TRANSACTIONS OP THE SECTIONS. 59 



antitheses, expressive, under different conditions, of the phenomena resulting from 

 greater or less resistance to the transmission of increased pressure. 



The gravitation of any two bodies to each other is attempted to he mathematically 

 explained as the mechanical consequence of the relations of the mutual pressures of 

 the two bodies, and the resistances of the medium or other bodies. 



The undulations of light, &c. appear as the consequence in a medium of certain 

 different relations of the outward pressure of two bodies. 



Polarization is considered as the condition of a line of motion in relation to a 

 mechanically conceived medium. In electrics, we study the different relations of the 

 ends; in optics and thermotics, of the sides, of a line of motion. 



The problem proposed by this theory for mathematical solution is — what are the 

 conditions of pressure and resistance to its transmission that would produce such 

 and such effects? And this theory would direct experiment to the comparison of 

 the different resistances of bodies to different conditions of increased or diminished 

 pressure. 



On the Philosophy of Physics. By John G. Mac vicar, D.D. 



The object of this communication is to simplify our first steps in physics, by di- 

 minishing the number of considerations which at present stand in the position of 

 independent data or postulates ; and more especially, to show that the all-important 

 properties of inertia, elasticity, and gravitation, instead of being unrelated, as is ge- 

 nerally supposed, do in reality form a group of properties which imply each other, and 

 are in fact nothing else but uniform phenomena resulting from one and the same law, 

 according as that law is viewed in reference to the substance or the form of a single 

 element of matter, or in reference to a system of such elements distributed in space. 



In order to reach this law, the author commences by rejecting from thought all the 

 specific properties of individual objects, so as to be left in possession of that which is 

 common to all. He thus finds Substance or Being ; of which he prefers the latter term, 

 as being positive and even absolute in its import, and therefore suitable to build science 

 upon. Moreover, in the very term itself he finds the law, of which inertia, elasticity, 

 and gravitation are the expressions and the results. 



Thus the term Be-ing implies that the subject of it both exists and (excluding 

 at present the consideration of living, self-changing Beings or Spirits) continues to be 

 as it is. Now this, expressed dynamically so as to give a physical law, implies that which 

 both exists and has the power of repeating its existing state in every successive 

 moment of its existence ; or as may be said, that which both exists and assimilates 

 itself to itself in successive moments of its existence (and that without limitation, and 

 therefore) through the whole sphereof itsagency, and thus assimilates other beings or things 

 within that sphere, more or less, as well as itself. Whence obviously two grand func- 

 tions are implied in the operation of this law : first, Self-assimilation, implying the per- 

 manency of the type of the species, be it chemical element, crystal, plant, or animal; and 

 secondly, Mutual assimilation, implying the phenomena of Induction, Generic resem- 

 blance among species, and general Harmony in nature. This law the author regards 

 as the impress of the immutability and unity of the Creator in his works. And though 

 there is often (perhaps always) a mechanical apparatus by which it is worked out in 

 nature, yet it may, if found true, be accepted during our ignorance of that apparatus, 

 as a rational explanation of phenomena for which he holds that its relevancy is para- 

 mount. 



Inertia. — Under the law that has just been laid down this property immediately 

 appears. Thus, given a physical point, unit of matter, atom, or element of mere being, 

 the law of Being (which from its mode of action may also be called the law of assimi- 

 lation) calls upon that element to continue to be, nay, to be as it has been and is now, 

 to repeat its existing state, to assimilate itself to itself in every successive moment 

 of its being. And therefore if it be at rest, it must continue at rest, unable to leave the 

 place in which it is but through some force applied to it from without. If, again, it be 

 in motion, that is, continually leaving one point in space for the next point adjacent 

 to it, that also it must continue to do in every successive moment of its existence. 

 From which it follows, that not only is the perpetuity of the motion secured, but 

 the form of it is determined. Thus a translation from one point in space to the next 



