I lO 



NATURE 



[November 29, 1900 



the year 1898, mostly in the great river valleys and the 

 upper portion of the region of the Great Lakes. The 

 form of kite used was the Hargrave cellular (Fig. i), 

 with such modifications and improvements as trial and 

 experiment dictated. The surface dimensions of the 



FiG. 



-Kite mtteoio^iaph. 



kites varied from 45 to 72 square feet. The kite line was 

 carried on a large iron drum or reel, capable of resisting 

 a crushing pressure of at least 1000 tons, and consisted 

 of steel piano-wire '028 inch in diameter, and weighing 

 2' 15 pounds to the thousand feet, or 

 1 1 '35 pounds to the mile. The tensile 

 strength of this wire at the breaking- 

 point was about 200 pounds. 



With a kite flying at an elevation 

 of from 5000 to. 7000 feet, from 8000 

 to 10,000 feet of wire would be out, 

 making a weight of from 90 to 115 

 pounds which must be sustained by 

 the kite. 



The meteorograph (Fig. 2), or auto- 

 matic recording apparatus, was de- 

 vised by Prof. C. F. Marvin, of the 

 Weather Bureau. It weighs but a 

 fraction over two pounds, is inclosed 

 in an aluminium case, and, while quite 

 complicated in construction, is re- 

 markable for its compactness and 

 lightness. The cylinders carrying the 

 record sheets are actuated by clock- 

 work, and four different meteorological 

 conditions are recorded, viz., pressure, 

 temperature, relative humidity and 

 wind velocity (Fig. 3). The wind 

 direction, of course, becomes apparent 

 by observing the azimuth of the kite. 



It soon became evident that there 

 was no possibility of obtaining a daily 

 synchronous chart. The principal 

 difficulties were the very frequent 

 absence of suflficient wind to sustam 

 the kites, and inability to obtain ascen- 

 sions in stormy weather. Taken as a whole, ascensions 

 were possible during only 46 per cent, of the time from 

 May to October, inclusive, the percentage varying from 

 75 at Dodge, Kansas, to 12 at Knoxville, Tennessee. 



NO. 1622, VOL. 63] 



The hours of the day at which ascensions could be made 

 also varied greatly. 



But however disappointing the results obtained may 

 have been from the viewpoint of the weather forecaster, 

 they were not so when considered from another. Much 

 valuable data was obtained from the 12 17 ascensions and 

 3835 observations, particularly regarding vertical tem- 

 perature gradients, and it is believed that there has been 

 a very material contribution made to our previous know- 

 ledge of this subject. Briefly summarised, the results of 

 the observations were as follows : — 



The mean rate of diminution of temperature with in- 

 crease of altitude was found to be 5° F. for each 1000 

 feet, or only 0-4^ less than the true adiabatic rate. The 

 gradient was greatest up to 1000 feet, where it was 7*4° F. ; 

 from thence up to 5000 feet there was a steady decrease 

 to 3"8' a thousand feet, the rate of decrease varying in- 

 versely with the altitude. Above 5000 feet there was a 

 tendency toward a slight increase. 



The mean gradients on the Atlantic coast were much 

 smaller than those in the interior, the difference being 

 mainly due to the lower morning values of the former, 

 those of the afternoon differing but slightly. Inversions 

 of temperature were quite frequent, and were most pro- 

 nounced when the upper air currents were from south- 

 east to south-west. Clouds, as a rule, caused a decrease 

 in the rate of temperature fall, sometimes so decided as 

 to result in an actual temperature inversion. A series 

 of observations was made at Pierre, South Dakota, 

 during the winter of 1898-99, and a cursory examination 

 of the records there made showed such persistent tem- 

 perature inversions during periods of cold weather as to 

 furnish convincing evidence that during a cold wave the 

 stratum of cold air is not much over one mile in height, 

 and frequently but little over half a mile. 



The relative humidity at and above the earth's surface 

 differed but little, and, generally speaking, the upper air 

 percentages were the lower. The mean results were 60 



Fi«;. 3.— Record obtained at Arlington, Virgin! i, on June 14, 18 



and 58 per cent, respectively, a difference of 2 per cent. 

 There were, however, some marked differences at indi- 

 vidual stations. At Washington, D.C., it was 14 per 

 cent. ; at Omaha, Nebraska, 29 per cent. ; and at Spring- 



