescribable2 to them fame is more than a mere fancied life in others' breath4 ,dr4 ,aitken's continued experiments1 often of rare ingenuity and brilliancy1 show that no truth is altogether barren2 and even that which looks at first sight the very simplest and most trivial may turn out fruitful in precious results4 ,small things must not be overlooked1 for great discoveries are sometimes at a man's very door4 ,dr4 ,aitken has shown us this in many of his discoveries which have revolutionised a branch of meteorology4 ,prudence1 patience1 observing power1 and perseverance in scientific research will do much to bring about unexpected results1 and not more so in any science than in accounting for weather-lore on a rational basis1 which it is in the power of all my readers to further4 ,the old order changeth1 giving place to new4 ,with kaleidoscopic variety ,nature's face changes to the touch of the anxious and reverent observer4 ,and some of these curious weather-views will be disclosed in these pages1 so as1 in a brief but readable way1 to explain the weather1 and lay a safe basis for probable forecastings1 which will be of great benefit to the man of business as well as the man of pleasure4 ,felix1 qui potuit rerum cognoscere causas4 --,,virgil4 ,,chapter ,,ii ,,the ,,formation ,,of ,,dew ,the writer of the ,book of ,job gravely asked the important question1 ,who hath begotten the drops of dew8 ,we repeat the question in another form1 ,whence comes the real dew8 ,does it fall from the heavens above1 or does it rise from the earth beneath8 ,until about the beginning of the seventeenth century1 scientific men held the opinion of ordinary observers that dew fell from the atmosphere4 ,but there was then a reaction from this theory1 for ,nardius defined it as an exhalation from the earth4 ,of course1 it was well known that dew was formed by the precipitation of the vapour of the air upon a colder body4 ,you can see that any day for yourself by bringing a glass of very cold water into a warm room2 the outer surface of the glass is dimmed at once by the moisture from the air4 ,m4 ,picket was puzzled when he saw that a thermometer1 suspended five feet above the ground1 marked a lower temperature on clear nights than one suspended at the height of seventy-five feet2 because it was always supposed that the cold of evening descended from above4 ,again he was puzzled when he observed that a buried thermometer read higher than one on the surface of the ground4 ,until recently the greatest authority on dew was ,dr4 ,wells1 who carefully converged all the rays of scientific light upon the subject4 ,he came to the conclusion that dew was condensed out of the air4 ,but the discovery of the true theory was left to ,dr4 ,john ,aitken1 ,f4,r4,s41 a distinguished observer and a practical physicist1 of whom ,scotland has reason to be proud4 ,about twenty years ago he made the discovery1 and it is now accepted by all scientific men on the ,continent as well as in ,great ,britain4 ,what first caused him to doubt ,dr4 ,wells' theory1 so universally accepted1 that dew is formed of vapour existing at the time in the air1 and to suppose that dew is mostly formed of vapour rising from the ground1 was the result of some observations made in summer on the temperature of the soil at a small depth under the surface1 and of the air over it1 after sunset and at night4 ,he was struck with the unvarying fact that the ground1 a little below the surface1 was warmer than the air over it4 ,by placing a thermometer among stems below the surface1 he found that it registered #ah deg4 ,fahr4 higher than one on the surface4 ,so long1 then1 as the surface of the ground is above the dew-point 7i4e4 the temperature when dew begins to be formed71 vapour must rise from the ground2 this moist air will mingle with the air which it enters1 and its moisture will be condensed and form dew1 whenever it comes in contact with a surface cooled below the dew-point4 ,you can verify this by simple experiments4 ,take a thin1 shallow1 metal tray1 painted black1 and place it over the ground after sunset4 ,on dewy nights the inside of the tray is dewed1 and the grass inside is wetter than that outside4 ,on some nights there is no dew outside the tray1 and on all nights the deposit on the inner is heavier than that on the outside4 ,if wool is used in the experiments1 we are reminded of one of the forms of the dewing of ,gideon's fleece--the fleece was bedewed when all outside was dry4 ,you therefore naturally and rightly come to the conclusion that far more vapour rises out of the ground during the night than condenses as dew on the grass1 and that this vapour from the ground is trapped by the tray4 ,much of the rising vapour is generally carried away by the passing wind1 however gentle2 hence we have it condensed as dew on the roofs of houses1 and other places1 where you would think that it had fallen from above4 ,the vapour rising under the tray is not diluted by the mixture with the drier air which is occasioned by the passing wind2 therefore1 though only cooled to the same extent as the air outside1 it yields a heavier deposit of dew4 ,if you place the tray on bare ground1 you will find on a dewy night that the inside of the tray is quite wet4 ,on a dewy night you will observe that the under part of the gravel of the road is dripping wet when the top is dry4 ,you will find1 too1 that around pieces of iron and old implements in the field1 there is a very marked increase of grass1 owing to the deposit of moisture on these articles--moisture which has been condensed by the cold metal from the vapour-charged air1 which has risen from the ground on dewy nights4 ,but all doubt upon this important matter is removed by a most successful experiment with a fine balance1 which weighs to a quarter of a grain4 ,if vapour rises from the ground for any length of time during dewy nights1 the soil which gives off the vapour must lose weight4 ,to test this1 cut from the lawn a piece of turf six inches square and a quarter of an inch thick4 ,place this in a shallow pan1 and carefully note the weight of both turf and pan with the sensitive balance4 ,to prevent loss by evaporation1 the weighing should be done in an open shed4 ,then place the pan and turf at sunset in the open cut4 ,five hours afterwards remove and weigh them1 and it will be found that the turf has lost a part of its weight4 ,the vapour which rose from the ground during the formation of the dew accounts for the difference of weight4 ,this weighing-test will also succeed on bare ground4 ,when dealing with hoar-frost1 which is just frozen dew1 we shall find visible evidence of the rising of dew from the ground4 ,you know the beautiful song1 ,annie ,laurie1 which begins with-- ,maxwelton's braes are bonnie1 ,where early fa's the dew-- well1 you can no longer say that the dew falls1 for it rises from the ground4 ,the song1 however1 will be sung as sweetly as ever2 for the spirit of true poetry defies the cold letter of science4 ,,chapter ,,iii ,,true ,,and ,,false ,,dew ,ever since men could observe and think1 they have admired the diamond globules sparkling in the rising sun4 ,these dew-drops were considered to be shed from the bosom of the morn into the blooming flowers and rich grass-leaves4 ,ballantine's beautiful song of ,providential care tells us that ,ilka blade o' grass keps it's ain drap o' dew4 ,but1 alas6 we have to bid good-bye to the appellation dew-drop4 ,what was popularly and poetically called dew is not dew at all4 ,then what is it8 ,on what we have been accustomed to call a dewy night1 after the brilliant summer sun has set1 and the stars begin to peep out of the almost cloudless sky1 let us take a look at the produce of our vegetable garden4 ,on the broccoli are found glistening drops2 but on the peas1 growing next them1 we find nothing4 ,a closer examination shows us that the moisture on the plants is not arranged as would be expected from the ordinary laws of radiation and condensation4 ,there is no generally filmy appearance over the leaves2 the moisture is collected in little drops placed at short distances apart1 along the edges of the leaves all round4 ,now place a lighted lantern below one of the blades of the broccoli1 and a revelation will be made4 ,the brilliant diamond-drops that fringe the edge of the blade are all placed at the points where the nearly colourless veins of the blade come to the outer edge4 ,the drops are not dew at all1 but the exudation of the healthy plant1 which has been conveyed up these veins by strong root-pressure4 ,the fact is that the root acts as a kind of force-pump1 and keeps up a constant pressure inside the tissues of the plant4 ,one of the simplest experiments suggested by ,dr4 ,aitken is to lift a single grass-plant1 with a clod of moist earth attached to it1 and place it on a plate with an inverted tumbler over it4 ,in about an hour1 drops will begin to exude1 and the tip of nearly every blade will be found to be studded with a diamond-like drop4 ,next substitute water-pressure4 ,remove a blade of broccoli and connect it by means of an india-rubber tube with a head of water of about forty inches4 ,place a glass receiver over it1 so as to check evaporation1 and leave it for an hour4 ,the plant will be found to have excreted water freely1 some parts of the leaves being quite wet1 while drops are collected at the places where they appeared at night4 ,if the water pressed into the leaf is coloured with aniline blue1 the drops when they first appear are colourless2 but before they grow to any size1 the blue appears1 showing that little water was held in the veins4 ,the whole leaf soon gets coloured of a fine deep blue-green1 like that seen when vegetation is rank2 this shows that the injected liquid has penetrated through the whole leaf4 ,again1 the surfaces of the leaves of these drop-exuding plants never seem to be wetted by the water4 ,it is because of the rejection of water by the leaf-surface that the exuded moisture from the veins remains as a drop4 ,these observations and experiments establish the fact that the drops which first make their appearance on grass on dewy nights are not dew-drops at all1 but the exuded watery juices of the plants4 ,if now we look at dead leaves we shall find a difference of formation of the moisture on a dewy night3 the moisture is spread equally over1 where equally exposed4 ,the moisture exuded by the healthy grass is always found at a point situated near the tip of the blade1 forming a drop of some size2 but the true dew collects later on evenly all over the blade4 ,the false dew forms a large glistening diamond-drop1 whereas the true dew coats the blade with a fine pearly lustre4 ,brilliant globules are produced by the vital action of the plant1 especially beautiful when the deep-red setting sun makes them glisten1 all a-tremble1 with gold light2 while an infinite number of minute but shining opal-like particles of moisture bedecks the blade-surfaces1 in the form of the gentle dew-- ,like that which kept the heart of ,eden green ,before the useful trouble of the rain4 ,,chapter ,,iv ,,hoar-,,frost ,all in this country are familiar with the beauty of hoar-frost4 ,the children are delighted with the funny figures on the glass of the bedroom window on a cold winter morning4 ,frost is a wonderful artist2 during the night he has been dipping his brush into something like diluted schist1 and laying it gracefully on the smooth panes4 ,and1 as you walk over the meadows1 you observe the thin white films of ice on the green pasture2 and the clear1 slender blades seem like crystal spears1 or the lashes of light that trim the stars4 ,you all know what hoar-frost is1 though most in the country give it the expressive name of rime4 ,but you are not all aware of how it is formed4 ,hoar-frost is just frozen dew4 ,in a learned paper1 written in #aghd1 ,professor ,wilson of ,glasgow made this significant remark3 ,this is a subject which1 besides its entire novelty1 seems1 upon other accounts1 to have a claim to some attention4 ,he observed1 in that exceptionally cold winter1 that1 when sheets of paper and plates of metal were laid out1 all began to attract hoar-frost as soon as they had time to cool down to the temperature of the air4 ,he was struck with the fact that1 while the thermometer indicated #cf degrees of frost a few feet above the ground and #dd degrees of frost at the surface of the snow1 there were only #h degrees of frost at a point #c inches below the surface of the snow4 ,if he had only thought of placing the thermometer on the grass1 under the snow1 he would have found it to register the freezing-point only4 ,and had he inserted the instrument below the ground1 he would have found it registering a still higher temperature4 ,that fact would have suggested to him the formation of hoar-frost2 that the water-vapour from the warm soil was trapped by a cold stratum of air and frozen when in the form of dew4 ,one of the most interesting experiments1 without apparatus1 which you can make is in connection with the formation of hoar-frost1 when there is no snow on the ground1 in very cold weather4 ,if it has been a bright1 clear1 sunny day in ,january1 the effect can be better observed4 ,look over the garden1 grass1 and walks on the morning after the intense cold of the night2 big plane-tree leaves may be found scattered over the place4 ,you see little or no hoar-frost on the upper surface of the leaves4 ,but turn up the surface next the earth1 or the road1 or the grass1 and what do you see8 ,you have only to handle the leaf in this way to be brightly astonished4 ,a thick white coating of hoar-frost1 as thick as a layer of snow1 is on the under surface4 ,if a number of leaves have been overlapping each other1 there will be no coating of hoar-frost under the top leaves2 but when you reach the lowest layer1 next the bare ground1 you will find the hoar-frost on the under surface of the leaves4 ,now that is positive proof that the hoar-frost has not fallen from the air1 but has risen from the earth4 ,the sun's heat on the previous day warmed the earth4 ,this heat the earth retained till evening4 ,as the air chilled1 the water-vapour from the warmer earth rose from its surface1 and was arrested by the cold surface of the leaves4 ,so cold was that surface that it froze the water-vapour when rising from the earth1 and formed hoar-frost in very large quantities4 ,when this happens later on in the season1 one may be almost sure of having rain in the forenoon4 ,as hoar-frost is just frozen dew1 ,i can even more surely convince you of the formation of hoar-frost as rising from the ground by observations made by me at my manse in ,strathmore1 in ,june #ahib4 ,i mention this particularly because then was the most favourable testing-time that has ever occurred during meteorological observations4 ,june #ith was the warmest ,june day 7with one exception7 for twenty years4 ,the thermometer reached #hc deg4 ,fahr4 in the shade4 ,next day was the coldest ,june day 7with one exception7 for twenty years1 when the thermometer was as low as #ea deg4 in the shade4 ,but during the night my thermometer on the grass registered #cb deg4--the freezing point4 ,on the evening of the sultry day ,i examined the soil at #aj o'clock4 ,it was damp1 and the grass round it was filmy moist4 ,the leaves of the trees were crackling dry1 and all above was void of moisture4 ,the air became gradually chilly2 and as gradually the moisture rose in height on the shrubs and lower branches of small trees4 ,the moon shone bright1 and the stars showed their clear1 chilly eyes4 ,the soil soon became quite wet1 the low grass was dripping with moisture1 and the longer grass was becoming dewed4 ,this gave the best natural evidence of the rising of the dew that ,i ever witnessed4 ,but everything was favourable for the observation--the cold air incumbent on the rising1 warm1 moist vapour from the soil fixing the dew-point1 when the projecting blades seized the moisture greedily and formed dew4 ,had the temperature been a little below the freezing-point1 hoar-frost would have been beautifully formed4 ,,chapter ,v ,,fog ,to many nothing is more troublesome than a dense fog in a large town4 ,it paralyses traffic1 it is dangerous to pedestrians1 it encourages theft1 it chokes the asthmatic1 and chills the weak-lunged4 ,in the country it is disagreeable enough2 but never so intensely raw and dense as in the city4 ,on the sea1 too1 the fog is disagreeable and fraught with danger4 ,the fog-horn is heard1 in its deep1 sombre note1 from the lighthouse tower1 when the strong artificial light is almost useless4 ,but a peculiar sense of stagnation possesses the dweller of the large town1 when enveloped in a dense fog4 ,sometimes during the day1 through a thinner portion1 the sun will be dimly seen in copper hue1 like the moon under an eclipse4 ,the smoke-impregnated mass assumes a peculiar pea-soup colour4 ,now1 what is this fog8 ,how is it formed8 ,it has been ascertained that fogs are dependent upon dust for their formation4 ,without dust there could be no fogs1 there would be only dew on the grass and road4 ,instead of the dust-impregnated air that irritates the housekeeper1 there would be the constant dripping of moisture on the walls1 which would annoy her more4 ,ocular demonstration can testify to this4 ,if two closed glass receivers be placed beside each other1 the one containing ordinary air1 and the other filtered air 7i4e4 air deprived of its dust by being driven through cotton wool71 and if jets of steam be successively introduced into these1 a strange effect is noticed4 ,in the vessel containing common air the steam will be seen rising in a dense cloud2 then a beautiful white foggy cloud will be formed1 so dense that it cannot be seen through4 ,but in the vessel containing the filtered air1 the steam is not seen at all2 there is not the slightest appearance of cloudiness4 ,in the one case1 where there was the ordinary atmospheric dust1 fog at once appeared2 in the other case1 where there was no dust in suspension1 the air remained clear and destitute of fog4 ,invisible dust1 then1 is necessary in the air for the formation of fogs4 ,the reason of this is that a free-surface must exist for the condensation of the vapour-particles4 ,the fine particles of dust in the air act as free-surfaces1 on which the fog is formed4 ,where there is abundance of dust in the air and little water-vapour present1 there is an over-proportion of dust-particles2 and the fog-particles are1 in consequence1 closely packed1 but light in form and small in size1 and take the lighter appearance of fog4 ,accordingly1 if the dust is increased in the air1 there is a proportionate increase of fog4 ,every fog-particle1 then1 has embosomed in it an invisible dust-particle4 ,but whence comes the dust8 ,from many sources4 ,it is organic and inorganic4 ,so very fine is the inorganic dust in the atmosphere that1 if the two-thousandth part of a grain of fine iron be heated1 and the dust be driven off and carried into a glass receiver of filtered air1 the introduction of a jet of steam into that receiver would at once occasion an appreciable cloudiness4 ,this is why fogs are so prevalent in large towns4 ,next the minute brine-particles1 driven into the air as fog forms above the ocean surface1 are the burnt sulphur-particles emanating from the chimneys in towns4 ,the brilliant flame1 as well as the smoky flame1 is a fog-producer4 ,if gas is burnt in filtered air1 intense fog is produced when water-vapour is introduced4 ,products of combustion from a clear fire and from a smoky one produce equal fogging4 ,the fogs that densely fill our large towns are generally less bearable than those that veil the hills and overhang the rivers4 ,it is the sulphur1 however1 from the consumed coals1 which is the active producer of the fogs of a large town4 ,the burnt sulphur condenses in the air to very fine particles1 and the quantity of burnt sulphur is enormous4 ,no less than seven and a half millions of tons of coals are consumed in ,london4 ,now1 the average amount of sulphur in ,english coal is one and a quarter per cent4 ,that would give no less than #ic1gej tons of sulphur burned every year in ,london fires4 ,now1 if we reckon that on an average twice the quantity of coals is consumed there on a winter day that is consumed on a summer day1 no less than #cdg tons of the products of combustion 7in extremely fine particles7 are driven into the superincumbent air of ,london every winter day4 ,this is an enormous quantity1 quite sufficient to account for the density of the fogs in that city4 ,,chapter ,,vi ,,the ,,numbering ,,of ,,the ,,dust ,if the shutters be all but closed in a room1 when the sun is shining in1 myriads of floating particles can be seen glistening in the stream of light4 ,their number seems inexhaustible4 ,according to ,milton1 the follies of life are-- ,thick and numberless1 ,as the gay motes that people the sunbeams4 ,can these1 then1 be counted8 ,yes1 ,dr4 ,aitken has numbered the dust of the air4 ,i shall never forget my rapt astonishment the day ,i first numbered the dust in the lecture-room of the ,royal ,society of ,edinburgh1 with his instrument and under his direction4 ,this wonderfully ingenious instrument was devised on this principle1 that every fog-particle has entombed in it an invisible dust-particle4 ,a definite small quantity of common air is diluted with a fixed large quantity of dustless air 7i4e4 air that has been filtered through cotton-wool74 ,the mixture is allowed to be saturated with water-vapour4 ,then the few particles of dust seize the moisture1 become visible in fine drops1 fall on a divided plate1 and are there counted by means of a magnifying glass4 ,that is the secret6 ,i shall now give you a general idea of the apparatus4 ,into a common glass flask of carafe shape1 and flat-bottomed1 of #cj cubic inches capacity1 are passed two small tubes1 at the end of one of which is attached a small square silver table1 #a inch in length4 ,a little water having been inserted1 the flask is inverted1 and the table is placed exactly #a inch from the inverted bottom1 so that the contents of air right above the table are #a cubic inch4 ,this observing table is divided into #ajj equal squares1 and is highly polished1 with the burnishing all in one direction1 so that during the observations it appears dark1 when the fine mist-particles glisten opal-like with the reflected light in order that they may be more easily counted4 ,the tube to which the silver table is attached is connected with two stop-cocks1 one of which can admit a small measured portion of the air to be examined4 ,the other tube in the flask is connected with an air-pump of #aj cubic inches capacity4 ,over the flask is placed a covering1 coloured black in the inside4 ,in the top of this cover is inserted a powerful magnifying glass1 through which the particles on the silver table can be easily counted4 ,a little to the side of this magnifier is an opening in the cover1 through which light is concentrated on the table4 ,to perform the experiment1 the air in the flask is exhausted by the air-pump4 ,the flask is then filled with filtered air4 ,one-tenth of a cubic inch of the air to be examined is then introduced into the flask1 and mixed with the #cj cubic inches of dustless air4 ,after one stroke of the air-pump1 this mixed air is made to occupy an additional space of #aj cubic inches2 and this rarefying of the air so chills it that condensation of the water-vapour takes place on the dust-particles4 ,the observer1 looking through the magnifying-glass upon the silver table1 sees the mist-particles fall like an opal shower on the table4 ,he counts the number on a single square in two or three places1 striking an average in his mind4 ,suppose the average number upon a single square were five1 then on the whole table there would be #ejj2 and these #ejj particles of dust are those which floated invisibly in the cubic inch of mixed air right above the table4 ,but1 as there are #dj cubic inches of mixed air in the flask and barrel1 the number of dust-particles in the whole is #bj1jjj4 ,that is1 there are #bj1jjj dust-particles in the same quantity of common air 7one-tenth of a cubic inch7 which was introduced for examination4 ,in other words1 a cubic inch of the air contained #bjj1jjj dust-particles--nearly a quarter of a million4 ,the day ,i used the instrument we counted #d1jjj1jjj of dust-particles in a cubic inch of the air outside of the room1 due to the quantity of smoke from the passing trains4 ,dr4 ,aitken has counted in #a cubic inch of air immediately above a ,bunsen flame the fabulous number of #dhi1jjj1jjj of dust-particles4 ,a small instrument has been constructed which can bring about results sufficiently accurate for ordinary purposes4 ,it is so constructed that1 when the different parts are unscrewed1 they fit into a case #d-a_/b inches by #b-a_/b by #a-a_/d deep--about the size of an ordinary cigar-case4 ,after knowing this1 we are apt to wonder why our lungs do not get clogged up with the enormous number of dust-particles4 ,in ordinary breathing1 #cj cubic inches of air pass in and out at every breath1 and adults breathe about fifteen times every minute4 ,but the warm lung-surface repels the colder dust-particles1 and the continuous evaporation of moisture from the surface of the air-tubes prevents the dust from alighting or clinging to the surface at all4 ,,chapter ,,vii ,,dust ,,and ,,atmospheric ,,phenomena ,dr4 ,aitken has devoted a vast amount of attention to the enumeration of dust-particles in the air1 on the ,continent as well as in ,scotland1 to determine the effects of their variation in number4 ,on his first visit to ,hyeres1 in #ahij1 he counted with the instrument #ab1jjj dust-particles in a cubic inch of the air3 whereas in the following year he counted #bej1jjj4 ,he observed1 however1 that where there was least dust1 the air was very clear2 whereas with the maximum of dust1 there was a very thick haze4 ,at ,mentone1 the corresponding number was #ac1jjj1 when the wind was blowing from the mountains2 but increased to #dcj1jjj1 when the wind was blowing from the populous town4 ,on his first visit to the ,rigi ,kulm1 in ,switzerland1 the air was remarkably clear and brilliant1 and the corresponding number never exceeded #cc1jjj2 but1 on his second visit1 he counted no less than #aff1jjj4 ,this was accounted for by a thick haze1 which rendered the lower ,alps scarcely visible4 ,the upper limit of the haze was well defined2 and though the sky was cloudless1 the sun looked like a harvest moon1 and required no eagle's eye to keep fixed on it4 ,next day there was a violent thunder-storm4 ,at #f ,p4,m4 the storm commenced1 and #fj1jjj dust-particles to the cubic inch of air were registered2 but in the middle of the storm he counted only #ac1jjj4 ,there was a heavy fall of hail at this time1 and he accounts for the diminution of dust-particles by the down-rush of purer upper air1 which displaced the contaminated lower air4 ,at the ,lake of ,lucerne there was an exceptional diminution of the number in the course of an hour1 viz4 from #aga1jjj to #bh1jjj in a cubic inch4 ,on looking about1 he found that the direction of the wind had changed1 bringing down the purer upper air to the place of observation4 ,the bending downwards of the trees by the strong wind showed that it was coming from the upper air4 ,returning to ,scotland1 he continued his observations at ,ben ,nevis and at ,kingairloch1 opposite ,appin1 ,mr4 ,rankin using the instrument at the top of the mountain4 ,these observations showed in general that on the mountain southerly1 south-easterly1 and easterly winds were more impregnated with dust-particles1 sometimes containing #acc1jjj per cubic inch4 ,northerly winds brought pure air4 ,the observations at sea-level showed a certain parallelism to those on the summit of the mountain4 ,with a north-westerly wind the dust-particles reached the low number of #cjj per cubic inch1 the lowest recorded at any low-level station4 ,the general deductions which he made from his numerous observations during these two years are that 7#a7 air coming from inhabited districts is always impure2 7#b7 dust is carried by the wind to enormous distances2 7#c7 dust rises to the tops of mountains during the day2 7#d7 with much dust there is much haze2 7#e7 high humidity causes great thickness of the atmosphere1 if accompanied by a great amount of dust1 whereas there is no evidence that humidity alone has any effect in producing thickness2 7#f7 and there is generally a high amount of dust with high temperature1 and a low amount of dust with low temperature4 ,,chapter ,,viii ,a ,,fog-,,counter ,next to the enumeration of the dust-particles in the atmosphere is the marvellous accuracy of counting the number of particles in a fog4 ,the same ingenious inventor has constructed a fog-counter for the purpose2 and the number of fog-particles in a cubic inch can be ascertained4 ,this instrument consists of a glass micrometer divided into squares of a known size1 and a strong microscope for observing the drops on the stage4 ,the space between the micrometer and the microscope is open1 so that the air passes freely over the stage2 and the drops that fall on its surface are easily seen4 ,these drops are very small2 many of them when spread on the glass are no more than the five-hundredth of an inch in diameter4 ,in observing these drops1 the attention requires to be confined to a limited area of the stage1 as many of the drops rapidly evaporate1 some almost as soon as they touch the glass1 whilst the large ones remain a few seconds4 ,in one set of ,dr4 ,aitken's observations1 in ,february #ahia1 the fog was so thick that objects beyond a hundred yards were quite invisible4 ,the number of drops falling per second varied greatly from time to time4 ,the greatest number was #cbc drops per square inch in one second4 ,the high number never lasted for long1 and in the intervals the number fell as low as #cb1 or to one-tenth4 ,if we knew the size of these drops1 we might be able to calculate the velocity of their fall1 and from that obtain the number in a cubic inch4 ,an ingenious addition is put to the instrument in order to ascertain this directly4 ,it is constructed so as to ascertain the number of particles that fall from a known height4 ,under a low-power microscope1 and concentric with it1 is mounted a tube #b inches long and #a-a_/b inch in diameter1 with a bottom and a cover1 which are fixed to an axis parallel with the axis of the tube1 so that1 by turning a handle1 these can be slid sideways1 closing or opening the tube at both ends when required4 ,in the top is a small opening1 corresponding to the lens of the microscope1 and in the centre of the bottom is placed the observing-stage illumined by a spot-mirror4 ,the handle is turned1 and the ends are open to admit the foggy air4 ,the handle is quickly reversed1 and the ends are closed1 enabling the observer to count on the stage all the fog-particles in the two inches of air over it4 ,the number of dust-particles in the air which become centres of condensation depends on the rate at which the condensation is taking place4 ,the most recent observations show that quick condensation causes a large number of particles to become active1 whereas slow condensation causes a small number4 ,after the condensation has ceased1 a process of differentiation takes place1 the larger particles robbing the smaller ones of their moisture1 owing to the vapour-pressure at the surface of the drops of large curvature being less than at the surface of drops of smaller curvature4 ,by this process the particles in a cloud are reduced in number2 the remaining ones1 becoming larger1 fall quicker4 ,the cloud thus becomes thinner for a time4 ,a strong wind1 suddenly arising1 will cause the cloud-particles to be rapidly formed3 these will be very numerous1 but very small--so small that they are just visible with great care under a strong magnifying lens used in the instrument4 ,but in slowly formed clouds the particles are larger1 and therefore more easily visible to the naked eye4 ,though the particles in a fog are slightly finer1 the number is about the same as in a cloud--that is1 generally4 ,as clouds vary in density1 the number of particles varies4 ,sometimes in a cloud one cannot see farther than #cj yards2 whereas in a few minutes it clears up a little1 so that we can see #ajj yards4 ,of course1 the denser the cloud the greater the number of water-particles falling on the calculating-stage of the instrument4 ,very heavy falls of cloud-particles seldom last more than a few seconds1 the average being about #cbe on the square inch per second1 the maximum reaching to #abij4 ,this is about four times the number counted in a fog4 ,yet the particles are so very small that they evaporate instantly when they reach a slight increase of temperature4 ,,chapter ,,ix ,,formation ,,of ,,clouds ,in our ordinary atmosphere there can be no clouds without dust4 ,a dust-particle is the nucleus that at a certain humidity becomes the centre of condensation of the water-vapour so as to form a cloud-particle2 and a collection of these forms a cloud4 ,this condensation of vapour round a number of dust-particles in visible form gives rise to a vast variety of cloud-shapes4 ,there are two distinct ways in which the formation of clouds generally takes place4 ,either a layer of air is cooled in a body below the dew-point2 or a mass of warm and moist air rises into a mass which is cold and dry4 ,the first forms a cloud1 called1 from being a layer1 stratus2 the second forms a cloud1 called1 from its heap appearance1 cumulus4 ,the first is widely extended and horizontal1 averaging #ahjj feet in height2 the second is convex or conical1 like the head of a sheaf1 increasing upward from a level base1 averaging from #dejj feet to #fjjj feet in height4 ,there are endless combinations of these two2 but at the height of #bg1jjj feet1 where the cloud-particles are frozen1 the structure of the cloud is finer1 like mares' tails1 receiving the name cirrus4 ,when the cirrus and cumulus are combined1 in well-defined roundish masses1 what is familiarly described as a mackerel sky is beautifully presented4 ,the dark mass of cloud1 called nimbus1 is the threatening rain-cloud1 about #dejj feet in height4 ,at the ,international ,meteorological ,conference at ,munich1 in #ahib1 twelve varieties of clouds were classified1 but those named above are the principal4 ,in a beautiful sunset one can sometimes notice two or three distances of clouds1 the sun shedding its gold light on the full front of one set1 and only fringing with vivid light the nearer range4 ,although no man has wrought so hard as ,dr4 ,aitken to establish the principle that clouds are mainly due to the existence of dust-particles which attract moisture on certain conditions1 yet even twenty years ago he said that it was probable that sunshine might cause the formation of nuclei and allow cloudy condensation to take place where there was no dust4 ,under certain conditions the sun gives rise to a great increase in the number of nuclei4 ,accordingly1 he has carefully tested a few of the ordinary constituents and impurities in our atmosphere to see if sunshine acted on them in such a way as to make them probable formers of cloud-particles4 ,he tested various gases1 with more or less success4 ,he found that ordinary air1 after being deprived of its dust-particles and exposed to sunshine1 does not show any cloudy condensation on expansion2 but1 when certain gases are in the dustless air1 a very different result is obtained4 ,he first used ammonia1 putting one drop into six cubic inches of water in a flask1 and sunning this for one minute2 the result was a considerable quantity of condensation1 even with such a weak solution4 ,when the flask was exposed for five minutes1 the condensation by the action of the sunshine was made more dense4 ,hydrogen peroxide was tested in the same way1 and it was found to be a powerful generator of nuclei4 ,curious is it that sulphurous acid is puzzling to the experimentalist for cloud formation4 ,it gives rise to condensation in the dark2 but sunshine very conclusively increases the condensation4 ,chlorine causes condensation to take place without supersaturation2 sulphuretted hydrogen 7which one always associates with the smell of rotten eggs7 gives dense condensation after being exposed to sunshine4 ,though the most of these nuclei1 due to the action of sunshine in the gases1 remain active for cloudy condensation for a comparatively short space of time--fifteen minutes to half-an-hour--yet the experiments show that it is possible for the cloudy condensation to take place in certain circumstances in the absence of dust4 ,this seems paradoxical in the light of the former beautiful experiments2 but1 in ordinary circumstances1 dust is needed for the formation of clouds4 ,however1 supposing there is any part of the upper air free from dust1 it is now found possible1 when any of these gases experimented on be present1 for the sun to convert them into nuclei of condensation1 and permit of clouds being formed in dustless air1 miles above the surface of the earth4 ,in the lower atmosphere there are always plenty of dust-particles to form cloudy condensation1 whether the sun shines or not4 ,these are produced by the waste from the millions of meteors that daily fall into the air4 ,but in the higher atmosphere1 clouds can be formed by the action of the sun's rays on certain gases4 ,this is a great boon to us on the earth2 for it assures us of clouds being ever existing to defend us from the sun's extra-powerful rays1 even when our atmosphere is fairly clear4 ,this is surely of some meteorological importance4 ,,chapter ,x ,,decay ,,of ,,clouds ,from the earliest ages clouds have attracted the attention of observers4 ,varied are their forms and colours1 yet in our atmosphere there is one law in their formation4 ,cloud-particles are formed by the condensation of water-vapour on the dust-particles invisibly floating in the atmosphere1 up to thousands--and even millions--in the cubic inch of air4 ,but observers have not directed their attention so much to the decay of clouds--in fact1 the subject is quite new4 ,and yet how suggestive is the subject6 ,the process of decay in clouds takes place in various ways4 ,a careful observer may witness the gradual wasting away and dilution into thin air of even great stretches of cloud1 when circumstances are favourable4 ,in ,may #ahif my attention was particularly drawn to this at my manse in ,strathmore4 ,in the middle of that exceptionally sultry month1 ,i was arrested by a remarkable transformation scene4 ,it was the hottest ,may for seventy-two years1 and the driest for twenty-five years4 ,the whole parched earth was thirsting for rain4 ,all the morning my eyes were turned to the clouds in the hope that the much-desired shower should fall4 ,till ten o'clock the sun was not seen1 and there was no blue in the sky4 ,nor was there any haze or fog4 ,but suddenly the sun shone through a thinner portion of the enveloping clouds1 and1 to the north1 the sky began to open4 ,as if by some magic spell there was1 in a quarter of an hour1 more blue to be seen than clouds4 ,at the same time1 near the horizon1 a haze was forming1 gradually becoming denser as time wore on4 ,in an hour the whole clouds were gone1 and the glorious orb of day dispelled the moisture to its thin-air form4 ,this was a pointed and rapid illustration of the decay from cloud-form to haze1 and then to the pure vapoury sky4 ,it was an instance of the reverse process4 ,as the sun cleared through1 the temperature in the cloud-land rose and evaporation took place on the surface of the cloud-particles1 until by an untraceable1 but still a gradual process through fog1 the haze was formed4 ,even then the heat was too great for a definite haze1 and the water-vapour returned to the air1 leaving the dust-particles in invisible suspension4 ,but clouds decay in another way4 ,this ,i will illustrate in the next chapter on ,it always rains4 ,what strikes a close observer is the difference of structure in clouds which are in the process of formation and those which are in the process of decay4 ,in the former the water-particles are much smaller and far more numerous than in the latter4 ,while the particles in clouds in decay are large enough to be seen with the unaided eye1 when they fall on a properly lighted measuring table1 they are so small in clouds in rapid formation that the particles cannot be seen without the aid of a strong magnifying glass4 ,observers have assumed that the whole explanation of the fantastic shapes taken by clouds is founded on the process of formation2 but ,dr4 ,aitken has pointed out that ripple-marked clouds1 for instance1 have been clouds of decay4 ,when what is called a cirro-stratus cloud--mackerel-like against the blue sky--is carefully observed in fine weather1 it will be found that it frequently changes the ripple-marked cirrus in the process of decay to vanishing4 ,where the cloud is thin enough to be broken through by the clear air that is drawn in between the eddies1 the ripple markings get nearer and nearer the centre1 as the cloud decays4 ,and1 at last1 when nearly dissolved1 these markings are extended quite across the cloud4 ,whether1 then1 we consider the cases of clouds gradually melting away back into their original state of blue water-vapour1 or the constant fine raining from clouds and re-formation by evaporation1 or the transformation of such clouds as the cirro-stratus into the ripple-marked cirrus1 we are forced to the conclusion that in clouds there is not always development1 but sometimes degeneration2 not always formation1 but sometimes decay4 ,,chapter ,,xi ,,it ,,always ,,rains ,all are familiar with the answer given by the native of ,skye to the irate tourist on that island1 who1 for the sixth day drenched1 asked the question3 ,does it always rain here8 ,na6 answered the workman1 without at all understanding the joke2 feiles it snaas 7sometimes it snows74 ,yet1 strange to say1 the tourist's question has been answered in the affirmative in every place where a cloud is overhead1 visible or invisible4 ,whenever a cloud is formed1 it begins to rain2 and the drops shower down in immense numbers1 though most minute in size--the playful fancies of the mighty sky4 ,no doubt it is only in certain circumstances that these drops are attracted together so as to form large drops1 which fall to the earth in genial showers to refresh the thirsty soil1 or in a terrible deluge to cause great destruction4 ,but when the temperature and pressure are not suitable for the formation of what we commonly know as the rain1 the fine drops fall into the air under the cloud1 where they immediately evaporate from their dust free-surfaces1 if the air is dry and warm4 ,this is1 in other words1 the decay of clouds4 ,it is a curious fact that objects in a fog may not be wetted1 when the number of water-particles is great4 ,it seems that these water-particles all evaporate so quickly that even one's hand or face is not sensible of being wetted4 ,the particles are minutely small2 and they may evaporate even before reaching the warm skin1 by reason of the heated air over the skin4 ,there is a peculiarly warm sensation in the centre of a cumulus cloud1 especially when it is not dense4 ,a glow of heat seems to radiate from all points4 ,yet the face and hands are quite dry1 and exposed objects are not wetted2 but it is really always raining4 ,that is a curious discovery4 ,it is radiant heat that is the cause of the remarkable result4 ,the rays of the sun1 which strike the upper part of the cloud1 not only heat that surface but also penetrate the cloud and fall on the surface of bodies within1 generating heat there4 ,these heated surfaces again radiate heat into the air attached to them4 ,this warm air receives the fine raindrops in the cloud1 and dissolves the moisture from the dust-particles before the moisture can reach the surfaces exposed4 ,that a vast amount of radiant heat rushes through a cloud is clearly shown by exposing a thermometer with black bulb in vacuo4 ,on some occasions1 a thermometer would indicate from #dj deg4 to #ej deg4 above the temperature of the air1 thus proving the surface to be quite dry4 ,these observations have been corroborated on ,mount ,pilatus1 near ,lucerne--#ajjj feet higher and more isolated than the ,rigi4 ,the summit was quite enveloped in cloud1 and1 though one might naturally conclude that the air was dense with moisture1 yet the wooden seats1 walls1 and all exposed surfaces were quite dry4 ,strange to say1 however1 the thermometers hung up got wet rapidly1 and the pins driven into the wooden post to support them rapidly became moist4 ,a thermometer lying on a wooden seat stood at #fj deg41 while one hung up read only #dh deg4 ,this difference was caused by radiant heat4 ,it is well known that1 when bodies are exposed to radiant heat1 they are heated in proportion to their size2 the smaller1 then1 may be moist1 when the larger are dry by radiation4 ,the effect of the sun's penetrating heat through the cloud is to heat exposed objects above the temperature of the air2 and if the objects are of any size they are considerably heated1 and retain their heat more1 while at the same time around them is a layer of warm air which is quite sufficient to force the water-vapour to leave the dust-particles in the fine rain4 ,hence seats1 walls1 posts1 c41 are quite dry1 though they are in the middle of a cloud4 ,they are large enough to throw off the moisture by the retained heat1 or by the large amount of surrounding heat2 whereas1 small bodies1 which are not heated to the same degree and cannot therefore retain their heat so easily1 have not heat-power sufficient to withstand the moisture1 and they become wetted4 ,hence1 by the radiant heat1 the large exposed objects are dry in the cloud2 whereas small objects are damp1 and1 in some cases1 dripping with wet4 ,the fact is1 then1 that whenever a cloud overhangs1 rain is falling1 though it may not reach the earth on account of the dryness of the stratum of air below the cloud1 and the heat of the air over the earth4 ,so that on a summer day1 with the gold-fringed1 fleecy clouds sailing overhead1 it is really raining2 but the drops1 being very small1 evaporate long before reaching the earth4 ,as ,ariel sings at the end of ,the ,tempest of ,shakespeare1 ,the rain1 it raineth every day4 ,it rains1 but much of the melting of the clouds is reproduced by a wonderful circularity--the moisture evaporating1 seizing other dust-particles1 forming cloud-particles1 falling again1 and so on ad infinitum1 during the existing circumstances4 ,,chapter ,,xii ,,haze ,what is haze8 ,the dictionary says1 a fog4 ,well1 haze is not a fog4 ,in a fog1 the dust-particles in the air have been fully clothed with water-vapour2 in a haze1 the process of condensation has been arrested4 ,cloudy condensation is changed to haze by the reduction of its humidity4 ,dr4 ,aitken invented a simple apparatus for testing the condensing power of dust1 and observing if water-vapour condensed on the deposited dust in unsaturated air4 ,the dust from the air has first to be collected4 ,this is done by placing a glass plate vertically1 and in close contact with one of the panes of glass in the window1 by means of a little india-rubber solution4 ,the plate being thus rendered colder than the air in the room1 the dust is deposited on it4 ,construct a rectangular box1 with a square bottom1 #a-a_/b inches a side and #c_/d inch deep1 and open at the top4 ,cover the top edge of the box with a thickness of india-rubber4 ,place the dusty plate--a square glass mirror1 #d inches a side--on the top of the india-rubber1 and hold it down by spring catches1 so as to make the box water-tight4 ,the box has been provided with two pipes1 one for taking in water and the other for taking away the overflow1 with the bulb of a thermometer in the centre4 ,clean the dust carefully off one half of the mirror1 so that one half of the glass covering the box is clean and the other half dusty4 ,pour cold water through the pipe into the box1 so as to lower the temperature of the mirror1 and carefully observe when condensation begins on the clean part and on the dusty part1 taking a note of the difference of temperature4 ,the condensation of the water-vapour will appear on the dust-particles before coming down to the natural dew-point temperature of the clean glass4 ,and the difference between the two temperatures indicates the temperature above the dew-point at which the dust has condensed the water-vapour4 ,magnesia dust has small affinity for water-vapour2 accordingly1 it condenses at almost exactly the same temperature as the glass4 ,but gunpowder has great condensing power4 ,all have noticed that the smoke from exploded gunpowder is far more dense in damp than in dry weather4 ,in the experiment it will be found that the dust from gunpowder smoke begins to show signs of condensing the vapour at a temperature of #i deg4 ,fahr4 above the dew-point4 ,in the case of sodium dust1 the vapour is condensed from the air at a temperature of #cj deg4 above the dew-point4 ,dust collected in a smoking-room shows a decidedly greater condensing power than that from the outer air4 ,we can now understand why the glass in picture frames and other places sometimes appears damp when the air is not saturated4 ,when in winter the windows are not often cleaned1 a damp deposit may be frequently seen on the glass4 ,any one can try the experiment4 ,clean one half of a dusty pane of glass in cold weather1 and the clean part will remain undewed and clear1 while the dusty part is damp to the eye and greasy to the touch4 ,these observations indicate that moisture is deposited on the dust-particles from air1 which is not saturated1 and that the condensation takes place while the air is comparatively dry1 before the temperature is lowered to the dew-point4 ,there is1 then1 no definite demarcation between what seems to us clear air and thick haze4 ,the clearest air has some haze1 and1 as the humidity increases1 the thickness of the air increases4 ,in all haze the temperature is above the dew-point4 ,the dust-particles have only condensed a very small amount of the moisture so as to form haze1 before the fuller condensation takes place at the dew-point4 ,at the ,italian lakes1 on many occasions when the air is damp and still1 every stage of condensation may be observed in close proximity1 not separated by a hard and fast line1 but when no one could determine where the clear air ended and the cloud began4 ,sometimes in the sky overhead a gradual change can be observed from perfect clearness to thick air1 and then the cloud4 ,a thick haze may be occasioned by an increased number of dust-particles with little moisture1 or of a diminished number of dust-particles with much moisture1 above the point of saturation4 ,the haze is cleared by this temperature rising1 so as to allow the moisture to evaporate from the dust-particles4 ,whenever the air is dry and hazy1 much dust is found in it2 as the dust decreases the haze also decreases4 ,for example1 ,dr4 ,aitken1 at ,kingairloch1 in one of the clearest districts of ,argyleshire1 on a clear ,july afternoon1 counted #djjj dust-particles in a cubic inch of the air2 whereas1 two days before1 in thick haze1 he counted no fewer than #fd1jjj in the cubic inch4 ,at ,dumfries the number counted on a very hazy day in ,october increased twenty-fold over the number counted the day before1 when it was clear4 ,all know that thick haze is usual in very sultry weather4 ,the wavy1 will-o'-the-wisp ripples near the horizon indicate its presence very plainly4 ,during the intense heat there is generally much dust in the atmosphere2 this dust1 by the high temperature1 attracts moisture from the apparently dry air1 though above the saturation point4 ,in all circumstances1 then1 the haze can be accounted for by the condensing power of the dust-particles in the atmosphere1 at a higher temperature than that required for the formation of fogs1 or mists1 or rain4 ,,chapter ,,xiii ,,hazing ,,effects ,,of ,,atmospheric ,,dust ,the transparency of the atmosphere is very much destroyed by the impurities communicated to it while passing over the inhabited areas of the country4 ,dr4 ,aitken devoted eighteen months to compare the amount of dusty impurities in different masses of air1 or of different airs brought in by winds from different directions4 ,he took ,falkirk for his centre of observations4 ,this town lies a little to the north of a line drawn between ,edinburgh and ,glasgow1 and is nearly midway between them4 ,if we draw a line due west from it1 and another due north1 we find that1 in the north-west quadrant so enclosed1 the population of that part of ,scotland is extremely thin1 the country over that area being chiefly mountainous4 ,in all other directions1 the conditions are quite different4 ,in the north-east quadrant are the fairly well-populated areas of ,aberdeenshire1 ,forfarshire1 and the thickly populated county of ,fife4 ,in the south-east quadrant are situated ,edinburgh and the well-populated districts of the south-east of ,scotland4 ,and in the south-west quadrant are ,glasgow and the large manufacturing towns which surround it4 ,the winds from three of these quadrants bring air polluted in its passage over populated areas1 whereas the winds from the north-west come comparatively pure4 ,the general plan of estimating the amount of haze is to note the most distant hill that can be seen through the haze4 ,the distance in miles of the farthest away hill visible is then called the limit of visibility of the air at the time4 ,for the observations made at ,falkirk1 only three hills are available1 one about four miles distant1 the ,ochils about fifteen miles distant1 and ,ben ,ledi about twenty-five miles distant--all in the north-west quadrant4 ,when the air is thick1 only the near hill can be seen2 then the ,ochils become visible as the air clears2 and at last ,ben ,ledi is seen1 when the haze becomes still less4 ,after ,ben ,ledi is visible1 it then becomes necessary to estimate the amount of haze on it1 in order to get the limit of visibility of the air at the time4 ,thus1 if ,ben ,ledi be half-hazed1 then the limit of visibility will be fifty miles4 ,in this way all the estimates of haze have been reduced to one scale for comparison4 ,as the result of all the observations it was found that1 as the dryness of the air increases1 the limit of visibility also increases4 ,a very marked difference in the transparency of the air was found with winds from the different directions4 ,in the north-west quadrant the winds made the air very clear1 whereas winds from all other directions made the air very much hazed4 ,the winds in the other three areas are nearly ten times more hazed than those from the north-west quadrant4 ,that is very striking4 ,the conclusion come to is that the air from densely inhabited districts is so polluted that it is fully nine times more hazed than the air that comes from the thinly inhabited districts2 in other words1 the atmosphere at ,falkirk is about ten times thicker when the wind is east or south than it would be if there were no fires and no inhabitants4 ,it is interesting to notice that the limit varies considerably for the same wind at the same humidity4 ,this is what might have been expected1 because from the observations made by the dust-counter the number of particles varied greatly in winds from the same directions1 but at different times4 ,this depends upon the rise and fall of the wind1 changes in the state of trade1 season of the year1 and other causes4 ,during a strike1 the dearth of coal will make a considerable diminution in the number of dust-particles in the air of large towns4 ,with a north wind1 the extreme limits of visibility are #abj to #bjj miles2 and with a north-west wind1 from #gj to #bej miles4 ,an east wind has as limits #d to #ej miles1 and a south-east wind #b to #fj miles4 ,one interesting fact to be noticed1 after wading through these tables1 is this--that1 as a general result1 the transparency of the air increases about #c4g times for any increase in dryness from #b deg4 to #h deg4 of wet-bulb depression4 ,that is1 the clearness of the air is inversely proportional to the relative humidity2 or1 put another way1 if the air is four times drier it is about four times clearer4 ,,chapter ,,xiv ,,thunder ,,clears ,,the ,,air ,the phrase thunder clears the air is familiar to all4 ,it contains a very vital truth1 yet even scientific men did not know its full meaning until just the other day4 ,it came by experience to people who had been for ages observing the weather2 and it is one of the most pointed of the weather-lore expressions4 ,folks got to know1 by a sort of rule-of-thumb1 truths which scientifically they were unable to learn4 ,and this is one4 ,perhaps1 therefore1 we should respect a little more what is called folk-lore1 or ordinary people's sayings4 ,experience has taught men many wonderful things4 ,in olden times they were keener natural observers4 ,they had few books1 but they had plenty of time4 ,they studied the habits of animals and moods of nature1 and they came wonderfully near to reaching the full truth1 though they could not give a reason for it4 ,the awe-inspiring in nature has especially riveted the attention of man4 ,and no appearance in nature joins more powerfully the elements of grandeur and awe than a heavy thunder-storm4 ,when1 suddenly1 from the breast of a dark thunder-cloud a brilliant flash of light darts zigzag to the earth1 followed by a loud crackling noise which softens in the distance into weaker volumes of sound1 terror seizes the birds of the air and the cattle in the field4 ,the man who is born to rule the storm rejoices in the powerful display2 but kings have trembled at the sight4 ,byron thus pictures a storm in the ,alps3-- ,far along ,from peak to peak1 the rattling crags among ,leaps the live thunder6 ,not from one lone cloud1 ,but every mountain now hath found a tongue1 ,and ,jura answers1 through her misty shroud1 ,back to the joyous ,alps1 who call to her aloud6 ,franklin found that lightning is just a kind of electricity4 ,no one can tell how it is produced2 yet a flash has been photographed4 ,when the flash is from one cloud to another there is sheet-lightning1 which is beautiful but not dangerous2 but1 when the electricity passes from a cloud to the earth in a forked form1 it is very dangerous indeed4 ,the flash is instantaneous1 but the sound of the thunder takes some time to travel4 ,roughly speaking1 the sound takes five seconds or six beats of the pulse to the mile4 ,all are now taught at school that it is the oxygen in the air which is necessary to keep us in life4 ,if mice are put into a glass jar of pure oxygen gas1 they will at once dance with exhilarating joy4 ,it occurred to ,sir ,benjamin ,richardson1 some time ago1 that it would be interesting to continue some experiments with animals and oxygen4 ,he put a number of mice into a jar of pure oxygen for a time2 they breathed in the gas1 and breathed out water-vapour and carbonic acid4 ,after the mice had continued this for some time1 he removed them by an arrangement4 ,by chemical means he removed the water-vapour and carbonic acid from the mixed air in the vessel4 ,when a blown-out taper was inserted1 it at once burst into flame1 showing that the remaining gas was oxygen4 ,again1 the mice were put into this vessel to breathe away4 ,but1 strange to say1 the animals soon became drowsy2 the smartness of the oxygen was gone4 ,at last they died2 there was nothing in the gas to keep them in life2 yet1 by the ordinary chemical tests1 it was still oxygen4 ,it had repeatedly passed through the lungs of the mice1 and during this passage there had been an action in the air-cells which absorbed the life-giving element of the gas4 ,it is oxygen1 so far as chemistry is concerned1 but it has no life-giving power4 ,it has been devitalised4 ,but the startling discovery still remains4 ,sir ,benjamin had previously fitted up the vessel with two short wires1 opposite each other in the sides--part outside and part inside4 ,two wires are fastened to the outside knobs4 ,these wires are attached to an electric machine1 and a flash of electricity is made to pass between the inner points of the vessel4 ,the wires are again removed2 nothing strange is seen in the vessel4 ,but1 when living mice are put into the vessel1 they dance as joyfully as if pure oxygen were in it4 ,the oxygen in which the first mice died has now been quite refreshed by the electricity4 ,the bad air has been cleared and made life-supporting by the electric discharge4 ,it has been again vitalised4 ,now1 to apply this3 before a thunder-storm1 everything has been so still for days that the oxygen in the air has been to some extent robbed of its life-sustaining power4 ,the air feels close1 a feeling of drowsiness comes over all4 ,but1 after the air has been pierced by several flashes of lightning1 the life-force in the air is restored4 ,your spirits revive2 you feel restored2 your breathing is far freer2 your drowsiness is gone4 ,then there is a burst of heavenly music from the exhilarated birds4 ,thus a thunder-storm clears the air4 ,after the passage of lightning through the air ozone is produced--the gas that is produced after a flash of electricity4 ,it is a kind of oxygen1 with fine exciting effects on the body4 ,if1 then1 the life-sustaining power of oxygen depends on a trace of ozone1 and this is being made by lightning's work1 how pleased should we be at the occasional thunder-storm6 ,,chapter ,,xv ,,disease-,,germs ,,in ,,the ,,air ,the gay motes that dance in the sunbeams are not all harmless4 ,all are annoying to the tidy housekeeper2 but some are dangerous4 ,there are living particles that float in the air as the messengers of disease and death4 ,some1 falling on fresh wounds1 find there a suitable feeding-place2 and1 if not destroyed1 generate the deadly influence4 ,others are drawn in with the breath2 and1 unless the lungs can withstand them1 they seize hold and spread some sickness or disease4 ,from stagnant pools1 common sewers1 and filthy rooms1 disease-germs are constantly contaminating the air4 ,yet these can be counted4 ,the simplest method is that of ,professor ,frankland4 ,it depends on this principle3 a certain quantity of air is drawn through some cotton-wool2 this wool seizes the organisms as the air passes through2 these organisms are afterwards allowed to feed upon a suitable nutritive medium until they reach maturity2 they are then counted easily4 ,about an inch from each end of a glass tube 7#e inches long and #a inch bore71 the glass is pressed in during the process of blowing4 ,some cotton-wool is squeezed in to form a plug at the farther constricted part of the glass4 ,the important plug is now inserted at the same open end1 but is not allowed to go beyond the constricted part at its end4 ,a piece of long lead tubing is attached to the former end by an india-rubber tube4 ,the other end of the lead tubing is connected with an exhausting syringe4 ,sixty strokes of the #ah cubic inches syringe will draw #ajhj cubic inches of the air to be examined through the plugs1 the first retaining the organisms4 ,the impregnated plug is then put into a flask containing in solution some gelatine-peptone4 ,the flask is made to revolve horizontally until an almost perfectly even film of gelatine and the organisms from the broken-up plug cover its inner surface4 ,the flask is allowed to remain for an hour in a cool place1 and is then placed under a bell-jar1 at a temperature of #gj deg4 ,fahr4 ,there it remains1 to allow the germs to incubate1 for four or five days4 ,the surface of the flask having been previously divided into equal parts by ink lines1 the counting is now commenced4 ,if the average be taken for each segment1 the number of the whole is easily ascertained4 ,a simple arithmetical calculation then determines the number of organisms in a cubic foot1 since the number is known for the #ajhj cubic inches4 ,that is the process for determining the number of living organisms in a fixed quantity of air4 ,no less than thirty colonies of organisms were counted in a cubic foot of air taken from the ,golden ,gallery of ,st4 ,paul's ,cathedral1 ,london1 and #adj from the air of the churchyard4 ,an ordinary man would breathe there thirty-six micro-organisms every minute4 ,electricity has a powerful effect in destroying these organisms4 ,ozone is generated in the air by lightning1 and it is detrimental to them4 ,in fine ozoned ,highland air scarcely a disease-germ can be detected4 ,open sea air contains about one germ in two cubic feet4 ,it has been found that in ,paris the average in summer is about #adj per cubic foot of air1 but in bedrooms the number is double4 ,during the twenty-four hours of the day the number of germs is highest about #f ,a4,m41 and lowest about mid-day4 ,raindrops carry the germs to the ground4 ,hence the advantage of a thunder plout in a sanitary way4 ,a cubic foot of rain has been found to contain #eejj organic dust-germs1 besides #g1jjj1jjj1jjj of inorganic dust-particles4 ,in a dirty town the rain will bring down in a year1 upon a square foot of surface1 no less than #c1jjj1jjj of bacteria1 many of them being disease-bearing and death-bearing4 ,no wonder1 then1 that scientific men are using every endeavour to protect the human frame1 as well as the frame of the lower animals1 from the baneful inroads of these floating nuclei of disease and death4 ,,chapter ,,xvi ,a ,,change ,,of ,,air ,for weakness of body and fatigue of mind a very common and essentially serviceable recommendation is a change of air4 ,of course1 the change of scene from coast to country1 or from town to hillside1 may help much the depressed in body or mind2 and this is very commendable4 ,but1 strange to say1 there is a healing virtue in breathing different air4 ,at first one is apt to think that air is the same all over1 as he thinks water is--especially outside smoky towns2 but both have varied qualities in different parts4 ,you have only to be assured that in a cubic inch of bedroom air in the denser parts of a large town there are about #bj1jjj1jjj of dust-particles1 and in the open air of a heathery mountain-side there are only some hundreds1 to see that there is something after all on the face of it in the old wives' saw4 ,not that the dust-particles are all injurious2 for most of them are inorganic1 and many of the organic particles are quite wholesome2 yet there is a change wrought1 often very marked1 in going from one place to another for different air4 ,even in the country1 especially in summer-time1 one distinctly notices the great difference in the air of lowland and highland localities4 ,the ten miles change from ,strathmore to ,glenisla shows a marked difference in the air4 ,below1 it is close1 weakening1 enervating2 above1 it is exhilarating1 invigorating1 and strong4 ,so people must have a change--at least those who can afford it--for health must be seen to first of all1 if one has means to do so4 ,oh6 the blessing of good health6 ,how many who enjoy it never think of the misery of its loss6 ,in fact1 health is the soul that animates all enjoyments of life2 for without it those would soon be tasteless4 ,a man starves at the best-spread table1 and is poor in the midst of the greatest treasures without health4 ,in these days half of our diseases come from the neglect of the body in the overwork of the brain4 ,the wear and tear of labour and intellect go on without pause or self-pity4 ,men may live as long as their forefathers1 but they suffer more from a thousand artificial anxieties and cares4 ,the men of old fatigued only the muscles1 we exhaust the finer strength of the nerves4 ,even more so now1 then1 do we require a change of air to soothe our overwrought nervous system4 ,and when that magic power1 concealed from mortal view1 works such wonders on the health1 surely it is one's duty to save up and have it1 when it is within one's means4 ,for is not health the greatest of all possessions8 ,what a rich colour clothes the countenance of the young after a month's outing in the hill country6 ,how fine and pure has the blood become6 ,all stagnant humours1 accumulated in winter town life1 have been dispelled by the ozone-brightening charm4 ,the weary looking office or shop man is now transfigured into a sprightly youth once more1 ready with strongly recuperated power for another winter's labours4 ,the pale wife1 who has been stifled for months in close-aired rooms1 has now a healthy flush on her becoming countenance that speaks of gladly restored health4 ,and all this has been brought about by a change of air6 ,for a thorough change to a town man1 he should make for the ,highlands4 ,there he is never tired of walking1 for the air which he breathes is full of ozone4 ,this revivifying element in the air is produced by the lightning-bursts from hill to hill4 ,there is in the ,highlands a continual rush of electricity1 whether seen or not4 ,hence the air is very pure1 free from organic germs1 intensely exhilarating and buoyant4 ,sportsmen are livingly aware of the recuperative power of the ,highland air4 ,perhaps these city men do not benefit so much by the easy walking exercise on the grouse moors as in breathing the splendidly delight-inspiring air4 ,what a change one feels there in a very few hours6 ,a change of air is an old wives' adage4 ,but much of the weather-lore of our forefathers was based on real scientific principles only now coming to light4 ,nature is ever true1 but it requires patience to unravel her secrets4 ,we therefore advocate an occasional change of air to improve the health-- ,the chiefest good1 ,bestow'd by ,heaven1 but seldom understood4 ,,chapter ,,xvii ,,the ,,old ,,moon ,,in ,,the ,,new ,,moon',s ,,arms ,after the sun's broad beams have tired the sight1 the moon with more sober light charms us to descry her beauty1 as she shines sublimely in her virgin modesty4 ,there is always a most fascinating freshness in the first sight of the new moon4 ,the superstition of centuries adds to this charm4 ,why boys and girls like to turn over a coin in their pocket at this sight one cannot tell3 yet it is done4 ,no young lady likes to look at the new moon through a pane of glass4 ,and farmers are always confident of a change of weather with a new moon3 at least in bad weather they earnestly hope for it4 ,but1 banishing all superstition1 we welcome the pale silver sickle in the heavens1 once more appearing from the bosom of the azure4 ,and no language can equal these beautiful words of the youthful ,shelley3-- ,like the young moon1 ,when on the sunlit limits of the night ,her white shell trembles amid crimson air1 ,and while the sleeping tempest gathers might1 ,doth1 as the herald of his coming1 bear ,the ghost of its dead mother1 whose dim form ,bends in dark ether from her infant's chair4 ,that is a more charming way of putting the ordinary expression1 the old moon in the new moon's arms4 ,we are regularly accustomed to the moonshine1 but only occasionally is the earthshine on the moon so regulated that the shadowed part is visible4 ,this is not seen at the appearance of every new moon4 ,it depends upon the positions of the sun and moon1 the state of the atmosphere1 and the absence of heavy clouds4 ,i never in my life saw the phenomenon so marvellously beautiful as on ,may #gth1 #ahid1 at my manse in ,strathmore4 ,i took particular note of it1 as some exceedingly curious things were connected with it4 ,at nine o'clock in the evening1 the new moon issued from some clouds in the western heavens1 the sun having set1 about an hour before4 ,the crescent was thin and silvery1 and the outline of the shadowed part was just visible4 ,the sky near the horizon was clear and greenish-hued4 ,as the night advanced the moon descended1 and at ten o'clock she was approaching a purple stratum of clouds that stretched over the hills1 while the position of the sun was only known a little to the east1 by the back-thrown light upon the dim sky4 ,through the moisture-laden air the sun's rays1 reflected by the moon1 threw a golden stream from the crescent moon1 for the silvery shell became more golden-hued4 ,the horns of the moon now seemed to project1 and the shadowed part became more distinct1 though the circle appeared smaller4 ,by means of a field-glass ,i noticed that this was extra lighted1 with points here and there quite golden-tinged4 ,the darker spots showed the deep caverns2 the brighter points brought into relief the mountain peaks4 ,why was the surface brighter than usual8 ,i cannot go into detail about the phases of the moon2 but1 in a word1 ,i may say that1 while the sun can illuminate the side of the moon turned towards it1 it is unable to throw any light on the shadow1 seeing that there is no atmosphere around the moon to refract the light4 ,if we1 in imagination1 looked from the moon upon the earth1 we should see the same phases as are now noticed in the moon2 and when it is just before new moon on the earth1 the earth will appear fully illuminated from the moon4 ,we would also observe 7from the moon7 that the brightness of the illuminated part of the earth would vary from time to time1 according to the changes in the earth's atmosphere4 ,more light would be reflected to the moon from the clouds in our atmosphere than from the bare earth or cloudless sea1 since clouds reflect more light than either land or sea4 ,accordingly1 we arrive at this curious fact--that the extra brightness of the dark body of the moon is mainly determined by the amount of cloud in our atmosphere4 ,accordingly1 ,i concluded that there must be clouds to the west1 though ,i could not see them1 which reflected rays of light and faintly illuminated the shadowed part of the moon4 ,it had become much colder1 and ,i concluded that during the night the cloud-particles1 if driven near by the wind1 would condense into rain4 ,and1 assuredly1 next morning ,i was gratified to find that rain had fallen in large quantities1 substantiating the theory4 ,there is much pleasure in verifying such an interesting problem4 ,the dark body of the moon being more than usually visible is one of our well-known and oldest indications of coming bad weather4 ,and at once came to my memory the lines of ,sir ,patrick ,spens1 as he foreboded rain for his crossing the ,north ,sea3-- ,i saw the new moon late yestreen ,wi' the auld moon in her arm2 ,and if we gang to sea1 master1 ,i fear we'll come to harm4 ,this lunar indication1 then1 has a sound physical basis1 showing that near the observer there are vast areas of clouds1 which are reflecting light upon the moon at the time1 before they condense into rain by the chilling of the air4 ,according to the old ,greek poet1 ,aratus3 ,if the new moon is ruddy1 and you can trace the shadow of the complete circle1 a storm is approaching4 ,,chapter ,,xviii ,,an ,,autumn ,,afterglow ,a brilliant afterglow is welcomed for its surpassing beauty and a precursor of fine fixed weather4 ,a glorious sunset has always had a charm for the lover of nature's beauties4 ,the zenith spreads its canopy of sapphire1 and not a breath creeps through the rosy air4 ,a magnificent array of clouds of numberless shapes come smartly into view4 ,some1 far off1 are voyaging their sun-bright paths in silvery folds2 others float in golden groups4 ,some masses are embroidered with burning crimson2 others are like islands all lovely in an emerald sea4 ,over the glowing sky are splendid colourings4 ,the flood of rosy light looks as if a great conflagration were below the horizon4 ,i remember witnessing an especially brilliant sunset last autumn on the high-road between ,kirriemuir and ,blairgowrie4 ,the setting sun shone upon the back of certain long trailing clouds which were much nearer me than a range behind4 ,the fringes of the front range were brilliantly golden1 while the face of those behind was sparklingly bright4 ,then the sun disappeared over the western hills1 and his place was full of spokes of living light4 ,looking eastward1 ,i observed on the horizon the base of the northern line of a beautiful rainbow--the shepherd's delight for fine weather4 ,soon in the west the light faded2 but there came out of the east a lovely flush1 and the general sky was presently flamboyant with afterglow4 ,the front set of clouds was darker except on the edges1 the red being on the clouds behind2 and the horizon in the east was particularly rich with dark red hues4 ,gradually the eastern glow rose and reddened all the clouds1 but the front clouds were still grey4 ,the effect was very fine in contrast4 ,the fleecy clouds overhead became transparently light red1 as they stretched over to reach the silver-streaked west4 ,the new moon was just appearing upright against a slightly less bright opening in the sky1 betokening the firm hardness of autumn4 ,soon the colouring melted away1 and the peaceful reign of the later twilight possessed the land4 ,now why that brilliancy of the east1 when the west was colourless8 ,most of all you note the immense variety and wealth of reds4 ,these are due to dust in the atmosphere4 ,we are the more convinced of this by the very remarkable and beautiful sunsets which occurred after the tremendous eruption at ,krakatoa1 in the ,straits of ,sunda1 thirty years ago4 ,there was then ejected an enormous quantity of fine dust1 which spread over the whole world's atmosphere4 ,so long as that vast amount of dust remained in the air did the sunsets and afterglows display an exceptional wealth of colouring4 ,all observers were struck with the vividly brilliant red colours in all shades and tints4 ,the minute particles of dust in the atmosphere arrest the sun's rays and scatter them in all directions2 they are so small1 however1 that they cannot reflect and scatter all2 their power is limited to the scattering of the rays at the blue end of the spectrum1 while the red rays pass on unarrested4 ,the display of the colours of the blue end are found in numberless shades1 from the full deep blue in the zenith to the greenish-blue near the horizon4 ,if there were no fine dust-particles in the upper strata1 the sunset effect would be whiter2 if there were no large dust-particles1 there would be no colouring at all4 ,if there were no dust-particles in the air at all1 the light would simply pass through into space without revealing itself1 and the moment the sun disappeared there would be total darkness4 ,the very existence of our twilight depends on the dust in the air2 and its length depends on the amount and extension upwards of the dust-particles4 ,but how have the particles been increased in size in the east8 ,because1 as the sun was sinking1 but before its rays failed to illumine the heavens1 the temperature of the air began to fall4 ,this cooling made the dust-particles seize the water-vapour to form haze-particles of a larger size4 ,the particles in the east first lose the sun's heat1 and first become cool2 and the rays of light are then best sifted1 producing a more distinct and darker red4 ,as the sun dipped lower1 the particles overhead became a turn larger1 and thereby better reflected the red rays4 ,accordingly1 the roseate bands in the east spread over to the zenith1 and passed over to the west1 producing in a few minutes a universal transformation glow4 ,to produce the full effect often witnessed1 there must be1 besides the ordinary dust-particles1 small crystals floating in the air1 which increase the reflection from their surfaces and enhance the glow effects4 ,in autumn1 after sunset1 the water-covered dust-particles become frozen and the red light streams with rare brilliancy1 causing all reddish and coloured objects to glow with a rare brightness4 ,then the air glows with a strange light as of the northern dawn4 ,from all this it is clear that1 though the colouring of sunset is produced by the direct rays of the sun1 the afterglow is produced by reflection1 or1 rather1 radiation from the illuminated particles near the horizon4 ,the effect in autumn is a stream of red light1 of varied tones1 and rare brilliancy in all quarters1 unseen during the warmer summer4 ,we have to witness the sunsets at ,ballachulish to be assured that ,waller ,paton really imitated nature in the characteristic bronze tints of his richly painted landscapes4 ,,chapter ,,xix ,a ,,winter ,,foreglow ,little attention has been paid to foreglows compared with afterglows1 either with regard to their natural beauty or their weather forecasting4 ,but either the ordinary red-cloud surroundings at sunrise1 or the western foreglow at rarer intervals1 betokens to the weather-prophet wet and gloomy weather4 ,the farmer and the sailor do not like the sight1 they depend so much on favourable weather conditions4 ,of course1 sunrise to the aesthetic observer has always its charms4 ,the powerful king of day rejoices as a bridegroom coming out of his chamber as he steps upon the earth over the dewy mountain tops1 bathing all in light1 and spreading gladness and deep joy before him4 ,the lessening cloud1 the kindling azure1 and the mountain's brow illumined with golden streaks1 mark his approach2 he is encompassed with bright beams1 as he throws his unutterable love upon the clouds1 the beauteous robes of heaven4 ,aslant the dew-bright earth and coloured air he looks in boundless majesty abroad1 touching the green leaves all a-tremble with gold light4 ,but glorious1 and educating1 and inspiring as is the sunrise in itself in many cases1 there is occasionally something very remarkable that is connected with it4 ,rare is it1 but how charming when witnessed1 though till very recently it was all but unexplained4 ,this is the foreglow4 ,it is in no respect so splendid as the afterglow succeeding sunset2 but1 because of its comparative rarity1 its beauty is enhanced4 ,i remember a foreglow most vividly which was seen at my manse1 in ,strathmore1 in ,january #ahic4 ,my bedroom window looked due west2 ,i slept with the blind up4 ,on that morning ,i was struck1 just after the darkness was fading away1 with a slight colouring all along the western horizon4 ,the skeleton branches of the trees stood out strongly against it4 ,the colouring gradually increased1 and the roseate hue stretched higher4 ,the old well-known faces that ,i used to conjure up out of the thin blended boughs became more life-like1 as the cheeks flushed4 ,there was rare warmth on a winter morning to cheer a half-despairing soul1 tired out with the long hours of oil reading1 and pierced to the heart by the never-ceasing rimes2 yet ,i could not understand it4 ,i went to the room opposite to watch the sunrise1 for ,i had observed in the diary that the appearance of the sun would not be for a few minutes4 ,there were streaks of light in the east above the horizon1 but no colour was visible4 ,that hectic flush--slight1 yet well marked--which was deepening in the western heavens1 had no counterpart in the east1 except the colourless light which marked the wintry sun's near approach4 ,as soon as the sun's rays shot up into the eastern clouds1 and his orb appeared above the horizon1 the western sky paled1 the colour left it1 as if ashamed of its assumed glory4 ,a foreglow like that ,i have very rarely seen1 and its existence was a puzzle to me till ,i studied ,dr4 ,aitken's explanation of the afterglows after sunset4 ,i had never come across any description of a foreglow2 and1 of course1 across no explanation of the curious phenomenon4 ,the western heavens were coloured with fairly bright roseate hues1 while the eastern horizon was only silvery bright before the sun rose2 whereas1 after the sun appeared and coloured the eastern hills and clouds1 the western sky resumed its leaden grey and colourless appearance4 ,why was that8 ,what is the explanation8 ,i have not space enough to repeat the explanation given already in the last chapter of the glorious phenomenon of the afterglow4 ,but the explanation is similar4 ,before sunrise1 the rays of the sun are reflected by dust-particles in the zenith to the western clouds4 ,the colouring is intensified by the frozen water-vapour on these particles in the west4 ,one thing ,i carefully noted4 ,ere mid-day1 snow began to fall1 and for some days a severe snow-storm kept us indoors4 ,then1 at any rate1 the foreglow betokened a coming storm4 ,it was1 like a rainbow in a summer morning1 a decided warning of the approaching wet weather4 ,,chapter ,,xx ,,the ,,rainbow ,the poet ,wordsworth rapturously exclaimed-- ,my heart leaps up when ,i behold ,a rainbow in the sky4 ,and old and young have always been enchanted with the beautiful phenomenon4 ,how glorious is the parti-coloured girdle which1 on an ,april morning or ,september evening1 is cast o'er mountain1 tower1 and town1 or even mirrored in the ocean's depths6 ,no colours are so vividly bright as when this triumphal arch bespans a dark nimbus3 then it unfolds them in due prismatic proportion1 running from the red to where the violet fades into the sky4 ,a plain description of the formation of the rainbow is not very easily given1 but a short sketch may be useful4 ,beautiful as is the ethereal bow1 born of the shower and colour'd by the sun1 yet the marvellous effect is more exquisitely intensified in its gorgeous display when the hand of science points out the path in which the sun's rays1 from above the western horizon1 fall on the watery cloud1 indicating fine weather--the shepherd's delight4 ,one law of reflection is that1 when a ray of light falls on a plane or spherical surface1 it goes off at the same angle to the surface as it fell4 ,one law of refraction is that1 when a ray of light passes through one medium and enters a denser medium 7as from air to water71 it is bent back a little4 ,by refraction you see the sun's rays long after the sun has set2 when the sun is just below the horizon1 an observer1 on the surface of the earth1 will see it raised by an amount which is generally equal to its apparent diameter4 ,the rays of different colours are bent back 7when passing through the water7 at different rates1 some slightly1 others more1 from the red to the violet end4 ,the rainbow1 then1 is produced by refraction and reflection of the several coloured rays of sunlight in the drops of water which make up falling rain4 ,the sun is behind the observer1 and its rays fall in a parallel direction upon the drops of rain before him4 ,in each drop the light is dispersively refracted1 and then reflected from the farther face of the drop2 it travels back through the drop1 and comes out with dispersing colours4 ,according to the height of the sun1 or the slope of its rays1 a higher or lower rainbow will be formed4 ,and1 strange1 no two people can see the very same bow2 in fact the rainbow1 as seen by the one eye1 is not formed by the same water-drops as the rainbow seen by the other eye4 ,when the primary bow is seen in most vivid colours on a dark cloud1 a second arch1 larger and fainter1 is often seen4 ,but the order of the colours is quite reversed4 ,at a greater elevation1 the sun's ray enters the lower side of a drop of rain-water1 is refracted1 reflected twice1 and then refracted again before being sent out to the observer's eye4 ,that is why the colours are reversed4 ,a one-coloured rainbow is a curious and rare phenomenon4 ,it is a strange paradox1 for the very idea of a rainbow brings up the seven colours--red1 orange1 yellow1 green1 blue1 indigo1 and violet4 ,yet ,dr4 ,aitken tells us of a rainbow with one colour which he observed on ,christmas ,day1 in #ahhh4 ,he was taking his walk on the high ground south of ,falkirk4 ,in the east he observed a strange pillar-like cloud1 lit up with the light of the setting sun4 ,then the red pillar extended1 curved over1 and formed a perfect arch across the north-eastern sky4 ,when fully developed1 this rainbow was the most extraordinary one which he had ever seen4 ,there was no colour in it but red4 ,it consisted simply of a red arch1 and even the red had a sameness about it4 ,outside the rainbow there was part of a secondary bow4 ,the ,ochil ,hills were north of his point of observation4 ,these hills were covered with snow1 and the setting sun was glowing with rosy light4 ,never had he seen such a depth of colour as was on them on this occasion4 ,it was a deep1 furnacy red4 ,the sun's light was shorn of all the rays of short-wave length on its passage through the atmosphere1 and only the red rays reached the earth4 ,the reason why the ,ochils glowed with so deep a red was owing to their being overhung by a dense curtain of clouds1 which screened off the light of the sky4 ,the illumination was thus principally that of the direct softer light of the sun4 ,,chapter ,,xxi ,,the ,,aurora ,,borealis ,he must be a very careless observer who has not been struck with the appearance of the streamers which occasionally light up the northern heavens1 and which farmers consider to be indicators of strong wind or broken weather4 ,the time was when the phenomenon was considered to be supernatural and portentous1 as the chroniclers of spectral battles1 when fierce1 fiery warriors fought upon the clouds1 in ranks and squadrons1 and right form of war4 ,and even in the rural districts of ,britain1 the blood-coloured aurora1 of ,october #bdth1 #ahgj1 was considered to be the reflection of an enormous ,prussian bonfire1 fed by the beleaguered ,french capital4 ,in joyful spirit1 the ,shetlanders call the beautiful natural phenomenon1 ,merry ,dancers4 ,burns associated their evanescence with the transitoriness of sensuous gratification3--they flit ere you can point their place4 ,and ,tennyson spoke of his cousin's face lit up with the colour and light of love1 as ,i have seen the rosy red flushing in the northern night4 ,yet this phenomenon is to a great extent under the control of cosmical laws4 ,one of the most difficult problems of our day has been to disentangle the irregular webwork of aurorae1 and bring them under a law of periodicity1 which depends upon the fluctuations of the sun's photosphere and the variations on the earth's magnetism1 and which have such an important influence upon the fluctuations of the weather4 ,the name ,aurora ,borealis was given to it by ,gassendi in #afba4 ,afterwards1 the old almanacs described it as the ,great ,amazing ,light in the ,north4 ,in the ,lowlands of ,scotland1 the name it long went by1 of ,lord ,derwentwater's ,lights1 was given because it suddenly appeared on the night before the execution of the rebel lord4 ,in ,ceylon aurorae were called ,buddha ,lights4 ,the first symptom of an aurora borealis is commonly a low arch of pale1 greenish-yellow light1 placed at right angles to the magnetic meridian4 ,sometimes rays cover the whole sky1 frequently showing tremulous motion from end to end2 and sometimes they appear to hang from the sky like the fringes of a mantle4 ,they are among the most capricious of natural phenomena1 so full of individualities and vagaries4 ,to the glitter of rapid movement they add the charm of vivid colouring4 ,it is strongly asserted that aurorae are preceded by the same general phenomena as thunder-storms4 ,this was borne out by ,piazzi ,smith 7late ,astronomer-,royal for ,scotland71 who observed that their monthly frequency varies inversely with that of thunder-storms--both being safety-valves for the discharge of surplus electricity4 ,careful observers have1 moreover1 noticed a remarkable coincidence between the display of aurorae and the maxima of the sun's spots and of the earth's magnetic disturbances4 ,some have supposed that the light of the aurora is caused by clouds of meteoric dust1 composed of iron1 which is ignited by friction with the atmosphere4 ,but there is this difficulty in the way1 shooting stars are more frequent in the morning1 while the reverse is the case with the aurora4 ,the highest authorities have concluded1 pretty uniformly1 that aurorae are electric discharges through highly rarefied air1 taking place in a magnetic field1 and under the sway of the earth's magnetic induction4 ,they are not inappropriately called ,polar lightnings1 for when electricity misses the one channel it must traverse the other4 ,the natives of the ,arctic regions of ,north ,america pretend to foretell wind by the rapidity of the motions of the streamers4 ,when they spread over the whole sky1 in a uniform sheet of light1 fine weather ensues4 ,fitzroy believed that aurorae in northern latitudes indicated and accompanied stormy weather at a distance4 ,the same idea is still current among many farmers and fishermen in ,scotland4 ,is there any audible accompaniment to the brilliant spectacle8 ,the natives of some parts1 with subtle hearing-power1 speak of the whizzing sound which is often heard during auroral displays4 ,burns tells of their hissing1 eerie din1 as echoes of the far-off songs of the ,valkyries4 ,perhaps the most striking incident which corroborates this opinion occurred during the ,franco-,prussian ,war4 ,rolier1 a practised aeronaut1 left ,paris in a balloon1 on his mission of city defence1 and fourteen hours afterwards landed in ,norway4 ,he had reached the height of two and a half miles4 ,when descending1 he passed through a peculiar cloud of sulphurous odour1 which emitted flashed light and a slight scratching or rustling noise4 ,on landing1 he witnessed a splendid aurora borealis4 ,he must1 therefore1 have passed through a cloud in which an electrical discharge of an auroral nature was proceeding1 accompanied with an audible sound4 ,there is1 moreover1 no improbability of such sounds being occasionally heard1 since a somewhat similar phenomenon accompanies the brush discharge of the electric machinery1 to which the aurora bears considerable resemblance4 ,though no fixed conclusions are yet established about the causes of the brilliant auroral display1 yet1 as the results of laborious observations1 we are assured that the stabler centre of our solar system holds in its powerful sway the several planets at their respective distances1 supplying them all with their seasonable light and heat1 vibrating sympathetic chords in all1 and even controlling under certain--though to us still unknown--laws the electric streamers that flit1 apparently lawlessly1 in the distant earth's atmosphere4 ,,chapter ,,xxii ,,the ,,blue ,,sky ,if we look at the sky overhead1 when cloudless in the sunshine1 we wonder what gives the air such a deep-blue colour4 ,we are not looking1 as children seem to do1 into vacancy1 away into the far unknown4 ,and even1 if that were the case1 would not the space be quite colourless8 ,what1 then1 produces the blueness8 ,some of the very fine dust-particles1 even when clothed with an exceedingly thin coating of water-vapour1 are carried very high2 and1 looking through a vast accumulation of these1 we find the effect of a deep-blue colour4 ,why so8 ,because these particles are so small that they can only reflect the rays of the blue end of the spectrum2 and the higher we ascend1 the smaller are the particles and the deeper is the blue4 ,but it is also because water1 even in its very finest and purest form1 is blue in colour4 ,for long this was disputed4 ,even ,sir ,robert ,christison concluded1 after years of experimenting on ,highland streams1 that water was colourless4 ,of course1 he admitted that the water in the ,indian and ,pacific ,oceans has frequent patches of red1 brown1 or white colour1 from the myriads of animalcules suspended in the water4 ,ehrenberg found that it was vegetable matter which gave to the ,red ,sea its characteristic name4 ,but these1 and similar waters1 are not pure4 ,it is to ,dr4 ,aitken that the final discovery of the real colour of water is due4 ,when on a visit to several towns on the shores of the ,mediterranean1 he set about making some very interesting experiments1 which the reader will follow with pleasure4 ,it is a well-known fact that colour transmitted through different bodies differs considerably from colour reflected by them4 ,in his first experiment he took a long empty metal tube1 open at one end1 and closed at the other end by a clear-glass plate4 ,this was let down vertically into the water1 near to a fixed object1 which appeared of most beautiful deep and delicate blue at a depth of #bj feet4 ,scientific men know that1 if the colour of water is due to the light reflected by extremely small particles of matter suspended in the water1 then the object looked at through it would have been illuminated with yellow 7the complementary colour of blue74 ,a blackened tube was then filled with water 7which had a clear-glass plate fixed to the bottom71 and white1 red1 yellow1 and purple objects were sunk in the water1 and these colours were found to change in the same way as if they were looked at through a piece of pale-blue glass4 ,the white object appeared blue1 the red darkened very rapidly as it sank1 and soon lost its colour2 at the depth of seven feet a very brilliant red was so darkened as to appear dark brick-red4 ,the yellow object changed to green1 and the purple to dark blue4 ,but1 still further to satisfy himself that water is really blue in itself1 even without any particles suspended in it1 he tested the colour of distilled water4 ,he filled a darkened tube with this water 7clear-glass plates being at the ends of the tube71 and looked through it at a white surface4 ,the effect was the same as before1 the colour was blue1 almost exactly of the same hue as a solution of ,prussian blue4 ,this is corroborated by the fact that1 the purer the water is in nature1 the bluer is the tint when a large quantity is looked through4 ,some ,highland lochs have crystal waters of the most extraordinary blue4 ,of course1 some cling to the old idea that this is accounted for by the reflected blue of the clear heavens above4 ,no doubt1 if the sky be deep blue1 then this blue light1 when reflected by the surface of the water1 will enrich and deepen the hue4 ,but the water itself is really blue4 ,at the same time1 the dust-particles suspended in the water have a great effect in making the water appear more beautiful1 brilliant1 and varied in its colouring2 because little or no light is reflected by the interior of a mass of water itself4 ,if a dark metal vessel be filled with a weak solution of ,prussian blue1 the liquid will appear quite dark and void of colour4 ,but throw in some fine white powder1 and the liquid will at once become of a brilliant blue colour4 ,this accounts for the change of depth and brilliancy of colour in the several shores of the ,mediterranean4 ,when1 then1 you look at the face of a deep-blue lake on a summer evening--the heavens all aglow with the unrivalled display of colour from the zenith1 stretching in lighter hues of glory to the horizon--though to you the calm water appears like a lake of molten metal glowing with sky-reflected light1 so powerful and brilliant as entirely to overpower the light which is internally reflected1 yet blue is the normal colour of the water3 blueness is its inherent hue4 ,looking upwards1 we observe three distinct kinds of blue in the sky from the horizon to the zenith4 ,all painters in water-colours know that4 ,newton thought that the colour of the sky was produced in the same way as the colours in thin plates1 the order of succession of the colours gradually increasing in intensity4 ,,chapter ,,xxiii ,a ,,sanitary ,,detective ,the impure state of the air in the rooms of a house can now be determined by means of colour alone4 ,dr4 ,aitken has invented a very simple instrument for that purpose2 and this ought to be of great service to sanitary officers4 ,it is called the koniscope--or dust-detective4 ,the instrument consists of an air-pump and a metal tube with glass ends4 ,near one end of the test-tube is a passage by which it communicates with the air-pump1 and near the other end is attached a stop-cock for admitting the air to be tested4 ,it is not nearly so accurate as the dust-counter2 but it is cheaper1 more easily wrought1 and more handy for quick work4 ,all the grades of blue1 from what is scarcely visible to deep1 dark blue1 may be attached alongside the tube on pieces of coloured glass2 and opposite these colours are the numbers of dust-particles in the cubic inch of the similar air1 as determined by the dust-counter4 ,while the number of particles was counted by means of the dust-counter1 the depth of blue given by the koniscope was noted2 and the piece of glass of that exact depth of blue attached4 ,a metal tube was fitted up vertically in the room1 in such a way that it could be raised to any desired height into the impure air near the ceiling1 so that supplies of air of different degrees of impurity might be obtained4 ,to produce the impurity1 the gas was lit and kept burning during the experiments4 ,the air was drawn down through the pipe by means of the air-pump of the koniscope1 and it passed through the measuring apparatus of the dust-counter on its way to the koniscope4 ,it may be remarked that1 by a stroke of the air-pump1 the air within the test-tube is rarefied and the dust-particles seize the moisture in the super-saturated air to form fog-particles2 through this fog the colour is observed1 and the shade of colour determines the number of dust-particles in the air4 ,these colours are named just visible1 very pale blue1 pale blue1 fine blue1 deep blue1 and very deep blue4 ,when making a sanitary inspection1 the pure air should be examined first1 and the colour corresponding to that should be considered as the normal health colour4 ,any increase from the depth would indicate that the air was being gradually contaminated2 and the amount of increase in the depth of colour would indicate the amount of increase of pollution4 ,as an illustration of what this instrument can detect1 a room of #bd by #ag by #ac feet was selected4 ,the air was examined before the gas was lighted1 and the colour in the test-tube was very faint1 indicating a clear atmosphere4 ,in all parts of the room this was found the same4 ,a small tube was attached to the test-tube1 open at the other end1 for taking air from different parts of the room4 ,three jets of gas were then lit in the centre of the room1 and observations at once begun with the koniscope4 ,within thirty-five seconds of striking the match to light the gas1 the products of combustion had extended near the ceiling to the end of the room2 this was indicated by the colour in the koniscope suddenly becoming a deep blue4 ,in four minutes the deep-blue-producing air was got at a distance of two feet from the ceiling4 ,in ten minutes there was strong evidence of the pollution all through the room4 ,in half-an-hour the impurity at nine feet from the floor was very great1 the colour being an intensely deep blue4 ,the wide range of the indications of the instrument1 from pure clearness to nearly black blue1 makes the estimate of the impurity very easily taken with it2 and1 as there are few parts to get out of order1 it is hoped it may come into general use for sanitary work4 ,,chapter ,,xxiv ,,fog ,,and ,,smoke ,just two hundred and forty years ago1 ,mr4 ,john ,evelyn1 ,f4,r4,s41 a well-known writer on meteorology1 sent a curious tract to ,king ,charles ,,ii41 which was ordered to be printed by his ,majesty4 ,it was entitled ,fumifugium1 and dealt with the great smoke nuisance in ,london4 ,i find from the thesis that he had a very hazy idea of the connection between fog and smoke2 and no wonder1 for it is only lately that the connection has been fully explained4 ,we know that without dust-particles there can be no fog1 and that smoke supplies a vast amount of such particles4 ,therefore1 in certain states of the atmosphere1 the more smoke the more fog4 ,in ,mr4 ,evelyn's day the fog1 which he called presumptuous smoake1 was at times so dense that men could hardly discern each other for the clowd4 ,his ,majesty's only sister had complained of the damage done to her lungs by the contamination1 and ,mr4 ,evelyn was disgusted at the apathy of the people to do anything to remedy the nuisance4 ,he deplored that that glorious and ancient city of ,london should wrap her stately head in clowds of smoake1 so full of stink and darknesse4 ,he was of opinion that a method of charring coal so as to divest it of its smoke1 while leaving it serviceable for many purposes1 should be made the object of a very strict inquiry4 ,and he was right4 ,for it is now known that fog in a town is intensified by much smoke4 ,in a city like ,london or ,glasgow1 where a great river1 fed by warm streams of water from gigantic works1 passes through its centre1 fogs can never be entirely obliterated1 for the dust-particles in the air 7often four millions and upwards in the cubic inch7 will seize with terrible avidity the warm vapour rising from the river4 ,that is the main reason why fogs cannot there be put down4 ,smoke is being consumed to a great extent2 yet we find particles of sulphur remaining1 which seize the warm vapour and form fogs dense enough to check all traffic4 ,the worst form of city fogs seems to be produced when the air1 after first flowing slowly in one direction1 then turns on its tracks and flows back over the city1 bringing with it a black pall1 the accumulated products of previous days1 to which gets added the smoke and other impurities produced at the time4 ,what irritated ,mr4 ,evelyn was that1 outside of ,london1 the air was clear when passengers could not walk in safety within the city4 ,so vexed was he about the contamination1 that he made it the occasion of all the cathars1 phthisicks1 coughs1 and consumption in the city4 ,he appealed to common sense to testify that those who repair to ,london soon take some serious illness4 ,i know a man1 he said1 who came up to ,london and took a great cold1 which he could never afterwards claw off again4 ,mr4 ,evelyn proposed that1 by an ,act of ,parliament1 the nuisance be removed2 enjoining that all breweries1 dye-works1 soap and salt boilers1 lime-burners1 and the like1 be removed five or six miles distant from ,london below the river ,thames4 ,that would have materially helped his cause4 ,but there is more difficulty in the purification than he anticipated4 ,yet there was pluck in the old man pointing out the killing contamination and suggesting a possible remedy4 ,he had the fond idea that thereby a certain charm1 or innocent magick1 would make a transformation scene like ,arabia1 which is therefore styl'd the ,happy1 attracting all with its gums and precious spices4 ,in purer air fogs would be less dense1 breathing would be easier1 business would be livelier1 life would be happier4 ,few1 ,i suppose1 have laid their hands on this curious ,latin thesis1 or its quaint translation1 directing the ,king's attention to the fogs that were ruining ,london4 ,since that time the city has increased1 from little more than a village1 to be the dwelling-place of six millions of human beings1 yet too little improvement has been made in the removal of this fog nuisance4 ,king ,edward's drive through ,london would be even more dangerous on a muggy1 frosty day than was ,charles ,,ii4's1 when science was little known4 ,,chapter ,,xxv ,,electrical ,,deposition ,,of ,,smoke ,a good deal of scientific work is being done in the way of clearing away fog and smoke2 and this1 through time1 may have some practical results in removing a great source of annoyance1 illness1 and danger in large towns4 ,sir ,oliver ,lodge and ,dr4 ,aitken have been throwing light upon the deposition of smoke in the air by means of electricity4 ,if an electric discharge be passed through a jar containing the smoke from burnt magnesium wire1 tobacco1 brown paper1 and other substances1 the dust will be deposited so as to make the air clear4 ,brush discharge1 or anything that electrifies the air itself1 is the most expeditious4 ,if water be forced upwards through a vertical tube 7with a nozzle one-twentieth of an inch in diameter71 it will fall to the ground in a fine rain2 but1 if a piece of rubbed 7electrified7 sealing-wax be held a yard distant from the place where the jet breaks into drops1 they at once fall in large spots as in a thunder-shower4 ,if paper be put on the ground during the experiment1 the sound of pattering will be observed to be quite different4 ,if a kite be flown into a cloud1 and made to give off electricity for some time1 that cloud will begin to condense into rain4 ,experiments with ,lord ,kelvin's recorder show that variations in the electrical state of the atmosphere precede a change of weather4 ,then1 with a very large voltaic battery1 a tremendous quantity of electricity could be poured into the atmosphere1 and its electrical condition could be certainly disturbed4 ,if this could be made practically available1 how useful it would be to farmers when the crops were suffering from excessive drought6 ,it might be more powerfully available than the imagined condensation of a cloud into rain by the reverberation caused by the firing of a range of cannon4 ,but what is the practical benefit of this information8 ,if electricity deposits smoke1 it might be made available in many ways4 ,the fumes from chemical works might be condensed2 and the air in large cities1 otherwise polluted1 might be purified and rendered innocuous4 ,the smoke of chimneys in manufacturing works might be prevented from entering the atmosphere at all4 ,in flour-mills and coal-mines the fine dust is dangerously explosive4 ,in lead1 copper1 and arsenic works1 it is both poisonous and valuable4 ,lead smelters labour under this difficulty of condensing the fume which escapes along with the smoke from red-lead smelting furnaces2 and it was considered that an electrical process of condensation might be made serviceable for the purpose4 ,at ,bagillt1 the method used for collecting or condensing the lead fume is a large flue two miles long2 much is retained in this flue1 but still a visible cloud of white-lead fume continually escapes from the top of the chimney4 ,there is a difficulty in the way of depositing fumes in the flue by means of a sufficient discharge of electricity1 viz4 the violent draught which is liable to exist there1 and which would mechanically blow away any deposited dust4 ,but ,dr4 ,aitken suggests that regenerators might be used along with the electricity4 ,the warm fumes might be taken to a cold depositor1 where 7by the ordinary law of cold surfaces attracting warm dust-particles7 the impurities would be removed1 and1 when purified1 the air would again be taken through a hot regenerator before being sent up the chimney4 ,by a succession of these chambers1 with the assistance of electric currents1 the air1 impregnated with the most deleterious particles1 or valuable dust1 could be rendered innocuous4 ,the sewage of our towns must be cleaned of its deleterious parts before being run into the streams which give drink to the lower animals1 because an ,act of ,parliament enforces the process4 ,why1 then1 ought we not to have similar compulsion for making the smoke from chemical and other noxious works quite harmless before being thrown into the air which contains the oxygen necessary for the life of human beings8 ,there seems to be a good field before electricians to catch the smoke on the wing and deposit its dust on a large scale4 ,this seems to be a matter beyond our reach at present1 except in the scientist's laboratory2 but certainly it is a consummation devoutly to be wished4 ,,chapter ,,xxvi ,,radiation ,,from ,,snow ,one night a most interesting paper by ,dr4 ,aitken1 on ,radiation from ,snow1 was read by ,professor ,tait to the ,fellows of the ,royal ,society of ,edinburgh4 ,i remember that ,dr4 ,alex4 ,buchan--the greatest meteorologist living--spoke afterwards in the very highest terms of the subject-matter of the paper4 ,this was corroborated by ,lord ,kelvin1 ,lord ,mac,laren1 and ,professor ,chrystal4 ,dr4 ,aitken had been testing the radiating powers of different substances4 ,snow in the shade on a bright day at noon is #g deg4 ,fahr4 colder than the air that floats upon it1 whereas a black surface at the same is only #d deg4 colder4 ,this difference diminishes as the sun gets lower2 and at night both radiate almost equally well4 ,i select1 among the careful and numerous observations1 the notes on ,january #ai1 #ahhf2 for ,i took note of the cold of that day in my diary4 ,it was the coldest day of the whole of that winter4 ,the barometer was #bh4h inches1 and the thermometer #d deg4--that is1 #bh deg4 of frost4 ,according to ,dr4 ,buchan1 that ,january had only two equal in average cold for fifty years4 ,on ,january #ai1 at #aj ,a4,m41 when the air was at #bj deg4 and the sky clear1 a black surface registered #af deg4 and the upper layer of snow #ab deg41 showing a difference of #d deg4 when both surfaces were colder than the superincumbent air4 ,it is curious to note that1 on ,february #e of the same year1 at the same hour1 when the sky was overcast1 the air was at #bc deg41 the black surface registered #bi deg41 and the snow #be deg41 showing again the difference of #d deg42 but1 in this case1 both surfaces were warmer than the air4 ,in both cases the radiation at night was equal4 ,this small absorbing power of snow for heat reflected and radiated from the sky during the day must have a most important effect on the temperature of the air4 ,the temperature of lands when covered with snow must be much lower than when free from it4 ,and1 when once a country has become covered with snow1 there will be a tendency towards glacial conditions4 ,but1 besides being a bad absorber of heat from the sky1 snow is also a very poor conductor of heat4 ,on that very cold night 7,january #ah71 when there was a depth of #e-a_/b inches of snow on the ground1 and the night clear1 with strong radiation1 the temperature of the surface of the snow was #c deg4 ,fahr41 and a minimum thermometer on the snow showed that it had been down to zero some time before4 ,a thermometer1 plunged into the snow down to the grass1 gave the most remarkable register of #cb deg4 ,through the depth of #e-a_/b inches of snow there was a difference of temperature of #bi deg4 ,this was confirmed by removing the snow1 and finding that the grass was unfrozen4 ,as the ground was frozen when the snow fell1 it would appear that the earth's heat slowly thawed it under the protection of the snow4 ,the protection afforded by the bad-conducting power of snow is of great importance in the economy of nature4 ,how vegetation would suffer1 were it exposed to a low temperature1 unprotected by the snow-mantle6 ,so that1 though the continued snow cools the air for animals that can look after their own heating1 it keeps warm the soil2 and vegetation prospers under the genial covering4 ,the fine rich look of the young wheat-blades1 after a continued snow has melted1 must strike the most careless observer4 ,instead of the half-blackened tips and semi-sickly blades1 which we see in a field of young wheat after a considerable course of dry frost without snow1 we have a rich1 healthy green which shows the vital energy at work in the plants4 ,or even in the town gardens1 after a continued snow has been melted away by a soft1 western breeze1 we are struck with the white1 peeping buds of the snowdrop and the finely springing grass in the sward4 ,yet the snow-covering gives durability to cold weather4 ,this has been demonstrated by ,dr4 ,woeikof1 the distinguished ,russian meteorologist4 ,on this account the spring months of ,russia and ,siberia are intensely cold4 ,the plants1 then1 which in winter are unable by locomotion to keep themselves in health1 are protected by the snow-mantle which chills the air for animals that can keep themselves in heat by exercise4 ,what a grand compensating power is here6 ,,chapter ,,xxvii ,,mountain ,,giants ,some mysterious physical phenomena can be clearly explained by the aid of science4 ,the mountain giants that at times haunt the lonely valleys1 and strike with fear the superstitious dwellers there1 are only the enlarged shadows of living human beings cast upon a dense mist4 ,the two most startling of these eerie phenomena are the spectres of ,adam's ,peak and the ,brocken4 ,the phenomena sometimes to be observed at ,adam's ,peak1 in ,ceylon1 are very remarkable4 ,many travellers have given vivid accounts of these4 ,on one occasion the ,hon4 ,ralph ,abercromby1 in his praiseworthy enthusiasm for meteorological research1 went there with two scientific friends to witness the strange appearance4 ,the conical peak1 a mile and a half high1 overlooks a gorge west of it4 ,when1 then1 the north-east monsoon blows the morning mist up the valley1 light wreaths of condensed vapour pass to the right of the ,peak1 and catch the shadows at sunrise4 ,this party reached the summit early one morning in ,february4 ,the foreglow began to brighten the under-surface of the stratus-cloud with orange1 and patches of white mist filled the hollows4 ,soon the sun peeped through a chink in the clouds1 and they saw the pointed shadow of the ,peak lying on the misty land4 ,then a prismatic circle1 with the red inside1 formed round the shadow4 ,the meteorologist waved his arms about1 and immediately he found giant shadowy arms moving in the centre of the rainbow4 ,soon they saw a brighter and sharper shadow of the ,peak1 encircled by a double bow1 and their own spectral arms more clearly visible4 ,the shadow1 the double bow1 and the giant forms1 combined to make this phenomenon the most marked in the whole world4 ,the question has been frequently asked3 ,why are such aerial effects not more widely observed8 ,there are not many mountains of this height and of a conical shape2 and still fewer can there be where a steady wind1 for months together1 blows up a valley so as to project the rising morning mist at a suitable height and distance on the western side1 to catch the shadow of the peak at sunrise4 ,the most famous place in ,europe for witnessing the awe-inspiring phenomenon is the ,brocken1 in ,germany--#cgdj feet in height4 ,the only great disappointment there is that the conditions rarely combine at sunrise or sunset to have the spectre successful4 ,in ,july #ahib1 my daughter and ,i were spending some weeks at ,harzburg1 and1 of course1 we had to visit the ,brocken and take stock of the world-known phenomenon4 ,at mid-day1 the air at the flat summit was cold1 clear1 and hard4 ,the boulders are of enormous size2 and near the ,noah's ,ark ,hotel and ,observatory many are piled up in a mass1 on which the observers stand at the appointed time for having their shadows projected on the misty air in the valleys4 ,at five o'clock in the afternoon the sky was brilliantly clear on the summit of the ,brocken2 but the wind was rising from the sun's direction1 and the mist was filling up the wide-spread eastern valley4 ,we stood on the spectre boulders1 and our shadows were thrown on the grass1 just as at home4 ,however1 they fell upon large patches of white heather1 which there is very plentiful4 ,at six o'clock the sun was still shining beautifully1 and we anxiously waited for the time when it would be low enough to raise our shadows to the misty wall4 ,an hour afterwards1 a hundred visitors were out1 and many of us were on the spectre stones4 ,there was great excitement in anticipation of the weird appearances1 which had attracted us from such a distance4 ,but1 almost at the moment of success1 the sun descended behind a belt of purple cloud1 and all we saw was part of a rainbow on the misty hollow4 ,for the sun never appeared again4 ,this was intensely saddening1 seeing that1 but for that stratum of cloud above the horizon1 the phenomenon would have been graphically displayed4 ,the cold became suddenly intense1 and we had to sleep with a freezing mist enveloping the hotel4 ,in vain did we wait for the wakening call1 to tell us of sunrise2 for the sun could not pierce the mist1 and we had to return home disappointed4 ,sometimes the rainbow colours assume the shapes of crosses instead of circles4 ,occasionally a bright halo will be seen above the shadow-head of the observer1 concentric rainbows enclosing all4 ,in some recorded cases the grand effect must have been simply glorious4 ,scientific observation has done much to dispel the superstition which has clung so tenaciously to the ,highland mind4 ,the lonely grandeur of the weird mountain giants has been clearly explained as perfectly natural1 yet the awe-striking feeling cannot be entirely driven off4 ,,chapter ,,xxviii ,,the ,,wind ,once was the remark pointedly made3 ,the wind bloweth where it listeth4 ,and that is nearly true still4 ,the leading winds are under the calculation of the meteorologist1 but the others will not be bound by laws4 ,yet there are instruments for measuring the velocity and force of the wind1 after it is on2 but whence it comes is a different matter4 ,a gentle air moves at the rate of #g miles an hour2 a hurricane from #hj to #aej miles1 pressing with #ej lbs4 on the square foot exposed to its fury4 ,some of the gusts of the ,tay ,bridge storm1 in #ahgi1 had a velocity of #aej miles an hour1 with a pressure of #hj to #ij lbs4 to the square foot4 ,before steamers supplanted so many sailing vessels1 seamen required to be always on the alert as to the direction and strength of the wind1 and the likelihood of any sudden change2 and they chronicled twelve different strengths from faint air to a storm4 ,in general1 the wind may be considered to be the result of a change of pressure and temperature in the atmosphere at the same level4 ,the air of a warmer region1 being lighter1 ascends1 and gives place to a current of wind from a colder region4 ,these two currents--the higher and the lower--will continue to blow until there is equilibrium4 ,the trade winds are regular and constant4 ,these were much followed in the days of old4 ,a vast amount of air in the tropics gets heated and ascends1 being lighter1 and travels to the colder north4 ,a strong current rushes in from the north to take its place4 ,but the earth rotates round its axis from west to east1 and the combined motions make two slant wind directions1 which are called the trade winds1 because they were so important in trade navigation4 ,among the periodical winds are the land and sea breezes4 ,during the day1 the land on the sea coast is warmer than the sea2 accordingly1 the air over the land becomes heated and ascends1 the fine cool breeze from the sea taking its place4 ,towards evening there is the equilibrium of temperature which produces a temporary calm4 ,soon the earth chills1 and the sea is counterbalancingly warm--as sea-water is steadier as to temperature than is land--the air over the sea becomes warmer1 and ascends1 the current from the land rushing in to take its place4 ,hence during the night the wind is reversed1 until in the morning again the equilibrium is restored and there is a calm1 so far as these are concerned4 ,these are therefore called the land and sea breezes4 ,of course1 it is within the tropics that these breezes are most marked4 ,by the assistance of other winds1 a hurricane will there occasionally destroy towns and bring about much damage and loss of life2 but better that hundreds should perish by a hurricane than thousands by the pestilence which1 but for the storm1 would have done its dire work4 ,in countries where the differences of pressure are more marked than the differences of temperature1 in the surrounding regions the strength of the wind thereby occasioned is far stronger than the land and sea breezes4 ,the variable winds are more conflicting4 ,these depend on purely local causes for a time1 such as the nature of the ground1 covered with vegetation or bare2 the physical configuration of the surface1 level or mountainous2 the vicinity of the sea or lakes1 and the passage of storms4 ,among these winds are the simoom and sirocco4 ,the east winds1 which one does not care about in the ,british ,islands during the spring time1 are occasioned by the powerful northern current which rushes south from the northern regions in ,europe4 ,dr4 ,buchan points out a very common mistake among even intelligent observers who shudder at the hard east winds4 ,it is generally held that these winds are damp4 ,they are unhealthy1 but they are dry4 ,it is quite true that many easterly winds are peculiarly moist2 all that precede storms are so far damp and rainy2 and it is owing to this circumstance that1 on the east coast of ,scotland1 the east winds are searching and carry most of the annual rainfall there4 ,but all of these moist easterly winds1 however1 soon turn to some westerly point4 ,the real east wind1 so much feared by invalids1 does not turn to the west2 it is exceeding dry4 ,curious is it that brain diseases1 as well as consumption1 reach their height in ,britain while east winds prevail4 ,once in ,edinburgh1 during the early spring1 ,i had rheumatic fever1 and during my convalescence my medical adviser1 ,dr4 ,menzies1 would not let me have a short drive until the wind changed to the west4 ,the first thing ,i anxiously watched in the morning was the flag on the ,castle2 and for nearly two months it always waved from the east4 ,how heart-depressing6 ,creatures are we in the hands of nature's messengers4 ,we so much depend upon the weather for our happiness4 ,joyful are we when the honey-laden zephyr waves the long grass in ,june1 or when ,the gentle wind1 a sweet and passionate wooer1 ,kisses the blushing leaf4 ,compared with this1 how terrible is ,shakespeare's allusion to the appalling aspects of the storm3-- ,i have seen tempests1 when the scolding winds ,have rived the knotty oaks2 and ,i have seen ,the ambitious ocean swell1 and rage and foam1 ,to be exalted with the threat'ning clouds2 ,but never till to-night1 never till now1 ,did ,i go through a tempest dropping fire4 ,,chapter ,,xxix ,,cyclones ,,and ,,anti-,,cyclones ,the criticism of the weather in the meteorological column of our daily newspapers invariably speaks of cyclones4 ,it is1 therefore1 advisable to give as plain an explanation of these as possible4 ,cyclones are storm-winds4 ,their nature has to be carefully studied by meteorologists1 who are industriously at work to ascertain some scientific basis for the atmospheric movements4 ,what is the cause of the spiral movement in storm-winds8 ,in their centre the depression of the barometer is lowest1 because the atmosphere there is lightest4 ,as the walls of the spiral are approached1 the barometer rises4 ,dr4 ,aitken has ingeniously hit upon an experiment to illustrate a spiral in air4 ,all that is necessary is a good fire1 a free-going chimney1 and a wet cloth4 ,the cloth is hung up in front of the fire1 and pretty near it1 so that steam rises readily from its surface2 and1 when there are no air-currents in the room1 the steam will rise vertically1 keeping close to the cloth4 ,but if the room has a window in the wall1 at right angles to the fireplace1 so as to cause the air coming from it to make a cross-current past the fire1 then a cyclone will be formed1 and the vapour from the cloth will be seen circling round4 ,when the cyclone is well formed1 all the vapour is collected into the centre of the cyclone1 and forms a white pillar extending from the cloth to the chimney4 ,this experiment shows that no cyclone can form without some tangential motion in the air entering the area of low-pressure4 ,now to illustrate the spiral approach4 ,fill with water a cylindrical glass vessel1 say #ae inches in diameter and #f inches deep4 ,have an orifice with a plug a little from the centre of the bottom4 ,remove the plug1 the water runs out1 passing round the vessel in a vortex form4 ,but1 as the passage between the orifice 7or centre of the cyclone7 and the temporary division is narrower than in any other place1 the water has to pass this part much more quickly than at any other place4 ,and this curious result is observed3 the top of the cyclone no longer remains over the orifice1 but travels in the direction of the water which is moving most speedily4 ,similar to this is the cyclone in the atmosphere2 its centre also moves in the direction of the quickest flowing wind that enters it4 ,dr4 ,aitken is of opinion that1 in forecasting storms1 too little attention has been paid to the anti-cyclones4 ,they do more than simply follow and fill up the depression made by the cyclones4 ,they initiate and keep up their own circulation1 and collect the materials with which the cyclones produce their effect4 ,neither could work efficiently without the other4 ,suppose a large area on the earth over which the air is still in bright sunshine4 ,after a time1 when the air gets heated and charged with vapour1 columns of air would begin to ascend in a disorderly fashion4 ,but suppose an anti-cyclone is blowing at one side of this area4 ,when the upper air descends to the earth1 it spreads outwards in all directions2 but the earth's rotation interferes and changes the radial into a spiral motion4 ,the anti-cyclonic winds will prevent the formation of local cyclones1 and drive all the moist1 hot air to its circumference1 just above the earth4 ,the anti-cyclone forces its air tangentially into the cyclone1 and gives it its direction and velocity of rotation1 also the direction and rate of travel of the centre of depression4 ,the earth's rotation is the original source of the rotatory movements1 but both intensify the initial motion4 ,accordingly1 the cyclone must travel in the direction of the strongest winds blowing into it1 just as the vortex in the vessel with the eccentric orifice travelled in the direction of the quickest moving water4 ,this is verified by a study of the synoptic charts of the ,meteorological ,office4 ,the sun's heat has always been looked upon as the main source of the energy of our winds1 but some account must also be taken of the effects of cold4 ,it is well known that the mean pressure over ,continental areas is high during winter and low during summer4 ,as the sun's rays during summer give rise to the cyclonic conditions1 so the cooling of the earth during winter gives rise to anti-cyclonic conditions4 ,it is found during the winter months in several parts of the ,continent that as the temperature falls the pressure rises1 producing anti-cyclones over the cold area2 whereas1 when the temperature begins to rise1 the pressure falls1 and cyclones are attracted to the warming area4 ,small natural cyclones are often seen on dusty roads1 the whirling column having a core of dusty air1 and the centre of the vortex travelling along the road1 tossing up the dust in a very disagreeable way to pedestrians4 ,sometimes such a cyclone will toss up dry leaves to a height of four or five feet4 ,they are very common2 but it is only when dust1 leaves1 or other light material is present that they are visible to the eye4 ,,chapter ,,xxx ,,rain ,,phenomena ,the soft rain on a genial evening1 or the heavy thunder-showers on a broiling day1 are too well known to be written about4 ,sometimes rain is earnestly wished for1 at other times it is dreaded1 according to the season1 seed-time or harvest4 ,some years1 like #ahbf1 are very deficient in rainfall1 when the corn is stunted and everything is being burnt up2 other years1 like #aijc1 there is an over-supply1 causing great damage to agriculture4 ,the year #aijc will long be remembered for its continuous rainfall2 it is the record year2 no year comes near it for the total rainfall all over the kingdom4 ,rain is caused by anything that lowers the temperature of the air below the dew-point1 but especially by winds4 ,when a wind has blown over a considerable area of ocean on to the land1 there is a likelihood of rain4 ,when this wind is carried on to higher latitudes1 or colder parts1 there is a certainty of rain4 ,of course1 in the latter case the rain will fall heavier on the wind side than on the lee side4 ,for short periods1 the heaviest falls or plouts of rain are during thunder-storms4 ,when the raindrops fall through a broad1 cold stratum of air1 they are frozen into hail1 the particles of which sometimes reach a large size1 like stones4 ,of course1 water-spouts now and again are of terrible violence4 ,one of the heaviest rainfalls yet recorded in ,great ,britain was about #b-a_/d inches in forty minutes at ,lednathie1 ,forfarshire1 in #ahhg4 ,now #a inch deep of rain means #ajj tons on an imperial acre2 so the amount of water falling on a field during that short time is simply startling4 ,the heaviest fall for one day was at ,ben ,nevis ,observatory1 being fully #g-a_/d inches in #ahij4 ,in other parts of the world this is far exceeded4 ,in one day at ,brownsville1 ,texas1 nearly #ac inches fell in #ahhf4 ,on the ,khasi hills1 ,india1 #cj inches on each of five successive days were registered4 ,at ,gibraltar1 #cc inches were recorded in twenty-six hours4 ,the heaviest rainfalls of the globe are occasioned by the winds that have swept over the most extensive ocean-areas in the tropics4 ,on the summer winds the rainfall of ,india mainly depends2 when this fails1 there is most distressing drought4 ,reservoirs are being erected to meet emergencies4 ,from ,dr4 ,buchan's statistics it is found that the annual rainfall at ,mahabaleshwar is #bfc inches2 at ,sandoway #bad2 and at ,cherra-pungi #dgb inches1 the largest known rainfall anywhere on the globe4 ,over a large part of the ,highlands of ,scotland more than #hj inches fall annually1 while in some of the best agricultural districts there it does not exceed #cj inches4 ,of all meteorological phenomena1 rainfall is the most variable and uncertain4 ,symons gives as tentative results from twenty years' observations in ,london--7#a7 ,in winter1 the nights are wetter than the days2 7#b7 in spring and autumn1 there is not much difference2 7#c7 in summer1 nearly half as much again by day as by night4 ,the wearisomeness of statistics may be here relieved by a short consideration of the splash of a drop of rain4 ,watching the drop-splashes on a rainy day in the outskirts of the city1 when unable to get out1 ,i brought to my recollection the marvellous series of experiments made by ,professor ,a4 ,m4 ,worthington in connection with these phenomena4 ,of course1 ,i could not see to proper advantage the formation of the splashes1 as the heavy raindrops fell into these tiny lakes on the quiet road4 ,there is not the effect of the huge thunder-drops in a stream or pool4 ,the building up of the bubbles is not here perfect1 for the domes fail to close1 nor are the emergent columns visible to the naked eye4 ,it is a pity2 for ,r4 ,l4 ,stevenson once wrote of them in his delightful ,inland ,voyage1 when he canoed in the ,belgian canals1 as thrown up by the rain into an infinity of little crystal fountains4 ,beautiful is this effect if one is under shelter1 every dome seeming quite different in contour and individuality from all the rest4 ,but terrible is it when out fishing on ,loch ,earn1 even with the good-humoured old ,admiral1 when the heavy thunder-drops splash up the crystal water1 and one gets soaked to the skin1 sportsman-like despising an umbrella4 ,there is1 however1 a scientific interest about the splash of a drop4 ,the phenomenon can be best seen indoors by letting a drop of ink fall upon the surface of pure water in a tumbler1 which stands on white paper4 ,it is an exquisitely regulated phenomenon1 which very ideally illustrates some of the fundamental properties of fluids4 ,when a drop of milk is let fall upon water coloured with aniline dye1 the centre column of the splash is nearly cylindrical1 and breaks up into drops before or during its subsequent descent into the liquid4 ,as it disappears below the surface1 the outward and downward flow causes a hollow to be again formed1 up the sides of which a ring of milk is carried2 while the remainder descends to be torn a second time into a beautiful vortex ring4 ,this shell or dome is a characteristic of all splashes made by large drops falling from a considerable height1 and is extremely pretty4 ,sometimes the dome closes permanently over the imprisoned air1 and forms a large bubble floating upon the water4 ,the most successful experiments1 however1 have been carried through by means of instantaneous photography1 with the aid of a ,leyden-jar spark1 whose duration was less than the ten-millionth of a second4 ,but the simple experiments1 without the use of the apparatus1 will while away a few hours on a rainy afternoon1 when condemned to the penance of keeping within doors4 ,,chapter ,,xxxi ,,the ,,meteorology ,,of ,,ben ,,nevis ,several large and very important volumes of the ,royal ,society of ,edinburgh are devoted to statistics connected with the meteorology of ,ben ,nevis4 ,most of the abstracts have been arranged by ,dr4 ,buchan2 while ,messrs4 ,buchanan1 ,omond1 and ,rankine have taken a fair share of the work4 ,this ,observatory1 as ,mr4 ,buchanan remarks1 is unique1 for it is established in the clouds2 and the observations made in it furnish a record of the meteorology of the clouds4 ,it is #ddjf feet above the level of the sea2 and as there is a corresponding ,observatory at ,fort ,william1 at the base of the mountain1 it is peculiarly well fitted for important observations and weather forecasting4 ,the mountain1 too1 is on the west sea-coast of ,scotland1 exposed immediately to the winds from the ,atlantic1 catching them at first hand4 ,it is lamentable to think that1 when the importance of the observations made at the two ,observatories was becoming world known1 funds could not be got to carry them on4 ,ben ,nevis is the highest mountain in the ,british ,islands1 best fitted for meteorological observations2 yet these have been stopped for want of money4 ,dr4 ,buchan's valuable papers were published before any one dreamed of the stoppage of the work1 which had such an important bearing on men engaged in business or taken up with open-air sport4 ,from these ,i shall sift out a few facts that even mute1 inglorious meteorologists may be interested in knowing4 ,for a considerable time the importance of the study of the changes of the weather has come gradually to be recognised1 and an additional impetus was given to the prosecution of this branch of meteorology when it was seen that the subject had intimate relations to the practical question of weather forecasts1 including storm warnings4 ,weather maps1 showing the state of the weather over an extensive part of the surface of the globe1 began to be constructed2 but these were only indicators from places at the level of the sea4 ,the singular advantages of a high-level observatory occurred to ,mr4 ,milne ,home in #ahgg2 and ,ben ,nevis was considered to be in every respect the most suitable in this country4 ,the ,meteorological ,council of the ,royal ,society of ,london offered in #ahhj1 unsolicited1 ,l#ajj annually to the ,scottish ,meteorological ,society1 to aid in the support of an ,observatory1 the only stipulation being that the ,council be supplied with copies of the observations4 ,from ,june to ,october1 in #ahha1 ,mr4 ,wragge made daily observations at the top of the ,ben2 and simultaneous observations were made1 by ,mrs4 ,wragge1 at ,fort ,william4 ,a second series1 on a much more extended scale1 was made in the following summer4 ,funds were secured to build an ,observatory2 and1 in ,november #ahhc1 the regular work commenced1 consisting of hourly observations by night as well as by day4 ,until a short time ago1 these were carried on uninterruptedly4 ,telegraphic communications of each day's observations were sent to the morning newspapers2 and now we are disappointed at not seeing them for comparison4 ,the whole of the observations of temperature and humidity were of necessity eye-observations4 ,for self-registering thermometers were comparatively useless when the wind was sometimes blowing at the rate of #ajj miles an hour4 ,saturation was so complete in the atmosphere that everything exposed to it was dripping wet4 ,every object exposed to the outside frosts of winter soon became thickly incrusted with ice4 ,snowdrifts blocked up exposed instruments4 ,accordingly1 the observers had to use their own eyes1 often at great risks4 ,the instruments in the ,ben ,nevis ,observatory1 and in the ,observing ,station at ,fort ,william1 were of the best description4 ,both stations were in positions where the effects of solar and terrestrial radiation were minimised4 ,no other pair of meteorological stations anywhere in the world are so favourably situated as these two stations1 for supplying the necessary observations for investigating the vertical changes of the atmosphere4 ,it is to be earnestly hoped1 therefore1 that funds will be secured to resume the valuable work4 ,the rate of the decrease of temperature with height there is #a deg4 ,fahr4 for every #bge feet of ascent1 on the mean of the year4 ,the rate is most rapid in ,april and ,may1 when it is #a deg4 for each #bdg feet2 and least rapid in ,november and ,december1 when it is #a deg4 for #cjg feet4 ,this rate agrees closely with the results of the most carefully conducted balloon ascents4 ,the departures from the normal differences of temperature1 but more especially the inversions of temperature1 and the extraordinarily rapid rates of diminution with height1 are intimately connected with the cyclones and anti-cyclones of ,north-,western ,europe2 and form data1 as valuable as they are unique1 in forecasting storms4 ,the most striking feature of the climate of ,ben ,nevis is the repeated occurrence of excessive droughts4 ,for instance1 in the summer and early autumn of #ahhe1 low humidities and dew-points frequently occurred4 ,corresponding notes were observed at sea-level4 ,during nights when temperature falls through the effects of terrestrial radiation1 those parts of the country suffer most from frosts over which very dry states of the air pass or rest2 whereas1 those districts1 over which a more humid atmosphere hangs1 will escape4 ,on the night of ,august #ca of that year1 the potato crop on ,speyside was totally destroyed by the frost2 whereas at ,dalnaspidal1 in the district immediately adjoining1 potatoes were scarcely--if at all--blackened4 ,the mean annual pressure at ,ben ,nevis was #be4c inches1 and at ,fort ,william #bi4h1 the difference being #d-a_/b inches for the #ddjj feet4 ,for the whole year1 the difference between the mean coldest hour1 #e ,a4,m41 and the warmest hour1 #b ,p4,m41 is #b deg4 ,for the five months1 from ,october to ,february1 the mean daily range of temperature varied only from ,o4#f to #a4e4 ,this is the time of the year when storms are most frequent2 and this small range in the diurnal march of the temperature is an important feature in the climatology of ,ben ,nevis2 for it presents1 in nearly their simple form1 the great changes of temperature accompanying storms and other weather changes1 which it is so essential to know in forecasting weather4 ,the daily maximum velocity of the wind occurs during the night1 the daily differences being greatest in summer and least in winter4 ,a blazing sun in the summer daily pours its rays on the atmosphere1 and a thick envelope of cloud has apparently but little influence on the effect of the sun's rays4 ,thunder-storms are essentially autumn and winter phenomena1 being rare in summer4 ,according to ,mr4 ,buchanan1 the weather on ,ben ,nevis is characterised by great prevalence of fog or mist4 ,in continuously clear weather it practically never rains on the mountain at all4 ,in continuously foggy weather1 on the other hand1 the average daily rainfall is #a inch4 ,there is a large and continuous excess of pressure in clear weather over that of foggy weather4 ,the mean temperature of the year is #c-a_/b degrees higher in clear than in foggy weather4 ,in ,june the excess is #aj degrees4 ,the nocturnal heating in the winter is very clearly observed4 ,this has been noticed before in balloons as well as on mountains4 ,the fog and mist in winter are much denser than in summer4 ,whether wet or dry1 the fog which characterises the climate of the mountain is nothing but cloud under another name4 ,,chapter ,,xxxii ,,the ,,weather ,,and ,,influenza ,some remarkable facts have been deduced by the late ,dr4 ,l4 ,gillespie1 ,medical ,registrar1 from the records of the ,royal ,infirmary of ,edinburgh4 ,he considered that it might lead to interesting results if the admissions into the medical wards were contrasted with the varying states of the atmosphere4 ,the repeated attacks of influenza made him pay particular attention to the influence of the weather on that disease4 ,the meteorological facts taken comprise the weekly type of weather1 i4e4 cyclonic or anti-cyclonic1 the extremes of temperature for the district for each week1 and the mean weekly rainfall for the same district4 ,more use is made of the extremes than of the mean1 for rapid changes of temperature have a greater influence on disease than the actual mean4 ,the period which he took up comprises the seven years #ahhh-ahie4 ,there was a yearly average of admissions of #cich2 so that he had a good field for observation4 ,six distinct epidemics of influenza1 varying in intensity1 occurred during that period2 yet there had been only twenty-three attacks between #aeaj and #ahij4 ,accordingly1 these six epidemics must have had a great influence on the incidence of disease in the same period1 knowing the vigorous action of the poison on the respiratory1 the circulatory1 and the nervous systems4 ,the epidemics of influenza recorded in this country have usually occurred during the winter months4 ,the first epidemic1 which began on the #aeth of ,december #ahhi and continued for nine weeks1 was preceded by six weeks of cyclonic weather1 which was not1 however1 accompanied by a heavy rainfall4 ,throughout the course of the disease1 the type continued to be almost exclusively cyclonic1 with a heavy rainfall1 a high temperature1 and a great deficiency of sunshine4 ,the four weeks immediately following were also chiefly cyclonic1 but with a smaller rainfall4 ,the summer epidemic of #ahia followed a fine winter and spring1 during which anti-cyclonic conditions were largely prevalent4 ,but the epidemic was immediately preceded by wet weather and a low barometer4 ,it took place in dry weather1 and was followed by wet1 cyclonic weather in turn4 ,the great winter epidemic of #ahia followed an extremely wet and broken autumn4 ,simultaneously with the establishment of an anti-cyclone1 with east wind1 practically no rain1 and a lowering temperature1 the influenza commenced4 ,great extremes in the temperature followed1 the advent of warmer weather and more equable days witnessing the disappearance of the disease4 ,the fourth epidemic was preceded by a wet period1 ushered in by dry weather1 accompanied by great heat2 and its close occurred in slightly wetter weather1 but under anti-cyclonic conditions4 ,the fifth outbreak began after a short anti-cyclone had become established over our islands1 continued during a long spell of cyclonic weather with a considerable rainfall1 but was drowned out by heavy rains4 ,the last appearance of the modern plague1 of which ,dr4 ,gillespie's paper treats1 commenced after cold and wet weather1 continued in very cold but drier weather1 and subsided in warmth with a moderate rainfall4 ,the conditions of these six epidemics were very variable in some respects1 and regular in others4 ,the most constant condition was the decreased rainfall at the time1 when the disease was becoming epidemic4 ,anti-cyclonic weather prevailed at the time4 ,according to ,dr4 ,gillespie1 the tables seem to suggest that a type of weather1 which is liable to cause catarrhs and other affections of the respiratory tract1 precedes the attacks of influenza2 but that the occurrence of influenza in epidemic form does not appear to take place until another and drier type has been established4 ,as the weather changes1 the affected patients increase with a rush4 ,he is of opinion that the supposed rapid spread of influenza on the establishment of anti-cyclonic conditions may be explained in this way4 ,the air in the cyclonic vortex1 drawn chiefly from the atmosphere over the ocean1 is moist1 and contains none of the contagion2 the air of the anti-cyclone1 derived from the higher strata1 and thus from distant cyclones1 descending1 blows gently over the land to the nearest cyclone1 and1 being drier1 is more able to carry suspended particles with it4 ,he considers that temperature has nothing to do with the problem1 except in so far as the different types of weather may modify it4 ,the ,infirmary records point to the occurrence of similar phenomena1 recorded on previous occasions4 ,accordingly1 if such meteorological conditions are not indispensable to the spread of influenza in epidemic form1 they at least afford favourable facilities for it4 ,,chapter ,,xxxiii ,,climate ,one is not far up in years1 in ,scotland at any rate1 without practically realising what climate means4 ,he may not be able to put it in words1 but easterly haars1 chilling rimes1 drizzling mists1 dagging fogs1 and soddening rains speak eloquently to him of the meaning of climate4 ,climate is an expression for the conditions of a district with regard to temperature1 and its influence on the health of animals and plants4 ,the sun is the great source of heat1 and when its rays are nearly perpendicular--as at the ,tropics--the heat is greater on the earth than when the slanted rays are gradually cooled in their passage4 ,as one passes to a higher level1 he feels the air colder1 until he reaches the fluctuating snow-line that marks perpetual snow4 ,the temperature of the atmosphere also depends upon the radiation from the earth4 ,heat is quite differently radiated from a long stretch of sand1 a dense forest1 and a wide breadth of water4 ,strange is it that a newly ploughed field absorbs and radiates more heat than an open lea4 ,the equable temperature of the sea-water has an influence on coast towns4 ,the ,gulf ,stream1 from the ,gulf of ,mexico1 heats the ocean on to the west coast of ,britain1 and mellows the climate there4 ,the rainfall of a district has a telling effect on the climate4 ,boggy land produces a deleterious climate1 if not malaria4 ,over the world1 generally1 the prevailing winds are grand regulators of the climate in the distinctive districts4 ,a wooded valley--like the greatest in ,britain1 ,strathmore--has a health-invigorating power3 what a calamity it is1 then1 that so many extensive woods1 destroyed by the awful hurricane twelve years ago1 are not replanted6 ,some people can stand with impunity any climate2 their leather lungs cannot be touched by extremes of temperature2 but ordinary mortals are mere puppets in the hands of the goddess climate4 ,hence health-resorts are munificently got up1 and splendidly patronised by people of means4 ,the poor1 fortunately1 have been successful in the struggle for existence1 by innate hardiness1 otherwise they would have had a bad chance without ready cash for purchasing health4 ,it may look ludicrous at first sight1 but it seems none the less true1 that the variation of the spots on the sun have something to do with climate1 even to the produce of the fields4 ,on close examination1 with a proper instrument1 the disc of the sun is found to be here and there studded with dark spots4 ,these vary in size and position day after day4 ,they always make their first appearance on the same side of the sun1 they travel across it in about fourteen days1 and then they disappear on the other side4 ,there is a great difference in the number of spots visible from time to time2 indeed1 there is what is called the minimum period1 when none are seen for weeks together1 and a maximum period1 when more are seen than at any other time4 ,the interval between two maximum periods of sun-spots is about eleven years4 ,this is a very important fact1 which has wonderful coincidences in the varied economy of nature4 ,kirchhoff has shown1 by means of the spectroscope1 that the temperature of a sun-spot must be lower than that of the remainder of the solar surface4 ,as we must get less heat from the sun when it is covered with spots than when there are none1 it may be considered a variable star1 with a period of eleven years4 ,balfour ,stewart and ,lockyer have shown that this period is in some way connected with the action of the planets on the photosphere4 ,as we have already mentioned1 the variations of the magnetic needle have a period of the same length1 its greatest variations occurring when there are most sun-spots4 ,aurorae1 and the currents of electricity which traverse the earth's surface1 follow the same law4 ,this remarkable coincidence set men a-thinking4 ,can the varying condition of the sun exert any influences upon terrestrial affairs8 ,is it connected with the variation of rainfall1 the temperature and pressure of the atmosphere1 and the frequency of storms8 ,has the regular periodicity of eleven years in the sun-spots no effect upon climate and agricultural produce8 ,mr4 ,f4 ,chambers1 of ,bombay1 has taken great trouble to strike1 as far as possible1 a connection between the recurring eleven years of sun-spots and the variation of grain prices4 ,he arranged the years from #aghc to #ahhb in nine groups of eleven years2 and1 from an examination of his tables1 we find that there is a decided tendency for high prices to recur at more or less regular intervals of about eleven years1 and a similar tendency for low prices4 ,an occasional slight difference can be accounted for by some abnormal cause1 as war or famine4 ,amid all the apparently irregular fluctuations of the yearly prices1 there is in every one of the ten provinces of ,india a periodical rise and fall of prices once every eleven years1 corresponding to the regular variation which takes place in the number of sun-spots during the same period4 ,if it were possible to obtain statistics to show the actual out-turn of the crops each year1 the eleven yearly variations calculated therefrom might reasonably correspond with the sun-spot variations even more closely than do the price variations4 ,this is a remarkable coincidence1 if nothing more4 ,what if it were yet possible to predict the variations of prices in the coming sun-spot cycle8 ,such a power would be of immense service4 ,by its aid it could be predicted that1 as the present period of low prices has followed the last maximum of sun-spots1 which was in the year #aijd1 it will not last much longer1 but that prices must gradually keep rising for the next five years4 ,could science really predict this1 it would be studied by many and blessed by more4 ,yet the strange coincidence of a century's observations renders the conclusions not only possible1 but to some extent probable4 ,,chapter ,,xxxiv ,,the ,,challenger ,,weather ,,reports ,the ,challenger ,expedition1 commenced by ,sir ,wyville ,thomson1 and after his death continued by ,sir ,john ,murray1 with an able staff of assistants for the several departments1 was one of the splendid exceptions to the ordinary ,british ,government stinginess in the furtherance of science4 ,the results of the ,expedition were printed in a great number of very handsome volumes at the expense of the ,government4 ,and the valuable deductions from the ,challenger's ,weather ,reports by ,dr4 ,alex4 ,buchan1 in his ,atmospheric ,circulation1 have thrown considerable light upon oceanic weather phenomena4 ,for some of his matured opinions on these1 ,i am here much indebted to him4 ,humboldt1 in #ahag1 published a treatise on ,isothermal ,lines1 which initiated a fresh line for the study of atmospheric phenomena4 ,an isotherm is an imaginary line on the earth's surface1 passing through places having a corresponding temperature either throughout the year or at any particular period4 ,an isobar is an imaginary line on the earth's surface1 connecting places at which the mean height of the barometer at sea-level is the same4 ,to isobars1 as well as to isotherms1 ,dr4 ,buchan has devoted considerable attention4 ,in #ahfh1 he published an important series of charts containing these1 with arrows for prevailing winds over the earth for the months of the year4 ,in this way what are called synoptic charts were established4 ,in the ,challenger ,report are shown the various movements of the atmosphere1 with their corresponding causes4 ,it is thus observed that the prevailing winds are produced by the inequality of the mass of air at different places4 ,the air flows from a region of higher to a region of lower pressure1 i4e4 from where there is an excessive mass of air to fill up some deficiency4 ,and this is the great principle on which the science of meteorology rests1 not only as to winds1 but as to weather changes4 ,of the sun's rays which reach the earth1 those that fall on the land are absorbed by the surface layer of about #d feet in thickness4 ,but those that fall on the surface of the ocean penetrate1 as shown by the observations of the ,challenger ,expedition1 to a depth of about #ejj feet4 ,hence1 in deep waters the temperature of the surface is only partially heated by the direct rays of the sun4 ,in mid-ocean the temperature of the surface scarcely differs #a deg4 ,fahr4 during the whole day1 while the daily variation of the surface layer of land is sometimes #ej deg4 ,the temperature of the air over the ocean is about three times greater than that of the surface of the open sea over which it lies2 but1 near land1 this increases to five times4 ,the elastic force of vapour is seen in its simplest form on the open sea1 as disclosed by these ,reports4 ,it is lowest at #d ,a4,m4 and highest at #b ,p4,m4 ,the relative humidity is just the reverse4 ,when the temperature is highest1 the saturation of the air is lowest1 and vice versa4 ,so on land when the air1 by radiation of heat from the earth1 is cooled below the dew-point1 dew is produced1 and1 at the freezing-point1 hoar-frost4 ,the ,challenger ,reports1 too1 show that the force of the winds on the open sea is subject to no distinct and uniform daily variation1 but that on nearing land the force of the wind gives a curve as distinctly marked as the ordinary curve of temperature4 ,that force is lowest from #b to #d ,a4,m41 and highest from #b to #d ,p4,m4 ,each of the five great oceans gives the same result4 ,at ,ben ,nevis1 on the other hand1 these forces are just reversed in strength4 ,it is also shown by the ,challenger observations that on the open sea the greatest number of thunder-storms occur from #aj ,p4,m4 to #h ,a4,m4 ,and1 from this1 ,dr4 ,buchan concludes that over the ocean terrestrial radiation is more powerful than solar radiation in causing those vertical disturbances in the equilibrium of the atmosphere which give rise to the thunder-storm4 ,,chapter ,,xxxv ,,weather-,,forecasting ,to foretell with any degree of certainty the state of the weather for twenty-four hours is of immense advantage to business men1 tourists1 fishermen1 and many others4 ,the weather is everybody's business4 ,and the probabilities of accurate forecasts are so improving that all are more or less giving attention to the morning meteorological reports4 ,weather-forecasting depends on the principle from vast experience that1 if one event happens1 a second is likely to follow4 ,according to the extent and accuracy of the data1 will be the strength of the probability of correct forecasts4 ,and the great end of popular meteorology is to demonstrate this4 ,we have given some explanations of the weather in some respects unique2 and a careful consideration of these explanations will the more convince the reader of the importance of the subject4 ,no doubt the changes of the weather are extremely complex1 at times baffling2 and the wonder is that forecasts come so near the truth4 ,for instance1 the year #aijc almost defied the ordinary rules of weather1 for it broke the record for rainfall4 ,and1 last year1 so repulsive and unseasonable was the spring1 that there seemed to be a virtual withdrawal of the season4 ,i wrote on it as ,the ,recession of ,spring4 ,speak about ,borrowing ,days6 ,we had the equinoctial gales of ,march about the middle of ,april4 ,on very few days had we clear shining to cheer us after rain1 for the bitter cold dried up any genial moisture4 ,an old farmer remarked that ,we're gaun ower faur ,north4 ,no one could account for the backwardness of the season4 ,unless for the cheering songs of the grove-charmers1 one would have forgotten the time of the year4 ,in ,march of this year1 at ,strathmore1 the barometer fell from #cj4e inches 7the highest for years7 to #bh4fe in five days without unfavourable weather following4 ,it again rose to #cj4je1 then fell to #bh4de1 followed by a rise to #bh4g without any peculiar change4 ,but in two days it fell to #bh4d 7the lowest for years71 followed by a deluge of rain and a perfect hurricane for several hours1 while the temperature was fortunately mild4 ,it was only evident at the end that this universal storm had been brewing some days before4 ,all are familiar with the ordinary prognostics of good and bad weather4 ,a broch round the moon1 in her troubled heaven1 indicates a storm of rain or wind4 ,when the dark crimson sun in the evening throws a brilliant bronzed light on the gables and dead leaves1 we are sure that there is an intense radiation from the earth to form dew1 or even hoar-frost4 ,according to the meteorological folk-lore1 the weather of the summer season is indicated by the foliation of the oak and ash trees4 ,if the oak comes first into leaf1 the summer will be hot and dry1 if the ash has the precedence it will be wet and cold4 ,looking over the observations of the budding of these two trees for half a century1 ,i find that the weather-lore adage has been pretty correct4 ,the ash was out before the oak a full month in the years #ahaf1 '#ag1 '#ba1 '#bc1 '#bh1 '#bi1 '#cj1 '#ch1 '#dj1 '#de1 '#ej1 and '#ei2 and the summer and autumn in these years were unfavourable4 ,again1 the oak was out before the ash several weeks in the years #ahah1 '#ai1 '#bj1 '#bb1 '#bd1 '#be1 '#bf1 '#bg1 '#cc1 '#cd1 '#ce1 '#cf1 '#cg1 '#db1 '#df1 '#ed1 '#fh1 and '#fi2 the summers during these years were dry and warm1 and the harvests were abundant4 ,one can never think of this weather prognostic from nature without recalling the ,swallow ,song of ,tennyson's ,princess3-- ,why lingereth she to clothe her heart with love1 ,delaying1 as the tender ash delays ,to clothe herself1 when all the woods are green8 ,on a muggy morning a sudden clearness in the south drowns the ploughman4 ,and yet enough blue in the sky tae mak' a pair o' breeks cheers one with the assurance of coming dry and sunny weather4 ,the low flying of the swallows betokens rain1 as well as any unseasonable dancing of midges in the evening4 ,sore corns on the feet1 and rheumatism in the joints1 are direful precursors4 ,the leaves are all a-tremble before the approach of thunder4 ,but throughout this volume ,i have given many illustrations4 ,but one of the largest and most important practical problems of meteorology is to ascertain the course which storms follow1 and the causes by which that course is determined1 so that a forecast may thereby be made1 not only of the certain approach of a storm1 but the particular direction and force of the storm4 ,the method of conducting this large inquiry most effectively was devised by the ,french astronomer1 ,le ,verrier--the great aspirant1 with our own ,couch ,adams1 for the discovery of the planet ,neptune4 ,he began to carry this out in #aheh by the daily publication of weather data1 followed by a synchronous weather map1 which showed graphically for the morning of the day of publication the atmospheric pressure and the direction and force of the wind1 together with tables of temperature1 rainfall1 cloud1 and sea disturbances from a large number of places in all parts of ,europe4 ,it is from similar maps that forecasts of storms are still framed1 and suitable warnings issued2 and a mass of information is being collected by telegraph from sixty stations in the ,british ,islands1 c41 of the state of the weather at eight o'clock every morning1 and analysed and arranged at the ,meteorological ,office in ,london for the evening's forecasts over the different districts of the country4 ,a juster knowledge is being now acquired of those great atmospheric movements1 and other changes1 which form the groundwork of weather-forecasting4 ,the ,meteorological ,office1 ,westminster 7entirely distinct from the ,royal ,meteorological ,society71 is administered by a ,council 7,chairman1 ,sir ,r4 ,strachey2 ,scottish member1 ,dr4 ,buchan71 selected by the ,royal ,society4 ,it employs a staff of over forty4 ,the chief departments relate to3 7#a7 ,ocean ,meteorology1 including the collection1 tabulation1 and discussion of meteorological data from ,british ships1 the preparation of ocean weather charts1 and the issue of meteorological instruments to the ,royal ,navy and ,mercantile ,marine2 7#b7 ,weather ,telegraphy1 including the reception of telegrams thrice a day from selected stations for the preparation of the daily reports and weather forecasts4 ,representatives of newspapers1 c41 receive copies of the #aa ,a4,m4 forecast based on the #h ,a4,m4 observations2 and also of the #h4cj ,p4,m4 forecasts based on the observations received earlier in the day4 ,in summer and autumn harvest forecasts are issued by telegraph to individuals who will defray the cost4 ,the ,office also collects climatological data from a number of voluntary and some subsidised stations4 ,the first order stations include ,valentia1 ,falmouth1 ,kew1 and ,aberdeen4 ,these have self-recording instruments of high precision1 giving a continuous record of the meteorological elements4 ,a ,government ,commission which sat last year1 under the ,rt4 ,hon4 ,sir ,herbert ,maxwell1 ,bart41 have issued a ,report1 recommending a number of changes in the management and constitution of the ,meteorological ,office2 and considerable modifications are not unlikely to take place in the near future4 ,in his evidence before that ,commission1 the ,chairman of the ,council acknowledged that the great function of meteorologists is the collection of facts2 but the interpretation of those collected facts1 in a scientific manner1 is still in a very immature condition4 ,dr4 ,buchan1 in his evidence1 confessed that forecasting by the ,council is purely by rule of thumb4 ,it is not possible to lay down hard and fast rules for forecasting4 ,with regard to the storm-warning telegrams1 as a rule1 the earliest trustworthy indication of the approach of a dangerous storm to the coasts of the ,british ,isles precedes the storm by only a few hours4 ,delays are therefore very serious4 ,it is admitted by the best ,british meteorologists that the observations of the ,united ,states are better conducted1 although the best instruments in the world are set and registered at ,kew1 in ,england4 ,the work of weather forecasts and storm warnings is carried on with the highest degree of promptitude and efficiency at the ,washington ,central ,office4 ,this is because the work of predictions has been hitherto the chief work of the ,office3 the entire time of the observers1 on whose telegraphic reports the forecasts are based1 is controlled by the ,united ,states ,weather ,bureau2 and the right of precedence in the use of wires is maintained4 ,professor ,brueckner1 of ,berne1 has devoted a lifetime to the comparatively new treatment of climatic oscillations1 based upon observations made at #cba points on the earth's surface1 distributed as follows3 ,europe1 #aih2 ,asia1 #ci2 ,n4 ,america1 #ej2 ,cen4 and ,s4 ,america1 #af2 ,australia1 #ab2 ,africa1 #f4 ,one of his conclusions is that an average time of about thirty-five years is found to intervene between one period of excess or deficiency of warmth and the next1 accompanied by the opposite relative condition of moisture4 ,all are familiar with the hoisting of cone-warning as indication of a coming storm4 ,this work is exceedingly important1 especially for those connected with the sea by business or pleasure4 ,on the known approach of a cyclone of dangerous intensity1 special messages are sent from the ,london ,meteorological ,office1 warning the coasts likely to be affected4 ,when the cone is hoisted with its apex downwards1 it means that strong south or south-west winds are to be looked for4 ,when the cone is hoisted with its apex upwards1 it indicates that strong winds from the north or north-east are expected4 ,of course they are merely useful precautions2 but they are universally attended to by people on the sea-coast4 ,though one may have reasonable doubts about the use that can be made of weather forecasts for three days1 such as are now regularly issued1 on account of the finical1 coy1 spasmodic interludes on short notice1 yet there is a wonderful certainty in the daily prognostics of the direction and strength of the wind1 the temperature of the air1 and the likelihood of rainy or fair weather1 dependent on the broad uniformity of nature4 ,this is very serviceable for people who have now to live at high pressure in business1 in the enthralling days of keen competition4 ,and it is a great boon to those who are in search of health by travelling1 or who1 in innocent pleasure1 desire to live as much as possible in the open air4 ,very little credit is given to the gas of the isolated weather prophet2 but those who have confidence in the usual weather forecasts from the ,meteorological ,office are satisfied in their belief2 and those who1 in self-confidence1 ignore all weather prognostics1 are still weak enough to read them and act up to them4 99 99 99 99 99 ,in practical meteorology1 in the scientific explanation of popular weather-lore1 and in the study of atmospheric phenomena1 which so powerfully influence us1 for gladness or discomfort1 we may1 as with other branches of science1 even all our days1 cheerfully go on in the noiseless tenor of our way1 ,nourishing a youth sublime1 ,with the fairy tales of science and the long results of time4 ,,index ,abercromby1 spectre on ,adam's ,peak1 #hi ,adam's ,peak1 spectre1 #hi ,afterglow described1 #fb2 dust-particles to form1 #fd ,air1 change of1 #ee2 clearness and dryness1 #di2 devitalised1 #eb2 disease-germs in1 #ec2 thunder-clouds1 #di ,aitken1 ,dr41 afterglows1 #fg2 anti-cyclones1 #ig2 colour of water1 #ge2 condensing power of dust1 #b2 decay of clouds1 #ci2 dew-formation1 #ad2 dust and atmospheric phenomena1 #bi2 electrical deposition of smoke1 #hc2 false dew1 #ah2 fog-counter1 #hb2 foreglows1 #fg2 formation of clouds1 #ce2 haze1 #dd2 hazing effects of atmospheric dust1 #dg2 ,kingairloch experiments1 #cj2 one-coloured rainbow1 #gj2 radiation from snow1 #hf2 regenerators1 #he2 sanitary detective1 #gh ,ammonia and cloud formation1 #cf ,annie ,laurie1 #ag ,anti-cyclones1 forecasting by1 #ig2 formation1 #ig2 cause of influenza1 #aji ,aratus1 forecasting by moon1 #fa ,ariel's song1 #db ,aurora ,borealis1 #ga2 forebodings1 #ga-gc2 name by ,gassendi1 #gb2 other names1 #gb2 safety valve of electricity1 #gb2 sun's spots1 #gb2 sun control1 #gd2 symptoms1 #gb ,bagillt1 condensing lead fumes1 #hd ,ballachulish1 sunsets1 #fd ,ballantine's song1 #ag ,barometer1 indications1 #aj ,ben ,nevis1 dust-particles1 #cj2 instruments1 #ajd2 meteorology1 #ajb2 observations1 #aje2 rainfall1 #ajc2 regret at stoppage of ,observatory1 #ajc ,blairgowrie1 personal description of afterglow1 #fb ,blue sky1 #gd2 cause of1 #ge1 #gg ,borrowing days1 #aag ,brocken1 spectre1 #hi2 personal description1 #ij2 ,noah's ,ark1 #ij ,brueckner1 climatic oscillations1 #abb ,buchan1 ,dr41 ,aitken's radiation from snow1 #hf2 ,ben ,nevis1 papers on1 #ajc2 ,challenger ,reports1 #aad2 cold of #ahhf1 #hf2 east winds1 #id2 isobars1 #aae2 rainfall statistics1 #ajj2 on forecasting1 #aba ,buchanan1 ,ben ,nevis ,observatory1 #ajb2 great prevalence of fog1 #ajf ,buddha's ,lights1 of ,ceylon1 #gb ,burns1 allusions to aurora1 #ga1 #gc ,byron1 storm in ,alps1 #ej ,challenger ,expedition1 #aad2 temperature1 #aae2 thunder-storms1 #aaf2 winds1 #aaf ,chambers on sun-spots and grain prices1 #aac ,change of air1 #ee2 ,strathmore to ,glenisla1 #ef ,charles ,,ii41 fog and smoke1 #hj ,chlorine and cloud formation1 #cf ,christison and colour of water1 #ge ,chrystal on ,aitken's radiation from snow1 #hf ,cirro-stratus cloud1 mackerel-like1 #ci ,climate1 ,challenger notes1 #aae2 cone-warnings1 #abj2 ,gulf ,stream1 #aaa2 oscillations1 #abj2 rainfall1 #aaa2 sun-spots on1 #aab2 wooded country on1 #aaa ,clouds1 decay of1 #cg2 distances of1 #ce2 dry1 #db2 even without dust1 #cf2 formation of1 #cd2 height of1 #cd2 numbering of cloud-particles1 #cd2 sunshine on cloud formation1 #ce2 varieties of1 #ce ,cone-warnings1 #aba ,continental winds1 #ih ,cyclones1 #ie2 formation of1 #if1 #ih2 small natural1 #ih ,decay of clouds1 #cg2 in thin rain1 #da2 process1 #ch2 ripple markings1 #ci ,dew1 evidence of rising1 #bb2 experiments1 #ae1 #af2 false dew1 #ag2 formation of1 #ac ,disease-germs in air1 #ec2 causes1 #ec2 deposited by rain1 #ee ,diseases1 and east wind1 #id2 personal notes1 #ie ,dumfries1 dust in air at1 #df ,dust1 condensing power1 #dc2 from meteors1 #cg2 generally necessary for cloud formation1 #bf2 hazing effects1 #dg2 numbering1 #bf2 instruments for numbering1 #bg2 produces afterglows1 #fd2 produces foreglows1 #fg2 quantity in ,bunsen flame1 #bh2 at ,ben ,nevis1 #cj2 ,hyeres1 ,mentone1 ,rigi ,kulm1 #bi2 ,lucerne1 ,kingairloch1 #cj2 when not necessary1 #cf ,dust enumeration1 deductions on1 #ca ,earn1 ,loch1 splash of drop at1 #aja ,earthshine1 #ei ,ehrenberg1 on colour of water1 #ge ,evelyn1 fumifugium1 #hj2 remedy for smoke1 #hb ,falkirk1 ,dr4 ,aitken's experiments on haze1 #dg ,false dew1 #ai ,fitzroy on aurora as a foreboder1 #gc ,fog1 counter1 #ca2 dry1 #da2 formation1 #bd2 more in towns1 #be2 and smoke1 #hj ,folk-lore1 #ej ,foreglow1 described1 #ff2 how produced1 #fg ,fort ,william ,observatory1 #ajb ,frankland1 disease-germs1 #ec ,franklin1 lightning1 #ea ,gassendi1 named aurora1 #gb ,gillespie1 ,dr41 on weather and influenza1 #ajg ,glasgow1 fog1 #ha ,glass1 appearing damp1 #dd ,glenisla1 ozoned air1 #ef ,grain crops and sun-spots1 #aab2 ,chambers' tables1 #aac ,great amazing light in the north1 #gb ,gulf ,stream1 effects on climate1 #aaa ,gunpowder1 great condensing power1 #dd ,haze1 what is1 #dc2 how produced1 #dd2 in clearest air1 #de2 stages of condensation1 #df2 in sultry weather1 #df2 dryness of air and visibility1 #dh ,health improved by change of air1 #ef ,highland air1 few disease-germs1 #ee ,hoar-frost1 frozen dew1 #bj2 on under surfaces1 #ba ,humboldt1 isotherms1 #aad ,hydrogen peroxide and cloud formation1 #cf ,hyeres1 dust-particles1 #bi ,indian ,ocean1 colour1 #ge ,influenza1 weather and1 #ajg2 six distinct epidemics1 #ajh2 spread of anti-cyclonic conditions1 #aji ,isobars by ,buchan1 #aae ,isotherms by ,humboldt1 #aad ,italian lakes1 stages of condensation1 #de ,job1 on dew formation1 #ac ,kelvin recorder1 #hd2 ,aitken's radiation from snow1 #hf ,kew1 instruments set1 #aba ,kingairloch1 dust-particles1 #cj1 #df ,kirchhoff1 lower temperature of sun-spot1 #aab ,krakatoa1 eruption of1 dust-particles1 #fc ,le ,verrier and weathercharts1 #aai ,lockyer1 and sun-spots1 #aab ,lightning1 electricity1 #ea2 photographed1 #ea2 sheet and forked1 #ea2 ozone1 #eb ,lodge1 electrical deposition of smoke1 #hc ,london1 coals consumed1 #be2 sulphur and fog1 #be2 fog in reign of ,charles ,,ii41 #ha2 ,meteorological ,office1 #aa1 #abj ,lord ,derwentwater's ,lights1 #gb ,lower animals1 sensitiveness1 #aa ,lucerne1 dust-particles1 #cj ,mac,laren1 ,aitken's radiation from snow1 #hf ,magnesia1 small affinity for water-vapour1 #dd ,man in the street1 #aa ,mediterranean1 brilliant colour1 #gg ,mentone1 dust-particles1 #bi ,merry ,dancers of ,shetland1 #ga ,meteors1 producing dust1 #cg ,meteorological ,council1 ,london1 #ajc2 ,office1 #abj2 cone-warnings1 #aba2 regular forecasts1 #abc ,milne ,home on ,ben ,nevis1 #ajc ,milton1 dust numberless1 #bf ,moon1 old1 in new moon's arms1 #eh2 weather indications1 #ei1 #fa ,mountain giants1 #hh2 ,adam's ,peak1 #hi2 ,brocken1 #hi ,munich1 ,international ,meteorological ,conference1 #ce ,murray1 ,challenger ,expedition1 #aad ,nardius1 dew exhalation1 #ac ,newton1 colour of sky1 #gg ,nimbus1 cloud1 #ce ,oak and ash1 on climate1 #aah ,ochils1 one-coloured rainbow1 #gj ,pacific1 colour1 #ge ,paris1 aurora1 #ga2 disease-germs1 #ee ,paton1 ,waller1 bronze tints in sunsets1 #fd ,piazzi ,smith1 aurora1 #gb ,picket1 dew-formation1 #ad ,pilatus1 fine rain1 #db ,polar lightnings1 #gb ,radiant heat1 producing fine rain1 #da ,radiation from snow1 #hf ,rain1 #ih2 heavy rainfalls1 #ii ,rainbow1 #fh2 forecasts1 #fb1 #fi2 formation1 #fi2 one-coloured1 #gj ,rains1 it always1 #dj2 radiant heat in process1 #da2 ,ariel's song1 #dc ,rankin1 dust-particles1 ,ben ,nevis1 #cj ,richardson1 devitalised air1 #ea ,rigi ,kulm1 dust-particles1 #bi ,rolier1 aurora1 #gc ,st4 ,paul's1 ,london1 disease-germs in air1 #ed ,sanitary detective1 #gh ,shakespeare1 tempest1 #ie ,shelley1 old moon in new moon's arms1 #ei ,simoom and sirocco1 #id ,skye1 rainy1 #dj ,smoke1 electrical deposition of1 #hc2 regenerators1 #he ,smoking-room1 condensing power1 #dd ,snow1 bad conducting1 #hg2 radiation from1 #hf ,sodium dust1 condensing power1 #de ,spens1 forebodings of moon1 #fa ,splash of a drop1 experiments1 #aja ,stevenson1 ,r4 ,l41 splash of drop1 #aja ,stewart1 sun-spots1 #aab ,strachey on forecasts1 #aba ,strathmore1 observations on hoar-frost1 #bb2 on decay of clouds1 #ch2 to ,glenisla1 change of air1 #ef2 observations on old moon in new moon's arms1 #ei2 afterglow described1 #fb2 foreglow1 #ff2 cold of #ahhf1 #hf2 healthy by woods1 #aaa2 observations on barometer1 #aah ,strathpeffer1 #i ,sulphur as a fog-former1 #be ,sulphuretted hydrogen and cloud-formation1 #cf ,sunshine on cloud-formation1 #ce ,sun's spots1 and aurora1 #gb1 #aab2 and grain crops1 #aab ,symons1 rainfall1 #ajj ,synoptic charts1 #ih ,tait1 on ,aitken's radiation from snow1 #hf ,tay ,bridge1 fall of1 #ib ,tennyson1 aurora1 #ga2 dew1 #ai2 oak and ash1 #aai ,thermometer1 indications1 #aj ,thomson1 ,wyville1 ,challenger ,expedition1 #aad ,thunder-storm described1 #ej ,valkyries1 aurora1 #gc ,visibility1 limit of1 #dh ,washington1 ,meteorological ,office1 #aba ,water1 pressure to show plant exudation1 #ah2 colour of1 #ge2 experiments on distilled1 #gf2 dust-particles vary colour1 #gg ,weather and influenza1 #ajg ,weather-forecasting1 #aaf2 advantages1 #aag2 principle1 #aag2 examples1 #aah2 old moon in new moon's arms1 #ei2 by moon1 #fa2 oak and ash1 #aah2 cone-warnings1 #abb2 three days'1 #abc ,weather-lore1 #ej1 #aah ,weather talisman1 #i2 call on barometer and thermometer1 #aj2 exceptional years1 #aag ,wells1 ,dr41 on dew1 #ad ,wilson1 ,prof41 on hoar-frost1 #bj ,wind1 #ib2 rates1 #ib2 trade1 #ic2 land and sea1 #ic ,woeikof1 durability of cold1 #hh ,wordsworth1 rainbow1 #fh ,worthington1 splash of drop1 #ajj ,wragge1 observations at ,ben ,nevis1 #ajd ,printed by ,,ballantyne1 ,,hanson ,,co4 ,edinburgh ,london