

DISTRIBUTION IN THE ATMOSPHERE OVER ENGLAND. 259 



a mean accurate to 0'l C., and I do not care by giving decimals to pretend to a 

 degree of accuracy that does not exist. The temperatures are given in aljsolute 

 measure, MI id the first 2 is omitted to save space. 



Table V. shows the temperature gradient. The values might probably be smoothed 

 with MdvMiitii^v. hut they have been taken from Table III. The uniformity through- 

 out the year between 3 and 8 km. is very striking. 



The Daily Temperature Variation and the Effect of the Time of Observation on the 



Mean Values. 



The information available about the daily temperature variation is at present of a 

 somewhat meagre character when we pass the height that can easily be reached 

 by kites. 



On June 2nd and 3rd, 1909, starting at 7 p.m. on the 2nd, 25 balloons were sent 

 up at Manchester at hourly intervals, and 21 were recovered. The experiment was 

 vt-ry successful, for all but two reached 16 km. and eight reached 21 km. A similar 

 series of ascents was made on March 18th and 19th, 1910, when 28 were sent up and 

 18 recovered. 



The results are discussed in the ' Journal of the Royal Meteorological Society ' 

 (April, 1910, vol. xxxvi., No. 154; and January, 1911, vol. xxxvii., No. 157). 



Neither series shows anything in the higher strata resembling the ordinary daily 

 change of temperature at the surface, neither is a sudden change at sunrise shown, 

 such as would occur if the solar radiation had any serious effect on the instruments. 

 On June 3rd the temperature began to rise three hours before sunrise, and a minimum 

 occurred at noon. 



At a meeting of the International Aeronautical Commission, held at Monaco in 

 April, 1909, it was decided that 7 a.m. Greenwich time should be the time for sending 

 up balloons on the appointed days. Previously, nearly all the ascents made in 

 England had been made at or after sunset. The instruments used on the Continent 

 carry a clock, and thus the rate at which they are ascending or descending is known. 

 It is also known that for correct registration the velocity of the air current past the 

 thermograph must reach a certain value, and when the rate of ascent is shown by the 

 trace not to have reached this value the record is rejected. But in England we use 

 no clock, our instruments weigh alxnit one-tenth of those used on the Continent, and 

 hence the rate of ascent is unknown, and we cannot say if the thermograph was 

 sufficiently ventilated, and are thus compelled to depend on our unaided judgment as 

 to whether a doubtful trace should be accepted or rejected. 



Since the meeting at Monaco, balloons have been sent up at Pyrton Hill on most of 

 the appointed days at 7 a.m., but a fair number of additional balloons have also been 

 sent up at sunset, either the same evening or the evening before. This renders a 

 comparison possible in ten cases of the temperature at sunset and at 8 a.m., 8 a.m. 

 Mud not 7 a. m., because the ascent takes two hours. The values are given in detail 



2 L 2 



