MATTEB. 191 MATTERHORN. THEOBIES OF MATTER. Many theories have been advanced to account for the properties of matter; somo deny an ob- jective ri'ality to matter, others alliriii it. Jl is possible to show that all observed phenomena in nature may be predicted from certain general mathematical equations, the quantities in which are not necessarily connected with the percep- tions of man; and that our mode of interpreting these quantities in terms of matter is not the only possible one. Again, there was a theory of matter, due to Boscovich, in which all actions of matter, as revealed l)y our senses, are attrib- uted to 'force-centres,' which act on each other acconling to ditl'erent laws for different dis- tances. This theory fails to explain inertia. .Ml theories which allirm the objective reality of matter consider any portion of it as made up of "molecules' and 'atoms,' meaning by molecule the smallest portion of the given kind of matter which retains the properties of the whole (e.g. a molecule of copper, of water), and by atom one of the fragments of a molecule which at the present time with our present knowledge we can- not break up into smaller parts. There are many theories of this kind, which differ in the way they regard molecules and atoms; but they all agree in one respect, they consider both the molecules and atoms to be in motion. On the idea that molecules are in motion it is possible to e.plain the main differences between solids, liquids, and gases and the principal features of diil'usion, osmosis, evaporation, dissociation, heat-conduction, fluid pressure, viscosity, etc., and in particular to deduce the most important properties of a gas. Such theories as this are called 'kinetic theories.' On any kinetic theory the molecules of a gas are conceived to be in motion in paths long compared with their own size, the average length of jiath being called the 'mean free path.' It is possible by identifying certain actual physical quantities, such as pres- sure, viscosity, diffusion, with these quantities as predicted by mathematical treatment of the simple kinetic theory of gases, to arrive at an idea as to the order of magnitude of the num- ber of molecules in one cubic centimeter, and the length of the mean free path at different pres- sures, etc. The approximate number of mole- cules in 1 cubic centimeter at atmospheric pres- sure is X 10'% the mean distance apart of two molecules is about 2.tj X 10-' centimeters, the mean free path is about 1 X 10"° centimeters, and the volume actually filled by the molecules in 1 cubic centimeter is ji^is^ cubic centimeter. If the pressure is diminished, these quantities all change. If the pressure is reduced to .001 centimeter of mercury, the mean free jiath becomes about 1 centimeter. A space so exhausted of matter as this has special physical properties and is called a 't'rookes's vacuum' or the 'fourth state of matter.' In a liquid the molecules are supposed to be moving about, having encounters with each other, rebounding, etc., yet having practically no free path. In a solid the molecules are supposed to be held more or less in fixed positions, about which they may vibrate, thus forming an elastic con- figuration which can be strained or even perma- nentlv deformed. In the cases of all three — gases, liquids, and solids — while the molecules are moving about, the atoms in the molecule are supposed to be making innnenscly rapid vibrations, which pro- duce the ether waves manifested by thermal, luminous, and chemical effects when ttu'V are ab- sorbed. (See Rabiatiox.) These kinetic ideas of molecules and atoms can be used to form a concrete picture of nearly all the phenomena and properties of matter. The question remains, What is the 'atom'? One idea was that an atom is a perfectly elastic sphere, which is obviously incompatible with facts; but the theor.v which at present is under discussion and not disproved is that atoms are vortices (q.v.) in a perfect fluid. The simplest type of vortex is like a smoke-ring; but there are many more complicated forms, which can be shown to be stable, A vortex once formed in a perfect fluid will maintain its identitj' as it moves about, not being a wave-motion passing through the fluid, but always consisting of the same portion of the fluid; vortices are elastic; they can 'combine,' or come together, and form a single system. Thus, if atoms are simply vor- tices of ether moving freely through the ether, many of the properties of matter may be ex- plained. A still more recent theory of matter is based upon the fact that an electric charge iu motion has an inertia quite apart from that of the matter which carries the cliarge. Consult a series of papers, "Electrons," by Sir Oliver Lodge, in the Electrician (London, I90'2-03). BiBLioGBAPiiY. Jleyer, The Kinetic Theory of (loses (Breslau, 1877, Eng. trans.. London, 1899) ; Holman, Matter, Energy, Force, anil ^York (Xew York, 1898) ; Ris't'een, Molecules and the Molecular Theory (Boston, 1895) ; Jlax- well. Matter and Motion (id ed.. New York, 1892) ; Tait, Propei-ties of Matter (3d ed.. Lon- don and New York, 1894) ; Poynting and Thom- son, Properties of Matter (London and Philadel- phia, 1901) ; Lehmann, Molekiilar Phi/sik (Leip- zig, 1888-89); Maxwell. Theory of Heat (Lon- don, 1897); Kelvin, Popular Lectures and Ad- dresses, vol. i. (New York, 1891) ; Kindiall. The Physical Properties of Gases (Boston, 1890). MATTER, niA'tar', Jacques (179I-I864). A French philosopher, born in Alsace. He was edu- cated at Strassburg, Giittingen. and Paris, and in 18'20 was appointed professor of history and director of the College of Strassburg. In 1832 Guizot made him inspector-general of the Uni- versity of Paris. In 1845 he was chosen inspec- tor of the French public libraries. He I'ctired in 184(5 to Strassbuig to become a professor in the Protestant theological seminary there. He was the author of a great nundier of standard works, among which are: Histoirr unircrselle de I'cglise chrctienne (1829-32); Dp rinfluence des ma^urs sur les lois et des lois sur les nujeurs (1832), crowned by the Academy; De I'ctat moral, politiqtie et litterdraire de VAllemaijne (1874); and La philosophic de la religion (1857). MAT'TERHORN (Fr. Mont Cerrin, It. Monte I'erriiui). The grandest mountain mass of the Alps, located near Zermatt in Switzer- land, between the Canton of Valais and the Val d'Aosta in Italv, in the Pennine group (Jlap: Switzerland. B 3). Its height is 14,780 feet, but that fact alone gives little idea of the sublimity
