218 THE AMERICAN MONTHLY [June 



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 Diaphrag-m and 

 capable of furnishing- lig-ht of sufficient angle and intensity 

 to bring out the full efficiency 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 ang-le. 

 Adjusting- screws are provided to take 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 g-rades 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-g-lass 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. — Ag-ood cement for fastening- the 

 g-lass sides into the frame for an aquarium may be made 

 by melting- tog-ether in an iron vessel 1 pound of g-utta- 

 percha and 2 pounds of common pitch. The Techno- 

 Chemical Receipt Book g-ives the following-: Mix 9 parts of 



