218 THE AMERICAN MONTHLY [Juue 



bed .5 millimeters thick. The action and arrang-ement of 

 the sub-stag"e is clearly shown by the cut and is of the 

 most improved pattern, fitted with an adjusting- screw of 

 fine pitch admitting- of the most delicate adjustment, of 

 condenser. The mirror is two sided plane and concave, 

 and adjustable in all directions. Condenser, of larg^e size 

 of the double lens system, fitted with Iris Diaphragm and 

 capable of furnishing lig-ht of sufficient angle and intensity 

 to bring out the full efficieticy of the finest oil immersion lenses. 

 A ring- is provided below the iris diaphrag-m into which a 

 blue or g-round g-lass may be slipped when artificial lig-ht is 

 used. Coarse adjustment by rack and pinion. The rack 

 is of the finest workmanship, with teeth cut at an angle. 

 Adjusting- screws are provided totake up and wear that 

 may be caused by long continued use of the instrument. 

 The fine adjustment is by micrometer screw. 



The eye pieces and objectives furnished with this stand 

 are Reichert's standard quality. For sale by Richards & 

 Co.. limited. 



MICROSCOPICAL MANIPULATION. 



Gold and Bronze Paints. — The liquid employed with 

 which to mix the bronze powders- (which can be boug-ht of 

 all grades and shades of color) is, for ordinary indoor work 

 dextrin (400 g-.), containing- potassium bichromate (1 g-.) 

 and sufficient water. Use 65 g-. of bronze powder. For 

 more permanent work dilute water-glass may be used. 

 Borax-shellac solution, mixed with one-third alcohol, also 

 is used, something- like this: Bronze powder, 55 parts; 

 alcohol, 10 parts; borax-shellac solution, 25 parts. Or dis- 

 solve a dammar in benzol and neutralize with solution of 

 potassa by shaking- tog-ether and allowing to separate. 



Aquarium Cement. — A good cement for fastening the 

 glass sides into the frame for an aquarium may be made 

 by melting together in an iron vessel 1 pound of gutta- 

 percha and 2 pounds of common pitch. The Techno- 

 Chemical Receipt Book gives the following: Mix 9 parts of 



