FINDING the number of wood-cuts necessary to explain the parts of the Calculating Engine considerable, and the expense great, it appeared to me that the method of copying by casting might, perhaps, be employed for the purpose of diminishing the evil.
The plan which occurred to me was, to make a drawing of that portion of the mechanism required to be explained, which should contain every part necessary for its action, and, in some cases, even the frame-work requisite for its support. Such a drawing would be far too complicated for the ordinary reader, and might appear confusion even to the contriver of the machine. This drawing was then to be sent to the wood-cutter to be engraved, and on its return, it was to be sent to the stereotype founder, for the purpose of having any number of fac-similes made in type-metal. Now, each of these metallic plates would, like the original woodcut cut, sprees the drawing in relief, and, by cutting away any line in the plate, that line would be removed in the impression.
The first thing to "be done was, to remove from one of the stereotype plates every line, except those which formed the framing of the mechanism. The next step was, to re- move from another of those plates all the framing, and every other line, except (hose which represented two or three of the principal wheels and levers.
If there, should be many such parts, several plates might be taken, on each of which son few parts, not interfering with each other, might be allowed to remain. Other plates might be taken, on which the parts given on two or more of the former plates, might be allowed to remain, and. others again might contain combinations of three or more of these. Thus, by a series of plates, commencing with the simplest portions of the mechanism, we might gradually advance through the various combinations, up to the original woodcut, which, by means of such steps, might be made perfectly intelligible.
The original wood-cut will be more expensive, on account of the additional work contained in it; but its multiplication by casting is cheap process; and the cutting away some of the lines o; each plate, and dotting others, (by removing small portions at short intervals,) which might, in different plates, require to be represented as passing behind other lines, is not a work of much difficulty or expense. The number of illustrations, all printed with the letter-press, which this plan admits of, renders it possible to explain much more complicated machinery than could be accomplished by engraving, unless at an expense which would effectually preclude its application; whilst the successive picture of every wheel and lever, exhibited on separate plates if necessary, as well as of every one of the combinations which are employed, will render the machinery intelligible to a number of persons much larger than the class which usually studies such subjects.
The same principle may be applied to coloured geological sections and maps. The whole drawing having been sent to the wood-cutter, as many stereotype fac-similes may be made from this block as there are colours to be represented. One plate may then be taken, from which all the parts are to be scraped out which are not to be coloured brown; another may be taken from which all parts not to be coloured green; and so on for the rest of the colours. The perfect identity of the plates will render it easy to preserve what is technically termed the register, that is, to prevent the overlapping of any one colour on any other.
On the last page, the reader will find an illustration of this art; it is the same plate as that at page 200: it is not very favourable either as to the degree of difficulty, or as to the question of economy; but it is the only one that the subject of this volume admitted, and is quite sufficient to explain the principle.
The figure at the bottom of the page, No. 4, is the impression from a stereotype plate, which is a fac-simile from the original wood-cut, engraved for the illustration. No. 3, the next above, is the impression from another stereotype plate, from which the lines marked D and F, on No. 4, have been cut away. No. 2 is the impression from another plate from which the line E has been cut away; and No. 1 is an impression from a similar plate, from which the lines C and E have been cut out.
The four individual plates have been soldered together, and form the stereotype plate of the page referred to.
As the method here suggested is extremely simple, it is scarcely possible but that it must have occurred to others; and it may, perhaps — although I am not aware of it — have been employed on some occasions. I have, however, thought, that in giving publicity to it, I should be doing a service to those whose writings require pictorial illustration, and especially to those who cultivate the sciences of mechanics and geology. Perhaps, also, the same system might applied to multiply, at a cheap rate, the blocks used in colour printing, both upon paper and on woven fabrics.
14 December 2008