rod, the volume of water is forced out at the stern: which by pressing against the body of water behind the vessel, is intended to produce a resistance sufficient to drive the vessel forward.

The pump is proposed to be worked by a steam-engine, placed in such a situation in the vessel as not to throw it out of its balance, or to prevent its riding in a perfectly erect position on the water; the pump itself is to work vertically, and the pipes are to be disposed in any convenient way within the vessel, not under it on the outside. There may be more than two pipes employed, and the feed or ingress pipes may, instead of laying in a horizontal position as the egress pipes, be carried directly down from the pump, and draw the water from the bottom of the vessel.

[Inrolled, October, 1823.]

To WILLIAM WOODMAN, of York Barracks, Veterinary Surgeon of the 2nd Dragoon Guards, for his Invention of an improved Horse's Shoe, which he denominates the Bevelled-heeled expanding Shoe.

[Sealed 11th September, 1823.]

THE patentee, like every other projector of a new horse-shoe, points out the disadvantages and danger to the horse attendant upon the old modes of shoeing, in which the growth of the frog is impeded, and the horse ultimately lamed through corns. If a shoe was adopted that only covered the fore part or tread of the hoof, the frog would be relieved, but the horse would be subject to frequent inconvenience, by the tender part of the foot being exposed, and by that means the horny part behind would soon become soft. The proposed shoe, therefore, in general form, does not differ from the ordinary shoe;

but the back part, that is behind what is called the bar, is on the upper side bevelled off outwardly.. By this means, the bearing of the hoof is on the fore part of the shoe, that is anterior to the bar, and the hinder part of the hoof remaining unconfined, and not pressed by the shoe, allows the frog to expand and grow freely.

[Inrolled, November, 1823,]

To RICHARD PEW, of Sherborne, in the County of Dorset, Esq. for a New Composition for Covering Houses and other Buildings.

[Sealed 17th June, 1823.]

THE composition herein proposed, is intended to produce an artificial stone, and the materials of which it is to be made, are as follows: the hardest and purest limestone is to be selected; that which is most free from any admixture of sand, clay, marl, or other such matters, is very much to be preferred; statuary's marble, if it could be procured in this country, would best answer the purpose; it is therefore recommended to select that material which approaches nearest to it in point of purity, and hardness. These stones are to be calcined in a blast furnace, until all the water and fixed air, or carbonic acid is completely driven off.

Of this pure lime, when it has been reduced to a fine powder, take one part by measure, and add to it two parts of well burnt clay that has also been reduced to powder; or if burnt clay cannot be conveniently procured, powdered flints, the fine powder of lime-stone, or other hard substances capable of being reduced to powder, but such as is not soluble in water, may be employed; these are to be completely and intimately mixed toge

ther; then take one part of sulphate of lime moderately calcined, and reduced to powder, to which add two parts of the burnt and powdered clay, or other material before mentioned, and mix these together.

The two sets of powders, or compounded substances as above prepared, and in the quantities stated, are now to be combined, and well mixed, by stirring and working them for a long time until intimately united, when the composition may be considered complete, and fit for use, in which state if kept perfectly dry, and excluded from the air, it retains its virtue for a long time.

The patentee calls this composition SMALTO, or ENAMEL, and proposes to mix it with about one-fourth its weight of water, so as to produce a tolerably thick paste. It must be mixt up with the water in small quantities, as it quickly hardens, and if allowed to do so, will crumble in using, and lose its cohesive properties in a great measure. It may be spread upon laths, or any other suitable foundation, and will become as hard in time as the most durable stone, indeed, the patentee considers the substance, when properly prepared, as altogether indestructible.

Into this composition, when in a powdered or plastic state, any desired colouring matter may be introduced, which may be requisite for giving any particular hue to the artificial stone, especially in darkening the colour, which is proposed to be done generally by the admixture of lamp black, ivory black, pulverised charcoal, and several other colouring materials.

[Inrolled, August, 1823.]

Original Communications.

SIR,

To the Editor of the London Journal, &c.

A COMPOUND of pyroligneous acid and alcohol having been lately recommended and approved by the Society of Arts, as a desirable material for diluting the nitric acid used in biting in lines etched upon steel plates, I beg, through the medium of your Journal of Arts, to say a few words upon the subject.

In the first place, it is stated by the candidate in his communication to the Society, that the oxyde of iron, formed by the ordinary process of biting in, instead of being held in complete solution by the acid, forms a sediment, which settling in the lines, prevents the acid from acting on the bottom, while it continues biting the sides of them, causing the etched lines to become broad and shallow, and consequently the only remedy that can be adopted is a mixture which will not impede the action of the acid, and continue to hold the iron in complete solution, whereby the etched work would be certain of biting deep.

This is a true statement of the theory advanced, and the point said to be gained by the use of the above mixture. Let us now consider how far it agrees with the general opinion, or rather experience, which every practical engraver as well as myself has had in the pursuit .of this branch of the Arts.

It is well known, or at least generally considered, that bad biting may arise from a variety of causes; for instance, from bad metal, that is impure or alloyed; from

bad or imperfect ground; or from acid which has been. too much diluted, or accidentally mixed with deteriorating substances; and sometimes from accident, or want of sufficient attention in the operator. But strange to

say, this idea of a sediment, if any such thing has ever before been thought of, has never till now been considered as operating detrimentally, nor I think could it be so considered upon any principle of philosophy, or

reason.

If, indeed, there were but one kind of bad biting, and that was shallow lines, it might, to a careless observer, seem to apply; but what can be said when some plates will scarce bite at all, even though the acid is repeatedly strengthened, while others bite altogether so quick as to ruin the whole surface, if neglected, in a few minutes. Again, some plates will bite in rough or ragged, so that the lines are like the teeth of an old mutilated saw. One plate will bite ill, and another well, with the same acid; and lastly, some will bite in partially ill, and partially well at the same time, and of course with the same acid, and under the same operator; so that I may fairly presume no single theory, however systematic or plausi ble it might appear, can account for the numerous and uncertain effects of biting in. Indeed, this may be learned from the circumstance, that the process for which a goldmedal was given last year to the late Mr. Chas. Warren, who was really a man of science, and an excellent engraver, is now deemed incomplete, because it does not. include the idea of a sediment.

Having thus far discussed the theory, we now come to the practice, in which it may be well to state, that it is proposed, to every 5 oz. of diluent (viz. 4 oz. of pyroligneous acid, and loz. of alcohol), there should be added loz. of nitric acid; whereas, to the same quantity