cork if preferred, rests upon the centre of the cover-glass. A 

 little change in the curve of one or both of the plates at e, will 

 give any necessary change of pressure upon the slide or the cover. 

 An easy way to form this clamp is to cut strips of the metal as 



Fig. 113. 



long as from a to /, and as wide as at c. One is then bent upon 

 itself at c, and hammered down flat ; it is then tiled, in a vice, 

 with a uniform taper to a; the spring d is then bent up and the 



Fig. 114. 



curve e, formed with a pair of wire-nippers, and finally the long, 

 straight spring turned up at right angles at b. Fig. 113 is drawn 

 to natural size ; fig. 114 is two-thirds natural size. 



Preserving Alce. — Mr. Thomas Palmer contributes to "Sci- 

 ence Gossip " his method of preserving algae as microscopic spec- 

 imens. The seaweed is first washed in fresh water, which is left 

 running so as to be continually changed, until the salt is entirely 

 removed. It is then partially dried with blotting paper, and pre- 

 served in pure alcohol until wanted for mounting. For mounting 

 it is transferred through chloroform to balsam. This method sac- 

 solution of logwood. 



Mounting Selected Diatoms.— F. Kitton highly compliments 

 slides received from Herr Weissflog, in which the selected diatoms 

 ("not arranged in patterns, the doing which is a shameful waste 

 of time") are mounted on a thin cover and then inverted over a 

 cell consisting of a thin silver disk, of the same size as the cover, 

 and perforated with a small central opening, often as small as *S 

 inch. The object in this tiny cell is easily found, stray light is 

 largely cut off, and a very neat mount is produced. 



