PREPARATION OF OBJECTS FOR THE MICROSCOPE. 151 



around the edges will make the glass attach itself to the cell so 

 that it can hardly be moved. Then, with a small camel's hair 

 brush, take up the outside fluid, squeezing the brush between the 

 thumb and linger to dry it. When as dry as the brush will make 

 it, apply a coating of the marine glue around the edges of the 

 glass cover, and the slide is finished, so far as its safety and dur- 

 ability is concerned. 



In looking over and arranging my cabinet of specimens not 

 long since, I was greatly surprised at the great number of slides 

 that were merely opaque mountings fully one-half, I should 

 say. Now this implies that I have found as much beauty in 

 natural unprepared objects as in those which have been in some 

 way carried through a process of preparation, such as staining, 

 cleaning in potash or acids, carrying through alcohol and turpen- 

 tine into balsam, etc. There is an exhaustless field of attractive 

 objects in the scales of the insect tribes, the feathers of birds, 

 the shells of the protozoans, the spore cases of mosses and ferns, 

 the hairs and glands of plant leaves, in seeds and pollen. All 

 these require mounting as opaque objects ; and, in my view, the 

 best way to do it is to make cells either of shellac cement or of 

 the wax sheets, as I have already described, and in the center of 

 them paint with Brunswick black a round disk three-eighths or 

 one-half of an inch in diameter. On this disk, when thoroughly 

 dry, fasten the object with a minute drop of marine glue, and 

 fasten a thin glass cover on the cell with the same Cement. With 

 this form of mounting, the Lieberkuhn can be used or not, as 

 one may desire. I have found it necessary in almost every case 

 of dry mounting to leave a small opening into the cell, either by 

 filing a little notch on the ring and leaving this open when the 

 cover is cemented on, or by afterwards pushing a small cambric 

 needle through the ring. If the cell is hermetically sealed, the 

 expansion and contraction of the air within, by changing temper- 

 ature, seems to cause a slow movement in the cements that are 

 inside of it, no matter how much they have been previously 

 dried. The walls of the ring or the finishing varnishes will work 

 inward and spoil the mounting, or the object will be slowly 

 immersed in the black cement that forms the background. All 



