. An analytical compendium of the various branches of medical science, for the use and examination of students. Anatomy; Physiology; Surgery; Obstetrics; Medicine; Materia Medica. 16 CHEMISTRY. Stance; the alcohol will rise much higher in the tube than the mer. cury. Liquids are not equally expansible; in being heated from 32° to 202°, alcohol expands -^^th of its bulk; water ^^^d; mercury ^jth. The rate of expansion in liquids is not uniform,—it increases with equal increments of heat. Exception to the law that liquids expand by heat, in the case of water near the freezing point, which expand
. An analytical compendium of the various branches of medical science, for the use and examination of students. Anatomy; Physiology; Surgery; Obstetrics; Medicine; Materia Medica. 16 CHEMISTRY. Stance; the alcohol will rise much higher in the tube than the mer. cury. Liquids are not equally expansible; in being heated from 32° to 202°, alcohol expands -^^th of its bulk; water ^^^d; mercury ^jth. The rate of expansion in liquids is not uniform,—it increases with equal increments of heat. Exception to the law that liquids expand by heat, in the case of water near the freezing point, which expands on being cooled below 39°—hence ice swims on water; this expansion is due to a new arrangement of its particles in the act of freezing. Expansion of Gases,—Gases are much more expansible than either liquids or solids;—their rate of expansion is uniform, and is the same for all gases, being about 480th of the whole volume for every degree of Fahrenheit. Thermometers are instruments for measuring sensi- ble heat by means of the expansion and contractions of some fluid. Sanctorid's thermometer was the first invented;—it consisted of a glass tube terminating in a bulb, partially filled with air, and the open end plunged into some coloured liquid; the expansion or contrac- tion of the contained air was marked by the depression or rise of the liquid. This thermometer is liable to two objections: the expansibility of air is too great to mark very considerable changes of temperature; and it is liable to be influenced by atmospheric pressure. Leslie^s differential thermometer is a modification of Sanctorio's air thermometer; it consists of a glass tube bent at right angles, and terminating in two O,--X bulbs. Both bulbs contain air, but the greater \^ part of the tube is filled with a coloured fluid. So long as the same temperature acts upon both bulbs, no change can take place; but the slightest difference between the temperature of the two is detected by the movement of
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