2] 2 CEMENTS AND VARNISHES. 



412. Asphalt Varnish (Bitume de Judee). Unquestionably 

 one of the best of these media, either as a cement or a varnish, 

 provided it be procured of good quality. It can be procured 

 from the opticians or from the oilshops. KITTON (Month. Mic. 

 Journ., 1874, p. 34) recommends asphalt dissolved in benzol 

 with the addition of a small quantity of gold size. 



413. Brunswick Black. Best obtained from the opticians. 

 A receipt for preparing it is given in BEALE, How to Work, fyc., 

 p. 49. 



t ' If a little solution of india rubber in mineral naphtha be 

 added to it, there is no danger of the cement cracking when 

 dry." Carpenter states that without this addition it is 

 brittle when dry. Brunswick black is soluble in oil of 

 turpentine. A most useful cement, works easily and dries 

 quickly. It can be recommended for turning cells. 



414. Brunswick Black and Gold Size (EULENSTEIN, BEALE, How 

 to Work, Sfc., p. 49). Equal parts of Brunswick black and 

 gold size with a very little Canada balsam. 



415. Gold Size. Receipts for preparing it may be found in the 

 Micrographic Diet, or in COOLEY'S Cyclopaedia ; but it is certainly 

 best to obtain it from the opticians or oilshops. It is soluble 

 in oil of turpentine. A good cement, when of good quality, 

 and very useful for turning cells. 



416. Marine Glue. Found in commerce. Carpenter says 

 the best is that known as G 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 BEALE, p. 49, or 

 in COOLEY'S Cyclopaedia. 



417. Harting's Gutta-percha Cement (see BEALE'S How to 

 Work, fyc., p. 49). Marine glue serves the same purpose, viz. 

 that of attaching cells to slides. 



418. India Rubber and Lime French Cement (see BEALE, p. 

 58). 



419. Knotting (Journ. Roy. Mic. Soc., 1882, p. 745). 

 " Patent knotting " from oil and colour stores, exposed to 



