and on the axletree b. 7, a lever, or handle, affixed on the upper end of the spindle 6, for turning the spindle, and thereby the arms, and by means of the connecting rods turning the hinder axletree and its wheels to guide the carriage; this handle may, by means of a spring catch of any ordinary construction be held in such position as shall keep the hinder axletree parallel to the fore axletree when running upon railways. 8, a break and lever turning on a stud in the upright frame p, and acting

against the back of the fore-wheel of the carriage, the handle of the lever reaching up near to the seat of the driver.

Mr. Parkin states that he is aware that the lifting of a portion of the weight of a horse to ease his labour on descending hills has often heretofore been effected in carts by shifting the body of the cart backwards on the axletree, and in other cases by taking a part of the loading from the front and placing it at the back of the cart; and also that a method of lifting a portion of

ANOTHER FORMULA FOR CALCULATING THE SIDES OF RIGHT-ANGLED TRIANGLES BY THE SLIDING RULE.

Sir,—It is with great pleasure I have seen in your Magazine the able efforts of your correspondent, Mr. Woollgar, to bring into notice and to extend the power of that excellent and useful instrument of calculation, the sliding rule; an instrument, the value of which, I am sure, is far from being so well known and appreciated as it deserves to be.*

Having found out by experience its great use in checking, as well as in calculating problems of all kinds (involving multiplication or division), I was induced some time ago to make out for my own use, a complete set of formulæ for the solution of the most useful practical questions in trigonometry and mensuration, among which were the following two for calculating the lengths of the sides of a right-angled triangle, (the first problem given by Mr. Woollgar in your 849th number). They may not be perhaps quite so simple in practice as the one there shown, but they have this advantage, that they may be performed upon the common rule, without the necessity of laying down any new line of divisions.

The first formula is for the trigonometrical lines of Sines (marked S), and Tangents (marked T), upon the back of the slide; the second for the lines A. B. C. D. alone.

1. Let a and b be the two legs, and C the bypothenuse; A. B. C. being the three respective opposite angles: it is well known that c: sin. 90° :: b: sin. B, and also that, tan. B::: tan. 45: a, therefore, by finding intermediately this angle B, (or A as the case may require,) any side may be found when the other two are given, in the following manner : b Angle B

Al

Tang.

a

45

с

90

And it should be observed, that although two formulæ are required, yet, the fac

Erratum in Mr. Woollgar's letter in No. 849At p. 101, last line, for "1.049"-read "1.04q."

I should perhaps state, that by the common rule, I mean the one laid down by Mr. Bevan, and sold by most of the opticians in London. This being, I believe, the one most generally used for the purposes of calculation.

tors all lying very nearly together under the eye, and all that is requisite to connect the two, being to carry with the eye the intermediate angle found, from one line to the next adjoining, the operation is almost as simple as if there were only one: a few trials will prove this.

2. The other formula is only adapted to the case where the hypotheneuse is one of the sides given, and it is merely an application of the well known theorem that the product of the sum and difference of two numbers is equal to the difference of their squares." Thus, suppose c and b given to find a; then√(c+b) (c—b)

a = √c2 — b2, or = which, adapted to the rule is(c+b)

A |

B

C

D

(c-b)

a

MOODY'S METHODS OF PREPARING HIDES FOR MILITARY ACCOUTREMENTS, AND PREPARING FIBRED FLOCK FROM MILLED WOOLLENS.

Sir, In the year 1812, the late Mr. Alexander Moody, an extensive paper maker at Hawley Mills, near Dartford, in Kent, entered a caveat for a new mode of preparing hides for soldiers' accoutrements, &c., and meant as an improved substitute for the usual species of buff, or losh leather, hitherto used for that purpose. The specimens he produced, considering them as a first experiment, went

far to create in his favour a very striking probability of success. The first hides he thus brought to maturity were inspected by his late Royal Highness the Duke of York, accompanied by his then secretary, the present Lord Bloomfield, who both testified their highest approbation of the colour, brightness and texture of the articles, beyond those dressed by the other method; both kinds underwent a critical examination in contrast with others on the score of merit. Mr. Moody's hides had been brought to perfection, without having been subjected to the severe process of milling, which never fails to impair, in a great degree, the strength, closeness and fine surface of the animal substance; his specimens were compact and firm, of a beautifully clear bright colour, and previously to their being inspected by the above leading personages, they had been looked at by many of the best judges in the trade, and they unanimously gave the preference to his hides beyond the others, by the old method. The Duke of York was so highly pleased with their handsome appearance, that he expressed it as his determined intention that they should be adopted speedily by the army at large. The health of the soldiers too was an important consideration. It is well known that soldiers are subject to severe colds and ailments, owing to their accoutrements, which are made of a spongy porous leather, imbibing and retaining a great deal of wet. This defect, and it is a serious one, Mr. Moody's new species of buff leather,will totally remedy; but there was one drawback, and one only, (which he intended, had he lived to have remedied,) viz., a slight stain was communicated by its coming in contact with the soldiers regimentals in wet weather; this alone prevented the ingenious inventor from reaping an equivalent reward. Having myself inspected the hides in company with the late Mr. Beddome, tanner, I feel no hesitation in saying, supported as I am by that gentleman's superior testimony, that Mr. Moody's new method of manufacturing buff leather was an evident improvement upon the old one, barring the one defect which I have mentioned, and it is a pity he did not live to mature his laudible industry.

While my pen is in hand, I beg to mention another ingenious attempt of his, of manufacturing an open fibred

flock out of hard milled woollen rags; this he effected by means of powerful pressure between smooth plates, in an engine; whereas, the only method known of converting milled woollens into flocks, is by grinding their substance down, by the same process as reducing paper stuff into pulp. I am sorry to say, that Mr. Moody was snatched from this sublunary world just as many of his most useful ideas were expanding into fructification. I remain, Sir, your obedient servant, ENORT SMITH.

IMPROVED SHOP-SHUTTER CASE.

Sir,-Herewith I take the liberty of sending you the description of a plan which suggested itself to me several months ago, and having given it a careful examination, I am confirmed in the opinion, that its adoption would be of public utility. It is a design. for an improved shop-shutter box, to be sunk into the ground, and with its suitable lid let in flush with the pavement. It has a moveable bottom or tray, which, with all the shutters, except one, (when in the box,) is balanced by four equal and suitable weights passing over pullies and working in corresponding grooves. In putting the shutters away in the morning, they are to be placed, one after another upon the moveable bottom or tray, (which, having no load, will be near the surface,) and will remain stationary until the last shutter is put into its place, when the weight of shutters preponderating will cause the whole to descend. The cover is then dropped into its place, and closes flush with the pavement, thus concluding the process. On shutting up, the reverse takes place; the lid or cover is first raised, and, then one shutter; the rest will follow by the preponderance of the weights, rising gently and perpendicularly into the street, instead of being shot as they too often are, at the unconscious passers by out of a cellar window. At night when the shutters are out of the box, the moveable bottom lies immediately under the cover, so that it cannot be employed as a refuge for disorderlies, as in most cases the weight of one person would not be sufficient to depress the bottom, or the lid may be fastened by a lock for perfect security.

I am yours most respectfully,
WM. JONES.

Manchester, July 20, 1839.

GAS METER REGULATOR.

Sir,-Allow me through the medium of your Magazine, to suggest the following improvements, to the manufacturers of gas meters :

To the interior works of a meter, attach a balance and escapement, which will prevent the meter revolving quicker than may be necessary to give a good supply of gas to each burner connected with it. The escapement might be made similar to those in watches, and also regulated as easily, although when once done properly it would not require altering. Thus the escapement would check the evils that arise from changes of pressure, serving the same purpose as Bacon's Patent Moderator, described at page 98, with the advantage of being combined with the meter, and at a very inconsiderable increase of price over the

In France it is the practice for an applicant for a patent to lodge a description of his invention sealed, and from the day of this deposit, his right, as against all after applicants, is secured. These descriptions, or "Memoirs descriptif," as they are termed, are taken in turn, and examined by a Commité Consultatif, and the patent either granted, or the inventor recommended to withdraw his application. He may, however, demand his patent notwithstanding this recommendation, and it will be delivered to him at his own risk.

This mode of proceeding certainly is far more just in principle than that followed in Britain; but the recent practice has rendered it extremely vexatious to inventors and patentees. A correspondent from Paris informs us that he lodged a demand for a patent eight months ago, and he has not yet received the "Certificat de demand." He "attended at the office to ascertain the reason, and found that the packet of documents had not yet been opened by the consulting committee, but was lying along with a large mass of applications in the same state, some of which had been deposited in December last, so very numerous are the patents which are now

167

continually taking out, and so very niggardly is the economical spirit of the administration, that they will not put on extra hands to do the extra work, but allow it to accumulate in the manner just mentioned, to the great inconvenience of the public."

Our experience in the matter, in a great measure confirms the statement of our correspondent, although we have no applications so long in abeyance as since December last, and we think that there must be some other than the ordinary causes of delay to arrest the progress of those referred to. We trust the French government, who are generally so attentive to the advancement of matters of science and manufacture, will make an alteration in this state of things, and appoint additional officers to meet the increased business-otherwise the evil will mend itself in a way not so favourable to the French industry. Inventors, and particularly importers of patents, will cease to apply, where there is so great uncertainty and delay in obtaining their right; as they cannot of course take any active steps towards the sale or working of a patent until they know of its security. Circumstances

too, alter, and occurrences take place in the course of time, which might render an invention which is invaluable to-day, worthless to-morrow.

There is hardly any vexation equal to the vexation of delay;-opposition you may meet and overcome, but the laggard steps of tardy officials and formal processes you cannot hasten. We do not accuse any of the gentlemen constituting the present commité of neglect-far from it-we believe that they have used every exertion to get through the accumulated mass of memoirs. We hope soon to hear that some competent members have been added to their number-and that the anxious inventors who have been so long been kept waiting in suspense, will speedily know their fate. Finally, we would observe, that it is the interest of the government, both directly and indirectly-for the sake of their treasury -and of the industry of the kingdom, rather to facilitate than throw obstruc tions in the way of native inventors, and importers of foreign inventions.