the heat and flame of the carboleine, a well-stirred loam or clay-water should be very carefully mixed with the pulverized coal, so as to saturate every atom of the powder.

Add to this mass such a proportion of oil as may be required, and mix it very carefully with the materials. These processes of mixing may be easily performed, through very simple machines; and it matters not, whether the oil is mixed with the coal-powder before or after the clay-water has been combined with it. The mass having been thus mixed, may be formed into cakes, by any convenient means, either by hand or by machines.

These cakes, when made, may be placed either in heated rooms, to dry, or in the open air.

The loam or clay-water is composed of two, or two and a half parts of water, and one part loam or clay.

The proportionate quantities of the materials, of which the different qualities of carboleine may be composed, may be stated as follows:

For a fuel, which may be called No. 1, take twenty-four parts of coal or coke, six or seven parts of clay water, one part of oil, and one of bitumen or tar. For another artificial fuel, called No. 2, take twenty-four parts of coals or coke, six or seven parts of loam or clay water, and two parts of mineral, animal, or vegetable oil. Another fuel, No. 3, may be produced, the following proportions being observed:-Take forty parts of coal, thirty-six parts of loam or clay water, and four parts of animal, vegetable, or other oil, and mix them together, as above described.-[Inrolled in the Petty Bag Office, January, 1842.]

Specification drawn by Messrs. Newton and Son.

Scientific Notices.

REPORT OF TRANSACTIONS OF THE INSTITUTION

OF CIVIL ENGINEERS.

(Continued from page 132, Vol. XXI.)

March 15, 1842.

The PRESIDENT in the Chair.

"Description of the Iron Skew Bridge across the Regent's Canal, on the Eastern Counties Railway."

By Edward Dobson, Assoc. Inst. C. E.

This Bridge is built with a direct span of 54 feet, at an angle of 70° with the centre line of the canal. The level of the rails is 14 feet 6 inches above the water, and it is constructed to have a waterway of 44 feet, with a clear headway of 10 feet above the towing-path.

The dimensions of the several parts of the bridge, and the mode of putting them together, with the masonry and the cost of the construction, are described in detail, and illustrated by an elaborate working drawing.

As an appendix to this paper, a description is given of a bridge, over the same canal, on the line of the London and Birmingham Railway, on account of the similarity of its construction. The span of this latter bridge is 50 feet, but being made for two double lines of rails, it was thought expedient to have three main ribs instead of two, as in the former. The details of construction of this bridge are also given, with a drawing of one of the main ribs and its tie-bar.

"Remarks on the Ravages of the Worm (Teredo Navalis) in Timber."

By Robert Davison, M. Inst. C. E.

This communication describes the ravages committed by the "Teredo Navalis" upon the fir piles of the foundations of the old bridge at Teignmouth, five arches of which, after having been built only twelve years, fell suddenly; the construction of a new

bridge thus became necessary, and it is now in progress, under the direction of Messrs. Walker and Burges. The worm is described as entering the wood, through a hole not larger than a pin, and perforating the timber in all directions, but chiefly in the direction of the fibre, at the same time increasing the size of the holes, even sometimes to an inch diameter; a few of the worms had been found of the extraordinary length of 3 feet. They confine their operations between low-water mark and the bottom of the river, showing that they cannot exist out of water.

A specimen of part of a log, picked up off Jersey, was as much perforated, but in a different manner, the worms having penetrated the wood indiscriminately all over the surface; in some cases leaving in the holes a coat resembling the tail of a lobster, about 3 inches in length, which shewed that the ravages had been committed by the "Lymnoria Terebrans."

The paper was also accompanied by a specimen of wood sheathing, charged with nails, from the bottom of a vessel, believed to be about 100 years old, together with some of the worms, ("Teredo Navalis,") for the purpose of showing the peculiar shape of the head-resembling a pair of forceps, with which they cut away the wood.

66

Description of the Roof of Messrs. Simpson and Co's Factory." By John Boustead, Grad. Inst. C. E.

The truss of this roof is double, consisting of two frames of Memel timber. The principals are fitted into cast-iron shoes, resting on the walls, with projections let into the wall-plates ;they taper towards the ridge, and there abut against a cast-iron ring-piece, through which a wrought-iron bolt, 14 inch diameter, passes, and answers the purpose of a king-post, in supporting the collar-beam. To the under side of this beam is attached a heel and eye-plate, to either end of which are linked bolts, passing between the principals, and secured by nuts at the backs of the shoes, thus forming efficient ties to resist the thrust of the principal rafters.

The slate-boards are supported by five purlins, 4 feet apart, and abut against a ridge-piece, resting on the kings.

The span of the roof is 34 feet 3 inches. The pitch is about 3 to 1, and the principals are placed 9 feet apart.

The scantlings of the principal timbers are:-Principals 9 by 2 inches, tapering to 6 by 24 inches; collar-beam 7 by 3 in.; purlins 6 by 4 inches; wall-plates 6 by 4 inches; slate-boards 1 inch thick; ridge-piece 10 by 2 inches.

The principals were sawn out by a template, so as to insure the given taper and the accuracy of the angles of the ends: they were then laid in a horizontal position, placed at the required angle, and the collar-beam inserted inch deep into each principal and secured by bolts inch diameter; the mode of raising the roof is then described.

Some of the advantages of roofs of this construction are stated to be, economy in materials and workmanship, with lightness and simplicity, and that all sagging of the timbers may be rectified by screwing up the nuts of the kings and shoes.

The truss is recommended for buildings where lofty apartments or coved ceilings are required, and also for its presenting so few points for the suspension of heavy weights that may subject the timbers to strains for which no provision has been made.

From the examinations that have been made, this roof seems to answer satisfactorily: it has been erected three years and a half and has sustained heavy falls of snow, but the ridge and rafters have preserved their lines perfectly, and the walls show no signs of having been subjected to undue pressure. The design of the roof is simple, its appearance light, and it may be considered an interesting specimen of the art of simple carpentry, assisted by iron-work.

A drawing of the truss accompanied the paper.

March 22, 1842.

JOSHUA FIELD, V. P. in the Chair.

"Remarks on Machines recipient of Water Power; more particularly the Turbine of Fourneyron."

By Professor Gordon. (Glasgow.)

Notwithstanding the diminished importance of water power

since the almost universal application of the steam-engine, some situations may still be found, in the mining districts of Cornwall, of Derbyshire, and of Cumberland, the Highlands of Scotland, and generally in the districts comparatively destitute of cheap fuel, where it is desirable to render falls of water available.

The theory of water power, as it now stands, may be announced in general terms thus: "The mechanical effect obtained, is equal to that of the moving power employed, minus the half of the vis viva which the water loses on entering the machine, and minus the half of the vis viva which the water possesses when it quits the machine."

Bernoulli recognized the second cause, and soon after, Euler, the first. Borda, in his "Mémoire sur les Roues Hydrauliques," in 1767, gave the proposition in precise and general terms: whence he concluded, that to produce its total mechanical effect, "the water serving as moving power, must be brought on to the wheel with impulse, and quit it with velocity."

This principle being admitted, the circumstances next to be considered, are: the height of fall-the supply of water-and the nature of the work to be done.

These positions being laid down, the author proceeds to examine the relative efficiency of water-wheels of various constructions.

Thn undershot wheel, acted upon by the velocity of the water when confined in a rectilinear course, or when hung freely in a stream. In the former case, the efficiency of the machine is equal to 32 per cent. or nearly one-third; in the latter, the ratio is 42 per cent. or about two-fifths.

The breast-wheel is generally applied to falls of from 4 to 8 feet; in these the efficiency reaches as high as 60 to 65 per cent. of the mechanical effect of the fall of water. The buckets being filled to two-thirds of their capacity, their velocity is seldom less than from 7 to 9 feet per second.

The consideration of this wheel led Poncelet in 1824-25, to the invention of the "undershot wheel with curved floats," the efficiency of which has been found equal to from 65 to 75 per cent.