b H. MORLAND ON MOUNTING SELECTED DIATOMS. 



depth -j^ inch from either end, the die being afterwards sawn 

 from the ends a little beyond the drilled holes. A hole is 

 drilled through the centre of the die, by which the same can 

 be fastened down on a board or table as may be desired. 

 The die must, of course, be finished off by being duly hardened 

 and tempered. The punch consists of a piece of steel drill- 

 rod (Fig. 3) accurately fitting the small hole, with one end 

 filed off perfectly square, and the other end provided with a 

 brass or copper head driven on for receiving the blows when in 

 use. 



I may say that the die as shown is doubly reversible, viz., end 

 for end and top for bottom. To use the die and punch, enter 

 the latter in one of the holes as far as the upper edge of lower 

 saw-cut, and, after placing the thiii copper in the saw-cut, tap 

 the punch lightly with a very small hammer, when a small 

 copper disc will be pushed out below. After a supply of discs 

 has been punched out they will require flattening as they leave 

 the die slightly cupped, which adds to their height. To flatten 

 them I simply place a dozen or so on a thick glass slip, and 

 with another thick slip press them flat. It is as well to boil 

 the discs in soda to free them from any grease, and then to 

 pickle them a short time in aqua fortis, finally washing them 

 well in several changes of boiling water to get rid of all traces 

 of acid, drying off in a hot oven and corking them in a dry 

 specimen tube to preserve them from damp, which otherwise 

 would cause these copper discs to slightly oxidize and tinge the 

 balsam green when in use. 



