28 The Microscope. 



will be found to be baked just right unless the fire is very hot 

 indeed ; this can however be remedied by leaving the door open 

 a little way. 



The balsam when baked just right, will be found to chip off 

 readily with a knife, with a slight tendency to be tough next to 

 the edge of the cover glass. The slide can be best cleaned with 

 a sharp pointed pen knife, and while cleaning, an old tooth 

 brush is of great service to brush off" the dust and chips to see 

 ■what you have been doing. After roughly cleaning in this raan- 

 mer I take a shallow dish, fill it with alcohol, and with a short 

 stubby camel's hair brush, go over the whole slide and cover 

 until it is judged to be clean, when it is put in a large dish of 

 water. After all the slides have been cleaned in this manner, I 

 take one by one and wipe dry with a towel. They are now 

 ready to be ringed. No slide intended to be kept permanently, 

 should fail to be well ringed, as the balsam may evaporate, and 

 the mount is much more liable to become loosened, to say noth- 

 ing of the finished appearance the ring gives a slide. Whatever 

 is the cement used, the first coat or two should be of some kind 

 of a transparent cement, as should it run under the cover it will 

 not show difi'erently from the balsam, while a colored cement 

 will. 



The following formula for a transparent cement, copied from 

 ■" Packard's Entomology for Beginners " has been found so good 

 that I can recommend it. 



Gum dammar 5 drams. 



Gum mastic 3 " 



Canada balsam (dried) 3 " 



Chloroform 1 fluid ounce. 



Spirits of turpentine 1 " " 



Mix ; dissolve by shaking occasionally, and filter through paper. 



This cement can, if desired, be thinned by adding a few drops 

 of an anilin dye, dissolved in alcohol ; red, green, violet and 

 brown are good. 



The heavier the ring the safer is the mount. I generally put 

 on two coats of the transparent cement, and finish with two or 

 three coats of the tinted, letting them dry a day or two between 

 each coat. A slide prepared in this manner, and finished as de- 

 scribed, will be as permanent as the glass slide on which it is 

 prepared. 



