178 PROFESSOR H. L. SMITH ON A NEW METHOD OF 



pressed home, the whole may at once, without any danger of its 



"running in," be finished with the black varnish. Nothing can 



exceed the soft and delicate appearance of these wax backgrounds, 



nor can a cell be built up in any manner more readily. I use the 



sheets prepared for wax flowers, and of course colours may be 



selected to suit the object. The disks are punched by a solid 



plunger, which must frequently be cleaned by punching disks from a 



thick card either oiled or prepared with a little turpentine. Care 



will enable one to prepare these rapidly. The thin cells for large 



Diatoms, &c, to be mounted dry, I make as follows : — The wax 



disk — in this case say bright red — is put under another press, and 



the centre punched out, leaving a ring of wax. With my own 



press I do this readily, and I will try to describe, as well as I can 



without a figure, the operation. Concentric with the hole that 



receives the plunger to force out the centre of the wax disk is a 



larger hole (the same size as the wax disk) in a brass plate, the 



plate being a trifle thicker than the wax disk ; this plate is, say two 



inches long, and can be turned aside from over the hole in the bed 



plate of the press, on a screw, or pin, inserted near one end. 



Above this brass plate is another turning on the same pin, but 



having a hole only just the size of the solid plunger. The operation 



is as follows : The lower brass plate is brought into place, its hole 



concentric with the hole in the bed plate (this is determined by a 



limiting pin inserted in the bed plate) ; the wax disk, wetted in the 



mouth, is now dropped in, and the upper plate swung round over it, 



the hole in the latter of course coming into place against the 



limiting pin so as to receive the plunger. When the plunger is 



forced down, a ring of wax is left on the bed plate, and on swinging 



round the lower brass plate this ring drops out free. The only 



precaution is to keep the wax from sticking to the edges of the 



plunger and of the die (simple wetting will answer admirably, and 



will enable one to make these rings very nicely); if water is used, the 



steel plunger must afterwards be dried and oiled. Suppose now the 



rings made. We place one on the centre of a slide, putting upon it 



a piece of oiled paper (so dry as not to leave marks on the slide) ; 



press the wax forcibly on to the glass, and burnish it with the nail, 



or an ivory handle, not so hard, however, as to press it out of shape. 



The object is now put in the cell (or, if Diatoms, mounted on the 



cover), and the cover applied— it should be the same size as the ring, 



and may be held in place by one of the ordinary spring clips ; next, 



