1887] Microscopy. s 599 
point where the flame acts upon the copper plate the temperature 
will remain steadily at about 56° C. (133° F.), with the tempera- 
ture of the room at 22° C., or 71° F. As long as the tempera- 
at the same point. This constancy is due to the fact that the 
heat which is conducted through the copper plate with constant 
rapidity from its source—the burner—is radiated into the sur- 
nearly constant. 
In order to use the paraffine itself as an indicator of the proper 
temperature, and in that way dispense with a thermometer alto- 
gether, if desirable, it was necessary to use a new type of cup in 
which to melt the paraffine. The paraffine-cup or trough (P) 
shown in the figure is made of copper, tin-lined, and is six inches 
e flame. _ 
ions and possibilities of this new device will be 
z, A $ a f 
