thermoscopic (thermos kopʻik)

[ thermoscopical (ther-mō-skop'i-kal), a. [ IMG:content-0248.png:[blocks in formation] a, base; b, involute expansion-strip, composed of two metals having different coefficients of expansion, as bra and steel; r, adjustments crew, forming part of an electric circuit whenever & is expanded by heat so as to touch the point of the screw; d, d, conducting wires. an electric current, and thus move an armature that controls a damper, steam-valve, or other heat-regulating mechanism. Another form consists of a balanced thermometer that, under the movements of the mercury in a tube pivoted in the center in a horizontal position, would rise or fall, and thus control a damper or fire-door. Another form consists of a thermometer resembling a thermoelectric alarm (see thermo - electric ), except that the closing of the circuit by the rise of the mercury in the tube operates a fire-door or damper in place of sounding an alarm. Where a thermostat is merely used to ring a bell, it is called a thermostatic alarm. A very simple and yet delicately responsive form is a slender bar of gutta-perch a, fixed at one end, and attached at the other to a lever, which is caused to act by the expansion or contraction of the bar. Another form of thermostat consists of a bent tube partly filled with mercury. The heat expands the air in the larger end of the tube and displaces the mercury, and this in turn moves a piston controlling, by means of some mechanical device, a steam-valve or damper. Another form, used with steam-heating furnaces, consists of an elastic diaphragm in a cylinder, the pre ure of the steam against the diaphragm serving to move a piston that con the damper the furnace. Such appliances are also called heat - regulators. More recently, the name has been given to fusible plugs used to control automatic sprinklers, a rise in the temperature causing the plug to melt and release the water. This, however, is only a trade use of the word. thermostatic (ther-mo-stat'ik), a. [