at I he total solar Eclipse in 1882 341 



Construction of the Calorimeter. Fig. 3 is a principal 

 section of the instrument by the plane which contains its 

 axis OP and that of the earth QS. The dimensions of the 

 parts are most easily specified by their projections on the 

 axis OP and on a line at right angles to it ; but as the sections 

 at right angles to OP are all circular it will be sufficient 

 specification of the section of the instrument at any point, 

 say B, to give the distance LB on the axis from one extremity 

 L of the steam tube to B, and the radii of which the projec- 

 tions on the axis are the point B. These radii would be, in 

 order from the axis outwards, |, |, 3 and 4 inches. 



In the following table the first line contains the points on 

 the axis, the second contains their distance from Z, the lower 

 extremity of the steam tube, the third contains the radius of 

 the innermost circle, the section of the steam tube, and the 

 following lines contain the radii of the other circles in ascend- 

 ing order. 



The measurements are given in British units, because these 

 were used in its construction. The construction of the reflector 

 will be described later. The mirrors are carried on arms of 

 sheet brass which spring from a piece of brass tube which fits 

 telescopically over the condenser tube. Their outer extremities 

 are kept in position by being fixed to a flat ring of sheet brass, 

 -inch wide. Each mirror is made of a properly shaped band 

 of " reflector-metal," that is, of sheet copper to which a sheet 

 of silver has been made to adhere by being rolled under great 

 pressure. It is then bent round until its edges abut, when 

 they are soldered together 1 . 



The main condenser is the tube KC, 12 inches long and 

 2 inches in diameter. Out of it at the top springs the boiler 



1 In the original memoir it was erroneously stated that the silver of the mirrors 

 had been electrolytic-ally deposited on the copper. 



