Researches in the Theory and Calculus of Operations. 249 



equilibrated by the reaction of the medium; so that the 

 medial particles impingiDg upon the sphere throughout 

 equilibrate each other, and the excess of the spherical over 

 the medial force, or that which is not destroyed by the lat- 

 ter, constitutes the proper emanating force of the spherical 

 mass, which goes to contribute the ethereal medium of in- 

 finite space. 



In order to rectify our conception of the atomic theory, 

 recall to mind Herschel's graphic delineation of an exam- 

 ple of the genesis of waves, by the action of the winds upon a 

 field of grain. The amplitude of the grain- waves depends upon 

 the force of the impinging wind and the elaitic resistance and 

 rebound of the stalks of the grain, and not upon any pre- 

 existing central points. The genesis of atmospheric waves 

 by the vibratory action of an elastic spring, also offers a 

 case in point, and indeed a proof in point; for it is only ne- 

 cessary to substitute the conception of an oscillation* of ten- 

 sion for that of vibratory movement, to secure distinct mental 

 vision of the operation. So when treating of any medium 

 whatever, solid, fluid or gaseous, the atoms are not to be 

 regarded as having a priori definite magnitude and fixed 

 centres (the mathematical points of Boscovich) : on the con- 

 trary, these relations are developed by perturbations inflicted 

 upon the mass by interfering forces, which, proportionate 

 to the depth of their penetration and the tension of the in- 

 terfered medium, determine the magnitude of the atoms 

 thus called into existence, their centres being in each origin- 

 ated by reaction. 



7. When a body is struck in a movable direction, motion 

 is the result if the blow be sufficiently powerful. But if struck 

 in a direction in which it cannot be moved, as in the case 

 of hammering a piece of iron upon an anvil, the impulsed 

 superficial atoms react proportionately in opposition to the 

 force of the blow, being reinforced by the resistance of the 

 underlying strata of atoms : an atomic vibratory action com- 



Trans. im\] 32 



