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Of the Source of Motions upon the Earth, and of the means by 

 which they are sustained. By ROBERT E. Bkown, M.D., 

 Edinburgh. Communicated by the Author. 



Among many of the material substances of which our globe is 

 composed, a multitude of motions, changes, and transformations, per- 

 petually occur. And, if it be considered that each of these motions 

 individually, and of itself, tends to rest, — that each is in a downward 

 direction, so to speak, and has a definite termination at which it must 

 cease, the inquiry will present itself, ^^^ly does not a cessation of mo- 

 tion take place ? How do the various terrestrial motions arise, and 

 by what method is that constant and unimpaired activity maintained, 

 which the earth exhibits to us ? It is to the consideration of these 

 subjects, — to an attempt at the discovery of the origin, and of the 

 mutual relations of the various motions, and of the plan upon which 

 their continuance depends, that our attention is now to be directed. 



Let it be supposed, that, antecedently to the present order of 

 thing.'*, the earth existed in some remote region of space apart from 

 the influence of other matter. It may be conceived that the various 

 chemical and physical forces inherent in the matter of the earth, 

 might, during a long period of time, give rise to numberless motions, 

 and changes, and combinations, among its molecules. But in these 

 there would be no principle of perpetuity ; for no chemical action, 

 nor any series of chemical actions, can, by their own powers, main- 

 tain themselves in activity, any more than a mechanical motion or a 

 series of such, can give rise to a pei'petual motion. In neither case 

 can a motion call into existence a force equal to the reproduction or 

 to the maintenance of itself; for friction alike counteracts them both, 

 and i-enders them finite. After a time, therefore, it may be, of vio- 

 lent turmoil and commotion, these forces would have carried matter 

 through all the changes which they were capable of inducing, and 

 both force and matter would have arrived at a condition of neutraliza^ 

 tion and equilibrium, and perfect rest.* 



* It is to be noted that the above is a mere supposition, and that it is not 

 conceived to correspond to anything which ever took place in natiu-e. It is very 

 questionable whether any chemical actions could take place in the circumstances 

 which have been described. Besides, we know that all matter has not been car- 

 ried through the changes which its chemical forces are equal to produce, and 

 the supposition is made merely for the purpose of subsequently presenting more 

 clearly the effects wh'ch external nature has upon terrestrial matter. 



Here it may also be mentioned, that to speak of force being inherent in mat- 

 ter, and of its proceeding from one body and influencing another, are modes of 

 speech which, in all their modifications, it would have been better to have dis- 

 pensed with, inasmuch as they seem to imply the existence of some real entity 

 otlier than matter, and of the passage of something between the bodies, — which 

 is purely hypothetical. It would have been better, when there is occasion to 



