350 



DRAWING WITH HOUSE CURRENT 

 AVOIDANCE OF HEAT 



[On. X 



504. When the small currents from the house circuit are used 

 the heat is not great enough to injure most specimens mounted in 

 balsam. For live objects and objects mounted in glycerin or 

 glycerin jelly, etc., it would be wise to place a water-cell in the beam 

 before it reaches the microscope (see 364, 3Q4a, fig. 206). 



FIG. 196. 



DRAWING OUTFIT FOR THE HOUSE LIGHTING SYSTEM WITH A 

 BLACK CLOTH TENT OVER THE MICROSCOPE. 



This arrangement answers well for a moderately lighted room. Naturally 

 the opening for drawing should face toward some dark furniture or the dark 

 side of the room, not toward a window. 



5 Separable cap to attach to the separable plug in a socket of the house 

 lighting system. 



w r One of the supply wires cut and inserted into the binding posts of the 

 rheostat (see fig. 188). 



/ Small arc lamp for supplying the illumination. It is at the level of the 

 mirror and at right angles to the microscope. 



m Mirror of the microscope. 



t Cloth tent over the microscope. It appears semi-transparent as it was 

 left in position during but part of the time when the photograph was 

 taken. 



