172 SCOTT'S LAST EXPEDITION [April 



Simpson has been practising with balloons during our ab- 

 sence. This morning he sent one up for trial. The balloon is 

 of silk and has a capacity of i cubic metre. It is filled with 

 hydrogen gas, which is made in a special generator. The gen- 

 eration is a simple process. A vessel filled with water has an 

 inverted vessel within it; a pipe is led to the balloon from the 

 latter and 'a tube of india-rubber is attached which contains 

 calcium hydrate. By tipping the tube the amount of calcium 

 hydrate required can be poured into the generator. As the gas 

 is made it passes into the balloon or is collected in the inner 

 vessel, which acts as a bell jar if the stop cock to the balloon 

 is closed. 



The arrangements for utilising the balloon are very pretty. 



An instrument weighing only 2^4 oz - an d recording the tem- 

 perature and pressure is attached beneath a small flag and hung 

 10 to 15 ft. below the balloon with balloon silk thread; this 

 silk thread is of such fine quality that 5 miles of it only weighs 

 4 ozs., whilst its breaking strain is 1 y^ lbs. The lower part 

 of the instrument is again attached to the silk thread, which is 

 cunningly wound on coned bobbins from which the balloon un- 

 winds it without hitch or friction as it ascends. 



In order to spare the silk any jerk as the balloon is re- 

 leased two pieces of string united with a slow match carry the 

 strain between the instrument and the balloon until the slow 

 match is consumed. 



The balloon takes about a quarter of an hour to inflate; 

 the slow match is then lit, and the balloon released; with a weight 

 of 8 oz. and a lifting power of i]/ 2 lbs. it rises rapidly. After 

 it is lost to ordinary vision it can be followed with glasses as 

 mile after mile of thread runs out. Theoretically, if strain is 

 put on the silk thread it should break between the instrument 

 and the balloon, leaving the former free to drop, when the 

 thread can be followed up and the instrument with its record 

 recovered.. 



To-day this was tried with a dummy instrument, but the 

 thread broke close to the bobbins. In the afternoon a double 

 thread was tried, and this acted successfully. 



To-day I allotted the ponies for exercise. Bowers, Cherry- 

 Garrard, Hooper, Clissold, P.O. Evans, and Crean take ani- 

 mals, besides Anton and Oates. I have had to warn people 



