222 



THE AMERICAN MOKTHLY 



[December, 



Electric Light for the Microscope. 



An article upon this subject was 

 promised some time ago, but in the 



Fig. 30. — Incandescent Lamps. 



hope of having an opportunity to 

 the qualities of the incandescent la 

 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 

 ob servations 

 before long. 

 The cuts il- 

 1 u s t r a t i n s: 



test 

 mp 



this article have been copied from 

 the Zeitschrift fiir Alikroskopie^ 

 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 reduced. 

 In these the ordinary carbon filament 

 is replaced by a spiral of platinum 

 wire, which is heated to incandes- 

 I cence by the electric current. These 

 j lamps may be made of common glass, 

 I or, to modify the light, of opal glass. 

 j The manner of attaching the lamps to 

 I a miscroscope is shown in the elabo- 

 rate arrangement in Fig. 31. The 

 I larger lamp sei^ves 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 current 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 w^ith- 

 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. In the stage, 

 beneath the 

 object, there 

 is a spiral 

 of platinum 

 (b), which 

 becomes 

 heated when 

 the curi'ent 

 is allov^^ed to 

 pass through 

 it. The heat- 

 ^^ ing can be 

 ff p erf act ly 



Fig. 31. — Microscope with Electric Light. 



