314 MANIPULATION. 



Second Method. — Many persons adopt the plan of fixing the 

 cover to the slide by means of paper pasted over both, a small 

 hole is cut out of the centre of the paper for the object to be 

 examined; it has, however, been found in practice that all 

 preparations so mounted are very liable to the growth of 

 confervEB about them, occasioned by the moistening of the 

 paper by the employment of paste or other cement. A 

 preparation mounted after the manner of that first described, 

 with cement round the edges of the cover, will look very neat, 

 and be rendered much stronger by the addition of paper, 

 especially such as that employed by Mr. Topping and others 

 for the purpose, or that of which a specimen is given at the 

 end of a recent publication, entitled Microscopic Objects. 



Test objects are generally mounted with a very thin glass 

 cover, which is kept on with paper ; a much better plan, how- 

 ever, has been lately contrived by Mr. W. S. Gillett, whose 

 skill in these matters is so well known. In mounting the 

 siliceous loricae of Navicula hippocampus and angulata, the 

 scales of the podura and other insects for test objects, he has 

 found it necessary to employ, not only the thinnest kind of 

 glass for covers, but for the bottom plates also, as it be- 

 comes of the greatest importance that the powers employed 

 with the achromatic condenser should be high, and be brought, 

 therefore, as near the object as possible, the two best plans 

 adopted by Mr. Gillett may be here described. In the 

 first, two square pieces of the thinnest glass, of unequal size, 

 having been provided, the object is to be placed upon the 

 under surface of the smaller square, which is intended to form 

 the top or cover, a small piece of wax is now to be applied to 

 each comer, and the top may then be laid upon the bottom 

 piece, the wax serving to keep the two glasses together. 

 Two thin pieces of some kind of close-grained wood, three 

 inches long, one wide, and about one-tenth thick, as shown at 

 figs. 210 and 211, are also to be provided. Fig. 210, a h, 

 represents the outer surface of one of these; in the middle 

 there is an aperture, half-an-inch or more in diameter, whose 

 margin is bevelled oflf, as shown at c. Fig. 211, d e, exhibits 

 the inner surface of the corresponding piece, and At f f are 



