THE CALORIMETER SYSTEM AND MEASUREMENT OF HEAT. Ill 

 AIR-SPACES AND HEAT INSULATION. 



From the above description and the illustrations in figures 8, 23, and 

 24, it is seen that the calorimeter chamber and its wooden house con- 

 sist of a series of concentric shells, the inner one of copper being envel- 

 oped by a zinc shell and two wooden shells, with the different shells 

 separated by air-spaces. The important feature of this construction 

 is the insulation against heat. Between the outer and inner wooden 

 structures is the "outer" air-space, and between the inner wooden 

 casing and the zinc wall is the " inner " air-space. Between the two 

 metal walls is still a third air-space. The confined dead air in these 

 spaces is an excellent heat insulator. To render the air in these spaces 

 as nearly ' ' dead ' ' as possible, the panels are made very tight by the use 

 of matched boards, as above described, and at the edges are fitted very 

 closely to prevent escape or entrance of air. Further insulation against 

 heat is provided by coating both surfaces of the inner wooden casing 

 and the inner surface of the outer casing with asbestos paper. This 

 was applied to the surface of the panels by means of the ordinary paste 

 used by paperhangers, and it has shown no tendency to become loose ; 

 the fibrous nature of the asbestos furnishes a very good surface for 

 adhesion. 



It will be seen from the figures showing cross- sections that the up- 

 rights and joists of the framework divide the outer air-space into six 

 separate sections top, bottom, and four sides. The inner air-space 

 surrounding the zinc wall is continuous so far as the construction of 

 the wooden casing is concerned. It has been found desirable, how- 

 ever, in connection with the arrangements for controlling the temper- 

 ature of this space, described later, to divide it into sections. This is 

 accomplished by means of wooden strips, nearly as wide as the space 

 between the metal and wooden walls, running parallel to the floor and 

 the ceiling, one edge of the strip being attached to the inside of the 

 inner wooden wall and the other edge being provided with a felt flap 

 that rests against the zinc wall. The strips are attached to the wooden 

 walls by means of hinges, so that they may be turned up out of the 

 way when the calorimeter chamber is to be rolled out of the wooden 

 house. The strips are shown (/, /, /, /) in figures 23 and 24, and 

 may also be seen in figures 30 and 3 1 . The space above the top of the 

 chamber is divided into one section by the strips at the upper edges, 

 and that below the floor of the chamber is likewise separated into an- 

 other section by strips at the lower edges. The space surrounding 

 the four sides of the chamber is divided into two sections by strips half 

 way between the top and the bottom. 



