OF CRYSTALS AND OTHER BAD CONDUCTORS. 
501 
IV. Various Bodies Constantly Used in Physical Work. 
Where no diameter is given the plate is of irregular shape, and rather larger than the section 
of the bars. 
Shellac Plate, '068 cm. thick. Air, 14 0, 2 C. 
This plate was made between two microscope slides having plane surfaces. One 
slide was placed horizontal, and the upper surface covered with a smooth sheet of 
tinfoil. On the foil was laid a sufficient number of the thin films of shellac supplied 
by varnishmen to make a plate of the requisite size and thickness. The slide was 
then warmed gently from underneath till the shellac was soft, and the cold slide 
brought down on to the soft mass. In order to get the requisite thickness, and the 
surfaces of the plate parallel to each other, the two slides were kept apart by two 
short lengths of wire '068 cm. diameter laid across the lower slide near its ends, the 
upper slide being pressed against these. The tinfoil which attaches itself to the 
plate is readily dissolved off by mercury. This method is very convenient and gives 
excellent plates. 
Cool bar. 
Hot bar. 
v x 746 Aj 7'40 
v, 3-32 Q x 4183 
7 4183 x '068 x 1-001 
v x 20 95 Ao 2046 
v. 2 28-74 Q, -1159 
T -1159 x -068 x 1-001 
^ ~ 20-76 - 7'40 x 1-002 “ 000604 
3 ~ 20-76 x 1-002 - 7-40 _ UUUwU0 ' 
k mean = '000596. 
Paraffin Plate, '038 cm. thick. Air, 13 0, 4 C. 
This plate was made by dropping a little melted paraffin on to the cold upper 
surface of the lower slide, and placing the upper slide on it as described above. The 
cold surfaces are sufficient to ensure the paraffin being detachable from the glass. 
Cool bar. 
Hot bar. 
v x 8-90 A x 9-19 
v 2 4-49 Qj 4378 
j 'I 378 x -° 38 x 1 0002 
v x 18-10 A, 17-87 
v 2 26'48 Qn '1407 
, -1407 x -038 x 1-0002 „ 
~ 17-87 - 949 x 1-0006 ~ 000604 
~ 17-87 x 1-0006 - 9-19 “ UWDio 
k mean = •000610. 
