MOIST OBJECTS. 15 



watery contents. Hence only those objects can be 

 preserved in glycerine, which are not too transpa- 

 rent, and which are sufficiently firm to resist the ten- 

 dency to collapse. 



When the objects are tolerably flat, and suffi- 

 ciently firm to bear the pressure of the cover, they 

 may be mounted by adding a small quantity of gly- 

 cerine to them lying on a slide; the cover is then 

 applied, and a little of the cement mentioned below 

 applied warm with a hair-pencil around the edges of the 

 cover to fasten it to the slide. Care is required that 

 the glycerine applied be no more than sufficient ; for 

 wherever it has touched the cover or the slide, the 

 cement will not adhere. Superfluous portions may 

 be sucked up with a piece of clean moist sponge or a 

 corner of blotting-paper. 



When it is required to mount a large number of 

 objects in a short time, the cement need only be 

 applied to two opposite sides of the cover, leaving the 

 other two sides open. 



When the objects require to be protected from the 

 pressure of the cover, the sides of a cell must be 

 made with the cement or black japan upon the slide 

 before the cover is applied, a further quantity being 

 used to close the cell as usual. 



A very strong solution of chloride of calcium may 

 be used for the same purposes and in the same way 

 as the glycerine. It has the advantage of not making 

 the object so transparent; but it has the disadvan- 

 tage of crystallizing slightly in a dry atmosphere. In 

 most cases, I prefer it to glycerine. 



A large number of interesting objects cannot, how- 

 ever, be preserved in either glycerine or chloride of 

 calcium, without their value being impaired by the 

 cause mentioned above. Many kinds of liquid have 

 been recommended for preserving these, all agreeing 

 mainly in being inefficient. The objection to them 

 is, that they are evaporable ; and after the object has 



