(3) metallic copper 25 p.ct. of its weight; and the costs are approximately 100l. per ton. It is obvious that the materials are recoverable from the precipitating-bath, but at a certain added cost. We have no statements as to the proportion recoverable nor the costs incurred, and we are therefore unable to measure the total net cost of the regenerated cellulose by this process. It is certainly much less than by the collodion processes. As to the textile quality of the thread, the product has not yet been on a sufficiently wide selling basis for that to have been determined. There are a great many factors which enter here. Not merely the external characters of lustre, softness, and translucency, but the all-important quality of uniformity of thread. The collodion-spinning is a process still very defective in this respect, and the defect is no doubt referable to the difficulty of securing absolute physical invariability of the collodion. It is to be regretted, in the interests of scientific development, that none of the technologists who have published investigations of these processes have entered into the discussion of the fundamental factors of the spinning processes; we are, therefore, unable at this stage to discuss these elements of a full comparison in greater detail. We cannot, for this reason, say how far the cuprammonium process diverges in point of control from the standard of the collodion processes. Of the 'viscose' product we have a more intimate knowledge, and it certainly reaches a higher general standard than the older and now well-known artificial silks. The process is also sufficiently developed to enable the total costs of production to be estimated at a figure less than one-half that of the 'collodion' processes. This would assure to this system an entrée in this country, and a basis of expansion limited only by the ordinary laws of supply and demand.

This prospect is opened up precisely at the moment when, for various reasons connected both with the difficulties of

manufacture and the narrowing of the margin of profit, the proprietors of the two systems of collodion-spinning have decided to abandon all idea of manufacturing by these systems in this country. We leave the discussion of the industrial problem at this point.

In regard to other developments based upon the exceptional character and properties of the sulphocarbonate, their further discussion will exemplify no general principles; and as regards technical detail they have been dealt with in the papers previously noticed.

As a purely general question, if there is to be any industry in these artificial' forms of cellulose, commensurate with the magnitude that usually belongs to the cellulose industries, it must come by way of a plastic or soluble form prepared at low cost, and conserving the essential molecular properties of the cellulose aggregate. These are the particular features of the sulphocarbonate. The obvious difficulties in the way of its industrial applications are those caused by the presence of alkali and sulphur compounds. These are dealt with by appropriate chemical means; but the fact that there is a special chemistry of the product has rendered its industrial progress slow. The work of the last five years in this, as in other applications of cellulose in its many derived forms, has resulted in a considerable addition to the domain of practical chemistry.

Further developments will make an increasing demand upon our grasp of the fundamental constitutional problems, to which it is the main purpose of the present volume to contribute.

The recent failure of a French company founded for the exploitation of the cuprammonium process may be taken as showing that it presents very considerable technical difficulties. It is a matter of common knowledge that this company estimated the costs of production to be such as to enable the product to be sold at 12 fr. per kilo., whereas the costs actually obtaining were a large multiple of this figure.

INDEX OF SUBJECTS