136 EXPLORATION OF THE UPPER ATMOSPHERE 



was to be detected only after the most careful observations by means of the 

 nephoscope. 



The lowest temperature recorded during the ascent of the 6th was 63°, 

 with a surface temperature of 83°; the lowest barometric pressure was 26.40 

 inches, with a surface reading of 30.05 inches. The humidity ranged from 

 73 per cent at the surface to 98 per cent. A portion of the record was lost 

 owing to the stopping of the clock a few minutes before the highest elevation 

 was reached, but practically all the record during the ascending branch of the 

 curve was intact. The kite left the boat at 11.10 a. m., reached its greatest 

 elevation at 12.20 p. m., and was lowered at 1.12 p. m. The surface wind 

 was east-southeast throughout, as during all preceding flights. The kite 

 varied but little in azimuth from that of the surface wind; however, there was 

 always a slight change to a more southerly direction of the wind in the region 

 of the kite. 



The east-southeast wind carried the kite beyond the limits of the Island 

 in all but the firsf ascent. In the subsequent and higher elevations the kite 

 was always a considerable distance beyond the coast line over the sea. In 

 view of this fact and the small size of the Island, all of the observations may 

 be regarded practically as ocean conditions, excepting those recorded within 

 the first two or three hundred feet from the surface. 



TEMPERATURE RESULTS. 

 The rates of decrease in temperature from the surface to an elevation of 

 approximately 4000 feet are presented in tabular form, and charted in Figs. 

 5 and 6. Observations on the nephoscope for angular elevation of the kite, 

 and readings of the dial on the reel for length of wire out, were made by 

 Mr. Eouth every five to ten minutes and sometimes more frequently. From 

 these records and from the tracings of the kite meteorograph, averages were 

 computed and plotted for each 100 feet and each 500 feet of elevation. The 

 actual decrease in each 500 feet, the rate of decrease per 1000 feet, and the 

 number of feet of elevation causing a decrease of 1° F. are shown in the 

 following table: 



TEMPERATURE DECREASE. AVERAGE OF FOUR ASCENTS AND SEVENTY 



OBSERVATIONS. 



Elevation in feet 500 1000 1600 2000 2500 3000 3500 4000 Mean. 



Departure from surface tem- 

 perature, degrees 5 7 9 11 13 16 IS 20 



Rate of decrease per 1000 feet, 



degrees 10.0 7.0 6.0 5.5 5.2 5.2 3.1 5.1 6.1 



Number of feet per 1° decrease 



in temperature 100 143 167 182 192 192 196 196 164 



