With respect to the number of bodies, which, by our not being able to change one a them into the other, are Called elementary, or primitive and distinct ; it may be remarked, that new bodies are frequently discovered in proportion as new instruments, and the irnprovements of science in general. us with the means of discriminating them from others. We are thus naturally led to that in all probability there exists a vast number of other bodies, of which we at present have not the least suspicion. Some of these inay pedlar; be discovered hereafter, others inav re main utterly unknown to the human species for ever.
The natural bodies, which are the objects of research to the experimental philosopher, are either general, or particular. The general properties, which belong to all kinds of bodies, arc, as far as we know, not more than six ; viz., extension, divisibility, impenetrability, mobility, vis inertia?, or passiveness, and gravitation. We have said that these are the general properties as far as we know, beeause matter in general may possess other properties with •hich we are vet unacquainted. And the same observation may. be made with respect to the universality of these properties: for they are said to be general. because was ever found which wanted any one of them. But mankind are riot acqnainted with all the bodies of the universe. and niany which are known to exist, cannot be subjected to ex periments.
The peculiar properties, viz.. those which belong to cer tain bodies only, and not to others, are Ilensity, rarity. hard ness, softness, fluidity, rigidity, flexibility, elasticity, opacity, transparency, the properties of light, the properties of heat. the properties of electricity, the properties of magnetism, and three other kinds of attraction, (independent of gravi tation, of electricity and of magnetism.) viz., the attraction of aggregation, which the homogeneous parts of matter have towards each other, or by which they adhere together ; and such is the power by which two small drops of mercury, when placed contiguous to each other, rush, as it were, into each other, and form a single drop ; the attraction of cohesion, or that power by which the heterogeneous particles of bodies adhere to each other without any change of their natural properties, such as the adhesion of water to glass, of oil to iron. &e. ; and the attraction of composition, or of affinity,
which is the tendency that the parts of heterogeneous bodies have towards each other, by which they combine, and form a body, differing more or less from any of its comp It is to be remarked, that of all these properties we know their existence only, and some of the laws under which they act ; but Nye are otherwise utterly ignorant of their nature and dependenee.
The investi,ration of some of the above-mentioned pro perties, whether general or particular, has been carried 11111011 farther than the investigation of other properties. The results of these investigations have likewise been various. both in point of extent and of application. Some of them are so very extensive and so useful, as to form the fieindations of very important branches of science, or under peculiar appellations. Thn, upon the mobility. and the vis inerthe of bodies, the doctrine of motion. or dynamics. is grounded, which comprehends mechanics, hydrostatics. or the mechanical properties of 11 rids, pneumatic:. &c. Transparency and the properties of light form the important found:abut of optics. The attraction of affinity is the foundation of •hemistry, as as of various arts ; and so forth.
The pheman•na of the universe.are the appearances which take place in consequence of the above-mentioned properties of natural bodies. together ( respecting sione of them at least) with Original 11111)111Se. The phenomena which take place amongst the luminous velestial bodies, prop•rly so called, such as the stars. the planets, &c.. are examined by a particular science. called astronomy ; the meteors, or the which take place within the limits of the terres trial atmosphere, such as shooting stars, northern lights, halos, rain, fogs, hail, winds, &c., form the subject of meteorology.