ADDRESS. 



Ixvii 



increase in the oxidation of the nitrogenized constituents of the bodj-. After 

 calculating the mechanical equivalents of the combustion effected, they then 

 state, as their first conclusion, that " The burning of protein substances cannot 

 be the only source of muscular power, for we have here two cases in which 

 men performed more measurable work than the equivalent of the amount of 

 heat, which, taken at a most absurdly high figure, could be calculated to 

 result from the burning of the albumen." 



They fiu'ther go on to state that, so far from the oxidation of albuminous 

 substances being the only source of muscular power, " the substances by the 

 biirning of which force is generated in the muscles, are not the albuminous 

 constituents of those tissues, but non-nitrogenous substances, either fats or 

 hydrates of carbon," and that the burning of albumen is not in any way 

 concerned in the production of muscular power. 



We must not confuse the question of the food which forms and repairs 

 muscle and gives permanent capability of muscular force with that which sup- 

 plies the requisites for temporary activity ; no doubt the carnivora are the 

 most powerfully constituted animals, but the Chamois, Gazelle, &c., have great 

 temporary capacity for muscular exertion, though their food is vegetable ; for 

 concentrated and sustained energy, however, they do not equal the carnivora ; 

 and with the domestic graminivora we certainly find that they are capable of 

 performing more continuous work when supplied with those vegetables which 

 contain the greatest quantity of nitrogen. 



These and many similar classes of research show that in chemical in- 

 quiries, as in other branches of science, we are gradually relieving ourselves 

 of hypothetical existences, which certainly had the advantage that they might 

 be varied to suit the requirements of the theorist. 



Phlogiston, as Lavoisier said with a sneer, was sometimes heavy, sometimes 

 light ; sometimes fire in a free state, sometimes combined ; sometimes passing 

 throiigh glass vessels, sometimes retained by them ; which by its protean 

 changes explained causticity and non-causticity, transparency and opacity, 

 colours and their absence. As phlogiston and similar creations of the mind 

 have passed away, so with hypothetic fluids, imponderable matters, specific 

 ethers, and other inventions of entities made to vary according to the re- 

 quirements of the theorist, I believe the day is approaching when these will 

 be dispensed with, and when the two fundamental conceptions of matter and 

 motion will be found sufficient to explain physical phenomena. 



The facts made knowni to us by geological inquiries, while on the one 

 hand they aff'ord striking evidence of continuity, on the other, by the breaks 

 in the record, may be used as arguments against it. The gi'eat question 

 once was, whether these chasms represent sudden changes in the formation 

 of the earth's crust, or whether they arise from dislocations occasioned since 

 the original deposition of strata or from gradual shifting of the areas of sub- 

 mergence. Few geologists of the present day would, I imagine, not adopt 

 the latter alternatives. Then comes a second question, whether, when the 

 geological formation is of a continuous character, the different characters of 

 the fossils represent absolutely permanent varieties, or may be explained by 

 gradual modifying changes. 



Prof. Ansted, summing up the evidence on this head as applied to one 

 division of stratified rocks, writes as follows : — " Pateontologists have endea- 

 voured to separate the Lias into a number of subdivisions, by the Ammonites, 

 roups of species of those shells being characteristic of different zones. The 

 evidence on this point rests on the assumption of specific differences 

 being indicated by permanent modifications of the structure of the shell. 



e2 



a 



