160 THE AMERICAN MONTHLY [May 



light so very effective as magnesium. The rapidity and 

 power of its action, its cleanliness, and the ease with 

 which it can be used is ail in its favor. Why waste min- 

 utes of valuable time with oil lamps, when a second or 

 two will do the same thing with magnesium ? With the 

 above mentioned 70 mm. objective when I am photograph- 

 ing a transparent object I usually have to place two sep- 

 arate pieces of obscured glass between the light and the 

 object, as otherwise, however small a piece of ribbon I 

 burn, my plate would be overexposed. I do not need to 

 allude to any of the other methods of illumination as I 

 have practised this one now for so long and find it so 

 well adapted to the end in view by its simplicity and 

 cheapness, that I regard every other, except sunlight, as 

 inferior to it in every way. I invariably use Ilford Or- 

 dinary or Empress plates, as from the photo-micrographs 

 I made of the granulation of the silver in these plates 

 which were exhibited at a meeting of the British Astron- 

 omical Association two years ago, I found the silver in a 

 finer state of division in them than in those of any of 

 the other makers. — I. A. M. 



Cleaning Glassware. 



[From V. A. MooRE's Bacteriology.] 



It is necessary that the glassware employed should be 

 thoroughly cleaned before it is used. Several special 

 methods have been suggested for this purpose but the 

 one frequently employed, by chemists seem to be the most 

 easily handled and quite as efficient for general use as the 

 more elaborate, specialized processes. It consists in ap- 

 plying the chromic acid cleaning mixture after washing 

 the tubes and flasks with water. It is sometimes neces- 

 sary to employ other methods for cover-glasses which are 

 to be used in staining bacteria where a mordant is re- 

 quired. Clean all of the glassware, test tubes, fermen- 



