PREPARATION AND MOUNTING OF DOUBLE STAININGS. 157 



the cover. Therefore, as soon as a balsam mounting is dry enough 

 to have the superfluous balsam cleaned off with the point of a 

 knife around the thin glass cover, which will be in two or three 

 days, especially if aided by heat, a light coating of shellac 

 cement, colored with aniline blue or red, riot green or yellow, 

 can be spread with a camel's hair brush around the edge of the 

 cover, and the next day another coating, and perhaps the third 

 day another still. In this way the cover will soon be firmly set 

 and can be cleaned ; and the slide is a permanent mounting in 

 much shorter time than if left simply for the balsam to dry hard ; 

 and there is no risk of air working in from the drying of the 

 balsam. Canada balsam is by far the best and safest medium in 

 which to mount all stained preparations that will bear this 

 mounting. But there are many, such as those with delicate 

 hairs or glands, or with fine cellular markings, that will not 

 show to advantage in so refractive a medium as balsam. These 

 may be removed from alcohol into water containing three or 

 four drops of carbolic acid to the ounce of water. It will be 

 necessary also to mount them in the same fluid in the cells. 

 Well dried shellac cells may be used ; and if the tops are made 

 perfectly level by holding a bit of fine sand paper on them while 

 being turned on the turn-table, the thin glass cover will fit 

 closely, pressing out the superfluous water, which can be taken 

 up with a camel's hair brush. When well dried in this way, a 

 little gold size can be applied to the edges with perfect safety 

 against its running in. A very simple and almost universally 

 applicable cell I have recently made in the following manner : 

 My friend Win. Streeter, foreman in the works of Sargent & 

 Greenleaf, of Rochester, makes a neat little double punch for 

 the purpose of cutting out narrow circles from the thin colored 

 sheets of wax used by artificial flower-makers. Either single, 

 doubled or three-folded sheets can be used, according to the 

 thickness of cell that may be required. These circles may be 

 fastened on the slide, either by shellac cement or by simply 

 warming the slide. Then over all the cell, both inside and out, 

 a coating of gold size or of marine glue dissolved in coal naphtha, 

 must be spread with a camel's hair brush. When this is dry we 

 have a cell beautifully colored, and proof against all the fluid 



