260 THE AMERICAN MONTHLY [Sept., 



the stage. It will appear quite structureless at first. In two or 

 three minutes the thickened border will look crinkled and in a 

 few minutes small specks of color will commence, each centre 

 gradually spreading with flower-like crystals, until they meet 

 one another, when they should be quickly mounted in pure 

 Canada balsam. 



As it is advisable to mount them as soon as possible after you 

 have arrived at the state you wish to preserve, the glass cover 

 should be cleaned in readiness, while the slide is being heated 

 on the hot-plate. 



The simplest and most effectual way of cleaning the covers is 

 by making two round cork pads, which should be quite flat and 

 about H across at the back; with a short handle, like a stumpy 

 rubber stamp; the face should be covered with clean chamois 

 leather, pulled tight and tied around the pad with thread. Take 

 a clean cover out of the box with a small pair of tweezers, place 

 it on one of the pads, and rub it well with the other pad turn- 

 ing it over once or twice, when it will become clean. You can leave 

 it between the pads till you are ready to use it whicli will keep 

 it free from dust. 



To mount the preparation in pure Canada balsam; the clean- 

 est and safest way of using it is to have it in a collapsible tube, 

 the tube should be placed on the hot-plate to liquefy the balsam 

 but not be made too hot so as to raise air bubbles. Warm the 

 slide on the hot plate and drop as much Canada balsam on the 

 slide as will fill the circle of the glass cover when pressed down. 

 Should there be any air bubbles, warm the point of a needle and 

 touch them when they will disappear. If the needle point is red 

 hot the large bubbles will break but there will be a quantity of 

 small ones formed very difficult to get rid of. Take the slide off' 

 the hot plate and place it on the card-board guide being care- 

 ful to place the preparation with the thick edge away from you, 

 so that when you put the cover glass down on the balsam, 

 should there be any air bubbles they will readily escape at the 

 thin edge, while they would be imprisoned if the slide were turned 

 the other way. Then take the cover glass out of the pads with 

 tweezers and put it slanting to touch the balsam from the out- 

 side edge, letting it drop onto the slide and press it down to 

 spread the balsam so as to fill the circle and guide it as nearly 

 central as you can. Then put a small brass clip to hold it se 



