186 



THE MICROSCOPE AND ITS BEVELATIONS. 



the heated glass from contact with its surface. For holding-down cover- 

 glasses whilst the balsam or other medium is cooling, if the elasticity or 

 the object should tend to make them spring-up, the wire Spring-Clip 

 (Fig. 128), sold at a cheap rate by dealers in Microscopic apparatus, will 

 be found extremely convenient. Or, if a stronger pressure be required, 

 recourse may be had to a simple Spring-Press made by a light alteration 

 of the ' American clothes peg ' which is now in general use in this country 

 for a variety of purposes; all that is necessary being to rub down the 

 opposed surfaces of the 'clip' with a flat file, so that they shall be parallel 

 to each other when an ordinary slide with its cover is interposed between 

 them (Fig. 129). One of these convenient little implements may also be 



FIG. 129. 



Spring-Clip. 



Spring-Press. 



easily made to serve the purpose of a Slider-forceps, by cutting back the 

 upper edge of the clip, and filing the lower to such a plane that when it 

 rests on its flat side, it shall hold the slide parallel to the surface of the 

 table, as in Fig. 127. 



179. Mounting Instrument. A simple mode of applying graduated 

 pressure concurrently with the heat of a lamp, which will be found very 

 convenient in the mounting of certain classes of objects, is afforded by 

 the Mounting instrument devised by Mr. James Smith. This consists of 

 & plate of brass turned up at its edges, of the proper size to allow the 

 ordinary glass slide to lie loosely in the bed thus formed, this plate has a 

 large perforation in its centre, in order to allow heat to be directly applied 

 to the slide from beneath, and it is attached by a stout wire to a handle 

 -(Fig. 130). Close to this handle there is attached by a joint an upper 



Smith Mounting Instrument. 



wire, which lies nearly parallel to the first, but makes a downward turn 

 just above the centre of the slide-plate, and is terminated by an ivory 

 knob; this wire is pressed upwards by a spring beneath it, whilst, on the 

 other hand, it is made to approximate the lower by a milled-head turning 

 on a screw, so as to bring its ivory knob to bear with greater or less force 

 on the covering glass. The special use of this arrangement will be ex- 

 plained hereafter ( 210). 



180. Dissecting Apparatus. The mode of making a dissection for 

 Microscopic purposes must be determined by the size and character of the 

 object. Generally speaking, it will be found advantageous to carry on 



