222 



THE AMERICAN MONTHLY 



[December, 



Electric Light for the Microscope. 



An article upon this subject was 

 promised some time ago, but in the 



Fig. 30. • 



f e 



-Incandescent Lamps. 



hope of having an opportunity to test 

 the qualities of the incandescent lamp 

 in practical 

 work we 

 have deferred 

 its publica- 

 tion until 

 now. We are 

 still unable 

 to add any 

 results from 

 our own ex- 

 perience, but 

 hope to sup- 

 plement the 

 present arti- 

 cle with such 

 observations 

 before long. 

 The cuts il- 

 lustratin sr 



this article have been copied from 

 the Zeitschrift fur Mikroskopie^ 

 where the apparatus is more fully 

 described. 



In Fig. 30 are represented the in- 

 candescent lamps as provided for this 

 purpose by Miiller, in Hamburg, of 

 natural size, or only slightly i^educed. 

 In these the ordinary carbon filament 

 is replaced by a spiral of platinum 

 wire, which is heated to incandes- 

 cence by the electric current. These 

 lamps may be made of common glass, 

 or, to modify the light, of opal glass. 

 The manner of attaching the lamps to 

 a miscroscope is shown in the elabo- 

 rate arrangement in Fig. 31. The 

 larger lamp serves for opaque objects, 

 the smaller is beneath the stage. ' A 

 system of wires passes beneath the 

 microscope, which affords a means of 

 regulating the strength of the 

 current ; but this part of the 

 arrangement need not be de- 

 scribed. 



It is said that the cun^ent from 

 two Bunsen or Grove cells of 

 20 cm. height, or two Grenet's 

 cells, such as that shown in Fig. 

 33, will serve to light these 

 lamps. We are not told, how- 

 ever, how long the necessary 

 current will be sustained with- 

 out changing the material in the 

 cells. 



The lamp may also be mount- 

 ed on a separate support, such 

 as is shown in Fig 32. 



One feature of the arrange- 

 ment shown in Fig. 31 deserves 

 especial notice. \\\ the stage, 

 beneath the 

 object, there 

 is a spiral 

 of platinum 

 (b), which 

 becomes 

 leated when 

 the current 

 H is allowed to 

 pass through 

 it. Theheat- 

 i w^ can be 

 'S perfectly 



Fjg. 31. — Microscope with Electric Light. 



