The Mickoscope. 281 



TECHNOLOGY. 



TIN-FOIL CELLS. 



C. M. Vorce, F. R. M. S., of Cleveland, says : Tin foil 

 cells are extremely useful, and may be had of almost any desired 

 thickness, up to that of sheet-lead. A cheap die for cutting cells 

 can be made of three or four thicknesses of " telescoping tubing," 

 which can be had from the tube- drawers. The tubes, when 

 fitted, are to be cut into two lengths and "faced off" square 

 and smooth, the outermost tube being left longer than the others. 

 By putting a piece of foil on the squared ends of one set and oppos- 

 ing to it the squared ends of the other set, then forcing over all the 

 outer tube a disk will be cut off, then by pushing through each 

 alternate tube of the set, a series of rings will be cut out, leaving a 

 solid central disk, very useful for making diatom-cells for arranged 

 diatoms, by means of the punch previously described by me (in 

 1879) in the club letter- packets. The punch referred to consists of 

 a brass rod with central hole fitted by a steel wire; the rod sawed in 

 two, and turned into a disk and counter. — Note Book Am. Postal 

 Micro. Club. 



Acid Chromo-Osmic. — Dr. Max Flesch recommends the follow- 

 ing: 



Osmic acid, - - 0.10 



Chromic acid, - 0.25 



Water, - - - 100.00 

 The object may remain in this solution from 24 to 36 hours. It is 

 then washed in water, and placed in alcohol. — Jr. de Micrographie. 



ABSTRACTS. 



O. SCHULTZE'S METHOD OF PREPARING THE 

 AMPHIBIAN EGG. 



For hardening-fluids the following mixtures were found to give 

 perfectly satisfactory preparations when used in the manner described 

 below : 



1. Chrom-osmio-acetic Acid. 



Chromic acid (1 per cent.) 25 parts. 



Osmic " (1 " ) 10 " 



Water 16 " 



Acetic acid (2 per cent.) 5 " 



