CHAPTER VIII. 



UPPER AIR OBSERVATIONS MADE BY MEANS OF B.\LLOONS. 



{Metric units and cenligntde temperatures used in this chapter.) 



The balloons used were made of thin gutta-percha tissue. They had a cubical contents 

 of one cubic metre so that their diameters were approximately 126 cm. The weight of each 



balloon was 227 grams, and the average rate 

 of ascent of a free balloon was about 3' 8 metres 

 a second. 



The hydi'ogen used was obtained from calcium 

 hydride. A very simple form of generator was 

 devised by Mr. Dines and proved entirely satis- 

 factory in use. 



A vertical cylinder A, figure 84, 75 cm. 

 high and 20 cm. in diameter was filled with 

 water. Inside this a similar but somewhat smaller 

 cylinder, open at the bottom and closed at 

 the top B, acted as a gasometer. The latter 

 had a tube C fastened to the top through which 

 the gas passed by way of the tube T to the 

 balloon. A side tube D was attached to C and 

 the inner tube of a motor-cycle tyre was 

 fitted to it. The rubber motor tyre had been 

 filled with small pieces of calcium hydride and it 

 was a simple matter to feed these by hand into 

 the water to provide the gas. The large excess 

 of water allowed of complete disassociation of the 

 hydride, and also the temperature did not rise 

 to too high a value, especially if tlie cylinder bad 

 been filled with a mixture of snow and water as 

 was usually the case. 



The instruments used were made by Mr. 

 Dines and have been described by him in 



h- zoc-i— — H tlie publications of the London Meteorological 



Fig. 84. Hydrogen generator. Ollice. 



