While I agree with him in this, still it is well to remember that in the case of one of the very oldest of the fermentation industries, that of the production of alcohol, a comparatively simple body, the natural process has not yet been replaced by a chemical one, and I believe this applies also to the manufacture of vinegar. Chemical methods of bating may be used for leathers like chrome and alum leather, but even here natural processes like drenching, in which acids are produced gradually during the working of the skins, give more beautiful results. With vegetable tanning materials, the advantage is still on the side of the natural processes when these are conducted in a proper manner. Finally, the author regrets that the subject of the work is not an inspiring and lofty one, such as is astronomy for example.[186] Limited in extent, imperfect in execution, and in parts only suggestive in character, this little book may perhaps serve as a foundation, on which students of the science of tanning may raise the superstructure of their own experience and eventually perfect the processes touched upon, so that the use of such filthy materials may be entirely avoided. In that case the author’s intention will be fulfilled. [186] Celestial Objects, Webb, 1881. FINIS INDEX. Absorption phenomena, 70 Abt, Dr. G., 51, 72 Acid “turning” of drench, 237 Acids, action of, 156 ---- fractionating, 270 ---- deliming with, 9 ---- in drench, 265 ---- to remove lime, cost of, 11 Adulteration in dog-dung, detecting, 144 Agglutinin, 144 Alum, a term for puer, 3 “Alumed” calf skins, 3 Amend’s bate, 193 Amido compounds, 156 Amines, 163, 206 ---- in dung, 154 Ammonia in puer liquors, 41 Ammonium phosphate, 45 Analyses, bird excreta, 53 ---- dog dung, 26, 150, 152 ---- drench, 249 ---- gas, 247 ---- grains, 7 ---- guano, 150 ---- hen dung, 150 ---- puer, 26 ---- ultimate, of dung, 153 Andreasch, F., 244 Anti-bodies, 143 Anti-calcium, 236 Arginase, 133 Artificial drench, 263 Ash of skin, 39 Authors, list of, 290 _Bacillus butyricus_, 112 ---- _c_, 172 ---- _Coli commune_, 94 ---- _d_, 106, 173, 174 ---- _e_, 107, 173 ---- _erodiens_, 97 ---- from pigeon dung bate, 172 Bacteria, action of, 160 ---- bate, examination of, 87 ---- bran, pure culture of, 269 ---- dung, 89, 98, 102, 161 ---- growth in various media, 105 ---- pigeon dung, 103 ---- putrefactive, 125 ---- “Sweating,” 105, 213 Bacterial diastase, 131 _Bacterium furfuris_, 241, 264, 269 ---- _termo_, 118 Barium salts from pure cultures of _B. furfuris_, 271 ---- ---- of volatile acids, 253 Bate, Amend’s, 193 ---- Becker’s patent, 227 ---- bird dung, 52 ---- Boehringer’s patent, 197