"amount in number to the linear inch, it would be still better. I know not whether there are any practical difficulties in obtaining wires of such exceedingly small magnitude, but should there be any, I trust they may be overcome, as the resources of art and manufacture have seldom been found deficient in supplying the wants of men.

2. Let us now suppose the wire-plate to have been constructed, and to be in a fit state for engraving upon. The preparatory step is, to lay the plate down on a moveable cushion, having a plane level surface at top, where it is covered with soft leather, beneath which a blanket is stretched. In this state, if a gravingtool. be applied to the upper surface of the plate and drawn over it, a sunk line I will be formed, which, on turning the plate, will be found to have produced a raised edge or ridge on the other side, consequent on the depression of the wires taking place in the line of direction of the graving-tool. This effect must needs follow, because it requires a less effort for the graving-tool to press down the wires than to pass between them. It is from a number of such ridges and projections formed on the one side of the plate by the action of the graver's tool on the other side, that an engraving, similar to wood-engravings, is proposed to be taken off. Also in the progress of the work the plate may be operated upon on the one side or on the other, according as convenient, or as the artist may think good for the completion of his design.

When the plate has been fully engraved upon, the next step is, to give fixity to the wires in the places assigned to them by the graving-tool. This may be done by pouring over that side of the plate from which the engraving is not to be taken a composition of nielted wax or resin, or some similar compound which hardens on cooling, and which will thus form an abutment to the wires, so as to prevent them shifting their places on pressure being applied, as in taking off the engraving, &c. It will be a point of some nicety to determine the exact degree of facility the wires should present to being pressed down by the graving-tool, and that degree of firmness or resistance required to hold them in their places on ordinary occasions. This point might be attained by causing wax to occupy the interstices between the wires,

2

$447

or it might be produced by their simple adherence, merely caused by their lateral pressure within the frame.

I now come to treat of the advantages which this possesses over wood-engraving.

1. Wood-engraving is allowed to be a somewhat difficult process; the chief difficulty seeming to consist in cutting out minute portions of the wood to form the light parts of the engraving. How much more simple is the mode of execution with the wire-plate, wherein the same effect is produced by simple pressure;—where, instead of the difficult and laborious task requiring to be most carefully performed, all that is required, is a momentary pressure with the graving-tool. Surely an advantage like this cannot fail of being appreciated by artists occupied in engraving.

2. Another advantage of the wire-plate engraving is, that in the event of a false stroke being made, or if in any other respect the work done be not perfectly to the artist's mind, he has the power of repairing his error immediately, by merely turning the plate and operating on the other side, either to replace the wires in their former position, to be operated upon afresh, or else by a few strokes or touches, to produce the desired effect.

3. A third advantage of the wire-plate is, that after it has served one set of engravings, or one series of impressions has been worked off the plate, it may be made to serve another set, without any assignable limits. This may be done by restoring the plate to its original state, or to the state in which it was before being engraved upon, which is thus to be effected. The ground at the back of the plate is first removed, and the plate is then to be passed under a roller, or between two rollers, so as to press back the wires into their natural order, wherein -the ends of the wires constituted a plane or level surface on the two sides of the plate. These are, I believe, the chief advantages of the wire-plate system of engraving. I now come to a view of its disadvantages, or those at least which, whether well or ill-founded, it may be thought to labour under.

1. The wire-plate, it may be said, would be too expensive a construction to supersede the use of wooden blocks in engraving. To this it may be replied,

that the first expense would be all, as may be seen by a reference to No. 3 above. Besides which, let the expense of wooden blocks, arising from the continual demand for them in engraving, be considered. These two circumstances conjointly may tend to equalise more nearly than would at first be imagined, the difference in the cost of wire-plate and blocks of wood.

2. Another objection to the wire-plate system would be, that by these means no even or distinctly marked line could be impressed on paper, but that all such lines would be jagged and rough at their sides, or otherwise could only be marked by a succession of dots. The force of this objection is very considerable, for certainly no line engraving could be executed by the wire-plate. However, this objection does not hold good generally, or it cannot be considered quite fatal to the plan proposed, as, if so, it applies equally to every system of engraving, excepting that performed in the line manner. Now there is a style of engraving on copper which is not performed by lines, but by dots, and which, although perhaps not equal to line engraving, is still very beautiful in its way, and is certainly preferable in point of execution to any system of wood-engraving extant. The decision, or accurately defined impression of metal over wood, gives it certainly the preference where it can be employed; and this end, I think, may be attained by substituting wireplate for wood, in the particular mode of engraving for which both are adapted.

3. A third objection to the wire-plate may be its inability to indicate very fine lines on paper, as every such line must have a breadth equal at least to the diameter of the wires entering into the construction of the plate; and that in many cases the line will have a double breadth alternating with a single, according as the graving-tool shall take over one or two wires in succession. The only answer I can give to this objection is, that the wires are proposed to be so excessively small or minute in diameter, as to render the practical difficulties of the case, as here stated, a matter of very little consequence.

I believe I have now stated all that may be said, of chiefimportance at least, pro and con, respecting the wire-plate system of engraving; and I leave it to you, Mr.

Editor, and your readers, to determine to which side the balance leans. In the mean time, yours, &c. V. W. GARDINER.

NOTES AND NOTICES.

Patent Law."Sir, You will very much oblige an old subscriber, by giving hin your opinion upon the following point:-Ã master has had a machine at work in his factory for five years, but had not thought it worth patenting. He finds, however, that another person has lately taken out a patent for the same thing in principle, and with only a few alterations in the construction. Can the patentee stop the previous inventor and user from working his machine?-Your humble servant, N. B."-In answer to our correspondent, we refer him to the following extract from the Patent Law Amendment Act:-" And be it enacted, that if, in any suit or action, it shall be proved or spe cially found by the ver ict of a jury, that any person who shali have obtained letters patent for any invention or supposed invention was not the first inventor thereof, or of some part thereof, by reason of some other person or persons having invented or used the same, or some part thereof, before the date of such letters patent, or if such patentee or his assigns shall discover that some other person had, unknown to such patentee, invented or used the same, or some part thereof, before the date of such let'ers patent, it shall and may be lawful for such pa'entee or his assigns, to petition his Majesty in council to confirm the said letters patent, or to grant new letters patent, the matter of which petition shall be heard before the Judicial Committee of the Privy Council; and such Committee, upon examining the said matter, and being satisfied that such patentee believed himself to be the first and original inventor, and being satisfied that such invention or part thereof had not been publicly and generally used before the date of such first letters patent, may report to his Majesty their opinion that the prayer of such petition ought to be complied with, whereupon his Majesty may, if he think fit, grant such prayer; and the said letters patent shall be available in law and equity, to give to such petitioner the sole right of using, making, and vending such invention as against all persons whatsoever, any law, usage, or custom to the contrary thereof notwithstanding." In the Bill the following exception was here added: Save and except such person or persons as 'dil use the same invention before the date of the first letters patent." This saving clause was, however, lost in the passage of the Bill through Parliameut.-ED. M. M.

$450

BRUNTON'S PATENT GAS-Retort. Fig. 1 is a section of a retort with the various parts attached, viz. a feeder or hopper, A; a plunger or piston-case, B ; a round taper retort open at both ends, C; an end piece, D, with a dischargecylinder or shoot, F; and an exit pipe, G. The same letters indicate corresponding parts throughout.

The lid or cover f of the feeder A being raised, a certain portion of coal is introduced, and falls on a plate of iron or diaphragm n, and the lid closed, the lip of which falls into a narrow trough, bb, filled with fine sand, loam, or any compost, which will render it secure. The hollow piston or plunger a a in the case B is then propelled forward, either by a screw turned by a handle outside, as in fig. 1, or by a rack and pinion, as in figs. 3 and 4. By this mode a quantity of coals is forced from the space immediately before the piston and under the feeder into the retort, and the whole bulk moved forward, while that which has been carbonised and lies at the further end is discharged into the end-piece D and through the shoot F into a cistern of water E, from whence it may be removed by a rake or basket; the piston is then drawn back into the case, and the diaphragm n let down by slacking the spring catch i which confines the handle h (see figs. 2, 3, 4), so that the coal just introduced may drop into the space between the retort and piston, thereby shielding the apparatus from the heat, and being ready to be moved forward when a fresh charge may be required; the quantity and frequency of each charge must depend upon the quality of the coal used and the size of the retort. The gas passes through the exit pipe G, on the flange of which is a circular box I, furnished with a small cone or taper pipe, which is placed immediately over the aperture of the exit pipe, so that all the condensible matter may be prevented from falling on

the coke in the cistern E by being deposited in the box I, outside the cone, from whence it may be removed when required by a tap or plug. The endpiece D is furnished with a small cover or lid H, which may be at any time removed for the purpose of examining the interior of the retort; it is secured in its place by a cross bar and screw.

Fig. 5 represents a front view of three* retorts in one bed. No. 1 is furnished with a slide-valve L, the seat of which, K, being a fixture and secured by cement, obviates the necessity of frequently changing the luting in the trough bb. No. 2 shows the lid fopen, and thereby exhibits the hinges upon which it works. No. 3 is closed.

Fig 6 is an end view of the same retorts with the exit pipes G, boxes I, and lids H. The lid of No. 3 is off for the purpose of inspection.

The superiority of this retort above those in common use, consists in the facility with which it may be charged and discharged; the almost total absence of that suffocating and enervating heat and smoke necessarily attending the present system; the economy in the cost of wear and tear, as the middle of the retort only is exposed to the action of the entirely dispensed with; the saving of fire, and iron barrows, rakes, &c. are labour, and consequently wages, as any man or even stout boy, whatever his previous occupation may have been, may after a day or two's practice take the whole management of from fifteen to twenty-five of these retorts; the preventing that immense loss of gas which takes place when the retorts are charged; the more equal carbonisation of the coal, arising from the frequent agitation of it in its progress through the retort; and the whole process being uninterrupted by the admission of atmospheric air.

* One, two, three, four, or more retorts may be put in one bed.

451

ON THE LAW OF PATENTS. BY JUNIUS

REDIVIVUS.

(From the True Sun.)

After all the long disputes between the respective representatives of capital and labour, the question seems to have settled into a mutual conviction that they are necessary to each other, and must each be affected by the prosperity or adversity of the other. Yet notwithstanding this the existing laws are alike inefficient for the protection of either capital or labour. It is no uncommon thing for a partnership business to be carried on for a series of years, whereby a large capital is accumulated, and which by some absurd dispute between the parties is thrown into the Court of Chancery, there to be dispersed amongst the professors of the law and their various retainers. And all this might be prevented by the simple and efficient tribunal known in France as the Chamber of Commerce. A summary and cheap mode of reference is needed for those suffering under injustice. But great as this evil is on the capitalists who have accumulated property, there is an evil pressing yet more heavily on the workers who seek to accumulate property. There is no efficient protection for the mental labour on which all that is valuable in society depends. The capitalist is protected from direct encroachment on his property; the labourer and the working mechanic are

protected from any direct encroachment on their wages, or on their bargains for remuneration; but the originators of every class are so imperfectly protected, that they are exposed to both the direct and indirect plunder of all classes alike. This is a most unwise national policy, inasmuch as national progression must ever depend upon originators. Take away the originators from amongst us, and we shall become a stagnant nation like the Chinese. If, therefore, the nation desires to make progress, its wisest policy is to foster the originators, and hold out to them all possible inducements to follow the bent of their genius. It is quite true, that even if left to themselves, and exposed to hardships and injustice, they cannot quite repress the fire that is in them; but it is also true that the produce will be lessened. The field which is left uncultivated will in time be choked with weeds, though straggling plants may at intervals appear amongst them.

The principle on which the nation professes to protect the mental labour of originators in the case of books, is national advantage. Few persons would produce valuable works if the copyright were not secured to them; yet even in this case a heavy tax is exacted from the authors in the shape of a considerable number of gratuitous copies. And after all, if the work be popular, an unprincipled