426 



THE GEOLOGIST. 



of the manner in -^-liicli Q-ocl has chosen, to deal with Hig material 

 universe." 



The author then adopts, as the fundamental principle of geological 

 Reasoning, that — Tlie phenomtna icTdrh (jeology X->'^'Cscnts tons dJ 

 bhjecis 'of jphysical investigation are to he referred to natural causes, so 

 .far as it can he shown that they would he the necessary consequences of 

 ^uch causes acting under conditiom, the former existence of which may 

 he deemed adrnissihle. 



"The limitation expressed in the preceding enunciation is obviously 

 necessary, in drawing the line of demarcation between those conclusions 

 of the science which rest on certain, and those which rest on contro- 

 Tertible principles. Some assumption must also be made as to the nature 

 and action of the natural causes of which we recognize the agency in 

 those remote ages to which geologj^ refers." If researches analogous to 

 those which have been crowned with such complete success in reference 

 to the solar system should hereafter be made with respect to those 

 nebulce or clusters of stars which lie in the remoter regions of space, 

 they will doubtless be founded on the hypothesis of the universality of 

 gravitation, and of the laws which regulate the production and propa- 

 gation of light, heat, and electricity, or of any other physical law which 

 may be necessary in our investigations. And the same invariability 

 which we are prepared to recognize in reference to space, we would 

 equally recognize in reference to time ; and would distinctly assert the 

 law, thcd all j^hysical causes acting undrr given conditions are to he 

 regarded as having ^jroduced^ in all pad tirn<:, the same effects as the 

 same causes, acting under the same condiiion-'<, would produce at the 

 present time. Thus we assume the constancy of the law according to 

 which different particles of matter attract each other, and also of the 

 laws which govern the propagation of heat through solid and fluid 

 bodies, and of its influence in converting solids into fluids, or fluids 

 into gases. In short, we assume that all physical causes have always 

 acted according to the same laws, and, when acting^ under identical 

 conditions, with the same intensity. 



Tqis hypothesis has been more or less confounded with another 

 hypothesis — that the earth must have been for an indefinite period 

 of time in a physical state essentially the same as that in which it now 

 exists. To confound them is a great error ; for it is extremely diffi- 

 cult to understand how the causes of which we recognize the agency 

 in geology can have continued to operate for an indefinite length of 

 time without changing the state and condition oi the terrestrial mass 

 on which tbey have been acting. 



As some curves, known to geometricians, are so nearly related to 

 straight lines, that, if we were to examine any part of the extended 

 portion running besides its asymptote, it would appear so like the straight 

 line that our senses would not appreciate the difference, " so it may 

 be with our planet. However slow may have been the process of 

 change, even during all geological time, it may have been like the tardy 

 change of direction in our curve iu its infinitely extended branch, 

 towards its asymptotic direction. It may be that the earth, instead of 

 having never deviated materially from its present physical condition, 



