TEANSACTIONS OF SECTION B. 667 



attention is that of thermo-chenristry, a subject upon wbich in the future the, 

 foundation of dynamical chemistry must rest, and one which already proclaims 

 the truth of the great principle of the conservation of energy in all cases of 

 chemical as -well as of physical change. But here, although the materials hitherto 

 collected are of very considerable amount and value, the time has not yet arrived 

 for expressing these results in general terms, and we must, therefore, be con- 

 tent to note progress in special lines and wait for the expansion into wider areas. 

 Reference may, however, be properly made to one interesting observation of 

 general significance. It is well known that, while, in most instances, the act 

 of combination is accompanied by evolution of heat— that is, whilst the potential 

 energy of most combining bodies is greater than that of most compounds — cases 

 occur in which the reverse of this is true, and heat is absorbed in combination. 

 In such cases the compound readily undergoes decomposition, frequently suddenly 

 and with explosion. Acetylene and cyanogen seem to be exceptions to this 

 rule, inasmuch as, whilst their component elements require to have energy added 

 to them in order to enable them to combine, the compounds appear to be very 

 stable bodies. Berthelot has explained this enigma by showing that, just as we 

 may ignite a mass of dynamite without danger, whilst explosion takes place if we 

 agitate the molecules by a detonator, so acetylene and cyanogen burn, as we 

 know, quietly when ignited, but when their molecules are shaken by the detonation 

 of even a minute quantity of fulminate, the constituents fly apart* with explosive 

 violence, carbon and hydrogen, or carbon and nitrogen being set free, and the 

 quantity of heat absorbed in the act of combination being suddenly liberated. 



In conclusion, whilst far from proposing even to mention all the important 

 steps by which our science has advanced since the year 1848, 1 cannot refrain 

 from referring to two more. In the first place, to that discovery, more than fore- 

 shadowed by Faraday, of the liquefaction of the so-called permanent gases by 

 Pictet and Cailletet ; and secondly to that of the laws of dissociation as investi- 

 gated by Deville. The former, including Andrews's discovery of the critical point, 

 indicates a connection, long unseen, between the liquid and the gaseous states of 

 matter; the latter has opened out entirely fresh fields for research, and has given us 

 new views concerning the stability of chemical compounds of great importance 

 and interest. 



Turning for a moment to another topic, we feel that, although science knows 

 no nationalities, it is impossible for those who, like ourselves, exhibit strong* 

 national traits to avoid asking whether we Anglo-Saxons hold our own, as 

 compared with other nations, in the part we have played and are playing in 

 the development of our science. With regard to the past, the names of Boyle^ 

 Cavendish, Priestley, Dalton, Black, Davy, are sufficient guarantees that the 

 English have, to say the least, occupied a position second to none in the early 

 annals of chemistry. How has it been in the era which I have attempted to 

 describe ? What is the present position of English chemistry, and what its look- 

 out for the future ? In endeavouring to make this estimate I would take the 

 widest ground, including not only the efforts made to extend the boundaries of our 

 science by new discovery, both in the theoretical ■ and applied branches, but 

 also those which have the no less important aims of spreading the knowledge of 

 the subject amongst the people, and of establishing industries dependent on chemi- 

 cal principles by which the human race is benefited. Taking this wide view, I 

 think we may, without hesitation, affirm that the progress which chemistry has 

 made through the energies of the Anglo-Saxon race is not less than that made by 

 any other nation. 



In so far as pure science is concerned I have already given evidence of the not 

 inconsiderable part which English chemists have played in the progress since 1848. 

 We must, however, acknowledge that the number of original chemical papers now 

 published in our language is much smaller than that appearing in the German 

 tongue, and that the activity and devotion displayed in this direction by the heads 

 of German laboratories may well be laid to heart by some of us in England ; yet,, 

 on the other hand, it must be remembered that the circumstances of different coun- 



