158 INQUIRIES ANSWERS TO INQUIRIES. 4 in the unit's place (viz. 64); I then add the 4 to the 9, which is 13; I know, therefore, that 3 is the figure for the tens place: our operation will then stand thus, 40,000+800+ 30+6=40,836, the answer. And here it may be observed, that though I have shown how the operation may be performed to the extent of five figures, it is, in actual practice, of little consequence to the measurer who is in the habit of using the rule, being chiefly confined to the journeyman carpenter, sawyer, &c.; and the dimensions they have to take scarcely ever exceed two figures for the multiplier and two for the multiplicand, for in that case other methods are found preferable. These observations will apply to any of the following Problems; I shall therefore only give them as regards the method of using the rule for their solution. G. A. S. (To be continued in our next.) NO. 129.-TEST OF BAY SALT. The test for ascertaining the quality of St. Ubes, commonly called Bay Salt, and the reason why some samples dissolve sooner than others? A house in this city, very extensively engaged in the manufacture of provisions, purchased a cargo of very fine-looking salt two years since, but complaints were received from all quarters of there not being salt enough, though the usual quantity was put into the cask. The salt was of a fine white colour and large grain. No. 128.-FELT SHOES AND GLOVES. SIR,-We remember seeing, some years ago, a pair of Felt Shoes, and, the other day, a pair of Felt Gloves. If any of your Correspondents could inforin us where or by whom they are manufactured, they would very greatly oblige, Sir, Your obedient servants, HANDS AND FEET. ANSWERS TO INQUIRIES. NO. 111.--SPRING WEIGHING MACHINE. SIR, I think your Correspondent F. S. M., vol. 1., p. 415, will find that the weight of the line itself (if suspended during the experiment, as I apprehend it must have been), between the spring machines and the difference in the scale of weights carriage, will be nearly equal to the drawn forth. It is well known to seamen, that a long cable materially assists itself by its own weight, and that less strain is brought upon the ANSWERS TO INQUIRIES.. anchor by a long cable than a short one, the strain on both being lessened by the weight between the ship and the anchor. This is particularly exemplified in the use of chain as cable, the difference in weight compensating for the difference in length in the proportion of two to one. Thus, with a chain cable of 100 fathoms, a vessel is supposed to ride as safely as with a rope cable of 200 fathoms. Should my attempt at elucidation afford F. S. M. any part of the information he requires, it will give me much pleasure. I am, Sir, 159 NO. 100.-CUTTING AND POLISHING CALCAREOUS STONES, ETC. SIR, A Correspondent who signs himself "Lapis," in p. 352, Number 78, is desirous of information respecting the best method of Cutting and Polishing Calcareous and Siliceous Stones; if you think the following description of a Mill is worthy of insertion in your Magazine, it is very much at your service. The apparatus is extremely simple and convenient, and may be made by new, but has been sold for some any one poseessing a lathe. It is not years by Mr. Mawe, in the Strand, at from six to eight guineas. The accompanying drawing represents a section of the apparatus. E I D AB is an oblong wooden box, in which the axles, CD, FG, revolve, and which serves also for a case. E represents a wheel with a grooved edge, and at H is a series of smaller wheels, likewise grooved, by means of which the velocity of the mills may be regulated at pleasure, and the string which connects them may be made more or less tight. At the end, F, of the axle, FG, which projects through the top of the box, is a screw, on which the different mills for grinding and polishing are to be fastened, and by turning the handle, C, it is at once obvious that they will revolve with great velocity. The string may be of catgut, or any thing else more convenient. In this manner hard siliceous stones may be ground down on the leadmill, with emery, in a few minutes, and afterwards polished on different mills, using flour of emnery and putty. When slitting is required, then the slitting-mill, consisting of a thin plate of iron, is to be screwed on, and the stone to be cut applied to its edge.. J. M. N. CONSTRUCTION OF CHIMNEYS. SIR,-The best form or construc tion of chimneys I know of, for conveying the smoke, is that of the circle, which should not be less than ́ one foot in diameter for a commonsized apartment. I am aware, however, that this form is objected to by architects, as it requires one-third of brick extra in thickness for the chimney shaft. As to the cause why so many smoke the wrong way, I think it is owing more frequently to the carelessness of the bricklayer in building than to any thing else. In fact, neither the architect nor the clerk of the works ever pays much attention to them. Sometimes they are too suddenly contracted at the throat of the flue (a little above the arch of the fireplace); and in other cases, when the flues run crooked, the bricklayers contract them to not more than nine inches by ten inches, nay, I have seen them less than that. The waste lime from the trowel, too, usuallyfinds its way down these flues, 160 ANSWERS TO INQUIRIES-CORRESPONDENCE. and lodges in the most crooked parts, and stops, in a great measure, the vent of the smoke. Sweep-boys, also, when they are cleansing the chimneys, are almost always sure to leave part of the rubbish. If J. T." will take a bricklayer's advice, he will contract his chimneys regularly at the throat, and make them rather smaller there than in any other part. He will also take care not to make them less than nine by fourteen inches, to have them gathered over regularly in all the crooked parts, and to render, the whole perfectly smooth. If these particulars are attended to, there will be no fear but the smoke will go the right way. I am, Sir, Your obedient servant, A YOUNG BRICKLAYER. or cold endways than sideways. This may be proved in the following manner:-Let a hole be punched through the centre of a square plate of iron, touch the edges with a little tallow or soft wax; then put a hot bar of iron through the hole, and that edge on which the tallow first melts will be the endways of the iron; the elastic nature of the iron, and the stocks giving way, are the causes of the irregularity in the screw. I am, Sir, Your most obedient servant, NOTICES ΤΟ CORRESPONDENTS.. No. 109.-CUTTING SCREWS. Hammer "believes that the invention of the gun mentioned by O. (page 132, vol. IV.) belongs neither to Blanche nor Pauly, having seen it applied to a flintlock above twenty years ago." The Inquiries of H. and F. were undesignedly overlooked. Communications have been received from M. M.-N. H.-T. C.-Charles M. -B.-G. U. A.-W. K.-C.-A. G. G.Montis, jun.-W. E. K.-Tempus-An Old Subscriber-R. M'Pherson. SIR,-A Correspondent, in p.399, vol. III., wishes to know the cause of Screws being largest at the ends, when cut by the stocks and dies, and how they are to be cut true. This may be effected with good stocks and dies in the following manner: Take a piece of round bar iron, or a cylinder that has previously been turned in the lathe; let the pin be two or three inches longer than you intend to cut the screw; lay it in a good charcoal fire; suffer it to get cold of its own accord; clean off the scales by draw-filing, and screw it firmly in the vice; open the stocks and put them on the pin, about an inch from the end; screw them sufficiently tight to mark out the threads on the pin; turn them down to within an inch of the other end; tighten the stocks, and bring them up again, and so on, until a full thread is used. I find, from a number of experiments, that wrought Printed by Mills, Jowett, and Mills (läte iron more strongly contracts heat 4 ERRATA.-Page 133, col. 1, line 1, for loaded read leaded gun.-Page 140, col 1, line 14 from the bottom, for 24751, read 54757. Communications (post paid) to be addressed to the Editor, at the Publishers', KNIGHT and LACEY, 55, Paternoster-row, London. Bensley), Bolt-court, Fleet-street. 182 IMPROVED PRINTING PRESS. IMPROVED PRINTING PRESS. SIR,-I have sent you a description, &c. of the improved "Russell Press;" as I am now manufacturing them, perhaps you may be pleased to insert it in your Mechanics' Magazine; if so, it is at your service. I am, Sir, Yours sincerely, HENRY RUSSELL. London, June, 1825. On inspecting the drawing, it may be readily perceived that the power of this press is derived from the twofold application of that principle which was introduced to the printing press by Lord Stanhope, and which nearly all succeeding press-makers have found it advisable to adopt. It is now about four years since my attention was turned (practically) to this subject, and the result was the production of that press, called the "Russell Press," which name it received from Messrs. Taylor and Martineau, engineers, in whose service I was at that time employed. I had, I believe, then seen only the Columbian, the Stanhope, and the original screw press; but very soon after, I had the pleasure of seeing Ferguson's Lectures, edited by Dr. Brewster, in the additional volume of which is a description of a printing press on the same principle, though constructed in a very different manner, by Mr. Wells, of Hartford: but the construction of the press to which I now wish to call your attention, although the principle is the same, differs very much from them both. An adjusting screw is introduced, the head of which is marked A, and has on it a ratchet, into which a spring, B, catches, to secure it from turning when the press is in operation: the bottom end of this screw, which is of an hemispherical figure, enters the upper pressure column, C, which is hollowed out hemispherically, in a manner suitable for its reception; the bottom of this column is hemispherical, and in like manner enters the bolt, a, which passes through the cross lever, L, and is in like manner fitted to the under column, which is also hemispherical, and enters the circular plate, which is secured to the top of the plattin by the two eye-bolts, bb. These eye-bolts are entered from the back by a forked lever, which passes through an eye, and has at its end a weight, which bears up the piattin, &c. and keeps the upper column in contact with the ad justing screw: c, a rod, connecting the end of the cross lever, d, to the lever e, which we may consider part of the lever bar, on which is the bar handle, h. That remain parallel with the table, or under the plattin, or upper surface, may always surface, two cylindrical rods, screwed into bosses on the upper side of the plattin, and at right angles to its surface, are accurately fitted to the inside of two cylindrical gun-metal guides, which are firmly secured to the back of the press by collar-headed bolts. It would be useless to describe the other parts, as they are common to most iron presses, except that, instead of employing the drum and girths for carrying in and out the table, &c. I have employed a wheel and rack; which, without considering the injuries sustained by workmen from the breaking of girths, and the loss of time in replacing them, when time is of great importance, I hope will be found preferable. The pressman having passed the table, with form, tympan, paper, &c. under the plattin, with his right hand draws the bar-handle towards him, until the lever, e, comes in contact with the back of the press; at the same time the connecting rod, c, draws after it the cross lever, Ld, which swings freely upon a perpendicular bolt, the head of which is seen at o. The length of the connecting rod, c, is such as to bring the pressure columns (each six inches in length) within 1-8th of an inch of perpendicular, at which time the impression is given, and the centre of the connecting rod comes within one inch of the centre of the bolt, r, which is the centre round which the bar-handle describes a section of a circle. The middle of the bar A handle, or where the pressman may be supposed to be to take hold of it, is 20 inches from the centre, r. The power at the termination of the pull may, therefore, be estimated in the following manner:-The length of the lever bar (20 the connecting rod from the centre, r inches) being divided by the distance of (one inch), gives a quotient, by which is to be multiplied the power applied to the bar-handle, say 28lbs. 20 × 28=560; Τ 560lbs. power is therefore applied to the end of the lever, Ld, in length 5 inches, which carries the bolt, a, by which the pressure columns are brought to the po sition required. This bolt, a, is 2 inches from the centre, o; we have therefore 20 the columns. = 11200, ·× 560- lbs. applied to The power of either column may be found by dividing its altitude by its deviation from a perpendicular fine, let fall from the centre of the adjusting screw, which we have before stated to |