Cubic inch of water at 32° = 252·45 grains. " " mercury " = 3425·35 " Fluid oz. of water = 437·50 " " " measures = 1·73 cub. in. 1 f. drachm = 54·68 grains. 1 pint (New York) = 27·68 cub. in. 1 oz. bromine = 2-1/2 f. drachms. 1 grain, Troy or Apoth. = 1·097 gr. Avoir. 1 lb. Avoir. = 7000 Troy grs. 1 " = 7680 of its own grs. The drachm Avoirdupois is never used except in weighing silk. Pendulum vibrating seconds at New York = 39·102 inches. In weighing solids, few weights are really necessary if they are properly assorted; nothing less than half a grain is likely to be useful, and the series following will weigh any quantity from the half grain to two thousand one hundred and ten and a half grains, by differences of only a single grain. The numbers are in grains, but the same principle may be carried out with any other denomination, whether ounces, pounds, or tons. 1/2, 1, 2, 3, 4, 10, 20, 30, 40, 100, 200, 300, 400, 1000, &c. The artist should be provided with not less than three glass measures--one of a pint, graduated to ounces--one of two ounces, graduated to drachms--and one of two drachms, graduated to minims. * * * * * =Lewis's Patent Glass Baths= for Nitrate of Silver Solutions.--Since the foregoing pages have been in print this new article of Baths has been introduced, and will probably supersede all others now in market. They are encased in a box made expressly to hold them, and form a valuable and important improvement in the apparatus used in the various Glass processes. INDEX. Aberration, chromatic, 23; spherical, 22. Acetic acid, 66. Albumen, 63; preparation of positive paper with, 206. Alcohol, 70; used in sensitizing paper, 201. Ammonia, 71. Ammonio-nitrate of silver, preparation and use of, 152. Animal charcoal, 74. Barium, chloride of, 77. Baths, glass, 211; gutta-percha, 34. Bichloride of mercury for whitening positives, 159. Bromide and iodide of potassium and silver, 60. Bromide of potassium, 73. Bromine, properties of, 72. Bromo-iodized collodion for positives, (ambrotypes), 58, 59; for negatives, 60.