2000

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8000

, and probably of a line in diameter. Their minuteness and transparency place them beyond the power of the microscope. It is probable that these eggs, raised by currents of air and the evaporation of water, may fill the atmosphere, and sustain little injury from aridity, because they appear to settle and develope themselves every where, and are perhaps perceptible in the organized matter, the pyrrhine of the atmosphere observed by chemists. But as to living infusoria and meteoric animals, or what are called Atmospheric Zoophytes, found in currents of air, we cannot believe in their existence until better evidence than the present is brought forward. The forms not hitherto satisfactorily observed are,

1. Kolpodapyrum, Müller, according to Gleichen.

2. Indeterminate infusoria, according to Bory.

Outline of a Plan for combining Machinery with the Manual Printing-Press. By JOHN CLERK MAXWELL, Esq. of Middlebie*. (With a Plate).

ON a former evening of this session, (Jan. 5.) a paper by Mr Fraser, suggesting various improvements on the Art of Printing, was read before the Society, in which, after pointing out the excellency of the Printing Machines, invented by Messrs Cowper and Applegath, and by Mr Napier, for the purpose of publications of large numbers of copies, and where expedition was required, he noticed, that, for fine printing, they were inferior to the manual press, although they excelled in one point, viz. the uniformity in inking, and consequent equality of colour of the printed sheets. He also observed, that, for economy in the case of small publications, the manual presses had the advantage. And concluded by stating, that a contrivance which should give the manual press the benefit of uniform inking, with a diminution of labour, was a desideratum in the art of printing.

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* Read before the Society of Arts for Scotland, 8d March 1831.

Mr Fraser says, "As to the inking apparatus, that attached to the machines of Messrs Cowper and Applegath might be placed immediately behind the tympans of the Stanhope or Columbian presses, and be worked by steam-power as at present. Were the tympans and carriage of the press in separate pieces, but made so as to fit very exactly into each other, the carriage might, after each impression, be taken from the hand, on reaching a certain point, by the inking apparatus, and, upon the types being rolled, returned to the same point. In the interim, the pressman could be laying on and off his sheets; and by the time he had done so, the form would again be stationed at his hand, and ready for his taking another impression. It is obvious, that the great difficulty to be overcome here, will be the construction of the machinery for receiving and returning the carriage, and making the carriage so nicely to fit the frame-work of the tympans, as to preserve register, as it is called; but after the ingenious contrivance of Mr Napier, in his machine, for receiving and giving off the paper, there can be little doubt of these difficulties being soon obviated. In this way, the great desideratum of securing an equality of colour would be supplied, and the expense of an apparatus for each press, with an engine-power for the whole, would be compensated by only one-half of the men being required."

Having been named a member of the Committee appointed to consider and report on Mr Fraser's suggestions, my attention has been turned to this subject, and some contrivances have occurred to me, which seem fitted, in some degree, to accomplish what has been considered to be desirable. I have now the honour of laying them before the Society, as they occurred to me, thinking, that the shewing of the original conception is better adapted to elucidate the principles of the contrivance, than a description of a more perfect form of machine, with its parts more compactly arranged, and, on that account, more difficult to be described; besides, I conceive the principles of a contrivance more interesting than the details.

If any hint contained in the sequel should prove of use to those who may make trials to effect what Mr Fraser has proposed, it would be a proof of the value of this Society, and of the benefits to be derived from statements like Mr Fraser's,

calling attention to what is felt to be wanting to improve any art,—for if my humble endeavours contribute any thing to the art of printing, it is owing to Mr Fraser's paper that my thoughts were turned to the subject.

In inquiring into what had been done by others in regard to inking, I learned that there have been contrivances for this purpose, but that they had not answered expectations, and for this cause, besides others, that, although the inking was done by machinery, the constant pulling the press was too severe labour for the workman, if the usual number of impressions in a given time were demanded. In the common way, two men work together, and relieve each other, by taking in turns the duties of inking and of pulling. I have therefore attempted a plan to save the labour of the pull, as well as to ink the types by machinery.

Explanation of the Sketch. (Plate V.)

In this sketch, which is intended merely to give a general notion of the plan without details, no part of the necessary frame-work is represented, except the cheeks of the press, and the range of the frame-work of the inking apparatus, which are slightly shaded. The inking apparatus is arranged on the plan of Messrs Cowper and Applegath, with an inking table, which is understood to produce the best work.

The drawing represents the press in a state of rest. A the coffin and forme, with tympan open, B the inking table, C the inking rollers, D the distributing rollers, E the ink-trough, with its rollers, to be put in motion by the pulleys and bands (both dotted in the sketch); but the proper rates of motion are not attempted to be shown,-only the mode of communication, and where an alternate motion is improper, the pulleys would be furnished with a ratchet and spring, so that they would revolve in one way only. F is the supplying roller, which is raised to touch the ink-trough rollers, on the advance of the ink-table by the wedge H, on the carriage of the ink-table acting on G. Under these parts is an oblong rack-work, connected by a hinge with the under side of the ink-table; at the right hand end of this there is a wheel supposed to be in constant motion, connected with the moving power. On the end of the rack is a projecting pin I, intended to slide along the bar, K, and fall over the end of it, when the lower corner of the rack would rest on the bar L, on its return.

The tympan has a carriage of its own, separate from the coffin and forme, (which might be called an outer coffin), which is made with three sides, the true coffin and forme in it being intended to slide out, in order to be carried to be inked. This is shewn at fig. 2, where the shaded part marks the outer coffin, with marks for the hinges of the tympan, and within it the true coffin and forme ; beside these, is drawn the ink-table; this has two pegs with notches, which go into corresponding holes in the coffin, attaching and locking them together in the same way as the fastening of the bit in a carpenter's brace. On the

tympan, as shown in fig. 1, there is a quadrant of a spiral curve M; this is an important part. When the tympan is open, the coffin is free to be drawn out, and it is locked to the inking table; but in shutting down the tympan, this part, by the spiral curved edge, wedges the coffin and forme hard home in the tympan carriage, so as to secure its true position to preserve register, and at the same time the sides of the quadrants press back studs which unlock the coffin from the inking table.......

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The press may be of any approved shape or material, and it has its spindle acted on by an excentric wheel V, which is to be put in motion when the coffin is run home in the press, by its pressing on the end of the lever N, which throws the press into action, the shaft or axle O being in motion from the moving power, and properly sustained by a fly-wheel. The press then descends, and, on its return, the wiper P throws this part out of gear, and at the same time presses back N, which, striking on the coffin, gives the signal for the pressman to run it out. The platten is counterpoised by S, and the excentric wheel by R, so that when free the parts settle in the position ready for action, the wiper P being behind the lever N; on the lower end of N is marked two notches, with a round part between them, with a catch pressed upwards by a spring; this is to make the lever N settle in the positions of being quite out of gear or perfectly in gear.

The working of this apparatus by one man would be thus arranged; he would commence with the tympan down, and by acting on the treadle T he raises the rack, so that the pin I may slide along the bar K; the wheel then carries the inking table alone under the inking rollers and others, and returns it to its position; this is to be repeated till it is fully charged with ink, then he opens the tympan and touches the treadle, and the forme is carried off to be inked, while he places white paper on the tympan; the forme being re turned to its place and the tympan shut down, he runs it home into the press, the inking table being left at rest. The pressman would bear on the winch till the press falls, and then reverse his action, ready to run the forme out whenever the lever N strikes it back. Having run it back and opened the tympan, he touches the treadle, and proceeds to change the sheet while the inking process goes on, and repeats these operations while he continues to work.

I have thus described the contrivance in its most simple arrangement. The ordinary plans of framing, and the various modes of relieving friction, and all accessories met with in modern machines, are supposed to be used where wanted.

One of the objections most probable to arise at first sight is the inconvenient length of the machine, but this may be obviated in many ways. 1st, If shortness be an object of importance, it can best be obtained by applying those contrivances for inking which do not require the inking table; for if the distribution of the ink be done entirely by rollers, for example such as those used in Napier's machine, then these could be placed un

der the gallows of the tympan, and the forme would have to be moved little more than its own breadth. 2d, Supposing the inking table retained, as the method best suited for fine printing, the long rack-work may be superseded by a short one, and the necessary extent of movement effected by the use of wheels and pinions, or by pulleys and bands, the diameters of the pul leys being so proportioned as to increase the motion; and here it may be observed, that it may probably be found advisable in all cases to interpose pulley and band between the toothed work and the inking table, to free it as much as possible from tremor. 3d, Instead of the long rack-work, circular work may be used, either by using alternately the outside and the inside of a toothed circumference, as is done in the Patent Mangle, or by using two wheels, moving in opposite directions, having teeth on one half of their circumference, acting on two lines of rack-work; and if multiplying pulley and band work were interposed between these wheels and racks and the inking table, they might be reduced to a very moderate size.

With regard to the contrivance for working the press, I may observe, that the excentric wheel has the advantage of a motion slow and powerful in proportion, at the first, in order to overcome the vis inertia of the apparatus of the press, and also at the point of greatest pressure; while it is quicker in the middle parts of the action, both in the rising and the falling of the press; and the resistance of the wiper in throwing the work out of gear, would serve to exhaust the momentum of the excentric wheel, its axles, &c. &c.

In the Sketch, the shaft for putting the press in motion is supposed to pass right over the press, and the excentric wheel to act directly on the spindle of the press; but it is evident the effect may be obtained by the intervention of a lever at whatever distance the shaft may be; and so the contrivance may be suited to any situation, and, instead of acting on the spindle, it might be arranged to move the bar of a common press.

When a few impressions or proofs merely are wanted, the inking apparatus need not be used, the hand-roller, used in the common way, serving instead; and as the inking apparatus and that for working the press have no connection, one or other, or both, may be used at pleasure; and if the press were fitted with a bar,