THE MICROSCOPE AND ITS PARTS. 33 



To permanently mount dry objects, such as pollen, 

 seeds, scales from insect wings, and other things suita- 

 ble for this method of preservation, arrange the specimen 

 in the cell, place the cover over it preferably a circle in 

 this case, the diameter of the cell being a little greater 

 than that of the cover so that the cement shall project 

 a short distance beyond the edges of the thin glass, and 

 with a camel's-hair brush paint a thin layer of shellac 

 over the place where the cover and ring meet. There 

 should be but little cement on the brush for the first 

 coat, because if too much is used, or it is too thin, it 

 will probably run into the cell by capillary attraction 

 and spoil the object. This is one great trouble in all 

 microscopical mounting. But after the first coat is dry, 

 another is to be added, and repeated until the cover 

 is firmly fastened to the ring. "Brown's Rubber Ce- 

 ment," for sale by the dealers, is useful for this pur- 

 pose, as it is very fluid, dries with great rapidity, and 

 has little tendency to " run under." 



The cell having been made, the object is to be placed 

 within it in a drop of water, the thin cover dropped 

 over it, and the preparation will then be ready for ex- 

 amination. But how is this minute, generally invisible 

 object to be got into the cell ? A glass tube about one- 

 tenth inch in inside diameter, and as long as may be 

 convenient, several needles in wooden handles, and a 

 camel's-hair brush, with a small smooth stick thrust into 

 the quill, will be needed. 



The needles are used for spreading any small mass 



