816 TRANSACTIONS OF THE AMERICAN INSTITUTE. 



difficulty of the problem if subjected to a rigid mathematical inves- 

 tigation. 



We may however consider the application of the general priu- 

 ciples already arrived at to these aggregations, and, guiJed by 

 the results of actual experience, and a perception of the harmony, 

 symmetr3'^and uniformity which pervades the universe, we shall per- 

 ha[^s find some of these difficulties less formidable than they at 

 first appear, and be led to conclusions which will enable us to 

 unlock ^ome of the great secrets of nature. 



Let us then suppose that the excess of atomic motion or heat 

 over potential gravity, produces, in the gaseous condition, a vir- 

 tual repulsion of th» atoms, alternating with and preponderating 

 over a powerful attraction. This attraction, moreover, reinforces 

 the momentum which is converted, after collision or -pericentre 

 passage, (by which is meant the nearest approach to the centre of 

 gravity,) into repulsion. 



The paths by which the most direct approaches, and yet the 

 widest separations could be made, in an aggregation of uniform 

 atoms, would seem to be rectilinear ones, crossing each other at 

 right angles, in three directions, and dividing the space occupied 

 into small imaginary cubes. Along the edges of these culjes we 

 may suppose six atoms to simultaneously collide, or pass their peri- 

 centre, at the cubical angles, and then to continue in their courses, 

 diverging from each other, their places being successively supplied 

 by atoms from the adjacent cubical angles or molecular centres. 

 A single pair of atoms will collide or pass their pericentre on their 

 passage from angle to angle at the middle of every cubical edge. 



Matter thus constituted will constantly tend to expand, but when 

 confined between solid or liquid surfaces, these surfaces will sus- 

 tain a " pressure," equivalent to the surplus of momentum over 

 potential gravit}^, in the entire aggregate* of atoms. 



This pressure is not produced by an actual contact, but by the 

 passage of the atoms of the gas around those of the solid or liquid 

 under the laws of gravitation and momentum, in a manner similar 

 to that in which a comet passes around the sun. The exacL equality 

 of the opposite gravitational disturbance or of action and reaction, 

 causes the sun to be impelled in one direction with precisely the 

 same force that the comet is thrown in the other, the diftbrence 

 between the velocities of the two bodies being in inverse ratio to 

 their masses or aggregate inertias. 



It will be seen, that supposing the atoms to move in rectilinear 



