2C2 THE THERMOMETER. 



thrown over it to close up every chink, and a low door was cut through 

 the walls with a knife. A bed-place was next formed, and neatly faced 

 up with slabs of snow, which were then covered with a thin layer of fine 

 branches, to prevent them from being melted by the heat of the body. 

 At each end of the bed, a pillar of snow is erected to place a lamp upon ; 

 and lastly, a porch was built before the door, and a piece of clear ice was 

 placed in an aperture cut in the wall for a window. The purity of the 

 material of whi.oh the house was formed, the elegance of its construction, 

 and the translucency of its walls, which transmitted a very pleasant 

 light, gave it an appearance far superior to a marble building, and one 

 might survey it with feelings somewhat akin to those produced by the 

 contemplation of a Grecian temple raised by Phidias ; both are temples 

 of art, inimitable in their kinds." 



THE THERMOMETER. 



In general, when heat is imparted to a body, an enlargement of bulk 

 will be the immediate consequence, and at the same time the body will 

 become warmer to the touch. These two effects of expansion and 

 increase of warmth going on always together, the one has been taken as a 

 measure of the other; and upon this principle the common thermometer 

 isconstructed. That instrument consists of a tube of glass, terminated in a 

 bulb, the magnitude of which is considerable, compared with the boreofthe 

 tube. The bulb and part of the tube are filled with mercury, or some 

 other liquid. When the bulb is exposed to any source of heat, the 

 mercury contained in it, being warmed or increased in temperature, is at 

 the same time increased in bulk, expanded or dilated, as it is called. 

 The bulb not having sufficent capacity to contain the increased bulk of 

 mercury, the liquid is forced up in the tube, and the quantity of expan- 

 sion is dertermined by observing the ascent of the column in the tube. 



An instrument of this kind, exposed to heat or cold, will fluctuate 

 accordingly! the mercury rising as the heat to which it is exposed is 

 increased, and falling by exposure to cold. In order, however, to render 

 it an accurate measure of temperature, it is necessary to connect with it a 

 scale by which the elevation or depression of mercury in the tube may 

 be measured. Such a scale is constructed for thermometers in this 

 country in the following manner: Let us suppose the instrument 

 immersed in a vessel of melting ice : the column of mercury in the tube 

 will be observed to fall at a certain point, and there maintain its position 

 unaltered: let that point be marked upon the tube. Let the instrument 



