306 



SUMMARY OF CURRENT RESEARCHES RELATING TO 



wires and hooks are e/, e'/', and m n, and the incandescent carhon 

 at C. For the smaller lamp two, and for the larger three Bunsen or 

 Grove elements (20 cm.) are sufficient. If it is desired to throw a 

 strong light on the object, part of the lamp may be silvered, as at a ?> d, 

 or opal glass may be used if less illumination is required. The 

 great steadiness of the lamps renders them specially serviceable for use 

 with the Vertical Illuminator, and they can obviously be very conveni- 

 ently applied at the side of the Microscope. If a very intense beam of 

 parallel rays is required to be thrown on the object, an Abbe or other 

 condenser should be used and the lamp placed exactly in the focus. 

 For photo-micrographic purposes a camera similar to that of B, 



fig. 49, can be used, a h being the box for the plate, and the whole being 

 attached to the body-tube by the screw c. Dr. Stein is somewhat 

 enthusiastic on the use of the electric light for photo-micrography and 

 urges that all microscopists should employ it. He has photographed 

 Pleurosigma angidatum x 500 with an exposure of only 70 seconds, 

 and an incandescence lamp of five volts. 



Dr. Stein has recently designed the battery figs. 53 and 54 

 specially for use with the Microscope. Holding 300 gr. of bichro- 

 mate solution it will actuate for two hours lamps of 2-8 volts 

 and 1-6 candles. The speciality of the battery is the contrivance, 

 f X 8 n g y t,iov lifting the cells a ?* up and down to increase or 



