APPARATUS, MATERIAL, AND REAGENTS. 



61S 



Collapsible tubes, for containing Canada balsam ; very serviceable for 

 transport and general use. 



Turn-table for sealing cover-glass preparations, with rings of cement. 



Boxes for preparations, book-form. 



Tickets and labels, various sizes. 



Soft rags or old pocket-handkerchiefs, for removing cedar oil from 

 immersion lens, cleaning cover-glasses, etc. 



Chamois leather for wiping lenses. 



Warm Stages. — In addition to those already described, Schafer 

 and Strieker have constructed warm stages for accurate observations. 

 Schafer's apparatus consists of a vessel (/), filled with water which 

 has been boiled to expel the air, and heated by means of a gas-flame 

 at g. The warmed water ascends the indiarubber tube (c) to the 



Fig. 246. — Schajbr's Wakm Stage. 



brass box (a). The box is pierced by a tubular aperture to admi1> 

 light to the object, and has an exit tube (c'), by which the cooled 

 water from the stage returns to be reheated by the flame g. At d 

 is a gas-regulator, so that a constant temperature at any desired 

 point- can be maintained. 



Strieker's stage, in which warm water or steam can be used for 

 heating, and by the employment of iced water also used for observing 

 the effects of cold, is shown in Fig. 247. It consists of a hollow 

 rectangular box, with a central opening (G) permitting the passage 

 of light. The water makes its exit and entrance at the side tubes 

 (a, a), and the temperature is indicated by a thermometer in front. 



