32 Richards . — The Evolution of 
surface upon which the warmth may act. An element of 
this form, made out of iron wire of about i mm. and German- 
silver wire of about *75 mm. in thickness, beaten out to form 
points about 6 mm. in width at the widest point, was the one 
employed (see woodcut). Before use care was taken that it 
should be thoroughly coated with shellac to protect it from 
possible chemical action, and a large part of the element, 
where it would be likely to come in contact with the hands 
or other outside object, was covered with thick strips of cork 
cemented on with sealing-wax. 
Diagram of the thermo-electric element employed ; somewhat reduced. The 
shaded portion and the outer straight wires are of iron : the inner bow of German- 
silver. 
The galvanometer was one of the usual mirror-type, with 
scale and telescope, of which no especial description is neces- 
sary. The distance of the scale and telescope from the 
galvanometer itself was about 2*5 metres, but the telescope 
was sufficiently powerful to make each division of the scale 
appear as much as 3 millimetres across, so that a quarter or 
