surface of which was equal to that of the tile; the tile was left to dry in a room heated to 60 degrees and did not lose all the water it had imbibed in less than six days. In most parts of Surrey, tiles are uniformly used for roofs of houses, and in some instances on barns; but between Dorking and Horsham a heavy, but very durable sort of slate stone is used. Nearer London either Westmorland or Welch slates prevail. The finest sort of blue slate is sold at Kendal, for 3s. 6d. per load, which comes to 11. 15s. per ton, the load weighing two hundred weight. The coarsest may be had for 28. 4d. a load, or 11. 3s. 4d. per ton. Thirteen loads of the finest sort will cover 42 square yards of roof, and 18 loads of the coars est will cover the same space, so that there is half a ton less weight, put upon 42 square yards when the finest slate is used, than if it were covered with the coarsest kind, and the difference of the expense of the materials is only 3s. 6d. To balance in some measure the advantage arising from the lightness of the slate, it must be remarked that it owes its lightness, not so much to any diversity in the specific gravity of the stone from which it is split, as to the thinness to which the workmen reduce it; and it is not able to resist violent winds so well as that which is heavier. A common Cambridge tile aveighed 370z: seven hundred of these tiles are used at a medium for covering one hundred square feet, or about two and a half tons of tiles to 42 square yards. Without including the weight of what is used in lapping over, when a building is covered with any of the materials mentioned, 42 square yards of the roof will support a weight in the following proportion, to that which the same surface would sustain if covered by lead or copper or zinc. Tiles, 54 Cwt. 36 27 Fine slate, 26 4 1 Copper, From the foregoing statement it is evident that the consequences arising from covering with tiles are two-fold; first, that owing to the weight of them, the plates and rafters of the roof must be made proportionably stouter and heavier, than is necessary for slates, even of the coarser sorts; and consequently this encreased strength in the timber, must add to the expense of the roof, supposing that the same thickness of wall be sufficient. Secondly, it is proved, that, from the porosity of the tile, it imbibes one seventh part of its weight, or about five ounces of water, in ten minutes, and that it requires the heat of 60 degrees, for six days, to make it as dry as it was before it was saturated. It is probable that tiles may continue wet much longer during the moist winter months, if they ever dry completely at all on the roofs of houses in that season. And it appears evident that tiles lodging on timber in a state of dampness, at least for six months in the year, must considerably injure such timber. The foregoing extract from Mr. Malcolm's paper is given account of the useful information it contains relative to covering for roots. In the table of the comparative weight of equal surfaces of roofs covered with different materials, we have added the weight of a zinc covering, (from the facts contained in Mr. Sylvester's paper on the subject, of which an abridgement is given in this volume page 183) to make the table more compleat. The weight of Zinc is calculated at a pound to a square foot, which is almost three times the weight of the thinnest Sheet Zinc mentioned by Mr. Sylvester. Very durable roofs are made in India, where much rain falls, of a composition of clay and other materials: This renders it probable that cheap covering for houses might be made in this country in a somewhat similar manner, with Tarras, or other compositions that resist wet. The principle difficulty in the the formation of such roofs, would be to prevent their cracking; but it is supposed, that means might be found of obviating this evil, suited to the nature of the materials used, as well as it is done in India; and a few trials on the roofs of out-houses, would probably shew a method of doing this sufficiently perfect for dwelling houses. The Indian method of forming roofs, and singular manner of building houses shall be given in a future number, as it is supposed the utility of the subject will make it interesting, though its having been published in another periodical work before the commencement of this, must deprive it of novelty to a few of our readers. Of the great benefit derived from employing fumigations of oxy-muriatic acid, in preventing infections and stopping putrid fevers, by M. A. Hedouin, Physician, -Anns. de Chemie, Tom. 62. In the year 1801, M. Hedouin succeeded M. Romilly in the superintendence of the sick at the prison of Mont. St. Michel; which from its situation was extremely unhealthy, where he found more than half the number of prisoners ill of putrid fevers. Juniper berries and incense had been burned in the cells of the prisoners, but only disguised the smell, without producing any good effect. The cells had a fetid odour of so pungent and tenacious a nature, on M. Hedouin's arrival, that his cloaths retained it four and twenty hours after their exposure to the free air. In these circumstances he hastened to employ M. Guyton's process for fumigation; And a mixture of muriatic of soda, black oxyd of Manganese and sulphuric acid, was put into proper vessels and carried into the cells several times. These operations produced a very sensible diminution of the fetid smell, without being attended with any accident, and M. Hedouin had very soon the satisfaction of perceiving that the epidemy of putrid fevers diminished also. Afterwards several of the large apparatus for fumigation invented by M. Dumotiez were carried through the Hospital many times each day. Since the commencement of 1804 the number of prisoners was increased one third; the structure of the cells had not been changed; the same misery pervaded every part of them as before; nor had the amelioration in the food of the prisoners, arising from their labour, been sufficient to change the nature of the diseases with which they were infected; and yet the putrid fevers had almost entirely disappeared. The efficacy of M. Guyton's process in subduing the putrid fever in the prison, was farther confirmed by its being so epidemical at that time in several neighbouring districts, that the churches were fumigated by an order from the prefect, The following table of the deaths of the prisoners, and the number of them in the prison for 6 years, will prove the efficacy of the acid fumigations. On the effects of acid fumigations in contagious disorders of cattle, and destroying putrid odours. By M. Guyton de Morveau.-Anns. de Chemie. Tom. 62. About the end of Autumn 1806, the rot having made its appearance in some parishes in the department of Loire, the proprietor of two flocks of Merino sheep, was induced to order fumigations of oxy-muriatic acid to be made in the folds and stables; at first in open vessels, by pouring sulphuric acid on a mixture of sea salt and oxide of Manganese; and afterwards by means of the large apparatus of M. Dumotiez. This experiment was attended with so much success that a farmer in the same commune, who had already lost several sheep, applied the same remedy. He opened the apparatus twice a day for three minutes each time, according to the instructions he had received: The rot became mild; one half of the flock was not affected with it, and he did not lose a single sheep. Two other farmers of the same commune made a similar successful experiment. Their diseased flocks were allowed to pasture along with the healthy, the latter having been previously fumigated in the folds, and no contagion was communicated. Since this the apparatus has become general in the depart ment The following account of the efficacy of this fumigation in destroying putrid odours was communicated to M. Guyton, by the directors of the hospitals at Besançon. Several hundred weight of meat had been left for some time neglected in the cellar of the public hospital: it diffused such a fetid smell, that it was impossible to enter the place to carry it away, and it was at last drawn out by a pitchfork. A flask of the mixture for producing the oxy-muriatic acid gas, was afterwards introduced, and the door of the cellar closed. When this flask was withdrawn a few hours afterwards, there existed no smell whatever in the cellar, except that which was diffused by the oxy-muriatic gas: Its emanations having been very strong, the window was opened in order to procure a current of fresh air : The cellar was then so completely purified that fresh meat was put into it, and well preserved. The stench occasioned by the body of a dead rat, was also destroyed in a few minutes, The apparatus contrived by M. Dumotiez of Paris, consists of a vessel of thick glass which holds about three half pints; the edge of the vessel, which is very thick, has a strong glass cover ground on it, so as to fit very close; This vessel is fixed in a small wooden frame, resembling a press, which has a wooden screw, in its upper part, that presses the glass cover down so as to perfectly confine the gas. The charge for this vessel, is one ounce three drams of black oxyd of Manganese in powder, the fifth of a pint of pure nitric acid, and the same quantity of marine acid. Another smaller apparatus was prepared by Dumotiez on the same principles, and enclosed in a case of box-wood so as to be portable in the pocket. The charge for this sort, is about one drachm of black Manganese, about the 50th part of a pint of nitric acid, and the same quantity of marine acid. There. are many mixtures which produce the oxy-muriatic gas, but M. Guyton de Morveau found the above preserve its properties longer in closed bottles than any other. Portable fumigating bottles, on a plan similar to the last mentioned, have been long since made by Mr. Lloyd, 178, Strand, for sale, at the suggestion of the writer of this article, from the conviction of the great benefit they might be to the public. On the use of Sulphur in destroying Insects on plants, and its benefit to vegetation, by Mr. Joseph Hume of Long Acre. In our number for March, an account was given of the application of Lower of sulphur to destroy insects on plants, extracted from a paper of Mr. Hume's Hume's; who has last month published the following particulars on the same subject. The sulphur may be tied up in a piece of muslin or fine linen, and with this the leaves and young shoots of the plants should be dusted; or it may be thrown on them by means of a common swan-down puff, or even by a dredging box. Mr. Hume has received fresh assurances of the powerful influence of sulphur against the whole tribe of insects and worms which infect and pray on vegetables. He has also been informed that the sulphur has been found to promote the health of the plants on which it was sprinkled: and that peach trees in particular were remarkably improved by it, and seemed to absorb it. It was likewise observed, that the verdure and other healthful appearances were perceptibly increased; for the quantity of new shoots and leaves formed subsequently to the operation, and having no sulphur on their surfaces, served as a kind of comparative index, and pointed out distinctly the accumulation of health. Account of a tubular compensating pendulum made 30 years ago. It has been believed by many that the tubular pendulum, (constructed on the principle of Harrison's gridiron pendulum, to preserve the same length in various temperatures by the contrary expansions of different metals) is but a late invention. The following account of one made npwards of thirty years ago, which proves this opinion to be fallacious, will therefore it is supposed be interesting to some of our readers. This pendulum is now in the possession of Mr. Patoureaux, watch and clock maker, 15 Wardour Street: It was made by Mr. Wm. Brown, a clock maker well known to the trade, who has been dead upwards of five years, and who formerly resided near the seven dials; his brother, a jeweller residing at 15, Coyentry Court, Haymarket, was his executor, and sold the pendulum to Mr. Barrett, clock maker of Compton street, some years ago, from whom Mr. Patoureaux bought it; Mr. Brown the jeweller asserts that this pendulum had been made by his brother upwards of thirty years ago, just after he had served his time to Mr. Chandler, of King Street, Seven Dials, (whom he afterwards succeeded in his business;) and that it was made by direction of Mr. Chandler, who, as far as he knew was the inventor of it; and, in corroboration of this assertion, Mr. Hampson, working clock maker, 22, Greek Street, Soho, declares that he made several pendulumis of the same construction for Mr. Brown upwards of seven years ago. This tubular pendulum, which at present we must attribute to the ingenuity of Mr. Chandler, is composed of two tubes and a rod of iron, and two tubes of brass. The iron rod is about a quarter of an inch in diameter, and is suspended by a spring in the common manner, it is enclosed by the first brass tube, to which it is connected at bottom; an iron tube supported by the top of the brass tube then descends a little below it; and supports by its lower extremity the second brass tube; which rises a little above the former tubes; and from the top of it, the second iron tube descends below all, about two inches into the substance of the pendulum bob, which is very large and heavy: the bottom of this last tube contains a nut, into which a screw (having a milled head beneath, that sustains the bob) passes from below and raises or lowers the bob as required for the adjustment of the rate of going of the clock. We may date the invention of the tubular pendulum from the foregoing information, about the year 1775; Tho' it may yet be found to be of a still earlier period: The foreman of Mr Villaumy, clockmaker to the Prince of Wales, Pall Mall, declares that he remembers a tubular pendulum to have been made by a Mr. Finney, a well known clock maker of Liverpool, upwards of forty years ago, and that it is now in the possession of Mr. De Membry, Richmond. Extract from a paper on a new method of managing and applying Turnip Crops as food for animals, by Mr. John Saunders of Stroud.-—Agl. Mag. N. 8. Mr. Saunders' plan for the management of turnips, principally consists in thinning them frequently, and feeding pigs and other animals, with the tops and. and other parts; from which method he thinks extraordinary profit might be derived. In corroboration of this idea he mentions the great produce got from a plot of garden ground, cropped with carrots, reddishes, and lettuces, thinned out, as they advance in growth, and the profit which gardeners obtain from raising cauliflower, brocoli, and cabbage plants for sale in a similar manner. From being thinned more regularly than usual, and having a greater space allowed to each to grow in than is customary, turnips will yield a great return in weight and measure. Mr. Saunders quotes a paper signed Agricola Northumbriensis, to shew that the actual weight produced from a thinner crop may be greater than that from a thick crop. If in the one, the rows are thirteen inches asunder, and the turnips twelve inches apart in each row, then the produce will be 40,200 to an acre; and if in the other the distance of the rows is twenty-seven inches and the intervals between the turnips eleven inches, the number to an acre will be 21,100. The crops will then be to each other in point of number nearly as 2 and a fraction to 1; but by the large intervals the size of the turnips will be encreased at least two inches in diameter, more than those planted with smaller spaces between them; then supposing the small intervals to produce turnips of 6 inches in diameter, and the large intervals, turnips of 8 inches across, the weight of 21,100 of the latter, will be to that of 40,200 of the former, nearly as 129 to 86; consequently when the first are worth 41. per acre, the last will be worth 61. Mr. Saunders afterwards makes the following observations: If a farmer would take the pains to cast his eyes over a turnip field, he would find thonsands of turnips which might be hoed out, with advantage to the crop, and given to the cattle. An acre of turnips, and perhaps one of carrots, cabbage, parsnip, rape, or cole, thus managed, and gradually thinned out, would yield annually nearly twice the produce they do at present, and some of the above crops might be mixed with the turnips to advantage. A further supply of food for cattle might be obtained in spring after all thinning had ceased, by cutting off with a scythe the tops from all the turnips within two inches of the bulbs, by which they would be checked in their disposition to run to seed, and the bulbs be preserved for a month, or six weeks longer, while an ample store of green food would be obtained for swine and other cattle, at a desireable, and scarce season of the year. It is the turnip field principally that looks so green in the winter season. It then yields its produce when the corn fields, though green, yields no return and the grass land has exchanged its verdure for the russet hue. It is evident that grass land would retain its pasture for two or three months longer, and the aftermath would come in at a most desirable season, if the animals on a farm were withheld from it by occasionally subsisting them on turnip greens. Besides the hay-mow should be preserved in all farms as long as possible; and if the greater proportion of the cattle of a farm should be occasionably subsisted on the greens for five or six months in the year, the hay stack will preserve its size in proportion, and the farmer who shall adopt the mode, will not have to lament his want of foresight in the ensuing winter and spring months. The great, yet simple rule, with respect to the turnip, and every other crop, while in a growing state, should be to permit each plant to approach but not to come into actual contact with its neighbours. Pursuing this easy pian, the farmer may continue to thin his crops till they shall have ceased to grow. And thus with a sufficient stock of animals, his lauds will be better manured than by any other mode; his breed of animals will be enlarged, and his crops be nearly, if not quite doubled. Mr. Saunders thinks the small animals, which breed often, are more profitable than oxen; the Hog kind comes first under this head; Pigs, he observes, from the age of three weeks, and in every intermediate state up to the latest growth are fit for the table. There can be no better eating than a porker from six weeks up to two, three, and four months old; a sow also will produce her young much under the age of a twelvemonth, and her fecundity is alke remarkable: the superiority of Hogs dung, for manure is likewise incontestible. On |