56 De. Macatlcab's Adaptation of the Philosophy of 



in a form thus conceived, as originally wholly plastic and perfectly 

 homogeneous and exempt from internal change, a perfect elasticity. 

 Here, therefore, we again make another great step towards the concep- 

 tion of matter or body ; for all observation, all calculation, lead to the 

 inference that if we could but reach the last elements of matter, they 

 would be found to be perfectly elastic. It is true that in this deduc- 

 tion of elasticity, only the law under which it exists is given, and not 

 the mechanism by which it is accompUshed. The latter is of more 

 difficult deduction, and only appears in general terms in the following 

 paragraphs. 



But Form implies relations of parts, and of these relations the most 

 eminent is that of all the parts to one, which is the centre. And here 

 it becomes necessaiy for us (without postulating any particular form 

 as that of the setherial atoms), to view them as having each a centre ; 

 which, while it may be designated according to the object in view, 

 Centre of inertia, or Centre of elasticity, may be designated generally as 

 Centre of force. But the setherial centres of force as given by nature 

 are obviously in a state of separation from each other. Each setherial 

 element, therefore, has volume ; and around its centre of force there is a 

 self-isolating, and, of course, elastic ambient, which we may call its 

 atomosphere or atmosphere. 



Now, in this centre and its atmosphere, it appears, that on the 

 application of a force from without, in connection with elasticity, and 

 explaining it, two other modes of action must present themselves. 



Op Repulsion. 



III. In every case but that in which the setherial element, molecule 

 or mass, is conceived to move away as fast as the force is impressed, 

 which is impossible, the elastic action of the whole must imply the 

 oscillation or vibration of the centre, or of the centres of force found in 

 the molecular mass— a vibration which will be greater or less according 

 as the force impressed or the resistance opposed is greater or less. 

 Moreover, this oscillation or vibration of the centre must, in its turn, 

 set agoing and maintain in the atomosphere around it, a system or 

 systems of undulations of the same periods as itself, and determined 

 in form and direction by the law of assimilation as usual. Now, such 

 systems of undulae, when of the same periods and dimensions, as, for 

 instance, when emanating from the centres or nuclei of similarly 

 constructed molecules, must constitute an apparatus of mutual repulsion 

 between these atoms or molecules ; for tlae undulse advancing from the 

 different centres or nuclei must meet each other face to face ; — each 

 wavelet must resist the farther progress of the other, whence, that 



