For building purposes generally, and interior use, 4-ply offers many advantages. Where the buildings are temporary and intended for subsequent removal elsewhere (e. g. workmen's huts when engaged in railroad construction), the lightness of this material renders it eminently adapted for construction in removable sections; and for more permanent structures it is equally advantageous for numerous reasons. It does not harbour moths or other vermin; in the hottest weather, under a broiling tropical sun, it remains unchanged, and emits no unpleasant odour; it requires no painting, and exempts from the necessity of using pot and brush year after year to prevent corrosion, or to make a neat surface, or render water-tight, being weatherproof in itself. If required for interna] decoration, however, it will take paint readily, and, indeed, forms an admirable foundation for the painter and decorator to work upon, in this respect having marked advantages over felt, with which material it has nothing in common, although the two can, if desired, be used in conjunction.

In case of fire, although not absolutely indestructible, yet "Willesden" will not readily feed the flames, the copperising and compacting process by which it is mad rendering it far less inflammable than such substances as painted or tarred felt, or wooden shingling; its lightness moreover renders much less massive timbering requisite for the support of roofs, thus again diminishing the risk of damage by conflagration, there being actually less combustible matter about a building erected with this material than is necessary when the weight of a slated or tiled roof has to be supported. A special method of fixing walls and roofs of Willesden paper is recommended (see 'spons' Mechanics' Own Book,' pp. 618-20). Many such roofs are now standing in perfectly good condition, after upwards of 8 years' exposure to weather of all sorts; similarly, pipes conveying both water and steam have been in use upwards of 3 years below ground at the Willesden works, without any visible deterioration.

Willesden 2-ply is susceptible of being used for many purposes for which 4-ply is applicable, more especially when a less degree of body and, substance will suffice. One special purpose to which it is excellently well adapted, is for laying upon or under floor-boards and joists, to avoid damp and draughts. Used as a floor-cloth for stairs and offices, it wears well and is most effective, the cost being only a fraction of that of linoleum, kamptulicon, and similar articles.

Boats made of the paper answer very well in fresh water, but have not been tested in salt water. One advantage in making boats of the paper is that they are lighter than those made of wood, and, in the next place, are very easily repaired. Photographic dishes can easily be made by taking a sheet and pinching up the corner, bulging being prevented by running a thread through the corners. These dishes can be used for chemicals, though it is not advisable to put in a second chemical if the first has remained in the dish for some time. The action of acids upon the card depends upon the concentration as well as the nature of the acid and the temperature. If the card were boiled in a beaker, with weak sulphuric or hydrochloric acid, beyond doubt copper in solution would be found, and, no doubt, there would be less copper in the card than there was before; but, in the cold, very little copper is dissolved out. It is unlikely that the solution of copper in this way would affect the stability of the material for use in galvanic cells. Whether this material can be used for vats for bleaching purposes, is a matter which experience alone can decide, though there is nothing in the character of the material which would unfit it for the purpose.

At the same time it is doubtful whether oil of vitriol could be kept in a vessel made of Willesden paper. With regard to ropes being only superficially tinged with the coppery material, that partly arises from the circumstance that the rope is purposely not immersed sufficiently long to enable the fluid to penetrate deeply. As the action of the solution is to dissolve and disintegrate fibres, if thin ropes were saturated all through, they would lose a certain amount of strength. It is not necessary that a rope shall be saturated throughout. As to the paper treated at Willesden, complete penetration of the fluid into each ply of paper is a necessity, in order to obtain a proper product. The principal difficulty in carrying out the process consists in exactly regulating the strength of the solution as regards the amount of copper and ammonia, the nature of the paper and the length of time during which it has to pass through the vat, in order that the solution shall pass into the interior of the paper to the proper extent and no more; for if the action of solution is overdone, the material becomes too soft and tender to be dealt with by the machine.

Both the canvas and paper are susceptible, of use as a medium for painting, though canvas has not been long in use; but there is every reason to believe that works of art on canvas treated by this process will be less subject to deterioration through injury to the foundation. The paper would have no effect upon any mineral colour employed for decorative purposes. The action of copper upon certain organic dyes is well known, but these substances are rarely used for painting. The paper can be moulded into any shape. As to the analogy between this paper and paper parch-mentised with sulphuric acid, the 2 processes are dissimilar, though chemically the change produced on the paper fibre is of much the same character. There is a certain amount of analogy between the processes; if, for example, a sheet of writing paper is impregnated with cuprammonium to a fair extent, it has much the same texture when finished as parchmentised paper, and microscopically there is the same kind of structure. The quantity of copper left in the paper after treatment will vary very much according to the length of time the paper is allowed to remain in the solution, and the quantity taken up, but in round figures, an analysis of 4-ply paper shows that it contains about 4 per cent. of metal.

Among other uses to which the paper may be put, are covering bricks in the brickfield, and making shelters for vineries. Upon the question of whether Willesden paper is a non-conductor for electricity or not, probably if the material were rolled up into a pipe and used for telegraph cables, it would serve very efficiently, though scarcely with any advantage over guttapercha. It certainly does not conduct electricity readily; but as it contains copper, if there happened to be a leaky wire, reduction of metallic copper might be caused, whereby metallic communication would be set up from the wire to the earth, and, therefore, it is doubtful whether the substance could serve for the purpose of insulation. For chemical laboratories, and household matters, there are a considerable number of applications where the material will come in most handily.