FIBROUS RESIDUES 361 



economically possible. The object kept in view was to turn to account not one only, 

 but both the classes, animal and vegetable, of intermingled ingredients; and this 

 result is accomplished by the new method without the aid of the acid or alkaline 

 disintegrants heretofore employed; without, in fact, any chemical agency stronger 

 or more costly than that of water, applied in the form of a high-pressure steam 

 atmosphere. This process is so extremely simple that its nature, and the mode of 

 practising it, can be explained in half a dozen sentences. 



' The mixed rags, or other analogous mixed residue, are introduced into an ordinary 

 autoclave digester, and there kept for about three hours (more or less) surrounded 

 with an atmosphere of steam heated to a pressure of from three to five atmospheres. 

 The exact pressure and temperature requisite vary with the materials under treatment ; 

 wool requiring a higher temperature than leather, for example, and silk than wool. 

 The materials condense a proportion of the steam and absorb its heat. The joint 

 action of the moisture and heat is to convert the animal matter into a friable sub- 

 stance, which, however, still retains its original form and aspect. Thus the wool of 

 mixed rags retains after digestion the same fibrous appearance that it had before, 

 though it crumbles to powder when handled. It will be understood that ordinary 

 crushing and beating machinery readily reduces this brittle coal-like product to 

 dust, and detaches it from the interwoven vegetable matter, which preserves its 

 fibrosity unimpaired. The beater is provided with a sieve, which retains the vege- 

 table fibre, but suffers the animal dust to fall through. Ultimately the vegetable 

 fibre is projected from the machine as a paper-material ready for use ; _the animal 

 dust, meanwhile, being propelled by an Archimedian screw, and raised by a 

 Jacob's-ladder till it reaches the mouths of the sacks successively placed for its 

 reception. 



' In the details of this process, and in the fuel- and labour-saving arrangements for 

 drying the rags and handling them in their passage through the several departments 

 of the factory, there are peculiarities not bearing on the broad principles of the plan, 

 though essential to its successful prosecution. Special precautions of this kind, as 

 they are learned, point by point, by "costly manufacturing experience, cannot, with 

 propriety, be divulged; nor, indeed, would they interest any reader not specially 

 charged with the conduct of the operation. I "pass on, therefore, to a brief con- 

 sideration of the products. 



' The fibrous product, or paper-material, presents but few peculiarities for notice. 

 It consists principally of cotton, but usually contains also a percentage of flax and 

 hemp, which increase its tenacity and value. The fibre is, for the most part, set free 

 in the form of long parallel threads, the warp of the fabrics treated: but it also pre- 

 sents many shreds of an ordinary rag portions, doubtless, of the calico with which the 

 stuffs were lined. As the cotton warps of union fabrics are usually dyed in fast colours, 

 often black, and as they are apt to retain a small percentage of the altered wool-dust, they 

 require to be boiled under somewhat higher pressure than ordinary coloured rags ; 

 with which, in other respects, they are pretty much on a par as paper-material. Until 

 the right pressure for boiling them had been ascertained, it was found difficult to 

 bleach them to perfect whiteness ; and some early failures, thus occasioned, rendered 

 the material unpopular among paper-makers. Nevertheless, when properly ma- 

 nipulated, this material produces excellent white paper, as the samples exhibited 

 show. 



' The animal product, being an entirely novel article, requires particular attention. 

 It issues from the beating machine as a dark- coloured powder, intermingled with 

 small lumps of the same substance, which lumps are sifted out and crushed. This 

 powder, as practically produced, with the dust and gric of the rags in it, contains, on 

 an average, nearly 12 per cent, of nitrogen; a proportion corresponding to 14'5 per 

 cent, of ammonia. The nitrogen exists to a small extent as ready-formed ammonia 

 held in combination with brown acids ulmic and humic developed during the pro- 

 cess. The bulk of the nitrogen, however, is present, not in the form of ammonia, 

 but as a constituent of the wool-product itself. This organic compound is partially 

 soluble, and more so as more moisture is supplied to the rags during their digestion. 

 As ordinarily produced, it is a manure of highly ammoniferous power, the whole of 

 its nitrogen being liberated as ammonia, under the influences with which it meets in 

 the soil. The rate of this development holds a happy medium between that of ordinary 

 woollen rags, which are reckoned too "slow" a manure, and that of guano, which is 

 often as much too " sudden." The farmer desires an equable as well as a copious 

 development of ammoniacal plant-food, whereof abrupt and superabundant supplies 

 are apt, as he expresses it, to " burn" the roots ; which have, moreover, subsequently 

 to endure privation of the very food thus worse than wasted. 



' The new manure may, I think, be regarded as being for plants what moderately- 

 cooked food is for animals ; the artificial preparation being, in both cases, carried 



