KITE-FLYING IN 1891. 



59 



kites ascend they find, as usual, a decreasing temperature for a 

 while, but it suddenly rises as the instruments enter the radiating 

 waves of caloric — sometimes as many as seventeen degrees. In 

 advance of and during cold waves the temperature falls uniformly 

 and rapidly in the ascent. Observations at Washington, jSTew York, 

 and Blue Hill coincide in showing that approaching warm and cold 

 waves are perceived, at a height of a thousand feet or more, from 

 six to twelve hours earlier than their prevalence at the surface of 

 the earth. One reason for this is that the air moves freely and rap- 

 idly at the height of a few thousand feet, while it meets with many 

 obstacles below. 



There is an interesting bit of information from the kites for us 

 in regard to Boston's much-denounced east wind — though in the 

 heated term it is generally quite a relief. It has been ascertained 

 at Blue Hill that these chilling inflows begin at the surface and 

 thrust themselves wedgewise under the local stratum, working up- 

 ward. At their greatest expansion, however, these eastern winds 

 rarely have a depth of more than twelve hundred feet. 



At the surface of the earth, as every one knows, there is usually a 

 marked increase of the temperature during the day, and a decrease 

 at night; but at an elevation of three thousand feet this variation 

 disappears entirely, the days being there as cold as the nights. The 

 changes of temperature aloft are very large, but they are not diurnal. 

 At this height, also, the days are marked by a damp atmosphere, 

 while the nights are dry. This is simply a phase of the dewfall, 

 and to a degree also of the clouds and the rainfall. 



The behavior of kites in the vicinity of cumulus clouds is pe- 

 culiar. When one of these tracts of snowlike baseless hills sails 

 calmly over, the kites ascend more or less rapidly toward it, often 

 following as far as the line will permit. Every observer has re- 

 marked the rounded shapes of these fair-weather clouds, like high 

 upheavals of condensed steam; and it has long been held that they 

 were the result of — or, at least, attended by — upward eruptions of 

 air, perhaps from heat expansion. 



The nimbus cloud, from which most of our rainfall conies, has 

 little effect on the kites other than disqualifying them for flying 

 because of wet. Kites usually find little or no obstacle in the stra- 

 tus. Among the memoranda of flights is noted, of one such passage 

 in summer, the emergence of the kite above a cloud of this kind of 

 a computed depth of five hundred feet. The hygrometer showed 

 that in the midst of the cloud the humidity was one hundred per 

 cent — full saturation; so that a slightly cooler wave of atmosphere 

 would have caused precipitation; yet above the cloud the atmos- 

 phere was quite dry. 



