CONTINUITY. 205 



vegetable; for concentrated and sustained energy, however, 

 they do not equal the carnivora ; and with the domestic gra- 

 minivora 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 enquiries, as in other branches of science, we are gra- 

 dually 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, some- 

 times combined; sometimes passing through 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 inven- 

 tions of entities made to vary according to the requirements 

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

 will be dispensed with, and when the two fundamental con- 

 ceptions of matter and motion will be found sufficient to 

 explain physical phenomena. 



The facts made known to us by geological enquiries, while 

 on the one hand they afford striking evidence of continuity, 

 on the other, by the breaks in the record, may be used as 

 arguments against it. The great 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 submergence. 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 per- 

 manent varieties, or may be explained by gradual modifying 

 changes. 



Professor Ansted, summing up the evidence on this head 

 as applied to one division of stratified rocks, writes as follows : 



