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through. Fig. 3 is a similar plate of thick sheet-iron, not rivetted fast, but screwed on the upper side of the stock with four screws aaaa in the holes eeee of fig. 1, so as to be taken off at pleasure. Fig. 5 is one of the dies, aud fig. 6 the other, with wedges, which will be de scribed again. Fig. 4 isfa screw for moving the die (fig. 5) on between the plates as it cuts. Fig. 7 is a inaster-tap for cutting similar dies; and fig. 8 is a view of fig. 6, with the wedges in the proper places, as they ought to be, when you wish to cut a right-handed screw.

It will be seen that in the dies there is no rake or thread, consequently when set in between the plates, in the stock, the ends of the die, fig. 6, being previously supplied with four wedges of equal thickncss, the notches or indentations in each die would be perfectly opposite and pa rallel to each other, and would not cut a screw, but would be in the proper position for cutting a master-tap, fig. 7, or for the master-tap when made to cut the dies. From this it will be seen, that one mastertap could be turned in the lathe with three or more indentations of different sizes, abc, &c. fig. 7, which would cut as many different sized pairs of dies. Take off the plate, fig. 3, by unscrewing the screws aa aa, and also take the moveable die, fig. 6, out; then, instead of wedges of equal thickness, introduce those of fig. 6, and the die will have the position of fig. 8; screw the plate, fig. 3, on again, and the instrument is in its proper place for cutting a right-handed screw. If you unscrew as before, and shift the wedges, that is, put a thick one in the place a thin one occupied before, screw the plate back in its place, and you have the instrument in its proper place for cutting a left-handed screw. It will be seen by an inspection of fig. 8, that the end a is lowered down the thickness of one thread, and the other end b raised a little to make the threads or indentations on that side perfectly agree with its opposite die. The shape of the wedges are given (a thick and a thin one) so as to keep the die firm in its place between the plates, and to give it its proper inclination; the other die is made to fit and slide nicely in the stock and between the plates, so as to he moved onwards by the screw, fig. 4, as it cuts. By having another set of wedges, so as to lower the end a, fig. 8, one-half a

thread, the other made to match its opposite die as before, a right and left-handed double-threaded screw may be cut; those wedges are very easily made and fitted.

The great superiority of this method to the common dies now in use, the most indifferent observer cannot help observing; the ease and simplicity with which they are constructed, and the extent of the work performed, will no doubt render it preferable, and also insure its inmediate adoption in the mechanical world. Yours, &c.

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378

IMPROVED HANDLE FOR STREET WATER-POSTS.

the screw is formed is the same as that which was employed by the late Mr. Allan for cutting a true screw for his dividing-engine; but the machine now described will perform what his would not, viz. cut a screw of any length.

Description of a Machine for Cutting correct Screws.

CCCC is a frame of metal, between the bevelled edges of which a piece of box-wood E slides, in which is an angular notch for the reception of the cylinder upon which the screw is to be cut. The box-wood is used in order that as soon as a thread is cut upon the cylinder a similar one may be formed by its action upon the wood, and by this means ensure all the succeeding threads to be repetitions of the primary one. Under this piece of wood a plate of brass is fastened to the end of a screw, which passes through the handle F. The nut G is also tapped, and, being confined to its situation by a sinall screw (the point of which enters a groove formed round the nut), will when turned round force the brass plate and block of wood up towards the cutter D. A is a divided micrometer-head, the lower half of which is connected with the tube B. This tube is again fastened into the centre of the upper plate of the frame C. The upper half of the divided head A has in its centre a cylindric piece of metal accurately fitting the tube before-mentioned confined in its place by a small screw at the side of the tube B, and formed so as to receive at its extremity the cutter D, which cutter is also firmly fixed by a small side-screw.

In order to use the machine it is necessary, in the first place, to fix the cutter D at right angles to the axis of the cylinder upon which the screw is to be cut. For this purpose, let there be prepared a cylinder of steel, hardened, round which is turned an angular groove; release the small screw at the side of the tube B, so that the divided head A and cutter D attached to it shall be free to move round. Now insert the above-mentioned cylinder of steel in the notch of the box-wood E, so that the groove in the steel cylinder may receive the cutter D. Gently force

it up against the cutter by turning the nut at the end of the handle. Now turn round the steel cylinder, and it will placé

the cutter at right angles to the groove in
the wood E. This being done, in order
to cut a screw with any given number of
threads per inch, calculate trigonometri-
cally what angle the thread must form
with the axis of the required screw. Set
then the cutter to this angle by the gra
duations on the upper half of the head A,
and fix it by screwing up the screw at
the side of the tube B. Having the
cylinder upon which the screw is to be
cut turned true in every respect, place it
in the notch of the piece of wood E.
Screw it up (slightly at first) against the
cutter by means of the nut at the end of
the handle F, and turn the cylinder cau-
tiously round; the screw will then be
formed upon it, and by degrees may be
cut to any required depth. For a left-
handed screw the cutter must, of course,
be set in the contrary direction to that
required for a right-handed one; and I
should also state, that the cylinder upon
which the screw is to be cut should be
inserted about an inch or so into the ma-
chine at the cominencement of the opera
tion, that it may have a good bearing.
I am, Sir, yours respectfully,
N. S. HEINEken.

Sidmouth, April 26, 1836.

IMPROVED HANDLE FOR STREET WATER-
POSTS.

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Sir,-Within the last twelve months the New River Company have adopted the commendable precaution of prevent ing a needless waste of their water, by

locking up the water-posts throughouj the metropolis; but they have not been at all happy in the plans they have résorted to for this purpose. In the first place, a ring was fastened on the octagonal at the top of the post, and a chain brought down from it to a staple fixed at the side, and secured by a padlock. This was, for many reasons, a very objectionable arrangement, and has been recently superseded by another modification, unfortunately not much better. In the present contrivance the octagonal ring is attached to a long arm which terminates in a chain-link, and eye to embrace the staple. When water is required, the padlock has to be opened, the ring, arm, &c. taken off, and a key placed on the octagon pin, when the cock may be turned.

Annexed is a rough sketch of a contrivance, that I am inclined to think would be much more convenient, and far more advantageous, than any of those that have been hitherto employed. ab is a curved iron arm or lever permanently fixed to the plug-head of the cock, and hinged at a, with an eye to embrace the staple at b; the padlock making all fast.

When water is required, the padlock being removed, the arm is raised to the position shown by the dotted lines, and forms of itself a handle, by which the water may easily be turned off or on at pleasure. By an arrangement of this kind, no key, except that to the padlock, is required to be carried by firemen and others who have occasion to use the water, and a cock so secured may be opened in less than half the time taken up by the three-fold operation at present required.

The foregoing sketch exhibits the mode of applying this principle to posts at present standing; but in any new castings it might be applied in a more elegant

manner.

I remain, Sir, yours respectfully, WM. BADDELEY. London, August 23, 1836.

DR. M'CORMAC'S ROTARY PRINTING-
MACHINE.

Sir,-While looking over your valuable journal for July, I find at p. 271 the announcement of a patent rotary printing-machine. Such a one occurred to me several years ago; and about five years since, I had a small machine con

structed of three cylinders, upon one of which I imposed the type, and upon an other come woollen cloth; the remaining one was for the purpose of applying the ink. I found it to answer very well for illustrating the principle of rotary printing; and a correct impression was given with any degree of speed by turning à crank. I employed both moveable type and bent stereotype plates. Upon visiting London, however, I found the latter in use; but no one with whom I came in contact seemed to have conceived the idea of the former, nor was it any where in operation. My discovery was communicated to a number of friends here; and in London, I mentioned it to Dr. Birkbeck, Dr. Bowring, Mr. Spottiswoode, Mr. Bramah, Mr. Clowes, Mr. Morgan, and others, and I directed a respectable firm of solicitors to take the preliminary steps for securing a patent right. This, however, I declined prosecuting to the close, partly on the score of the expense, and partly from the interference of professional pursuits. When I mentioned my proposed method to Dr. Bowring, he said that it had been long in use; and was only convinced of his error by inspecting, along with me, the improved printing-machine at Mr. Hansard's, Paternoster-row. Mr. Clowes, while he accompanied me through his establishment near Stamford-street, admitted the applicability of my method, but contended that the improved machine then in use was adequate to meet every demand.

It is quite obvious, that an arrangement whereby a revolving cylinder is covered with type must produce results very much superior even to those of the very best engines now manufactured. The establishment of the Times newspaper has been noted for its efficiency, yet a rotary-machine would as much excel that which is employed therein, as the latter surpasses those ordinarily in use. This will be evident if we consider, first, that the area of the form of type employed in the existing improved machine does not perhaps exceed a fourth of that of the cylinder by which the paper to be printed is applied to the surface of the form; second, that the cylinder in question, in place of continuously revolv ing, has its motion reversed,* in order to

* Our correspondent is in error here; the cylin ders revolve continuously, but the bed upon which the form of type is laid reciprocates.-ED. M. M.

380

LUBRICATION BY WATER.

permit the form to resume its place, by which the area of the latter is virtually reduced to one-sixth of that of the cylinder; and, third, that the existing improved machine only admits of a limited degree of velocity; whereas that of the machine which I propose is restricted in this respect only by the capacity of the materials, and an equable rotary motion would permit considerable rapidity-but if we only say six times that of the ordinary improved machine, it will, if added to the increased area, produce an increase of rapidity virtually twelve times greater. It is obvious, however, that a duplicate engine might be so arranged that both sides of the sheet might be printed almost at the same instant; hence the ultimate rapidity will be about twenty-four times that of the existing improved machine. As the improved paper-making machines can turn out sheets of any required length, such would probably answer better in the proposed rotary printing-machine than the small sheets now in use.

The bent stereotype-plate I found in use when I went to London, but I was previously ignorant of the fact. One would have supposed that the utility of extending the plates over the whole cylinder would have been obvious, but in Mr. Clowes' machines the plates covered but a small portion of it indeed; and the motion, in place of being a continuously revolving one, alternated backward and forward, by which half the area of the cylinder, or, in other words, half the time was lost. It might have also been thought that the superposition of stereotype-plates on a cylinder might have led to the superposition of moveable types also; but it was not so, at least it was no where in use, nor did I ever hear of it before the conception arose in my own mind. The method by which it occurred to me that this might be realised was simple enough; the type must be wedgeshaped or pointed, or the spaces which separate them must be so. I chose the latter in the rude machine which I had constructed, for the simple reason that I had no means at hand of procuring wedge-shaped type, or for having them. cast. It is quite clear that no other contrivance will avail to secure the necessary parallelism of type when applied to the surface of a cylinder. I proposed to secure the type together by a small iron

chase, with four sides, two of which were suitably curved and applied to the cylinder by means of screws. The size of the chase was to be that of the half sheet; and the types were to be duly secured in it by lateral screws. In this manner I locked together, and applied to my little cylinder, an advertisement casually taken from a printing-office, which sufficed, with my limited mechanical means, i to show the practicability of the principle of rotary-printing. The chase, with the contained type and lateral screws, I showed to several individuals in London, and finally left it at the National Repository, Charing Cross.

I remain, Sir,
Your very obedient servant,

HENRY M'CORMAC, M.D.

Belfast, August 24, 1836.

LUBRICATION BY WATER.

Sir, I perceive in the report of the Times of the proceedings of the scientific meeting at Bristol, that Dr. Lardner suggests placing watering-pots before the wheels of a train of railway-carriages to reduce the friction. The fact of a train running lighter on a wet day is well known to every engine-driver; and it occurred to me to avail myself of the water leaking from instance, into my ash-pan (described in the boiler or tender, passing it, in the first No. 680), from which the excess drops in a small jet behind the engine-wheels; thus the engine travels over the dry, and the tender and train over the wetted part of the rail. In the event of the boiler being so tight that the leakage would be insufficient, two small tubes, with regulating cocks, should pass from the tender or cistern, and discharge a small jet on the rails as the train passes along. I shall feel obliged by your insertion of this letter in your earliest Numberin order to advance my title to the priority of this useful adaptation of what would be otherwise lost water.

I remain, Sir,
Your obedient servant, 14
W. J. CURTIS.

Deptford, August 29, 1836.

MR. MACKINTOSH'S ELECTRICAL THEORY OF THE UNIVERSE.

Sir, Mr. Mackintosh informs me in his last article (No. 681) that I labour under a mistake with regard to his elec

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