May, 1903.] 



KNOWLEDGE 



115 



was takeu practically at the cloud level, the second at 



about a thousand 

 feel above, and the 

 third at fully a mile 

 above the limit of 

 1 he cloud. Tet even 

 in this last ease the 

 cloud appeared but 

 as an extended iloor 

 lying only a few feet 

 below the car; and 

 .^^ «^^l_^^^^ i^i» judged by the 



^|g|hi''^>li|||fe|g|M|wiPI^^M^^V eye it seemed iu- 

 ""^ ~ explicable how the 



trail rope, a hundred 

 yards long, was not 

 immersed in it. 

 Thus anyone who 

 had not tested the 

 depth of the intervening distance and describing simply 

 what he appeared to see, would record that the upper 

 surface of the cloud in question closely resembled a 

 snow field whose surface had been slightly ruffled into 

 shallow parallel ridges. If the same impei'feetly informed 



individual were 

 judging simply from 

 such appearances as 

 are presented by the 

 second photograjjh 

 he would give a 

 modified but scarcely 

 more accurate 

 ilescriptiou. 



The true nature of 

 the cloud limit as 

 investigated from its 

 own level wdl be 

 discussed directly. 

 Meanwhile it will 

 scarcely need poiut- 

 Pjq 2 ing out that what a 



balloonist commonly 

 sees on a cloudy dux at cloud level is simply a dense 

 stratum of mist, such as constantly rests on the surface 

 of the earth, often upwards of a thousand feet in depth, 

 dark in its lower regions, but growing lighter as you 

 ascend until, if the sun be brightly shining above, you 



are on reaching the 

 fringe bathed in an 

 atmosphere of the 

 most dazzling lumi- 

 nosity. Then in a 

 general way as you 

 '■merge you find 

 Niiurself surrounded 

 I'V huge Hcecy 

 I'lllows tossed mo>in- 

 lains high, the true 

 regularity of which 

 only becomes appa- 

 rent when you have 

 climbed high enough 

 to look down on 

 the billow crests and 

 find them in arrange- 

 ment (as shown in Fig. 1), somewhat resembling the 

 surface of a storm-tossed sea, though they have always 

 appeared to me to resemble more closely the arrangement 

 of wreaths of smoke trailing behind a passing train, or 

 streaming from an ill-stoked factory chimney, and due to 



\ 



iUG i. 



the rhythmic " cling and release " of the gaseous cloud ere 

 it issues from the aperture 



A closely analogous appearance may often be noticed 

 when a thui layer of snow on a level close-cut lawn has 

 been thawing vmder the action of a breeze of some little 

 strength. The snow may be seen to thin away, not so 

 much in patches as in furrows, leaving broken but regular 

 ridges lying athwart the direction in which the wind is 

 blowng. 



When cloudlets wander by at nearly the level of the 

 observer — and it is astonishing how often such cloudlets 

 though at close range will be found drifting at a different 

 speed from that of the balloon — they are seldom of the 

 roughly globular masses which, through foreshortening, 

 they appear from below. They are generally rather 

 elongated columns leaning forward with the wind. Larger 

 detached cloud-masses may retain their heaped appear- 

 ance, but as they are in a condition of wasting away their 

 entire surface at a close view is frayed and withered. 



Such a cloud is shown in the accomj)anying photograph, 

 and bears the shadow of the balloon somewhat strikingly 

 displayed upon it. Indeed this shadow, projected with 



TbrSb:irlow ..r til,' Ball.) 



iip^u til.' rk.iui. 



clearly-defined outlines ujKin so filmy a background, and 

 suiTouuded, as it generally is, with iridescent rings, invi- 

 sible in a photograph, but of great, beauty, never fails to 

 elicit expressions of delight and astonishment from those 

 who behold it for the first time. The clouds I am here 

 describing are in their nature and composition very 

 different from the comjiact and newly-created cumulus 

 cloud, whose surface is of closer texture, and whose level 

 underside betrays so clearly the j^lane of demarcation of 

 the air stratum above which it has been formed, and on 

 the surface of which it, so to speak, floats. The most 

 remai-liable levelling of the under-surface of a cloud 

 occurs perhaps when the doud-uiasses are drifting up from 

 a moist quarter, while below them is flowing a dry air 

 stream, most often from the east. Under these circum- 

 stances the base of the cloud is, as it were, mown perfectlv 

 flat. 



Another remarkable feature, to be noticed on the upper 

 surface of clouds, and which has K'cn revealed probably 



