766 



BOSCOVICH'S THEORY. 



Boscovich'? 

 theory of 



Natural 

 Philoso- 

 phy. 



Mobility. 



omponi- 

 bility equi- 

 valent to 

 divisibility. 



Gravity. 



Cohesion. 



Variety of 



particles 

 accounts 

 lor 



continuing in the same state of rest, or uniform mo- 

 tion. 



Mobility is a consequence of the curve of forces, 

 which, expressing by its ordinates the determinations 

 to access or recess, necessarily implies mobility, or 

 the possibility of motion. Some have mentioned 

 quiescibility, or the capability of being at rest, as a 

 property of matter. Boscovich thinks it does not 

 exist in nature, at least as at present constituted ; and 

 he endeavours to demonstrate the truth of this senti- 

 ment, by arguments drawn from the nature of infini- 

 ties, and the law of continuity. He proceeds next to 

 theconsiderationof the law of equal action andreaction, 

 which had"been already proved in the second part. 



Invisibility is assumed by many as a property of 

 matter, and, with respect to continued space, infinite 

 divisibility is undeniable ; but, when we consider 

 matter as made up of a finite number of points, the 

 divisibility has evidently a limit ; for, if we suppose 

 it carried so far as that the intervals are less than the 

 distance between the points of matter, subsequent 

 sections will divide not matter but empty space. But 

 although there be no divisibility in iyijinitum, accord- 

 ing to our author, yet there is what he calls compo- 

 nibility, which answers the same purpose : That is 

 to say, between any two points of matter there may 

 be interposed a third, another between this new one 

 and each of the first ; and so on without limit. So 

 that, within a given space, however small, there may 

 be such a number of points as if distributed through- 

 out a greater space, may leave no cubic space so 

 small a6 to be altogether free of matter. 



Universal gravity, at all sensible distances, is also 

 a part of our theory ; and perhaps the curve of forces, 

 after extending to the utmost limits of our planetary 

 and cometary system, may intersect the axis, and 

 pass to repulsion. This would obviate the objection 

 made to the Newtonian doctrine of attraction, that 

 the planets, stars, and all matter, must be thereby at 

 length condensed into one mass. If such a repukion 

 takes place, the curve may even wind again about the 

 axis, and form limits of cohesion. And in this way 

 it is possible that our sun, with all the fixed stars, 

 may form a particle of an order superior to those 

 which compose our system, and belonging to a sys- , 

 tern vastly greater. 



From gravitation we proceed to cohesion, which 

 has never been so well explained as by the theory of 

 Boscovich. It arises immediately from the limits of 

 cohesion, of which we have already treated in the 

 first part of that article, and, therefore, we need not 

 here enlarge upon it. 



We proceed now to the particular properties of 

 bodies, by which the infinite variety of nature is 

 accounted for. And here the -Variety offered to 

 us by the theory is indeed immense : For, in the 

 first place, there may be different numbers of points 

 constituting particles of the same bulk ; then the 

 bulks may vary so, that no two particles have the 

 same bulk, mass, or density ; or, these being the 

 same, the figure may be infinitely varied ; and the 

 points may be altogether placed towards the exte- 

 rior surface, or dispersed throughout the mass ; or 

 of different densities in different parts of the particle. 

 And great as may be the variety in the number and 



distribution of the points, the variety in the mutual 

 forces of the particle is still more unlimited. 



The parts of fluid bodies are easily separated from, 

 and moved among, one another. This seems owing to 

 their being spherical and homogeneous. Their forces 

 are in a great measure directed to their centres. 

 They are therefore at liberty to be moved round 

 each other, and will yield in any direction to a very 

 small force. Between the particles of some there ia 

 very little, if any attraction, as in sand, dry powders, 

 and seeds, which approach much to fluidity; others 

 hare a sensible attraction, as water, or, more percep- 

 tibly, mercury, and the like, since they form them- 

 selves into drops ; in a third sort, as air, there is a 

 powerful repulsion, and, unless confined, they will 

 dilate themselves to a great extent ; the particles 

 must therefore be not in limits of cohesion, but in a 

 repulsive arc of the curve expressing their forces. 



When the figure of the particles recedes much from 

 being spherical, or the distribution of the points is 

 unequal, the free circular motion cannot take place, 

 and the consequent lateral forces will produce all the 

 phenomena of solidity. Thus, if two parallelopipeds 

 be situated beside ea-h other, and in some limit of 

 cohesion, the one cannot move away without bring- 

 ing the other with it by the increasing attraction, 

 or move towards the other, without pushing it before 

 it by the increasing repulsion. And if it be any way 

 inclined, the other parallelopiped will be attracted on 

 one side, and repelled on the other, and of course 

 will follow the inclination of the first. A continued 

 series of parallelopipeds will form a long fibre, or a 

 solid rod, of which if the base or end be inclined, the 

 whole will follow. The same is true of all other fi- 

 gures, however unequal. 



If the limits in which the particles are situated be 

 powerful, the bodies will appear hard and inflexible; 

 but soft and flexible, if these limits be weaker. If the 

 arches of attraction and repulsion do not extend far 

 on either side, the particles may come in flexure to 

 new limits, and remain without any effort to recover 

 their shape, as lead, and other ductile bodies. If the 

 arches be very small, and if after that no action or a 

 repulsion take place, the body is fragile, or brittle. 

 If the arches are longer, the same force will continue 

 to act, and bring back the body to its former posi- 

 tion ; nay, in consequence of the accelerated motion, 

 the parts will pass their former positions, and vibrate 

 backwards and forwards, by which means we account 

 for elasticity. 



Viscous bodies occupy the mean between solids and 

 fluids ; having less cohesion than the one, and more 

 than the other. Besides their mutual tenacity, they 

 have a force of attraction, whereby they stick to 

 other bodies, and moisten them. This humidity is 

 relative. Water will stick to some "bodies, and is 

 expelled by others. 



The composition of crystallized and organic bo- 

 dies appears very wonderful. But if we consider 

 that particles may be so formed as in certain parts of 

 their surfaces to attract certain other particles, in 

 others to repel them, it is easy to conceive how they 

 may only coalesce in certain c peculiar figures ; and in 

 this way secretion, nutrition, and vegetation, may be 

 equally explained. 



Boscovich '$ 

 Theory of 

 Natural 

 Philoso- 

 phy. 



Fluidity 

 and 



Solidity. 



Hardness 

 flexibility, 

 elasticity, 

 &c. 



Viscosity. 



Organiza- 

 tion. 



