[26] “Two very different hypotheses have been formed to explain the nature of matter, or the mode of its formation; the one known as the _atomic_ theory, the other, the _dynamic_. The founder of the former and earlier was Leucippus: he considered the basis of all bodies to be extremely fine particles, differing in form and nature, which he supposed to be dispersed through space, and to which his follower Epicurus first gave the name of atoms. To these atoms he attributed a rectilinear motion, in consequence of which such as are homogeneous united, whilst the lighter were dispersed through space. The author of the second hypothesis was the famous Kant. He imagined all matter existed, or was originated, by two antagonist and mutually counteracting principles, which he called attraction and repulsion, all the predicates of which he referred to motion. Most modern philosophers, and foremost amongst them Ampère and Poisson, have adopted an hypothesis combining the features of both the preceding. They regarded the atoms as data, deriving their origin from the Deity as the first cause, and consider their innate attractive and repulsive force as a necessary condition to their combination in bodies. The main features of this hypothesis are borrowed from Aristotle, inasmuch as he supposed the basis of all bodies to be the four elements known to the ancients, the particles of which, endued with certain powers, constituted bodies. According to Ampère, all bodies consist of equal particles, and they again of molecules that, up to a certain distance, attract each other. Their distance from each other he supposed to be regulated by the intensity of the attractive and repulsive forces, the latter of which preponderates.”--Peschel’s _Elements of Physics_; translated by E. West, 1845. [27] This was first proved by the researches of Dr. Dalton: the subject will be again alluded to under the consideration of atomic volumes. [28] These peculiar phenomena may be studied advantageously in the works of most of the eminent European chemists. In our own language the reader is referred to Dr. Thompson’s _Outline of the Sciences of Heat and Electricity_, 2nd edition; Brande’s _Manual of Chemistry_--Art. _Specific Heat_; Graham’s _Elements of Chemistry_; and Daniell’s _Introduction to the Study of Chemical Philosophy_. [29] The conversion of the diamond into graphite and coke was first effected by the agency of the galvanic arc of flame, by M. Jaquelini, and communicated to the Academy of Sciences in 1847, in a Memoir entitled, _De l’action calorifique de la pile de Bunsen, du chalumeau à gaz oxygène et hydrogène sur le carbon pur, artificiel et naturel_. See _Comptes Rendus_, 1847, vol. xxiv. p. 1050; also _Report of the British Association_, for 1847, (_Transactions of Sections_) p. 50.