cially where heavy masses, such as parts of machinery required to be moved about-he would always adopt the system in constructing a manufactory.

Mr. Smith observed that an arched roof would be found as cheap as one of wood and slates, and in the relative durability there could be no comparison.

Mr. Marshall desired it to be borne in mind, that the cut stone front of the mill had greatly enhanced the cost, and that being the first building of the kind erected in the neighbourhood of Leeds it had naturally been more expensive than others would be.

"Account of the Explosion of a Steam Boiler at the Penydarran Iron Works, South Wales." By Adrian Stephens.

The boiler, the explosion of which is described in the paper, was one of a pair for furnishing steam to a high-pressure engine, with a cylinder of 26 inches diameter, working expansively, the steam being cut off at half the stroke; each of these boilers was 41 feet long, and 7 feet diameter, with a centre tube flue of 4 feet 2 inches diameter; the thickness of the plates throughout was inch; the ends were flat, with rings of angleiron, and the pressure of the steam to which the safety valves were weighted was 50 lbs. on the square inch.

From appearances after the explosion, it was conjectured that the tube, which was collapsed in a remarkable manner in its entire length, had been softened by the heat, having probably been left dry along the upper side.

No opinion is given as to the cause of the explosion, but it is particularly mentioned that the supply of feed-water depended upon the regular attention of the engineer, and that the feed-pipe was placed so that the water fell directly upon the hottest part of the tube flue, and it is remarkable that the tube is most extensively fractured at that spot.

All the appearances presented by the boiler, both before and after the explosion, and the injury done by the event, are accurately detailed, and the paper was illustrated by a drawing of the boiler and the setting.

Mr. Carnegie presented one of Hunter's Stone Boring Machines to the Institution, and explained its action to the meeting.

The machine is composed of two parallel bars of steel, supporting a traversing carriage, through the centre of which passes a spiral auger attached to a screwed bar; this bar fits into a female screw clamp above the carriage, and on the upper end is a winch with four handles.

When the instrument is in use, it is fixed by two cramps upon the stone to be pierced, and the auger being made to revolve by means of the winch, scoops out at each revolution as great a depth of stone as is equal to the distance which the screw descends; the chips ascending through the spiral channel of the auger are thrown off at the top. The peculiar shape of the point of the auger prevents its being abraded, as it operates by chipping the stone, and not by grinding it away. This, with the means of forcing it down by the screw, is the chief novelty of the machine. It has been extensively used at the works of the new harbour of Arbroath, by Mr. Leslie, who speaks of it in the following terms:

"Mr. Hunter's Boring Machine has been advantageously employed for above a year, in boring trenail holes in the stones used at the new harbour of Arbroath. The holes are 1 inch diameter, and from nine inches to 2 feet in depth: the aggregate of the holes already bored amounts to upwards of 30,000 linear feet. The machine may be adapted for boring holes of any dimensions. It does the work considerably cheaper than the "jumper," and much more correctly, as it makes the holes perfectly straight, cylindrical, and equal throughout, instead of the irregular form made by the common jumper. This machine is very well adapted for boring railway blocks, and has been much used in this quarter for that purpose. I consider it to be more especially valuable from the facility which it affords of boring and trenailing down the stones used in sea buildings, in any exposed situation; as I have found that trenailing is a great security to such building while in progress, when the upper courses are much exposed, and liable to be washed off, unless they be held down by other means than their own absolute weight. "The expense of boring the old red sandstone rock, here, is about three-halfpence per linear foot."

Mr. Vignoles bore testimony to the advantages of the machine: he was now employing it for piercing holes in stones going from Arbroath to the West Indies, for the construction of a patent slip-there was great economy of cost and time by its use, in addition to the superior manner in which the holes were made.

Mr. Smith was convinced of the advantage of the machine in working almost all kinds of stone, but more especially for those resembling the Arbroath stones, which were from a bed beneath the old red sandstone: they were of fine grit mingled with schistose debris. The action of the tool was like that of the stone-planing machine, to burst chips

off instead of grinding down the surface by small portions and destroying the edge of the tool at the same time. With the planing machine it was common to take off a thickness of 3 inches at one passage of the toolit acted like a "pick ;" and being fixed in a frame weighing about 14 ton, the power was great; at the same time there was little abrasion of the tool and it never became heated or softened. It was probable that with other qualities of stone a screw with another pitch of thread might be required to force the auger forward, but with the thread now used in boring stones from the Arbroath quarries, the economy of time and cost appeared very great. In each of the blocks for the Arbroath railway it was requisite to bore two trenail holes 1 inch diameter and 6 inches deep-and to level a space 9 inches diameter to receive the cast-iron chair: this had been contracted for at twopence halfpenny per block, which was a material diminution of the usual cost. He was convinced that the instrument only required to be known to be extensively used.

May 24, 1842.

"On the Machinery used for working the Diving Bell at Kingstown Harbour, Dublin." By Peter Henderson, Assoc. Inst. C.E.

After referring for the details of the machinery to the two drawings which accompany the paper, the author describes the foundations of the pier head to have been laid in a depth of 20 feet at low water on rock and firm sand. For 14 feet from the bottom, the wall is formed of Runcorn sandstone of fine quality, each stone containing about 50 cubic feet and thoroughly squared. This has been preferred to granite on account of its cheapness and the facility with which it is worked under water.

After the foundation course is secured, from 300 to 350 cubic feet of this walling are frequently set in a perfect manner by the diving-bell during a fair working day of eight hours. The first stone was set on the 5th of August, and by the 1st of January 16,000 cubic feet had been laid.

From 6 feet below low water to the coping, it is proposed to make use of granite in blocks of 50 cubic feet each, which is procured cheaply and in abundance in the immediate neighbourhood.

The piers are finished in the interior by walling of rubble stone carefully laid.

For the purpose of forming this excellent harbour an area of 251 acres has been inclosed between two substantial stone piers of 8,340 feet in length, affording clear anchorage in a depth of water from 15 to 27 feet at low spring tides. The interior shows

no natural tendency to collect deposits likely to reduce the depth of water, nor do any of the works exhibit symptoms of deterioration, while its continual occupation by vessels of every description, together with the comparative freedom from accident in Dublin Bay, afford convincing proof of its great utility.

"Description of a Steam Dredging Engine used upon the Caledonian Canal." By Walter Elliot.

The machine described in this communication was constructed in the year 1814, expressly for the formation of the Caledonian Canal, and it was also used for deepening the channels through the shoals in Loch Dochfour and Loch Ness. The length of the vessel is 80 feet, by 23 feet in width; the bucket frame is 42 feet long, with 25 buckets, worked by a condensing steamengine of six horses' power. The dimensions of all the principal parts of the machinery are given minutely, with accounts of several experiments for extending the use of the dredger.

On one occasion, as it was found that the buckets had much difficulty in penetrating the hard mountain clay, every alternate bucket was removed, and a pair of steel cutters substituted for each, in the expectation that the clay would be loosened, and the succeeding bucket would take it up more easily. They did not, however, act satisfactorily, and a risk of fracture was incurred, which induced the abandonment of the plan.

On another occasion in forming a portion of the canal between Loch Ness and the locks at Fort Augustus, where the height of the ground above the water averaged from 20 to 30 feet, and the excavation was required to be about 16 feet beneath it; that part of the cutting above the water level was commenced by manual labour, while the dredging machine did the excavation under water: it was soon found however that the engine having completed its share of the task, continued to undermine the upper portion, which being of a loose nature fell into the water, and was raised by the buckets so rapidly that the manual labour could not compete with the machine, and it was then used to complete the undertaking, which it did in eight months, having in that time excavated about 170,000 cubic yards of material.

When working in favourable situations the quantity generally raised equals 90 tons per hour; 17 of the buckets are discharged per minute, with an expenditure of coal of about 15 cwt. per day.

The communication was illustrated by two detailed drawings of the boat and its machinery.

NOTES AND NOTICES. Concussion Shells.-In the course of some experiments which took place in the Marshes, at Woolwich, on the 26th instant, twelve of Captain Norton's Concussion Shells were fired from a ten-inch gun, at a wooden frame, at a range of twelve hundred and fifty yards. Four of the shells struck the frames, and instantly exploded by the concussion. Eight shells struck the mound, and five out of the eight exploded by the concussion, the instant of striking; three shells that struck the mound did not explode. Each shell had a bursting charge of five pounds of gunpowder; the charge of the gun was twelve pounds. This successful experiment of Captain Norton's Concussion Shell establishes his principle, and fixes the perfect efficiency of his shell.-United Service Gazette.

Precipitation of Metals.-On the 6th instant, M. Arago read before the Academy of Sciences an analysis of a paper by M. Ruolz, on the means of fixing one metal upon another. In some former experiments communicated to the Society, M. Ruolz had gone no further than the precipitation of pure metals; it remained to be ascertained whether mixed metals might not also be precipitated. This is what M. de Ruolz has done; and, as a proof, several specimens, covered with a precipitate of copper and tin, in the proportions which constitute bronze, were submitted to the Academy.-Atheneum. [If this statement be correct, then M. Ruolz has indeed accomplished a great desideratum-the precipitation of alloys of metals. But we have reason to believe the statement is not correct: all that M. Ruolz does is, to precipitate the copper on the tin, or the tin on the copper, (separately,) which is not new, and a very different thing from precipitating the metals in atomic combination.-Ed. M. M.]

-Prof. Vignoles' Lectures on Civil Engineering. A Dark Day.-An interesting account is given of a day of this sort, in North America, in a paper read at a late meeting of the Meteorological Society, by Major Stack. The darkness on the day referred to did not partake of the nature of cloud or smoke, but closeness in the air, which appeared to thicken, and to descend from above, till the bright noonday brilliancy was converted into darkness that might be felt. It came on between 11 and 12 a. m.; extreme darkness, half-past 1 at 5 p. m. it was sufficiently clear for persons to return to their occupations, as all labour was necessarily suspended, and the phenomenon soon disappeared.

He

Diving-bells for Men-of-war.-Commander Henry Downes, R.N., the hon. director of the United Service Institution, has suggested a plan which, in cases of need, he thinks may be found of use. recommends that in line-of-battle ships, and in the larger frigates, one of the tanks of water should be so constructed as to do, if required, the double duty of tank and diving-bell; and be stowed at the mouth of the hatchway, so as to be the first one to be emptied. One instance may be adduced, wherein a trial has already been made with a ship's tank, and most successfully too, under the skilful and persevering exertions of Captain Dickinson, R.N., in recovering the treasure wrecked in the Thetis frigate.

Prizes for Scientific Essays.-Count Pillet Will, a corresponding member of the Royal Academy of Sciences at Turin, has sent a donation to the Aca

demy of 10,000 fr., to be distributed in prizes to authors of works best calculated to promote a taste for the positive sciences. The Academy have divided the sum into four prizes of 2,500 fr. each, for the best introductions to the study of physics, chemistry, mechanics, and astronomy. Each work is to contain a concise summary of the principles, history, important facts, and chief application of the science treated upon, so as to be used as an elementary book in the colleges. The competition is open to men of all nations. The manuscripts must be sent to the secretary of the Academy (post free) before the 1st of July, 1846. The successful works will be printed at the expense of Count Pillet Will.

Metal Forging and Cutting Machine.-Although at the late meeting of the British Association in Manchester, there were many very interesting specimens of mechanism exhibited, there was, nevertheless, one in particular, which threw all others completely into the shade, when considered either as to the novelty of the invention, or its evident practical applicability to the every day concerns of life-and may with truth be said to have been "the lion of the exhibition,"-viz., a machine for the working or forging of iron, steel, &c. This truly surprising machine is quite portable, occupying only a space of 3 feet by 4 feet, and cannot be deemed other, even by the most critical judges, than one as purely original in principle, as well as practical in its application, as much so perhaps as was the splendid invention of the fluted roller of Arkwright, by which the art and perfection of drawing the fibrous substances became known, or that still more splendid discovery of Watt, the condensing of steam in a separate vessel, by which the power of the steam-engine of that day may be said to have been doubled. But now for some explanation of the machine, and its probable general application. It is, then, as has before been said, very portable, not requiring more space than from three to four feet, and may be worked by steam or water power, and when moved by the former, as was the case at the exhibition, made 650 blows or impressions per minute; but from their very quick succession, and the work being effected by an excentric pressing down, not striking the hammer or swage, not the least noise was heard. There are five or six sets of what may be called anvils and swages in the machine, each varying in size. The speed and correctness with which the machine completes its work, is perfectly astonishing, and must be seen in order that its capabilities in this respect may be duly appreciated; for instance, when it was put into motion for the purpose of producing what is known as a roller, with a coupling square upon it, (and which had to be afterwards turned and fluted,) the thing was accomplished in fifty seconds! of course at one heat, to the astonishment of the bystanders. But what appeared as the most extraordinary part of the affair, was, that the coupling square was produced direct from the machine, so mathematically correct, that no labour can make it more so! The machine will perform the labour of three men and their assistants or strikers, and not only so, but complete its work in a vastly superior manner to that executed by manual labour. For engineers, machine makers, smiths in general, file makers, bolt and screw makers, or for any description of work parallel or taper, it is most specially adapted; and for what is technically known as reducing, it cannot possibly have a successful competitor-in proof of which it may be stated, that a piece of round iron 14 inch in diameter, was reduced to a square of in., 2 ft. 5 in. long, at one heat. The merit of this invention belongs, it is said, to a gen tleman at Bolton, of the name of Ryder.-Leeds Mercury.

Sir, Having taken a more than ordinary interest in the above structure, almost from its commencement, on account of the novelties to be developed, and availed myself of opportunities of examining the progress from time to time-first, through having a slight acquaintance with the late Mr. Humphreys, the engineer, and, secondly, through the kindness and polite deportment of Mr. Guppy, the present resident manager-I feel myself in a position to fulfil my promise to you, of furnishing such general information of the construction of the vessel and engines, as I think will be highly interesting to many of your numerous readers. And I trust I may so far succeed in my description, as to convey a tolerably correct idea of the magnificent vessel, and of the peculiar machinery in preparation.

It is highly probable that some of my dimensions may not be truly correct, (though I believe, in the mass, they will be found not very far from the truth;) but as my notes and rough dimensions were obtained-some of them by pacing, others by a graduated walking-stick-the outline by an optical unerring instrument-some by their apparent magnitude, and comparison with known dimensions-and a few from the information of the Company's servants, deputed to show and explain to the public during the late interesting Agricultural Meeting at Bristol, and, as the collection of these materials has spread over a long period, I trust, should a few errors or inaccuracies be found to exist, they will be quite unimportant.

From my notes and dimensions I have also prepared a few sketches, which, should you consider them of sufficient value for insertion, will the more readily convey an idea of the construction.

Description of the entire Ship. To prevent any confusion arising from the necessity of using the same letters of reference in describing the vessel as in the machinery, I will first dismiss one alphabet, by spreading it over the ship, and then repeat the same over the details of machinery.

Fig. 1 represents a longitudinal vertical section of the entire vessel, showing the various compartments; and fig. 2* a

STEAM-SHIP, (LATE "MAMMOTH.") BY ESQ., C. E.

side view, in the state it was a month ago.

A B. Surface line of upper deck.

C. Principal promenade saloon; length 110 feet, by 48 feet at the widest part; height, 7 feet; to be fitted up with twenty-four single berths on cach side: two staircases at each end.

- D D. First class saloon, or diningroom: length, 100 feet; greatest width, 50 feet, (which is about equal to the widest part of the "Victory," celebrated in former days;) height, 8 feet: stairs at each end.

E. The cargo deck, 65 feet long, by 9 feet high, running narrow towards the

stern.

F is an iron fresh water tank, 18 feet wide towards midships, 7 towards stern, (taking the form of the vessel;) length, 40 feet; height, 6 feet.

G. A room of 24 feet long, 15 feet high, by the width of the vessel: probably a coal-store, and for engineers. H. Elevation of engines.

I. Ditto of boiler.

J J. Iron deck over boiler, for cooking apparatus.

K. Fore, or second class saloon, 84 feet long, 7 feet 9 inches high.

L. Lower fore saloon, length and height as above; 40 bed-places on each side of these saloons.

M and N. Iron-floored cargo decks. O. Air-chamber from boiler to forc bulk-head, of the shape of the ship, about 4 feet high.

P. Officers' berths, &c.

Q. Sailors' mess-room.

R. Sailors' berths; r, small watertank.

S. Water-closets.

T. Ship's stern-post, through which the screw passes, and to which the sideplates are riveted.

U. Shaft from engines to screw.

V. Diagonal stay from the ship's side to the stern-post.

W. Side view of screw stern-post, in which the end of the screw spindle revolves.

X. Keel under the screw, uniting the stern-post to the vessel.

Y. Hollow rudder foot, and of such a thickness as to receive the stern-post, which forms its pivot.