that the diameter of the fellies cannot be increased without being drawn out from the spokes; and, therefore, either the iron rim will be loose upon the felly, or the spokes will be loose in the mortises, whereas in the dished wheels the only effect of an extension in the length of the rim is that the spokes become a little less dishing or more upright, to accommodate themselves to this additional length of the rim, which, by the by, is another cause of the spokes getting more upright by the wear.

Such appear to me the arguments in favour of the bent axle and tapering rims. They are perhaps fallacious, though I have been unable to discover in what respect; but as I have never before seen any thing written in their favour, and have turned my attention particularly to the subject only since your Chairman informed me of his wish to examine me respecting them, I would not have what I have said to be taken as orthodox without the inquiry which the subject deserves. Neither do I mean to say that the inclined conical wheels are free from the objections which have been made to them, that they increase the wear of roads, and the difficulty of draught, particularly when these observations are applied to broad wheel carriages, and when their tires are made to bear equally for their whole width upon the surface of the road, and I allow that all waggons ought to be made so, although but few if any are really so. I have represented the tire of Fig. 7 as flat, in order to avoid confusion, and because I consider any deviation from this as an evasion of the principle which may be practised under any of the plans. Fig. 13 is, however, the precise figure, from measurement, of the rim of the wheel of a six inch waggon as it comes from the hands of most of the makers, than which no form can be more destructive to the roads. Fig. 14 is the form of the same wheel after the rim has been worn some time. And Fig. 15 is the wheel of a new nine inch country waggon; all these are drawn to a scale. I have frequently remarked, that notwithstanding the supposed friction of the outer rim of conical wheels, by being dragged upon the road, I never could observe that this ring of the tire of a waggon was more worn than the inner, although they are both set originally at the same angle to the road; and the difference between expe

riment and experience is here to be noticed, as in some degree accounting for this. A model drawn gently along upon a smooth table moves forward without any shaking or irregular motion, and the drag of the conical wheel is very apparent, from the greater weight it requires to move it; but when a waggon is jolted and shaken upon a pavement or a road, the twist forward upon its axle to preserve the straight line, which is caused by the bend in that direction that is given to the set of the arms, so as to bring their front surfaces perpendicular to the line of motion, is obtained during these jolts, and the drag of the wheel and grinding of the materials of the road is much reduced. Mr. Edgeworth, though a strenuous advocate against the present system, compared a model of conical wheels, of which the inside diameter of the wheels was to the outside as 33 to 27, with a pair of cylindrical wheels, of which the diameter was as 34, and found that when upon smooth deal boards, the conical wheels required an addition of 50 per cent to the moving power to make their velocity equal to that of the cylindrical; but that when the experiment was made upon a fine gravel road in summer, the 50 per cent was reduced to 8; and that upon gravel stones, like a newly made coarse road, there was no perceptible difference between the cones and the cylinders, although the wheels were only eight inches high and four inches broad; that is, the breadth of the sole or rim was onehalf the height, whereas the breadth of the wheels of a six inch waggon is only one-tenth of the height of the hind, and one-seventh of the fore wheel. The tire of coaches and light carriages is under two inches in width, and the taper or coning of the rims is so very small, that I doubt of the difference being perceptible under any circumstances. The tire of the mail coaches is only one and a half inch wide, and even in that width it is formed rounding; so that not so much as an inch in width touches the road, and the bend down or set of the arms of the axle is just such as to compensate for the taper of the arm, and to bring its lower surface to be horizontal. This property of the tapering arm is by the by wor thy of attention, and shows that that shape is not deserving of the censure which has been thrown upon it, for by it the

upper surface of the arm, which has no weight to support, is so inclined as to give the proper angle to the upper part of the wheel, while the lower part that bears the weight of the carriage, is in light carriages horizontal and perpendicular to the direction of the spokes which are under it. The width of the mails, including the tire, is four feet eight inches upon the ground, and five feet three inches at the top of the wheels, and the difference in chaises and light carriages is often less. The wheels are at the same time made considerably concave, so that the spokes which rest upon the ground have more inclination outwards from the perpendicular than waggons have, experience having taught the propriety of keeping the plane of the wheels (fg, Fig. 11) on account of the draught, as upright as is consistent with the strength and stiffness; and it is, I conceive, to this continued experience, and not to any a priori deductions of science that the present system of wheels which I have attempted to defend is to be ascribed. I cannot, however, but say, that famous as this country is for its machinery, I do not know any machine which, for a combination of lightness and strength, is superior to a well-built London carriage.

My opinion generally is, that any legislative measures should be confined chiefly to the width and flatness of the tire, and to the regulation of weights proportioned to the width of the wheels, as the only points in which the interests of the roads and of the coach owners can be much at variance; and I would extend this observation in many respects to heavy carriages, until better proof is given of the extent of the injury to the roads arising from the present shape of wheels, and of the other effects that may be consequent upon the remedying of that evil. The question is, whether by expelling the use of cylindrical wheels the reduction of the horse's labour and of the wear of the roads will more than compensate for the reduction in the strength and wear of the wheels. To assist in solving this question, a waggon might be made with cylindrical wheels on the one side, and conical ones on the other. The tire of the wheel that is best for the horses and for the roads would last the longest, and the difference in the wear of the frame of the wheels would at the same

time be seen. Or a waggon or dray belonging to the same owner might be formed in each way, and care taken to send them out together, with equal loads, which might be done by the large brewers and others without any trouble or inconvenience. I have mentioned my opinion of the injurious ef fect of the present mode of forming the rim of the broad wheels, so that a small width only meets the ground; such ought not surely to be entitled to claim a reduction of tolls under the narrow ones, or to carry more weight than they do. They are equally injurious to the roads. The title to a reduction should be regulated by the width of flat surface bearing upon a horizontal plane, and a test for this might be fixed at the toll-houses, by bringing the wheels over a flat iron plate, and applying a proper wedge-shaped gauge to them when they are in that position. The large headed nails by which the tire is fixed to the fellies, are also very injurious upon gravel roads, when left projecting, as they usually are, from the surface of the tire, and it serves no good purpose to leave them so, unless to save the wheelwright the trouble of flattening them,

As the highways are important only as being the channels for communication by land carriage, the consideration of them involves questions equally important as the roads themselves; and I can easily conceive regulations which would be both oppressive and impolitic, although their immediate effect might be to lessen the expense of repairing the roads, and even to preserve them in better order than otherwise they could possibly be. The labour of horses for carrying a ton of goods for one mile, on the average of the kingdom, is not less certainly than one shilling; while the wear of the roads, judging from the tolls, is under one penny. As far, therefore, as the conveyance of goods is concerned, regulations which lessen the expense of the roads one one-half will, if they at the same time increase the horses labour only four per cent, really do no good; the toll would be reduced one halfpenny, and the horse hire increased one halfpe ton. Before, therefore, fixing such exorbitant toll ing the weight upon narrow wheeled carts and such a manner as would amount to a penalty for

ner

both sides of the account ought to be fairly considered. From the great resistance which is made to broad wheeled carriages, properly so named, one is inclined to think that the draught of the horses is much easier with narrow ones. But to what extent is this? Is the difference of the wear of the roads

greater than the difference of tolls? Or if all heavy carriages were made with broad wheels, would the general improvement in the roads be such as that in the course of time both expense would be saved in the roads, and the draught be easier than with the narrow wheels upon the present roads? On the average of gravelled roads, and when the weight is more than the fair load for one horse, I should be inclined to answer this in the affirmative; but my opinion is the result of general observation, and requires to be strengthened by experiments, conducted on a proper scale, and embracing both sides of the question.

ART. XII.-Meteorological Observations, made at the Radcliffe Observatory, Oxford, in the years 1822 and 1823. Communicated by the Rev. A. ROBERTSON, F. R. S. Savilian Professor of Astronomy at Oxford,

THE following is a table of the mean temperature of each month, for the years 1822 and 1823, obtained from a register of Fahrenheit's thermometer, taken at ten o'clock in the morning, and at ten in the evening.

From hence we have the mean temperature of the two years

October, 51.9 47.3
November, 46.8

December, 33,6

as follows: