290 CHAPTEE XXI. 



456. WARD'S Brown Cement is a shellac-alcohol solution, 

 made by E. Ward, Oxford Koad, Manchester, and presumably 

 now obtainable from the opticians. Its best solvent, Mr. 

 ROUSSELET writes me, is a mixture of wood-naphtha and 

 alcohol. He considers it the best shellac varnish he has met 

 with, better than BELL'S. 



457. BELL'S Cement. Composition unknown. May be ob- 

 tained from the opticians, or from J. Bell & Co., chemists, 

 338, Oxford Street, London. 



This varnish flows easily from the brush, and sets quickly. 

 For glycerin or other fluid mounts the cover should be ringed, 

 as above described, with glycerin jelly before applying the 

 varnish. This precaution is especially necessary with 

 glycerin. This is the best varnish for fluid mounts known 

 to me. It is soluble in ether or chloroform. It is not 

 attacked by oil of cedar. 



458. MILLER'S Caoutchouc Cement. Composition unknown. 

 May be obtained from the opticians. A very tenacious and, 

 which is frequently an important point, a quickly drying 

 cement. It may be diluted by a mixture of equal parts of 

 chloroform and strong alcohol (see ROUSSELET, Journ. Quek. 

 Club, v, ii, 1895, p. 8). 



459. CLARKE'S Spirit-proof Cement. Mr. CH. ROUSSELET has 

 highly recommended this to me. It may be procured from 

 Mr. J. Bolton, 25, Balshall Heath Road, Birmingham. 



ROUSSELET finds it the best he has tried for alcoholic 

 liquids, but not perfectly proof against watery media. 



460. Asphalt Varnish (Bitiime de Jnde'e). 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 oil-shops. 



461. Brunswick Black. See previous editions, or BEALE, 

 How to Work, etc., p. 49. 



462. Gold-Size. Receipts for preparing it may be found in 

 the Micrographic Diet, or in COOLEY'S Cyclopsedia ; but it is 



