its wheel-work are placed on a fixed arbor, which hath a pinion on the end of it which drives both the solar and lunar motions, by means of a large wheel of 288 teeth turning once round upon it every 24 hours, which large wheel is drawn round by a pinion of 12 leaves, fixed on the arbor of the great wheel within the clock frames, which turneth once round in an hour; the wheel 288 thus turning round in 24 hours, carries about with it a wheel of 37 teeth and its pinion of 7 leaves, this pinion of 7 leaves turning round with wheel 37, drives another wheel having 45 teeth which carries round the Moon's ring and circle; on the opposite side of this wheelwork, a pinion of 8 leaves extends, and did drive a wheel, but said wheel and its pinion being taken away, the numbers of the wheel and pinion is unknown, the pinion of this wheel, however, turned round a wheel having 29 teeth, furnished with a pinion of 12 leaves, which turned round a large wheel having 132 teeth which carries round the Sun and the zodiacal matter. These were the numbers of the wheel-work remaining in the year 1711, but the before-mentioned wheel and its pinion were taken out formerly by some ignorant workman that was not able to amend the clock; they were however supplied, and the whole movement repaired by Mr. Lang Bradley, Fenchurch Street, London, vide Dr. Derham's Artificial Clock Maker, 3d edit. Lond. 1714, p. 121 and 122. This description gives a very clear idea how the several movements were actuated; but the numbers of a wheel and pinion in the solar train being unknown, leaves that movement incomplete, thus, X 29 × 42, so that the original combination of wheels and pinions for the annual motion unfortunately cannot with certainty be ascertained. The writer of the article Clock-work in Dr. Rees' Ency. (before referred to,) states, that after he had drawn up the various particulars re garding this clock, he felt an inclination to inspect it; this was on the 8th day of May, 1805, when he embraced an opportunity which occurred of gaining permission to ascend the lofty situation in which the clock is placed. It proved on a minute and careful examination of its several parts, that the whole of both the annual and lunar movements are different from the original ones reoorded by Dr. Derham; the lunar movements was found to be 2 × 45 294 days for a synodical lunation, the annual train was found to be × 47 × 150 = 365 days exactly; the central pinion was a double one consisting of a 10 and a 12, fixed as the former one of 8 is described to have been, and pinned together; they are of the wood called box, as are also the pinions 7 and 9, to prevent their cankering, (oxiding) the wheel 42 is made of brass, but the rest being

very large are made of iron; the gre at whee of 288 teeth which connects the clock work with the astronomical movements, appeared to be the only portion of the original work, both by its marks of antiquity and the number of its teeth, which are cut on its inner edge (interior circumference,) there are two cross bars rivetted to this indented rim to carry the celestial movements, and as there was no counterpoise to them, it was suspected that their rising and falling weight would alternately accelerate and retard the going of the clock, which is connected with it by means of a horizontal arbor of about three feet long by estimation, an enquiry into this matter proved the accuracy of this conjecture, for it appeared that the time of the day indicated was sometimes about five minutes too slow, and at other times as much too fast; the inscription "L. Bradley, 1711," is engraved on the frame of the going part of the clock, which has evidently been new, either the whole of it at that time, or some part of it since, so that what the original regulator was does not appear, the initials of the maker's name "N. O," are now not to be found; there are three barrels and weights, one for the going part which has a very long heavy pendulum, one for the striking part, and one for the quarters, the present scapement is a pair of pallets acting alternately into pins projecting from the plane of a wheel with a horizontal arbor or axis; according to Berthoud, this kind of scapement was invented by a Mr. Amant, a clock-maker at Paris, late in the eighteenth century. So it would seem that this clock had been again altered and repaired, somewhere between the years 1760 and 1800; in Grose's Antiquities, it is stated, that the astronomical furniture of this clock was invented by Thomas Tompion, the celebrated clock-maker; this account can. not be correct, for that ingenious artist lived in Dr. Derham's time. Tompion died in 1669, which period is about 129 years after its construction; it is probable, however, that he might have been employed upon it, and thus given circulation to this current account; the hands and circles are in the following order upon the dial-plate, 1st or interior circle is divided into 24 hours for the Moon's southings, after this manner, 12, 11, 10, &c. 2d, Moon's age circle divided into 29 equal parts; 3d circle is furnished with the ecliptic with its signs, and days of the month; 4th, Sun or hour hand revolving in 24 hours; 5th, the dial circle divided into 24 hours in the usual manner, thus, 12, 1, 2, &c. the Moon's phase is exhibited in a circular opening in the hour-hand, which covers more or less of a plate, part of which is blackened elliptically, placed under it; the form and action of this plate will be readily understood from a perusal of either Ferguson's

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Select Mechanical Exercises, or to the London Mechanics' Magazine, vol. xiv. page 289, which gives a short detail of my tide-table."

THE POTATOE.

A plant, second hardly to any in point of importance in furnishing food for man, requiring also the same climates, has been introduced into the same countries. This is the potatoe, for which India as well as the rest of the old world, is indebted to the new world. It has been found in a wild state, in 33° of S. latiStude, in Chili, in the mountains near Valparaiso and Mendoza, and also near Lima, Quito, and Santa Fé de Bagota; but in these situations it is supposed to have escaped from a state of cultivation, as the illustrious Humboldt argues that it must have travelled north in "the course followed by the Incas in their conquests." But it was introduced into England from Virginia, in 1586, by Sir W. Raleigh, and not known to the Mexicans in the time of Montezuma; he concludes it as probable, that if the English colonies did not receive it from South America, this plant was originally wild in some country of the northern hemisphere, as it was in Chili. This conjecture has been singularly confirmed by the potatoe being found wild on the Pie d'Orizaba by Deppe and Schiede (D. Don).

The potatoe, we are informed by Dr. Ainslie, was introduced into India from the Cape of Good Hope, and some of excellent quality are produced in the Mysore country, particularly at Bangalore and Nundydroog. They are grown all over India (Roxb.), and of a very fine quality in the cold weather, or from October to March, along the planes of India from Patna to Loondiana. Dr. Wallich states, that "they are planted in the valleys and lower hills of Nepal, so as to afford fresh crops all the year round: the roots are planted in February, June, and November, and gathered after three months." They are introduced into the northern mountains, and grown in the neighbourhood of Simla, at an elevation of 7,500 feet; and by Major Young, on the mountains north of Deyra, at an elevation of 6,700 feet; so that Mussooree made its first appearance on the map by the name of the Potch garden. Their quality was subsequently much improved by Captain Townsend raising some from

quality.

seed, which in hin the third year became of enormous size, and of very good They are now becoming very generally cultivated, both in the hills and plains of northern India; and it is fortunate, both for sellers and consumers, that those grown in the former come in when the others are going out of season.

Potatoes are in some places becoming adopted as food by the natives of India, though more slowly than could be wished'; at this we need not be surprised, as even in France their use was not generally adopted until after their introduction into Europe more than two hundred years, and then only owing to the persevering efforts of the philanthropic Pamentier, round whose tomb in Père la Chaise, they are now yearly planted; so that M. Fée remarks, “ verité frappante, toujours repetée et toujours nouvelle: il faut déployer plus d'activité et plus de ressources d'esprit pour faire du bien aux hommes que pour leur nuire."-Royle's Botany of the Himalaya Mountains, No. 8.

VENTILATION OF THE HOUSES OF
PARLIAMENT.

(Extracts from the Evidence of Dr. Reid, F.R.S.E., President of the Philosophical Society of Edinhurgh, &c., before a Select Committee.)

Have you at all turned your attention to the subject of ventilating and warming large public buildings, as well as to the practical application of acoustics to the construction of buildings?-I have paid considerable attention to both these subjects; I have had my attention particularly directed towards the subject of ventilating large buildings; more especially from the circumstance, that on some occasions in my class-room there are 2,000 experiments performed within the hour, and unless every thing were managed with the utmost precision, the student would be obliged to retire from the class-room in consequence of the fumes that are disengaged. The means I adopted were simply taking advantage of a current which is determined by means of a column of heated air; a large furnace is kindled, and wherever it is necessary to carry off fumes, or to ventilate an over-crowded or heated room, an aperture is made into that vent, or otherwise connected with it, leading the air or fumes from the place to be ventilated.

Where do you place the heating apparatus for that purpose? It is placed upon the floor-a few feet above it; it plays into a large

rge vent, and wherever an opening may be made in that vent, an internal current-a current into the vent-is immediately set in

motion, care being taken at the same time that there shall be as free room given for the entrance of fresh air at a different place, as there is for the exit of the heated air. 920Would you advise that such an apparatus should be placed on the floor of the House of Commons, which is the building to which the Committee is at this time devoting its attention?-By no means; I would have it worked in an independent apartment. It is fitted up on the floor in my class-room because we take advantage of the heat; we find we can carry on a number of furnace operations, of a particular description, with a moderate heat, with the same fire which induces and regulates ventilation; that being no object whatever, for the purpose required in the House of Commons, it would be, better to have the furnace in another place where it would not be inconvenient.

Whether you place the apparatus below, er in or above the room to be ventilated, it is immaterial 1?-It is of no great consequence; but this is to a certain extent of consequence, that if placed in such a manner that there shall be a current, we may draw the air from the House of Commons, not merely by the vent, but by the lower part which supplies the fuel of the furnace with air, thus furnishing it with additional power; I wish to take advantage not only of the current which is made to ascend from the lighter current produced by the heat, but also to draw from the House of Commons the air that feeds the fire. If the furnace were situated in an apartment immediately over the House of Commons, the air from the House of Commons would rise to it and create that draught, would it not? It might create a little draught, but the power as produced by the furnace is dependent upon the light and expanded air rising from the fire; at times we have the air warmer without than within, and were it not for the heat actually developed by specifie combustion, our currents might sometimes be reversed.

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But under any circumstances, do you propose for the purpose of ventilation to have the vent tube placed in the chamber to be ventilated?-There is not the slightest necessity for it; if a communication is made by a tube towards the vent, that is all that is essential.

From whatever place the supply of air is taken, ought it not to be a spot freely open to the action of the winds and atmosphere?-It would be preferable.

Do you contemplate that when the House is crowded the ventilating apparatus should also be used at the same time?-It should be ready for powerful action at all times; but I would not propose that the ventilating apparatus should be brought into full action until

it was absolutely necessary; it could be worked always in such a manner as the varying circumstances of the case might require; 1 should of all things wish to avoid any accumulation of bad air, so that it became necessary to use the ventilating apparatus with great power; but I would not put on the ventilating apparatus until Members actually began to assemble, and from that moment the ventilating apparatus being in action, it would be better to keep up the purity of the atmosphere by a general and equal flow, than by allowing bad air to accumulate and then

working it with great power. In many of

the buildings which I have seen there is not nearly sufficient exit and entrance provided for the quantity of air required, so that when the windows are afterwards thrown open, cross draughts are induced in every direction.

It is your opinion, that in constructing the building generally, reference should be had to the position of the doors and windows, as well as to any ventilating apparatus that may be applied to secure good and proper ventilation?-The utmost attention, I think, should be paid to this, if it be intended to use them at times to assist the ventilation; but I would strongly recommend that they should never ventilate at all by doors (that there should be double doors), nor by the windows, except under the most peculiar circumstances. There might be arrangements made with advantage for throwing open the room by doors and windows to a certain extent; but if provision be made by other means, the ventilation will be completely under control when there is a power which can be regulated. The moment we begin to ventilate by doors and windows we may refresh those who are very near, but we have a sweeping current that runs in a particular direction, and there is no equality of ventilation; some may be refreshed or perhaps injured by the draught under such circumstances, but there will be no cquality of diffusion; and others may receive no fresh air at all.

Do you suppose that the same ventilating apparatus might be made applicable to the House and the Committee-rooms of the House in the morning?-That is what I should wish to see done in every large establishment, not only the ventilation of the large room, but also tubes connected with the smaller apartment, and valves arranged so that the apparatus might work exactly in the same manner as water or gas in pipes laid through a city. If there be one great chimney or ventilator through which every thing is to pass, by opening or shutting a valve in every individual room or apartment, be it what it may, any degree of ventilation can be commanded that is required. But a general difficulty has arisen in consequence of these

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provisions in most places not having been made any thing to the extent that is abso lutely necessary; consequently, when in full action, the doors and windows are thrown open all at once, and it disturbs every thing like unity of operation. There is another thing connected with ventilation as conducted by heated air, namely, that it is not liable to the noise produced when the ventilation is induced by the working of a fanner or other common, mechanical power put in action by machinery. Further, the same power dependent upon the application of heated air will also enable cold air to be thrown in whenever it may be necessary, which may be artificially depressed in its temperature in warm seasons; this would give great relief when there are months together of continuous hot weather. I should wish to see, not only arrangements for renewing air and warming it in the winter, but for cooling it in summer, which I think might be done with very great facility.

You do not contemplate the principle of regulating it by a self-regulating action ?-I should almost doubt whether that could be done; I do not say it might not ultimately be effected; but I have seen such a great number of ventilators fail in this respect, being subject to such a number of influences, that unless we were almost to attribute to them a kind of mental reaction, they could scarcely adapt themselves with precision to the varied circumstances under which they must act; but any ordinary attendant may be taught, by a little attention to the thermometer and the number of Members present, to increase or diminish the working of the apparatus to any extent.

A thermometer might be placed in some great thoroughfare, so as to be open to inspection?-Yes, it might be placed in the body of the House, so as always to be before the Members. One might easily be constructed for this purpose, both large and sufficiently delicate to be a constant check upon the ventilating apparatus; the usual registerthermometer might also be used, so that a most complete check may be obtained over the machinery, and the attendance of the person engaged in conducting it, at times when no one might be present to examine the heat, &c.

Supposing the thermometer rose very suddenly, do you think that then the apparatus you are talking of would rapidly reduce that apartment to a proper state of ventilation?It could be made to work to any extent. I may mention, on several occasions, gentlemen may have come in from a distance, foreigners and strangers, to see the working of my ventilating apparatus; when there was nothing doing in the laboratory, we have put on the

fire with a few pieces of wood, and in the course of five minutes we were able with that to bring it into such a state of activity that fumes produced in showing some experiments were carried with great rapidity by these ventilators, which in the course of three minutes would have filled the room to such an extent that we should have been obliged to go out, had they not been in action..

With regard to one apparatus being effi cient in ventilating the new Houses of Parlia ment, and all the Committee-rooms and other buildings, should you adduce that as an advantage in point of economy, or in point of general equability of ventilation?—In every point of view; better than having more than one, for a very small power is quite sufficient to work a great number of small ones.

Taking the Houses of Parliament, without going to the other rooms, suppose there are thirty Committee-rooms, would you say that one apparatus should be sufficient to ventilate all this over a large surface of ground, as well as the House of Commons and the House of Lords in the same way?-They might all be ventilated by one large furnace.

It is rather a matter of judgment, arising from the extent and number of apartments, than any thing else, as to how many of those furnaces you would have?-It may be more economical to have two large ventilating furnaces if the rooms are very much apart, than to carry all the independent flues a very great length.

Can the tubes be conducted to any considerable distance from the room to the apparatus-To any length almost; I have seen them conducted hundreds of feet without any material difference.

You would not have the tube of so large a diameter as to occasion inconvenience in making the building originally ?-A tube so very large and inconvenient would not be required; but every thing would depend on the primary arrangement made by the architect; it is not a thing to be added, but to be seen from the foundation, and all those flues could be carried under ground, and there would not be the slightest necessity for one to be conducted in any way where it would interfere either with ornaments or any thing connected with the building. You may carry the air down as easily as you can carry it up. I admit, indeed, that the movements induced during the rarefaction of air are such that it would be more easily carried up than otherwise; but yet, with furnaces, the difference is not so great as to make a decided alteration in any plans connected with the arrangement of the ventilating tube.

You would be more liable to a return cur rent in case of any mismanagement of the tubes, in case you convey them down from