to these minutiae, and equally so, not to touch the articles when finished with damp or greasy fingers; hut, above all, not to dip them in oil, which causes them to become dull, and entirely destroys that lustre, which constitutes, or, at least, materially heightens, the beauty of the colour. With ordinary care, this blue remains unimpaired a very long time; nevertheless it is subject to change, and sometimes shows dull spots or blurs. It possesses the advantage, however, of being easily renewed, and the colour brought out in all its pristine freshness, by being polished and again submitted to the process we have described.

We have observed that iron never takes so fine a blue as steel, perhaps because it is not equally hard, nor is it capable of receiving so good a polish. A supposition has been hazarded—which, at all events, is rendered probable by the known affinity existing between carbon and oxygen—that the carbon contained in steel, and its absence in iron, has some influence on this operation.

CLERKENWELL MUTUAL IN-
STRUCTION SOCIETY.

We have received a communication from Mr. Butger, Secretary to the Clerkenwell and Pentonville Mutual Instruction Society, in which that gentleman records the success of the Society, established nearly two years since, and details various branches of elementary and scientific knowledge, in which classes are formed, and lectures by competent professors delivered. He also points out the advantage of an excellent lending library, to which members have free access, and which consists of more than 500 volumes; upwards of a hundred of this number having been, with a liberality well worthy of imitation, presented to the Society by B. Kotch, Esq., Barrister at Law. We need scarcely add that this, and all similar institutions for the promulgation of knowledge, have our best wishes; nor shall our exertions be spared to forward the benevolent views of the Committee, to whom, or the Secretary (36, Cold Bath Square), we refer such of our readers as may be desirous of becoming members, for further particulars.

MISCELLANEA.

Reconstruction of the Constellations.— None but those who have had experience of it, have the least idea of the confusion which prevails in astronomical catalogues.

A common globe will show, that the boundaries of the constellations are zig-zagged in all directions, and that sometimes a long strip from one constellation passes direct into the region occupied by another. This confusion is necessary to reconcile the irregular manner in which observers have registered their results, and the occasional misplacement of stars by error of calculation, or by confounding one star with another. Mr. F. Baily, President of the Royal Astronomical Society, we hear, meditates an extensive attack upon this confused system; and Sir J. Herschel has already given notice that, as far as the southern hemisphere is concerned, he will attempt the utter eradication of the existing constellations. Even supposing that it would be hardly possible to remodel the northern hemisphere entirely, we should hope it might be practicable to introduce something like plain and easy boundaries; and, surely, no one has so good a right to make the attempt, or so fair a prospect of uniting all suffrages, as the reformer (Mr. Baily) who has broken ground by revising, comparing, and reprinting nearly all the catalogues which have been given by those who formed constellations.—Athenaum.

The approaching Exhibition in Westminster Hall.—Much interest was excited by some of the cartoons that are to compete for the prizes to be awarded by Government for the best designs for frescoes to adorn the new Houses of Parliament, being sent and placed in the enclosed space that has for some weeks past been boarded off in Westminster Hall, preparatory to the approaching exhibition there of such designs. These cartoons, according to the rules prescribed by the commission, are all executed either in chalk or charcoal, or some similar material, and without the introduction of any colours. The subjects are chosen from British history, or from the works of Shakspeare, Milton, or Spenser; and the figures are not in any case smaller than life. The attention of those in the Hall was attracted by the tops of some of the cartoons being visible above the boarding, thus giving the spectators a glimpse that excited curiosity in no slight degree, although they gratified it to a very small extent in. deed, affording nothing more than the means of judging generally of the style and character of these competing designs for the Parliament Houses' frescoes.

The Society of Arts, Manufactures, S[c. —On the 1st instant an extraordinary general meeting of the vice-presidents and members of the Society of Arts, Manufac. til res, and Commerce, was held at the institution in the Adelphi, for the purpose of electing a president of the Society in the room of his late Royal Highness the Duke of Sussex, his Grace the Duke of Sutherland, K C.B , in the chair. It having been moved that his Royal Highness Prince Albert should be the president, the motion was immediately carried by acclamation; and his Royal Highness was declared elected preiident of the Society.

INSTITUTIONS.

LBCTOBB9 DIKING TUB WKKK.

Westminster Literary and Scientific Institution, 6 and 7, Great Smith Street.—Thursday. June 22, Mr. William Higgs, on Iron and the Iron Manufacture. At half-past eight o'clock.

Mutual Instruction Society, 16, Great Tower Street, City.—Monday, June 19, Mr. W. Scott, on Acoustics. At a quarter-past eight o'clock.

Literary and Scientific Society, No. 1, Whitfield Street, Hiisburj.—Tuesday,June20, Quarterly Meeting.—At eight o'clock precisely.

QUERIES.

How to melt brass in small quantities, from 1 ii.'. to lib., and the method ot making moulds for casting the same? The reason why flies are able to sustain themselves and move upon the ceiling of a room? A. C. R.

The complete process of analyzing beer? G. K. Freeman.

How and by what means can an impression be obtained, on paper, from a print or writing, that may be distinctly visible, and without injury to the original? O. W. B.

Can the electrical machine be used successfully for blasting? How are the springs for blinds made, and how to give a brilliant polish to copper? C. P.

ANSWERS TO QUERIES, . Tomake Boott and Shoet Waterproof.—" S. C." Linseed oil, 1 pint; bees' wax, 7 oz,: clear mutton suet, $ lb.; resin, 1 oz. Put the bees' wax and resin into a clean pipkin, and melt them over a clear fire; when melted, take it off, and add the oil and suet, mixing them all well together. Make the mixture luke warm, and rub it well all over the boots and shoes before the fire with a small brush. If the boots are in constant use, give them a coat once a week. The above I have constantly used, and it has never failed, even in snowy weather. There is one drawback, which is, it makes the boots as hard as a board, and prevents them from taking blacking; these objections are, however, obviated bv another method:—Take 1 oz. of the best India rubber (the white stuff called fungus will not do), and with a wet penknife cut it up into the smallest shreds you canI dry it well before the

fire, and put it into a clear glass bottle, with one pint of the best salad oil; put the bottle on the hob beside the fire, or in an oven, or in any situation where it may be kept constantly »iii in, and stir it up with a stick occasionally. In about a week (but the time depends on how you have cut up the India rubber) the India rubber will be dissolved in the oil, making it much thicker. Now thoroughly clean the boots from all mud, grease, and blacking, and well dry them before the fire. Place the bottle in a mug of hot water, to keep it warm, and rub the mixture all over the boots with a brush, rubbing it into the pores of the leather as much as possible, but do not leave any more remaining on the surface than is sufficient to moisten it; hang the hoots up where the air may have free access to them, and let them dry thoroughly, after which give them a second coating and a third, letting them dry between each coat: they will not require any more until they want mending. For the first two or three times that they are blacked, they will not take a good polish, but in about a week they will polish as well as any others, and be no harder than they were before the operation. I have found this proceeding answer extremely well, although I have not given it so severe a trial as the former. The chief difficulty in the latter is to make the boots dry between each coat, which takes it least a week, as the oil evaporates very slowly; and adding spirit to it will not do, as it prevents the boots from taking a polish afterwards. The difference of the processes is easily seen; the former covers the leather with a waterproof substance, the latter fills up the pores with India rubber. S. P. C.

TO CORRESPONDENTS.

/.' E. L. Kill call at the office, he will find < letter addressed to him on the subject of kit communication.

We have also written to S. P. C.; perhaps it will be to good at to tend to the Office for the Utter.

We refer C. P. to No. 128, page 76.- No. 127, page 83; and No. 1 38, page 174, where he will find some useful information on the art afpolithing. With regard to Mr. Benson's eerial machine, ice are assured by a party on whom we can depend, that it is actually being constructed, the steam-engine being already completed, and in a very creditable manner, we fully agree with our contemporary * The Artisan," that it it much to be regretted time, money, and ingenuity should be so wantonly squandered; indeed we tutptct the affair will, in the end, afford another practical illustration of the mountain in labour— Parturiunt montes—nascetur ridiculns mus.

London: Printed at "the Cur Pazss,"l, Long Lane, Aldersgate, by D. A. Duddhxt (to whom Books for Review and all communication* for the Editor must be addressed, postage paid); published ever; Saturday, by G. Brian, Holywell Street, Strand; and may be had of ill Bookseller! and Newsmen in Town and Country.

THE PATENT DISC STEAM-
ENGINE.

(See Engraving on front page.)

Fig. 1 is an elevation, and fig. 2 a aectinn through the engine of twenty-horse power. The parts are so simple, as scarcely to require explanation; A A are the eduction steam-pipes; B B, the induction steampipes; C C, the foundation to which the engine is firmly secured by screw-bolts.

The presumed advantages obtained by this description of engine, may be briefly stated to be—great economy in the first cost of engine-power, a very important reduction in the expenditure required for foundations and buildings in erecting an engine, a great saving in repairs, together with diminished liability to derangement, arising from the simplicity of construction, and a considerable economy in the expenditure of fuel. Engineers, however, are divided in opinion as to the actual merits of the disc engine, the one party maintaining the affirmative, and the other as tenaciously supporting the negative; we, therefore, present our readers with an abstract of the report of Mr. Josiah Parkes, C. E., a gentleman whose scientific attainments and experience in this particular department are indisputable, and, consequently, confer a high authority on any opinion he may express. Mr. Parkes was requested to conduct a series of comparative trials with a disc and reciprocating steam-engine; the results obtained are thus detailed.

These trials were made at the works of Messrs. Nasmyths, ftaskell, and Co. Patricroft, near Manchester. They were eonducted in the presence of a member of their firm, of their superintendent, Mr. Wilson, and of two of the patentees of the disc engine.

The object proposed being to ascertain, with the utmost possible accuracy, the relative quantities of water as steam, and, consequently, of fuel, which would be required to enable each engine to perform the same amount of work, it was a matter of the first importance to determine upon some work which would oppose an uniform resistance. After much consideration, I selected that which is presented by fans revolving at high velocities; considering that these machines, when driven at an uniform rate of motion, would offer a resistance so nearly invariable as to satisfy this primary condition.

The reciprocating engine was made by Messrs Nasmyths, Oaskell, and Co. It is a beam-engine, thoroughly well constructed, in excellent condition, and in

every respect unexceptionable as a specimen of its class. I found the diameter of the cylinder to be 14| inches; the length of stroke, 2 feet 2f inches; and the number of double strokes of the piston, during the trial, averaged 41-flj per minute.

The disc engine (called 16 horses' power) I found to have a steam chamber of 27 inches in diameter, and the mean number of revolutions effected, during its trial, was 118J per minute. With these proportions, and at these respective speeds, the volume of steam which should pass through each of the two engines in a niven time, as defined by the transit of the parts on which the steam acts, is very nearly the same; an equality which must be considered as tending to satisfy doubts as to the results of the trials having been affected by any other circumstances than those strictly arising out of the principles on which the two engines are constructed. Both engines were alternately supplied with steam from the same boiler. This I found to be very deficient in the extent of surface exposed to heat, and the setting was ill arranged; consequently, the proportion of water evaporated for the coal consumed was low; but, as I adopted on this as on former occasions, the mode which is considered to afford the only accurate means of ascertaining the expenditure of steam for a given effect—viz., that of determining the consumption of water as steam, the results obtained are free from all question which might otherwise arise as to the capability of the boiler, or the quality of the fuel made use of.

The two engines, being thus supplied with steam under identical circumstances, were employed, on alternate days, to drive the same fans at similar velocities.

It was found, by previous trials, that with the quantity of steam the boiler would conveniently produce, the disc afforded a greater amount of power than the -reciprocating engine; therefore the number of fans driven, their velocity, and the discharge of air, were so adjusted, as to provide for the resistance being within the capability of the latter engine; and thus I was enabled to keep the fans revolving at a very uniform velocity throughout both trials. This velocity was accurately indicated by a counting apparatus, connected with an intermediate shaft between the engine-shaft and the fans. The two engines were of the non-condensing class, and discharged their steam into the atmosphere.

For the registration of the water a vessel was provided, which was found to contain 338 lbs. by weight; and it was ar. ranged for the whole of the water used during the trials, to be measured by means of this vessel; and the boiler being furnished with a glass gauge, I endeavoured to have the same pressure of steam, and the same quantity of water in the boiler, at the conclusion, as at the commencement of each experiment. In this I succeeded within a variation of half-an-inch in the level of the water, for which due allowance was made.

The weight of coal burnt during each trial was also accurately ascertained; the fire at the conclusion being, as nearly as possible, in the same state as at the commencement.

Having thus taken the precautions I considered requisite to obtain results worthy of confidence, and having made some preparatory trials with each engine, the fans were connected with the reciprocating engine, and they were driven without intermission for six hours. During this time, the quantity of water as steam which passed through the engine, was 10,406 lbs., equal to 1734 Jlbs. per hour; and the coal consumed was 20cwts., equal 373^ lbs. per hour; the evaporation being in the low ratio of 4$ lbs. of water for 1 lb. of coal. The counter actuated by the intermediate shaft registered during this trial 14,301, the greatest difference in the velocity of the fans during any hour, being about six per cent., and the mean speed of the engine 41h strokes per minute.

On the following day the fans were connected with the disc engine, and driven for five hours and fifty-seven minutes, when the counter, connected as before, had registered 14.318, being seventeen more than on the previous day; the greatest difference in the velocity of the fans during any hour being little more than one per cent The quantity of water as "earn required to supply the engine, was 8097lbs., equal 1449J lbs. per hour; and the coal consumed was 16cwts., equal 29H§ lbs. per hour; the evaporative ratio being about 4^ lbs. of water for lib. of coal. The mean number of revolutions of the engine shaft per minute, was I 18jr.

Immediately after the conclusion of this trial, the fans were again connected with the reciprocating engine, and the same velocity being given to them, an indicator diagram was taken off which, by comparison with the diagrams of the preceding day's trial, showed that the resistance overcome by the disc engine, was somewhat greater than by the reciprocating engine, but the difference was very small.

In order to ascertain the amount of effective power exerted by the disc engine,

I availed myself of Mr. Davies' dynamo- meter.'' The principle of this very complete instrument is, that the force of the resistance taken on the periphery of a driving drum or toothed reciprocating engine, as exhibited by the indicator diagrams was equal to 25f "IS Per square inch, and the mean pressure in the chamber of the disc engine, as exhibited by a mercurial gauge constantly connected with it, was 23$ lbs. per square inch.

The above effects were obtained by the two engines when working unexpansively, and with steam at comparatively low pressures. As regards non-condensing reciprocating engines, I have not previously met with any (and I have conducted eiiperiments, similar to the foregoing, on many engines of this class) which has required less than 120 lbs. of water as steam per horse power per hour, even when, using steam athiyh pressure, a fact which establishes the excellence of the reciprocating engine subjected to trial, as it only consumed 102 lbs. per horse power per hour.

The results of these trials are thus exhibited in terms of the quantity of water as steam, actually expended in overcoming the same resistance by the two engines, and, also, according to the conventional phrase of horse power; but that quantity was greater in both cases than would have been required, had the steampipes and cylinders been coated. Though, however, these were uncovered, and B considerable quantity of steam must have been condensed, which had no share in producing the effect, the relative results are unaffected by this circumstance, as I found, that a nearly equal extent of surface (about 45 square feet) was so exposed in both cases.

When experiments of this kind are conducted in a manner liable to little error, evidence of their accuracy will arise from independent sources; and we possess direct means of verifying the correctness of the principal result obtained—viz. that the reciprocating required 19 percent, more steam than the disc engine, for equal effect.

The counter informed us, that the reciprocating engine made in the six hours 14978^ double strokes, which, multiplied into its capacity (passages,t &c, included),

* We intend, in an early Number, to give a design and description of a very simple, but ingenious apparatus for measuring the power of machineiy.—Ed. P. M.

+ The passages equalled 0,405 cubic feet; total capacity, 5,256 cubic feet.