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If now a piece of this wire be driven into the end of a brass pipe of such a size as to make a close fit with it, it is evident that that part of the pipe has thus been subdivided into as many smaller tubes as there are grooves in the wire. By using a draw-plate fitted to make smaller and shallower and more numerous grooves than are required in common pinion-wire, it is manifest that wires or cores may be produced, which, when driven into metal pipes, as already described, will subdivide them into capillary tubes of almost any degree of tenuity. Mr. H. Wilkinson's method is described in the following letter:
Pall Mall, May 25th, 1835. Sir, In the course of some experiments on artificial light, which I was en. gaged in about twelve months since, I was desirous of obtaining a great number of extremely minute apertures for a gas-burner; and, finding it impos. sible, in the ordinary way, to obtain them, a new method occurred to me, which immediately produced the desired effect. I showed it at the time to several eminent scientific men, who were unable to conceive how these apertures were formed; and, as I made no secret of the method, they were equally pleased at the simplicity of the operation; and the specimen herewith sent has been exhibiting at the Gallery of Practical Science for several months. I did not attach much importance to it myself; but, as I do not find that it is at all known, and now think it might be useful in a variety of ways, I have sent it to you to be laid before the Society; and should they be of the same opinion, I shall feel much pleasure in communicating the mode of operation, by which any number of apertures, hardly visible to the naked eye, and of any length (even a foot, if required), may be made in any metal in ten minutes!
I am, sir, &c. &c.
HENRY WILKINSON. A. AIKIN, Esq. Secretary, &c.
The process consists merely in turning one cylinder to fit another very accurately, and then, by milling the outside of the inner cylinder with a straight milling tool of the required degree of fineness, and afterwards sliding the milled cylinder within the other, apertures are produced perfectly distinct, and of course of the same length as the milled cylinder. A similar effect may be produced on flat surfaces, if required.
H. W. Duty of Cornish Steam Engines. The mode of estimating the performances of steam-engines, by the number of lbs. lifted one foot high by the consumption of a bushel of coal, was introduced into Cornwall by Watt, when it became requisite to keep a regular account of the work done and the coal consumed, for the purpose of calculating his share, which was onethird of the saving of coal effected by his engine in comparison with Newcomen's.
The performance of two atmospheric engines, at Poldice, had been ascertained as a standard of comparison, and declared by a committee: for convenience the present dynamic unit was afterwards adopted, and the work done when thus expressed was equal to 7,037,800 lbs. lifted one foot bigh by each bushel of coal. A dispute arose in 1798 between Messrs. Boulton and Watt and the mining adventurers in Cornwall, and it became necessary to ascertain the average duty, which was proved to be 17,671,000 lbs.: this was rather less than in 1793, when the average of seventeen engines was 19,569,000 lbs. After the expiration of the patent in 1800, no
Trans. Lond. Soc. Arts.
accounts were kept of the work performed by the engines under the direction of the mining engineers.
In August, 1812, the average duty of several engines on a month's trial proved to be only 13} millions, and the truth of the prevailing opinion became apparent, that less work was done than during Watt's patent. The present monthly report of work performed' was then established under the management of Mr. Lean, and since his decease has been conducted by his son, so that there exists a series of reports for twenty-two years, showing the duty for each month, of the engines employed in Cornwall, including the size of the pumps, and their depths, number of strokes, bushels of coal consumed, &c. &c.; a reference to which would point out at what period, and by whom, every increase of duty was obtained.
Woolf introduced the use of high pressure steam worked expansively in two cylinders, and first succeeded in performing fifty millions. Other engineers worked high steam expansively in one cylinder, which plan became general on the introduction of Trevithick's cylindrical boilers.
Several engines now constantly perform a duty exceeding 70 millions, double that of the best of Watl's, and of which one has reached 91,200,000; another mentioned last meeting by our President, averages about 90,000,000; its best performance was 97,300,000, for one month.
Part of the increase of duty must be attributed to the improved pitwork; the most rapid increase, however, took place on the introduction of a most complete system of clothing, the present practice of which is so efficient, that in two instances, though the steam in the jacket was at least 270°, the outside casing did not exceed 78°;—the thermometer was covered by a silk handkerchief to prevent the draught of air in the engine-house affecting the results;--the air outside was in one experiment 56°, and in the engine-house about 66°;—the surface of the ashes over the boilers was about 90°."
Ann. Report Cornwall Poiytech. Soc.—Lond, Mech. Mag. April,
Progress of Civil Engineering.
Observations on the Classification (and Details of the Architecture of the Middle Ages. By E. B. LAMB, Esq. Architect.
(CONTINUED FROM p. 141.) The Third Class commenced about 1377, and continued till 1460. In the first division of this class the cquilateral arch was given up for one struck with two centres, of an obtuse form, which was much used with the four-centred arch (Fig. 11,). The window heads were filled with tracery in the perpendicular lines (Fig. 12,) the predominating charac
ter of the whole of this class, and the mouldings, became gradually more complex. The windows, for some time, retained the simple arch, the
compound arch only being used in small openings. Windows were divided in their height by transoms, and sometimes columns were added to mullions. Fig. 13, is a selection of a small window jamb, at Ify Church, which shows the general character of the mouldings of the second division of this class. Figs. 13, 14, 15, 16, 17, all resemble each other, and mark the distinctness of the mouldings from those of the
second class. In these sections it will be observed, that, although the i mullions do not, in a very great degree, appear to differ from the mullion mouldings of the second class, yet the extended hollow moulding in
the jamb is perfectly in character with the depressed simple, and also with the compound, arch. It is very different from the easy flowing lines of the second class; and the mullions, though they appear, as I before mentioned, to resemble those of the other class, upon closer examination will be found generally to be of a more bulky character. The elegant flowing lines of the second class are, indeed, in no instance to be seen in this, and the expression is of a widely different nature; for,
while the former indicated a graceful undulating character, without interruption, the latter is expressive of a degree of abruptness and crispness peculiarly its own: at least, these are impressions made upon me by these two classes; and they appear to arise from the obvious difference in the expression. A profusion of heraldric devices were among the principal decorations of this period. Among the examples of this class are, of the first division, New College Chapel, Oxford; a window in Westminster Hall; and the west door of St. Saviour's Church, which is a fine specimen of the middle division; a window in St. Peter's Church, Oxford, of which Fig. 14, is the section of the jamb; also Merton College Chapel, Oxford, 1424; and King's College Chapel, Cambridge, 1443. of the latter, or transition, division of this class, may be mentioned the Chapel on the Bridge, Wakefield, Yorkshire.
The Fourth Class, is a continuation of the same general forms, from 1460 to about 1547. The mouldings, arches, ornaments, &c., were now wrought to a greater degree of richness; and the most delicate work was bestowed on canopies, nitches, groinings, and, in fact, on every part, the principal aim appearing to be to produce stone carving of a net-like character, rather than to preserve good composition by agreeable contrasts. The result of this lavish display of ornament ended in a generally depraved taste, and the consequent decline of the art. Examples of this class will be found in Mag. dalen College, Oxford, about 1473; centre tower of Canterbury Cathedral,
about the same date ; St. George's Chapel Fig. 17.
Windsor, 1481; and Henry VII's Chapel, Westminster, about 1503. In Henry Vil's Chapel
, and, in fact, in many of the buildings of the fourth class, we can trace a general decline in art, without alluding to the wearisome richness, which becomes fatiguing to the eye for want of repose. I have no doubt I lay myself open to much reproof for presuming to differ from the accepted opinion with regard to this class of architecture; but I think I need only refer to the exterior of Henry VII's. Chapel in vindication of my assertion. This exterior is cut into so many small parts, that there is scarcely any situation from which a pleasing view of it can be obtained; and the principal charm which it pos. sesses in point of effect is borrowed from its contrast with the Abbey: the whole exterior, in short, is a multiplicity of angular projections, which throw no shadow, and, consequently,
produce no relief. The interior is much better: the effect here is good; the light and shade, being distributed from the large clerestory windows, are more pleasing; and the fan-groining and pendants of the nave and aisles produce a rich effect: but, still, I cannot see the beauty of these angles and curves, even in the interior; though they are certainly better here than on the outside.
In the latter division of this class, the mouldings and mullions were changing their pure form, and becoming mixed with the Italian architecture, which was, about this time, making great progress in the formation of that mongrel style now called Elizabethan; and many examples of this transition work are to be seen in Oxford, Cambridge, and London. Eastbury House, Barking,
in Essex, is a fine specimen of the brick buildings of the early part of the reign of Henry VIII., and contains more pure mouldings than most of the other buildings of that time: it is built entirely of brick work; mullions, transoms, and the most delicate ornaments, being all executed in brick. Fig. 18, is a section of one of the window jambs and mullions. Fig. 19, is a section of a mullion and jamb of the transition character. In this figure it will be seen that the jamb mouldings are a hollow and ovolo, and that the mullion is a fillet on one side': the other side, in the same section, is to be seen in the second class occasionally. Fig. 18.
The Elizabethan architecture now became the prevailing style, and continued to hold its rank until Inigo Jones succeeded in changing the public taste in favor of what was then called the perfect Italian style.
The characteristics of the Elizabethan style, are the regular entablatures, columns, pedestals, and arches of Italian architecture, interwoven with the pointed arches, enriched spandrils, heraldric devices, and other decorations of the Gothic. Orders were used over orders, and in situations where they were placed in direct violation to all reason. In one of the Colleges at Oxford, the whole of the five orders are piled one above another in one narrow front. These entablatures and columns were adorned with the most clumsy devices; such as scrolls abruptly terminating in angles, carvings of vegetables in bunches, &c., and buildings being surmounted with obelisks, balls, scrolls, and numerous fantastic devices, without the least reason being shown for their use. In some instances, this style has a very picturesque effect; and, when a sufficient excuse can be shown for its introduction in public buildings, that is the time, and the only time, where it should be in. troduced; but national buildings should be in a more perfect style. The bad taste shown by the building committee for the Houses of Parliament, in recommending this style of architecture for their Senate House, must be obvious to every person who is the least acquainted with its details : there is ample scope for talent in the pure Gothic style; therefore, why revive a style which only marked the decline of the art?
It only remains for me now to say a few words relative to the Gothic mul. lion. Windows are divided into lights by mullions of various sizes and sections; and each window consists of an outer arch, or frame, the jamb or architrave mouldings of which are perfectly distinct from the mullion, or column. Mullions are divided into orders; and the small mullion, which generally consists of a hollow and a fillet, or of a splay and fillet, is the first order: it is from this order that the cusps spring in every class; and for that reason it is sometimes called the casp mullion. Windows of two, three, and some.