Fig. 13. Is an enlarged view of the inferior surface of the abdomen of the lampyris lucida, after the integument had been removed. a a a represent the three masses of luminous substance, which are applied to the three last rings of the abdomen. bbb the arrangement of the cel lular or interstitial substance on the other abdominal rings, which gives the pale colour to the whole belly of this insect. Fig. 14. Represents the common glow-worm, with the posterior portion on the back cut away to expose the sacs of luminous matter in situ on the last ring of the belly. a indicates the sac of one side; the intestine is seen to lie between them. Fig. 15 and 16. Are the sacs of the glow-worm prodigiously magnified to show their structure. Fig. 16 is cut open to expose the luminous matter it contains: the coat of the sac is still seen to preserve its figure. Fig. 17. Is the elater noctilucus, with the shell of the corselet removed on one side, by which the organ of light is uncovered. a the yellow transparent spot of the corselet. b the oval mass of luminous substance surrounded by an irradiation of the interstitial substance. c the ends of the muscles which were on the inside of the corselet, Fig. 18. Is the posterior angle of the corselet of the elater noctilucus magnified, a the radiated appearance which the interstitial substance has round the oval mass of luminous matter. This mass is seen to consist of a number of smaller parts. 6 shows the appearance of the interstitial substance, where it passes down between the muscles. the ends of the muscles of the back. d the shell of the corselet. Fig. 19. Represents the elater ignitus, a is the mass of luminous substance of one side, seen indistinctly through the back of the semitransparent portion of the corselet. is the luminous mass of the other side, exposed by removing part of the shell of the corselet. printing their own works VII. Hints on various Modes of Printing from Autographs. By SIR, As To Mr. NICHOLSON. your Journal is frequently enlivened by hints of improvement in the Arts, no less than by accounts of new inventions; allow me, when it is agreeable to you, to occupy a page or two with some thoughts on a subject particularly interesting to authors; and which might, if reduced to prac tice successfully, be of general service to mankind. Every original writer justly laments the expense, difficulty, and would be very fraud, he is subject to, if he gives his works to the press. If advantageous therefore any method could be devised, to enable a man of talents to be his own printer, and take off his own copies as they were demanded, without the intervention of a publisher, a new and brilliant era in the world of letters would be commenced; that would make thought and reflection, when justly employed, as valuable to the possessor as the talent for manual arts; and we might hope to see the day arrive, when the profession of letters might afford as probable a means of getting a fortune as any other profession what to men of letters. Materials suggested. Copper. ever. In order to accomplish this desirable end, I have, long ago, run over in comparison every substance, that might possibly contribute to this purpose. Metals, wood, clay, paper, have not been forgotten; and although I cannot offer any one as having been fairly tried, (owing to a variety of other occupations), yet I trust I may, by enumerating them, afford hints to others, that may ultimately be useful. My first idea was copper, written on by a stile through white wax, and when printed perused backwards by means of a mirror. But this would have demanded the talents of a Blake, who alone excels in that art: or we must have a I apprehend there is an omission here of some such words as the following. "It might be written upon backward,” thild educated so to write with correctness. Besides, copper is too dear ever to become useful. Yet this method might do for short pieces, if furnished with Dr. Lind's press, (a useful instrument, that I believe has never yet been described or published), and I have practised it, but is too costly to answer for large works. Let us therefore suppose Stencilling. a kind of copper or brass latten to be rolled thin for the purpose, and the writer to use a very corrosive ink, which in a short time would eat quite through the whole body. He would by this means produce a stencil as fast as he could write, by means of which he would be enabled to print the right way. Again let us suppose he were to make use of capital let- Paper stencil. ters only, acting as punches on paper, he would by this me thod have a paper stencil, that would last as long, perhaps longer, than the latten one. Tin foil again might be used in this way, or fine Tinfoil, or bis plates of bismuth, for common ingenuity might overcome muth. the difficulties of the O and other letters by ties. Many Many thoupeople will smile at the idea of a paper stencil, who are ig- sand impres sions may be norant of the nature of paper when oiled; but I have been taken from an witness to Dr. Lind, of Windsor, printing from a single pro- oiled paper file of the King, cut in paper, after he had used it for many thousand impressions, and saw that it was still unimpaired. stencil. Paris, and cut, Again let us imagine thin and cheap pannels of wood Wood covered dipped in fine plaster of Paris so as to coat both sides, and with plaster of then smoothed and well hardened by oil: would not such a in relief. block afford good impressions, if we were to cut down its surface, and leave the relief in cameo? This I have tried in blocks of plaster of Paris, and made clear and good impressions from a drawing thus cut out of a small block; which, if not so hard as wood, is still hard enough to impress with, and, where few impressions only are wanted, a very good substitute among men who can make their own drawings, especially where they are objects that do not require effect. down. I have also imagined, that for diagrams, or plans, very Paper glued on thick paper firmly glued to a smooth board would, when the wood and cut interior of the design was cut away, give relief enough for printing, provided the lines were close enough; but in printing Por tipool ware. Easy to engrave on pew ter, or on copper with white wax. Pencil draw printing such things as this, we ought to apply the paper extended quite straight, and strike it down by a blow from a flat smooth instrument of the size of the block. On a Pontipool teaboard I can with a common stile or dry point at any time, with as much ease as I can draw, make an etching where not much force is required. By the same rule I can write on it, and use it as an engraved plate. The paperteaboards might perhaps even be found more useful. Ou pewter, made very soft, it is easy to engrave, but very few people know, that on copper also it is as easy to, draw with an iron stile, provided you prepare your ground of slightly coated common white wax spread over it with a dabber when the plate is hot. This thin coat of white wax is useful to receive a pencil tracing of your drawing, which may be deposited on it by a slight friction applied to the back of the paper, or if large by the rolling press; and also serves effectually to prevent the dry point, or stile, from slipping when you begin to scratch the copper through the waxen coat. The burs you may take off by the common mode, or by charcoal partially if you want effect. ings easily engraved thus. But to return from this not quite a digression, (for if we can learn to write backwards this dry point graving, through white wax, would be the best method of executing plates to imitate writing, and is I believe now used by writing engravers), let us consider cheapness of block as an absolute Incombustible desideratum; and think whether, if we can find a material ink on wood. that resists the effect of flame, we may not write with that material, and char the rest a little way in, so as to leave a cameo letter and if such a plan could be executed, poplar and beech might by machinery be soon reduced to level and cheap blocks. You will perhaps yourself smile when I tell Blocks of car you, that I have used blocks (if they may be so called), of pieces of carrot, to impress mathematical figures of solid forms for the purpose of facilitating instruction; and that a pack of cards were thus made by a son of mine on an emergency, using indian ink instead of oil colour. rot. A seal for To stamp priuts, drawings, or such sort of property, a voprints or dra- lute shell ground down on a hone makes the securest seal ings not easily jmutated. in the world; for two cannot be made exactly alike. Sections of shells are indeed the best seals we can have, if we |