CEMENTS AND VARNISHES. 291 



certainly best to obtain it from the opticians or oil-shops. It 

 is soluble in oil of turpentine. A good cement, when of good 

 quality, and very useful for turning- cells. 



463. Marine Glue. Found in commerce. CARPENTER says 

 the best is that known as Gr K 4. 



It is soluble in ether, naphtha, or solution of potash. Its 

 use is for attaching glass cells to slides, and for all cases in 

 which it is desired to cement glass to glass. 



Receipts for preparing it may be found in BE ALE, p. 40, or 

 in COOLEY'S Cyclopaedia. 



464. Turpentine, Venice Turpentine (CSOKOR, Arch. mik. 

 Anat., xxi, 1882, p. 353; PARKER, Amer. Hon. Mic. Journ., 

 ii, 1881, pp. 229-30; Journ. Roy. Mic. Soc. [N. S.], ii, 1882, 

 p. 724). Venice turpentine (Terebinthina veneta) is the 

 liquid resinous exudation of Abies larix. Parker gives the 

 following directions : 



Dissolve true Venice turpentine in enough alcohol, so that 

 after solution it will pass readily through a filter, and, .after 

 filtering, place in an evaporating dish, and by means of a 

 sand-bath evaporate down to about three quarters of the 

 quantity originally used. After it has evaporated down to 

 about that much, drop some of the mass into cold water ; if 

 on being taken out of the water it is hard and breaks with 

 a vitreous fracture on being struck with the point of a knife, 

 cease evaporation and allow to cool. 



Or (CSOKOR), common resinous turpentine of commerce is 

 put in small pieces to melt over a water-bath, then poured 

 into a suitable vessel and allowed to cool. It should form a 

 brittle, dark brown mass, not yielding- to the pressure of a 

 finger. It is sometimes useful, in order to attain the right 

 degree of hardness in the cold mass, to add a little resinous 

 oil of turpentine to the melted mass, and then to evaporate 

 for several hours over the water-bath. 



This cement is used for closing glycerine mounts ; it is 

 applied in the following manner : Square covers are used, 

 and superfluous glycerin is cleaned away from the edges in 

 the usual way. 



The cement is then put on with a piece of wire bent at 

 right angles ; the short arm of the wire should be just the 



