THERMOSCOPE (from Gk. 0/feLn, theme, heat -F. ecorcn', skopein, to look). A device to indicate relative temperatures by making use of the property possessed by substances of changing their state or volume under the influence of heat. Thus, knowing the fusing-point of a solid, we are enabled to determine whether a certain tempera ture is above or below the temperature at which it melts, while with a liquid we have two such points, namely, the temperature of vaporization and that of solidification. Such substances form what are termed discontinuous intrinsic thermo scopes,and by virtue of their intrinsic properties enable us to ascertain relative temperatures. For example, butter would serve as such a ther moscope, since by its melting it would indicate that the temperature of the room was above its point of fusing. likewise we soon use other sub stances, including alloys, for this pnrpose, and ex tend our observations over a considerable range.
If the substance used as a thermoscope possesses the property of continuously varying in its con dition with an increase or diminution of tempera ture, so as to afford a continuous indication over a given range of temperature, as is the ease with mercury. then we have what is known as a con tinuous thermoseope. If this is so arranged that it can be graduated according to some previously arranged scale, it then forms a thermometer. The camphor thermoseope is a sealed tube of glass containing a solution of camphor in alcohol, which indicates changes in temperature by its appearance. At high temperature the liquid is clear, as the camphor is entirely dissolved, but with low temperature it crystallizes and appears as a white fleecy mass. This instrument does not, as is commonly supposed, indicate changes either in pressure or electrical condition of at mosphere.