260 MR. W. H. DINES ON THE VERTICAL TEMPERATURE 



in Table VI., the ascent at sunset is taken as the standard and the temperature of 

 the other expressed relatively to it. 



In winter at 8 a.n, the sun has hardly risen, and m any case ito rays have passed 

 through so large a mass of air that little heating power can remain. In summer t 

 hat L the balloon and meteorograph are exposed to full radiate, The balloon at 

 sunset is timed so that it may reach its maximum height when the sun is 



TABLE VI Difference of Temperature at Sunset and 8 v a.m. 



The ten pairs of observations available have been divided into two groups, one for 

 the summer half-year and one for the winter half-year. The preponderance of 

 negative signs in the winter half and of positive in the summer can hardly be 

 accidental, but I hardly know whether to ascribe it chiefly to solar radiation or to a 

 real change in the air. 



At Manchester two balloons have been sent up, one at night and one in the day, 

 each with a pair of instruments, one fixed inside the balloon and one hanging from it 

 in the usual position. As might have been expected, the temperature of the inside 

 of the balloon at night did not appreciably differ from tKat outside, but the inside 

 by day, i.e., 7 a.m. on July 2nd, was much hotter than the outside, 12 C. at 2'5 km., 

 17 C. at 5 km., 22 C. at 7'5 km., 30 C. at 10 km., and 35 C. at 12 km. The 

 balloon reached 20 km., and the air inside was close to the freezing-point at 16 km. 

 and above. Now the instruments are well protected from solar radiation by bright 

 metal, except when the sun is near the zenith, but the balloon of course shares the 

 horizontal motion of the air, and therefore ascends in what may be described as a 

 dead calm. The instrument follows and is in the wake of dead air which has 

 inevitably l>een in contact with the heated balloon. A balloon ascent in the daytime 

 is as though a globe of some 6 ft. in diameter and filled with warm water were kept 

 to windward of the thermometer screen. 



