166 
IOWA ACADEMY OF SCIENCE 
For temperatures near that of the ordinary laboratory tem- 
perature, the bath is heated by means of an immersed incan- 
descent lamp and the temperature electrically controlled by 
means of a contact toluene regulator in series with a telegraph 
relay and battery. For temperatures considerably above that 
of the room, a second lamp is connected in parallel with the first. 
By applying the heat from a Bunsen burner the bath may be 
quickly heated and adjusted to any desired higher temperature. 
Owing to the presence of the small cylinder, B, the bath is 
Fig. 4. — Diagram of heating apparatus. 
