corpuscules as said above, depends for its atoniic weight upon the number of corpuscides in it, and these corpuscules are all identical in nature. In these corpuscules we have the one first material, or protyle. It follows that the onlj- difference between atoms of different elements is in the number of corpuscules they contain. Any process which would change the number of corpuscules in the atoms of an element would change the element into another one, thus carrj-ing out the transmutation of elements. So far, one transmutation is accepted as etfectetl. Experiments in radio-activity go to prove that some elements, notably radium, project particles of in- conceivable minuteness into space. These particles have sometimes one-half the velocity of light. They are called corpuscules. The corpuscule is sometimes defined as a particle of negative electricity, which, in the existing state of electrical knowledge, is a very imperfect definition. They are all negatively elec- trified, and therefore repel each other. The condi- tion of equilibrium of groups of such particles, if held near to each other by another external force, has been investigated by Prof. J. J. Thomson, and liis investigations estabhsh a basis for a theory of the constitution of atoms. Thus, assume an atom to consist ol a number of corj^uscules, not touching each other, all negatively electrified so that they repel one another, and held within the limits of the atom by what may be termed a shell of attractive force. Professor Thomson shows that such particles, under the conditions outlined above, arrange them- .selves into groups of various arrangement, the latter depending on their number. If the number of particles in a group be progressively increa.sed, a periodic recurrence of groupings will occur. Assume a group of five particles. These will form a group of definite shape. If more particles are added to the group, the first additions will cause the five group to disappear, other groups taking its place, until the number reaches fifteen, when the original grouping of five wiU reappear, surrounded by the other ten particles. On adding more particles, the five and ten group disappear, to be succeeded by others, until the number of thirty is reached. At this point the original five group and the ten group reappear, with a new group of fifteen. The same recurrence of groupings takes place with forty-seven and sixty-seven particles. This gives the outlines of an explanation of the periodic law. If any num- ber of particles be taken they ^vill show groupings, characteristic of the number, and subject to periodical reappearance as the number is increased. This reappearance of groupings is exactly comparable to the phenomena of the periodic law. It is the re- appearance of similar properties at periodic inter- vals. The corpuscular theory also accounts for the variation of the elements in atomic weight. Cor- puscules are supposed to be all alike, so that the weight of an atom would depend on how many corpuscules were required to form it. Thus an atom of oxygen would contain sixteen times as many corpuscules as would an atom of hydrogen, weighing only one-sixteenth as much. The weight of an atom of hydrogen has been approximately calculated as expressed by the decimal, 34 preceded by thirteen ciphers, of a gram. This means that thirty-four thou- sand millions of millions of atoms of hydrogen would weigh in the aggregate one gram. These calculations are based on determination of the electric charge of corpuscules. Corpuscules are calculated as being about one-thousandth of the mass of an atom of hy- drogen. Professor Oliver Lodge gives the following compari.son: if a church of ordinary size represent an atom, a thousand grains of sand dashing about its inte- rior with enormous velocity would represent its con- srituent corpuscules. When atoms unite to form molecules, tney are said to saturate each other.
Elements varj- in the saturating power of their atoms. The saturating power is called atomicity or valency. Some elements have a valency of one, and are termed monads. A monad can saturate a monad. Others are termed dyads, have a valency of two, two monads being required to saturate one dyad, while one dyad can saturate another dyad. Valencies run on through triads, tetrads, pentads, hexads, heptads, and octads, designating valencies of three, four, five, six, seven, and eight respectively.
T. O'CoNOR Sloane.
Atomism, [a privative and riiivtiv to cut, i. e. indi- visible] is the system of those who hold that all bodies are composed of minute, indivisible particles of matter called atoms. We must distinguish be- tween (1) atomism as a philosophy and (2) atomism as a theory of science.
Atomism as a philosophy originated with Leu- cippus. Democritus (b. 460 b. c), his disciple, is generally considered the father of atomism, as prac- tically nothing is known of Leucippus. The theory of Democritus may be summed up in the following propositions: 1. All bodies are composed of atoms and spaces between the atoms. 2. Atoms are eter- nal, indivisible, infinite in number, and homogeneous in nature; all differences in bodies are due to a dif- ference in the size, shape or location of the atoms. 3. There is no purpose or design in nature, and in this sense all is ruled by chance. 4. All activity is reduced to local motion. The formation of the uni- verse is due to the fact that the larger atoms fall faster, and by striking against the smaller ones com- bine with them; thus the whole universe is the re- sult of the fortuitous concourse of atoms. Countless worlds are formed simultaneously and successively. Epicurus (342-270 B. c.) adopted the theory of De- mocritus, but corrected the blunder, pointed out b}- Aristotle, that larger atoms fall faster than smaller ones in vacuo. He substituted a power in the atoms to decline a little from the fine of fall. Atomism is defended by Lucretius Cams (95-51 b. c.) in liis poem,"De Rerum Natura." With the exception of a few alchemists in the Middle Ages, we find no rep- resentatives of atomism until Gassendi (1.592-lfi55) renewed the atomism of Epicurus. Gassendi tried to harmonize atomism with Christian teaching by
gostulating atoms finite in number and created by od. With the application of atomism to the sci- ences, philosophic atomism also revived, and became for a time the most popular philosophy. Present- day philosophic atomism regards matter as homo- geneous and explains all physical and chemical prop- erties of bodies by a difference in mass of matter and local motion. The atom itself is inert and devoid of all activity. The molecule, taken over from the sciences, is but an edifice of unchangeable atoms. Philosophic atomism stands entirely on the basis of materialism, and. though it invokes the necessary laws of matter, its exclusion of final causes makes it in the last analysis a philosophy of chance.
The atomic theory was first applied to chemistry by Dalton (1808), but with him it meant little more than an expression of proportions in chemical com- position. The theory supplied a simple explanation of the facts observed before him: that elements com- bine in definite and multiple proportions. The dis- covery in the same year by Ciay-Lussac of the law that gases under the same pressure and temperature have equal volumes was at the same time a confir- mation and an aid in determining atomic weights. Avogadro's law (1811) that gases under the same conditions of pressure and temperature have an equal number of molecules, and the law of Petit and Du- long that the product of the specific heat and the atomic weight of an element gives a constant num- ber were further confirmations and aids. The atomic