February 26, 1920] 



NATURE 



711 



of 288 to I. As a result, it was found that the sur- 

 fr.f-es of the end plug, the fore end of the piston, and 

 the circumference of the bore up to J in. from the 

 end of the plug had been fused to a depth of about 

 001 in., and were glass-hard; the surface of the 

 copper pin had been vaporised, and the copper sprayed 

 over the face of the end plug and piston. The end plug, 

 which had been hardened and tempered to a straw- 

 colour, showed signs of compression, and the bore of 

 the block for f in. from the plug was enlarged by 

 0023 in. in diameter, both indicating that a pressure 

 above loo tons per square inch had been reached. A 

 little brown amorphous carbon was found in the 

 chamber, which was easily destroyed by boiling sul- 

 phuric acid and nitre. There was no diamond residue 

 from this. Considering the light weight of the piston 

 and the verv short duration of the exposure to heat, 

 the effects would indicate that a very abnormal tem- 

 perature had been reached, many times greater than 

 exists in the chambers of large guns. .A calculation 

 made by Mr. Stanlev Cook, based upon the ratio of 

 compression and a final pressure of 15,000 atmo- 

 spheres, indicates that a temperature of between 

 15,250° and 17,700° C. was reached, the exact 

 temperature depending upon the amount of dissocia- 



Fiu. 8. 



tion or combination existing between the elements at 

 the time. 



Calculation of the Temperature Reached on the 

 Compression of Acetylene and Oxygen Experiment. 

 By Stanley S. Cook. 



The temperature reached may be estimated from 

 the final pressure, which the observed deformation of 

 the block and plug indicates to have been in the neigh- 

 bourhood of 100 tons per square inch. But it must be 

 remembered that there is a change of molecular 

 volume as a result of combustion. Thus the mixture, 

 which as C.Hj and 5(0) has 3^ molecular volumes, 

 would on combustion to 2CO2 and H,0 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 at a temperature of 290° C. absolute, a pressure of 

 too tons per square inch, after compression to i /288th 

 of its original volume, would indicate a temperature 

 of 15,250° C. If, however, complete combustion has 

 taken place, this pressure would correspond to a 

 temperature greater in ratio of 3^ to 3, viz. to 

 17,700° C. The actual temperature must therefore 

 have been something between these two values. 



Let us for a moment consider the pressures and ' 



NO. 2626, VOL. 104] 



temperatures possible' in Nature (in this I am in- 

 debted to kind assistance from Prof. Jeans). The 

 pressure at the centre of the earth is between 4000 and 

 10,000 tons per square inch, according to the varia- 

 tion in density of the concentric layers. 



Emden has estimated the probable pressure at the 

 centre of the more massive component of the binary 

 star S Hercules to be 360,000,000 tons per square inch. 



.Again, the densities of the brighter components 

 of certain binary stars are estimated by Opik 

 to be about that of iron, and if we assume that 

 their diameter is the same as that of the sun, that 

 each has an initial velocity in space not greater than 

 30 miles per second, and that they directly collide, 

 then, owing to their mutual attraction, Jeans cal- 

 culates that their velocity will have increased to 

 450 miles per second, and that the pressures in the 

 centre as they strike and flatten would be of the order 

 of 1,000,000,000 tons per square inch. He also esti- 

 mates that the heat equivalent of the energy would 

 be sufficient to vaporise the whole mass 100,000 times 

 over. This immense pressure would be maintained 

 for many minutes, perhaps for half an hour. 



Let us consider what is the greatest pressure that 

 can be produced artificially. If the German gun 

 which bombarded Paris were loaded with a solid steel 

 projectile somewhat shorter and lighter than the one 

 actually used, a muzzle velocity of about 6000 foot- 

 seconds might be ' reached (many years ago Sir 

 .Andrew Noble had reached 5000 foot-seconds) ; and 

 if it was fired into a tapered hole, as I have described, 

 in a large block of steel, this would give the greatest 

 instantaneous pressure that can be produced artificially 

 so far as we at present know, viz. about 7000 tons 

 per square inch: it is only about i/i5o,o(X)th part 

 of that possible by the collision of the largest stars. 



As to the temperature and conditions of matter 

 under these intense pressures, extrapolation from 

 known data is valueless. We have no knowledge of 

 the coefficients of compressibility of matter under 

 these conditions or of its specific heat. What may be 

 the effect on the atom? .And will elements under 

 such conditions be transformed into others of higher 

 atomic weight? 



.Some of us may recall that in 1888 a lecturer, 

 after describing in this room the experiment in which 

 oxygen at atmospheric pressure was passed in close 

 contact with a platinum surface heated by the oxy- 

 hydrogen burner to nearly its melting point, and then 

 immediately cooled by contact in water, said : 



"In this experiment ozone is formed by the action 

 of a high temperature, owing to the dissociation of 

 the oxvgen molecules and their partial recombination 

 into the more complex molecules of ozone. We may 

 conceive it not improbable that some of the elementary 

 bodies might be formed somewhat like the ozone in 

 the above experiment, but at very high temperatures, 

 bv the collocation of certain dissociated constituents 

 and with the simultaneous absorption of heat." 



It seems indeed probable that the centres of the 

 great stars and stars in collision mav be the labora- 

 tories where the elements as they gradually degenerate 

 are being continually regenerated into others of higher 

 intrinsic energv, and where endothermic processes, such 

 as the recombination of lead and helium into radium, 

 mav be taking place, absorbing in this process an 

 energy 2,500,000 times that develojjed by the explosion 

 of an equal weight of T.N.T. 



The transformation of only a minute fraction of 

 the mass of two colliding stars would therefore be 

 amply sufficient to absorb the whole energy of their 

 collision. 



Emerson said many years ago, " None but the 

 elements can themselves destrov." 



