Page:On the connexion of the physical sciences (1834).djvu/255

tides of solids and fluids; by this separation the attraction of aggregation is more and more weakened, till at last it is entirely overcome, or even changed into repulsion. By the continual addition of caloric, solids may be made to pass into liquids, and from liquids to the aëriform state, the dilatation increasing with the temperature; but every substance expands according to a law of its own. Metals dilate uniformly from the freezing to the boiling points of the thermometer; the uniform expansion of the gases extends between still wider limits; but as liquidity is a state of transition from the solid to the aëriform condition, the equable dilatation of liquids has not so extensive a range. The rate of expansion of solids varies at their transition to liquidity, and that of liquids is no longer equable near their change to an aëriform state. There are exceptions, however, to the general laws of expansion; some liquids have a maximum density corresponding to a certain temperature, and dilate whether that temperature be increased or diminished. For example,—water expands whether it be heated above or cooled below 40°. The solidification of some liquids, and especially their crystallization, is always accompanied by an increase of bulk. Water dilates rapidly when converted into ice, and with a force sufficient to split the hardest substances. The

r 2