}0 Prof. Leslie on Heat and Climate. [July, 



AH matter is, therefore, essentially the 6ame ; and the sublime 

 scene of the universe owes all its splendour and beauty merely 

 to the variety of its composition. We behold a system of perpe- 

 tual fluctuation. The materials remain indeed unaltered, but 

 nature labours incessantly to demolish and to repair her stupen- 

 dous fabric. 



All bodies are compressible, and the only difference is, that 

 some are more affected by the application of the same force than 

 others. Were human power unlimited, there would likewise be 

 no bounds to the condensation which we could produce. Hence 

 we may infer that matter consists of particles placed at certain 

 distances from each other. But bodies, whether compressed or 

 dilated, endeavour to recover their constitution, and therefore 

 their particles must occupy the limits between attraction and 

 repulsion. Bodies are also susceptible of various constitutions, 

 which proves that there are many quiescent or neutral positions. 



It follows consequently, that the particles of matter are endued 

 with certain attractive and repulsive powers, which run into each 

 other, and vary with the distance according to some law. The 

 action upon a remote object is attractive ; and as, in this case, 

 the exertion of all the particles may be reckoned equal, the joint 

 effect will be proportional to their number. Hence it is that, 

 whatever changes a body may undergo in its structure and par- 

 ticular properties, its weight will continue invariably the same. 

 On the other hand, when the distance between the particles is 

 extremely diminished, their mutual action must be repulsive, 

 else the universe would in time be collected into a single point. 

 If these elementary particles had any magnitude, their opposite 

 sides would exert a prodigious repulsion against each other, 

 and occasion a perpetual subdivision and dispersion. We are 

 oblige*! therefore to admit, that they are only mathematical 

 points, to which certain powers are directed. In short, the ex- 

 ternal world has a real existence, which yet consists in mere forces 

 and loci.* Such is the substance of the ingenious and profound 

 theory of the late Abbe Boscovich. Some of the conclusions 

 will perhaps be deemed paradoxical ; but such is the fate of all 

 our inquiries into the intimate essence of matter. And these 

 difficulties arise from the superficial, inaccurate notions adopted 

 in common life, which unfit us in a great measure for high ab- 

 straction. A mature reflection will convince us of the solidity 

 as well as beauty of the system. 



Whether the particles of light are the primaeval points, or 

 simple combinations of them, 1 shall not venture to decide. It 

 appears sufficiently from the experiments on inflection, and 

 those with thin plates, that, in approaching other substances, 



* A physical particle is only a cluster of primaeval points, whose attractions 

 and repulsions, sometimes conspiring, and sometimes counteracting each other, will 

 foim a compound action varying extremely according to the figure of the arrange- 

 ment. Hence the prodigious diversity in the properties of bodies. 



