320 



MANIPULATION. 



Fig. 217. 



instead of a larger piece. In the fifth is ex- 

 hibited the method of mounting, so that the 

 side of the object as well as the front may be 

 examined. 



When it is necessary that both sides of an 

 object should be viewed, a disc, an inch or 

 more in diameter, may be used, out of which 

 a small disc has been punched, as shown by 

 fig. 218, but not exactly in the centre; through 

 the broad part the pin is passed, and the ob- 

 ject may be cemented to one of the sides, or 

 what is better, if it can be managed, is to 

 separate, by means of a penknife, the chamois 

 leather from one of the cards, and into this 

 fissure to place the object, the application of a 

 little cement being required to keep it there. 

 Supposing the object to be a portion of fern, this 

 plan will enable an observer to view both sides 

 of it, or even look through it, and if at any time the disc were 

 laid flat on the table, the object would be preserved from 

 ^ injury by being situated in a plane inter- 



T mediate between the two outer sides. Sup- 



I posing very small discs are required, Mr. 



^||H^^^ George Jackson has devised an excellent 

 ^^^^^^1^^ method, whereby with pins and black seal- 

 ^H I ing-wax some useful ones may be made in 



^^^k^ ^^ the following way : — Take a long pin and 

 ^^Bjl^^^ slightly warm it in the middle, then take a 

 j stick of black sealing-wax and melt it in 



the flame of a candle or spirit lamp; having 

 put a small quantity upon the middle of 

 Fig. 218- the pin, hold the latter either in the flame 



of the lamp or near it, and as the wax melts, revolve the pin 

 on its axis ; if this be done rather quickly, the sealing-wax 

 win be equally distributed about the pin, the pin then should 

 be immediately removed from the flame, and placed upon 

 a piece of glass, and the wax pressed upon by another piece of 

 glass, so as to convert the globule into a flat disc. Upon 



