16 The Hon. Sir Charles Parsons [Jan. 23, 



the end ] Lug and piston. The end plug, which had been hardened 

 and tempered to straw colour, showed signs of compression, and the 

 bore of the block for g inch from the plug was enlarged by 0*023 inch 

 in diameter, both indicating that a pressure above 100 tons per square 

 inch bad been reached. 



A little brown amorphous carbou was found in the chamber, 

 which was easily destroyed by boiling- sulphuric acid and nitre. 

 There was no diamond residue from this. Considering the light 

 lit of tli«' piston and the very short duration of the exposure to 

 heat, the effects would indicate that a very abnormal temperature had 

 been reached, many times greater than exists in the chambers of 

 large guns. A calculation made by Mr. Stanley Cook, based upon 

 tin- ratio of compression and a final pressure of 15,000 atmospheres, 

 indicates that a temperature of between 15,250° C. and 17,700° C. 

 was reached, the exact temperature depending upon the amount of 

 dissociation or combination existing between the elements at the time. 



Calculation of the Temperature Reached ox the Compres- 

 sion of Acetylene and Oxygen Experiment. 



By Stanley S. Cook. 



The temperature reached may be estimated from the final pres- 

 sure, which the observed deformation of the block and plug indicates 

 to have been in the neighbourhood of 100 tons per square inch. But 

 it must be remembered that there is a change of molecular volume 

 us a result of combustion. Thus the mixture, which as C 2 H 2 and 

 5 (O) has 3| molecular volume, would on combustion to 2 CO* and 

 1 1 < > have only 3 molecular volumes. The final temperature deduced 

 from the pressure will therefore depend upon the extent to which 

 chemical combination has taken place. 



The original mixture being at atmospheric pressure and a tem- 

 perature of 290 C. absolute, a pressure of 100 tons per square inch 

 after compression to ._. i s of its original volume would indicate a 

 temperature of L5,250° C. If, however, complete combustion has 

 taken place, this same pressure would correspond to a temperature 

 greater in ratio of U to 3, viz. to 17,700 Q C. The actual tempera- 

 tun- must therefore have been something between these two values. 



Let us for a moment consider the pressures and temperatures 

 possible in nature (in this I am indebted to kind assistance from 

 Professor Jeans >. The pressure at the centre of the earth is between 

 looo and 10,000 tons per square inch, according to the variation in 

 density of the concentric layers. 



Emden has estimated the probable pressure at the centre of the 



