1869.] The President's Address. 585 



invention of separate condensation, wliicli is justly regarded as 

 forming the birth of the steam-engine. It needs no formal celebra- 

 tion to remind Britons of what they owe to Watt. Of him truly 

 it may be said "si monumentum requiras ci^'cumspice." 



No other physical science has been brought to such perfection 

 as mechanics ; and in mechanics we have long been familiar with 

 the idea of the perfect generahty of its laws, of their applicability 

 to bodies organic as well as inorganic, hving as well as dead. But 

 from mechanics let us pass on to chemistry, and the case will be 

 found by no means so clear. When chemists ceased to be content 

 with the mere ultimate analysis of organic substances, and set them- 

 selves to study their proximate constituents, a great number of 

 definite chemical compounds were obtained which could not be 

 formed artificially; but as the science progressed many of these 

 organic substances were formed artificially, in some cases from other 

 and perfectly distinct organic substances, in other cases actually 

 from their elements ; and we may say that at the present time a 

 considerable number of what used to be regarded as essentially 

 natural organic substances have been formed in the laboratory. 

 That being the case, it seems most reasonable to suppose that in the 

 jDlant or animal from which those organic substances were obtained, 

 they were formed by the play of ordinary chemical affinity ; and 

 since the boundary-line between the natural substances which have 

 and those which have not been formed artificially, is one which, so 

 far as we know, simply depends upon the amount of our knowledge, 

 and is continually changing as new processes are discovered, we 

 are led to extend the same reasoning to the various chemical sub- 

 stances of which organic structures are made up. 



Admitting this much, Professor Stokes proceeded to ask whether 

 the laws of chemical afiinity, together with those of capillary 

 attraction, of diffusion, and so forth, account for the formation of 

 an organic structure, as distinguished from the elaboration of the 

 chemical substances of which it is composed ? To this he replied 

 decidedly No ! No more than the laws of motion account for the 

 union of oxygen and hydrogen to form water, though the ponderable 

 matter so uniting is subject to the laws of motion during the act 

 of union just as well as before or after. In the various processes 

 of crystallization, of precipitation, and so forth, which we witness 

 in dead matter, there is not the faintest shadow of an approach to 

 the formation of an organic structure, still less to the wonderful 

 series of changes which are concerned in the growth and perpetu- 

 ation of even the lowliest plant. Admitting to the full, as highly 

 probable, though not completely demonstrated, the applicability to 

 living beings of the laws which have been ascertained with reference 

 to dead matter, the speaker proceeded to say that he felt constrained 

 at the same time to admit the existence of a mysterious sometldng 



