snow, which in a long and cold winter's march is absolute misery. It should fit comfortably over three or even four pair of woollen socks to keep the foot both warm and soft. It should be made of noose, dear, or ox hide well tanned, then soaked in strong brine for twentyfour hours, in order to soften the leather and keep it moist; when drained and half dry, steeped in train oil for several days until completely saturated, and afterwards gradually dried at a distance from the fire. Thus prepared they will last a great while without being penetrated by snow or water. Even shooting shoes or boots dressed in this way, are softer and more useful to sportsmen than all the anti-attrition compositions I have ever used."-A Winter March in Canada. United Service Journal for October, 1831.

The Tobogin, or Indian Sledge. Another article of importance in a winter march through the forests of America, is the Tobogin, or Indian sledge, for conveying baggage or provisions. It is made of a hickory or ash plank, scarcely a quarter of an inch thick, about 6 feet in leagth and a foot in breadth, so as to fit the track of a snow shoe. The head of a tobogin is turned up like the fingers of a hand half shut, in order to throw off the snow. Attached to it on each side are two light sticks, secured by thongs, which form the sides of the vehicle, which, when it is packed, prevent anything from falling off it. We added a pole behind, in order to assist the man who dragged it in front, by another pushing it on or keeping it back when going down hill. Each tobogin was supplied with a large tarpaulin, cut so as to pack in the most snug manner, the men's knapsacks being laid on the bottom of them, and the arms stowed ou the sides. A man can draw this carriage with a hundred weight on it, easier than he can carry his knapsack. -Ibid.

MINOR CORRESPONDENCE. Street-Paving-Sir, In No. 423, Mr. Baddeley writes thus, "J. B. admits, that more horses fall now than formerly through the smoothness of the street paving." For answer to this, I beg to refer to my former letter, p. 414, where it may Le seen that I merely admitted or supposed that to be the case for the sake of argument. Mr. B. next contradicts my statement respecting the fissures between the stones, which I asserted would widen in the course of a few weeks, and furnish sufficient abutment for horses passing over them, Mr. B. says, "No such effects take place, nor can they." What! not all the traffic of the metropolis widen the joints

31

between the courses of stones! If granite possessedTM the qualities of adamant, then might that be the fact, but not otherwise. Mr. B. then asserts, that if my "first objection were true, the second must of necessity be false." But, Sir, as the first and second were not dependant upon each other, and scarcely connected in any way, Mr. B.'s false consequence is by no means a necessary one. Mr. B. ascribes to the new paving the solid surfaces of ice and masses of snow which not infrequently obstruct our streets in winter. Would it not have been more reasonable to reprimand the scavengers, whose duty it is to reinove such annoyances "twice a week at least." As to Mr. B.'s coal-waggon case, unless he can show that the horses' shoes were roughed, it can reflect no blame whatever on the new street-paving. In fact, if Mr. B.'s" hints" were acted upon, the ice fault of which he complains would be worse, for none could expect the poor scavengers to pick the frozen matter out of Mr. B.'s abutment interstices.-Yours, &c. J. B. Sept. 19, 1831.

Pulpit Sounding-Boards.-Sir, In your "Miscellaneous Notices" of the last Number of the Mech. Mag. you allude to the Rev. Mr. Blackburn's sound. ing board, and mention its adoption by Professor Farish at Cambridge. If any Londoner is anxious to ascertain the properties of the invention, he may do so by going to St. Sepulchre's Church, Snowhill, in which a similar sounding-board has been put up within the last six months. A Reverend Divine, a friend of mine, preached some time since in the pulpit of Attercliffe-cum-Darnall, and he remarked, that when his head diverged from the right point his voice seemed to resound in all directions round his ears; but that when he regained the proper centre, his voice appeared to diverge without difficulty or confusion. It is, I suppose, to avoid such an effect that a line and knot are affixed immediately opposite the preacher's face. Yours, &c., A CONSTANT SUBSCRIBER, Sept. 30, 1831.

Burning-Mirrors.-Sir, In No. 417, Mr. J. Smith gives an account of the effects produced by Parker's lens; in the 5th of the effects stated it ought to have been mentioned, that fir was the sort of wood dried. But the most wonderful effect, or rather non-effect, is, that the finger might be placed within an inch of the focus without sustaining any injury. The same story is related in the Panorama of Science and Art. Will Mr. Sinith be so obliging as to explain the above phenomena? I always considered that the degree of heat produced by a lens was proportional to the degree of concentration.-Yours, &c. A. MACKINNON.

MISCELLANEOUS.

Erasure of Writing A piece of Indian rubber, slightly moistened with water, will take out ink marks from paper, as effectually as a penknife, without in the least injuring the fabric.

Horse Food and Drink.-Some of the innkeepers ou the western roads have lately begun to follow the practice recommended by the Bath Agricultural Society, of boiling the corn given to horses, and giving them the water to drink. It is most satisfactorily ascertained, that three bushels of oats or barley so prepared will keep a horse in better condition than double the quantity in a crude state.

Peppermint Drops.-Professor E. Davy, in a letter to the Dublin Society, says, "Last evening, I observed in a little child's hand some white pepper mint sugar drops having bright red spots on them. Suspecting they were coloured with a substance im. proper for children, I was induced to examine them, and I found that their colouring matter is red lead. As the combinations of lead are known to be poisonous, and the habitual use of peppermint drops containing red lead may lay the foundation of inve terate diseases in children, such a pernicious appli

cation of this pigment ought, of course, to be inade known to the public, and, if possible, prevented,"

New Substance for Hats and Bonnets.-A wooden substance, called by its inventor, M. Barnardiere, Silvestrene, has lately been much used in Paris, in the manufacture of hats and bonnets, It is composed of very thin leaves or shavings of wood, which are laid side by side on a light and flexible pasteboard, so as to cover the entire surface, and to render it very difficult to distinguish the line at which the various slips unite. Each of these wooden leaves may be stained of a different colour, and this variety, combined with the delicacy of the texture and the polish of surface, give to the whole the appearance of variegated silk,

Irish Public Works." It was not now the practice to ascertain before hand the sum of money proposed to be laid out in any public work; and there was no check on the expenditure after the money had been granted. Works, too, were undertaken under the pretext of public utility, but really for purposes of private advantage, of which it might have been thought gentlemen would be ashamed. In the county of Mayo, money had been expended for the professed purpose of making a bridge, which, when completed, was found to be of no public utility, and was then converted into an embankment! Gentlemien might be astonished to hear of a bridge being made into an embankment, and might wonder how it was done; it was simply, as a witness said, by stopping the arch, permitting the tide to retire at Jow water, and admitting it at high water by a floodgate! It was utterly useless as a bridge, for there was no road on either side; and a witness stated, that there was no occasion for a road, for there was another bridge about a quarter of a mile off! This might be an exaggerated case; but it was notorious, that roads were made for no other purpose than that they might go by this gentleman's house, or through that gentleman's demesne."-Mr. Stanley, House of Commons.

The

Evaporation of Plants.-Evaporation takes place in plants to an inconceivable degree in certain circumstances. It is known by the experiments of Dr. Hales, that a sun-flower plant will lose as much as 1lb. 14 oz. by perspiration, in twelve hours; and that, in general, in equal surfaces and equal times, a man would perspire 1-50. the plant 1-165, or, as 50:15;" and that, taking all things into account, a sun-flower perspires 17 times more than a man. same accurate observer found that a cabbage perspired in twelve hours, 1 lb. 9oz.; a Paradise stock, in a pot, 11 ounces; and a lemon plant, 8 ounces. Guetard states, that he found Cornus Mascula perspire twice its own weight in a day; and Mr. Knight has remarked, a vine in a hot day losing moisture with such rapidity, that a glass placed under one of its leaves was speedily covered with dew, and in halt an hour, the perspiration was running off the glass. In damp or wet weather the evaporation is least; in hot or dry weather it is greatest."-Lindley's Guide.

Great Tunnel at Liverpool.-At the annual meeting of the proprietors of the Liverpool and Manchester Bailway, held last week, it was announced. that in order to dispense with the necessity which now exists, of going by Omnibuses from the office in Dale-street, to the station in Crown-street, from which the carriages start, it was intended to form a tunnel, to commence about 150 yards distant from the railway gates in Wavertree-lane, to come out in Lime-street, at the Cattle-market. It will be about 1 1-3 mile in length, 25 feet and 22 feet wide, with an ascent from Lime-street to Wavertree of 1 in 106. It will be brilliantly illuminated with gas, well ventilated, and so formed as to admit of the temperature within the tunnel, being the same as that of the atmosphere without. The roof of the tunnel will be

coated with Roman cement; and the general appearauce will exceed that of the Thames Tunnel, which is so great an object of general curiosity and adration. The expense will be under £100,000-a sum equal to the interest of which is now paid for omnibuses to convey passengers from Dale-street.Liverpool Paper.

Liverpool and Manchester Railway-The receipts for the last half year, from the 1st of January, 1831, to the 30th of June, were £65,693. 78. 5d.; the expenses, £35,379; the clear residue, £30,314. 13s. 7d.; dividend per share, 4. 10.

New Printing-Press.-A Mr. M. W. Carrall announces, in the Yorkshire Gazette, that he has "succeeded in bringing to pertection a working model of a new pinting-machine, which he can confidently recommend as superior to any now in use, on account of its simplicity and cheapness; and which is an original invention of his own. The present model is capable of producing 1000 impressions per hour; and may be so constructed as to print from 15 to 1600 per hour with perfect ease to the workmen."

Timber Produce.-An oak tree was a short time ago felled near Ludlow, in Shropshire, the produce of which was 39 tons of timber, 55 cords of wood. 200 park pales, and 5 cords of brackets. A bough broke off before the tree was cut down, which weighed seven tons and a half. Three men were employed a month in stacking it. The whole tree was valued at £165.

Naturalized Exotics. -Since the discovery of the New World, our English gardens have produced 2,345 varieties of trees and plants from America, and upwards of 1,700 from the Cape of Good Hope, in addition to many thousands which have been brought from China, the East Indies, New Holland, various parts of Africa, Asia, and Europe, until the list of plants now cultivated in this country exceeds 120,000 varieties.

IRON STEAM-BOAT ADAPTED TO CANAL

AND COASTING NAVIGATION.

We inserted some time ago (vol. xv. p. 297) an interesting Report from the Governor and Committee of the Forth and Clyde Canal Company on the progress made in the application of steam to canal navigation. It appeared from that Report that there were two iron steamboats-the Cyclops and the Lord Dundas -already employed to great advantage as regular traders for the conveyance of goods and passengers between Port Dundas (on the Clyde) and the port of Alloa,

on the northern shore of the Frith of Forth; and that Mr. Fairbairn, of Manchester, who built the Lord Dundas, and had paid great attention to the subject of canal navigation, had been commissioned to construct a third steam passage-boat, on an improved plan, for the same Company. We have now before us a book published by Mr. Fairbairn,* in which he gives a particular description of these boats, and an account of the various experiments by the results of which he has been guided in his successive improvements. From this work we glean the following particulars.

Her

The Cyclops is constructed on the American plan, with the whole of its machinery placed in the rear of the vessel. She is 68 feet in length, and 15 feet 6 inches in her greatest breadth; 7 feet 3 inches deep from keel to deck; and weighs altogether about 38 tons. paddle-wheel works in a rectangular trough, cut out of the stern, being closed on each side and in front, but quite open to the water behind and below. The space occupied by the paddles, when placed, as usual, on the side of the vessel, is thus saved-a circumstance of the first importance in narrow lines of navigation and the great swell which sidepaddles occasion, and from which injury might be apprehended to the banks, is also avoided. This mode of construction is not, however, without its disadvantages. The paddle-wheel, from being so confined, is inadequately supplied with water; the water in front of the wheel is always lower than that in the rear; and

* Remarks on Canal Navigation, illustrative of the Advantages of the Use of Steam as a Moving Power on Cauals, &c. By William Fairbairn, Engineer. 93 pp. 8vo. Longman and Co.

a considerable portion of the broken water coming from the paddles, strikes on the sides of the trough or box, and retards the progress of the vessel. In consequence, too, of the machinery being all placed in the stern, it causes the boat to hang by the stern when lightly laden, as mere passage-boats commonly are; that is, the bow is raised and the stern depressed till the paddle-wheel is sunk to such a depth, that it may be said rather to churn the water than to produce any effective impulse. When to these objections it is added, that the Cyclops "bears about her a quantity of iron sufficient to build nearly two boats of the same size, and of equal strength," and that "her engine, which ought to have been high-pressure, is low-pressure, and though a sweet-going machine, much too heavy”—we are presented with the picture of a vessel, not untruly described, as replete with faults." Still, when well laden, and with a cargo so trimmed as to counteract the tendency to hang by the stern, the Cyclops appears to do work which no common sailing-vessel is capable of performing, and which is scarcely surpassed by the best of the steam-boats with side-paddles.

66

"The Cyclops has been regularly trading between Glasgow and Alloa, and has made her voyages to and from that place during several of the most stormy days of this winter (1830-31), leaving Grangemouth on her voyage to Alloa when no vessel could venture out. She has carried in these voyages a cargo at one time of 40 tons; and performs the voyage from Alloa to Port Dundas in little more than half the time which is consumed in tracking a vessel of the same burden from Grangemouth to Port Dundas, about two-thirds of the distance. Every person must be struck with the great burden of this vessel on a small draught of water; and I question much if there be a steam-boat in the kingdom which on a draught of almost double that of the Cyclops, can carry such a cargo." -P. 41.

"The whole time consumed by the Cyclops (on one occasion without any cargo) in the voyage from Alloa to Port Dundas, a distance of 40 miles, including the passage of 20 locks, a considerable time lost at Grangemouth making some inspections and several other delays, and a long stop at the entrance of the Union Canal, was something less than ten hours

and a half; and if she had been properly loaded with a cargo of 20 or 30 tons, the voyage would have been accomplished in less time. The estimate of Mr. Johnstone, who is to have the management of the Cyclops, and myself, is, that with a cargo of from 40 to 50 tons, she will do the voyage to Alloa, even against a headwind, in eight hours and a half."-Letter from Mr. Thomas Grahame to Mr. Fairbairn.

The Lord Dundas was constructed with a view to speed alone; and this in consequence of Mr. Houston's successful experiments on the Ardrossan or Paisley Canal in the early part of 1830, which showed that by the use of light, gigshaped boats, not only was a much greater speed attainable on canals than had ever before been imagined, but that the greater the speed, the less was the surge, and risk of injury to the banks. (See Report of the Committee of the Forth and Clyde Canal Company, vol. xv. p. 300.) Her length is 68 feet; her breadth of beam, 11 feet 6 inches; her depth, 4 feet 6 inches; her steam-engine of 10-horse power; her total weight only 7 tons 16 cwt.; and her draught of water, 16 inches. The sheeting of the iron ribs is less than 1-16th of an inch in thickness. The Dundas is what is called a twin steam-boat-that is, a vessel with a long trough, or hollow through-and-through space, in the cen tre, in which the paddle-wheel works. In the course of the experiments on the Ardrossan Canal it had been found that from the length, narrowness, and lightness of the single gig-boat, it was unsteady in the water, and easily_swayed from side to side; but that when two such boats were linked together, with a narrow space left between them, there was more steadiness and less surge; and this result is stated to have suggested to Mr. Fairbairn the idea of the "light, twin, iron steam-boat," Lord Dundas. We can see but little resemblance, however, between two narrow boats linked together, and one larger boat with a hollow trough in the centre, having but one prow and one stern. Neither can we be persuaded, that the double-boat experiment alluded to, established more, than that a somewhat greater breadth of beam was desirable than the single gig boat presented. It was not a very well-conducted experiment, and is opposed to an

35

other (p. 20), which showed that a single gig-shaped boat, 60 feet in length, only 4 feet 6 inches in breadth of beam, and with ten inches draught, was "quite steady in the water,"" by no means crank," and as free from surge as could be desired when drawn (by horses) at the rate of nine miles an hour.

"The quicker the boat went, the moro entire was the disappearance of all wave" and surge, except when the water escaped in the centre of the canal and met in two very noisy and rapid currents from each side of the boat at the rudder. The noise and rush of water was so great as to induce persons on board to look round, expecting to see a great wave or surge on the bank of the canal, but on the banks there was hardly a ripple."-P. 22.

Evidently, there was no reason for expecting more from a double boat than from a single one; and as it is, Mr. F. has produced in the Lord Dundas a vessel which though called a twin one, has no pretensions to the name. It is not the less single that it has a hollow trough in its centre; and differs from other sin gle steam vessels in this only, that the paddle-wheel is transferred to that central trough, instead of being placed either at the side or in the rear. What the considerations were which induced this change of position does not very clearly appear. Mr. F. relates (p. 69-57) some experiments which were made under his direction on the Forth and Clyde Canal, with the view of ascertaining the comparative efficiency of a single paddlewheel placed in the centre of a vessel compared with two paddle-wheels one on each side; but he admits that they were not attended with any satisfactory result. "It was found," he says, "from the defective state of the machinery that little more could be done than to show the action of the float-boards in the trough, and the consequent wash that might be produced on the banks;" and on that head, all that was ascertained was, that the agitation caused by a wheel working in a central trough 66 never approached the banks, but was discharged from the stern, running like a mill-stream in an extended line for some distanee in the middle of the canal." As it is not pretended, however, that any agitation injurious to the banks of the canal is caused by the Cyclops, which has its paddlewheel in the rear, it can scarcely be said