40.52 lbs., and in winter 46.5 lbs., which shows the road is not so good as it was in the preceding year, 1830, but better than it was in the first year, 1829. Again, in the year 1832, it is found that the average summer draught is 53 6 lbs., and the winter draught 63·18 lbs.: by comparing these numbers with any of the preceding years, it will at once be evident that the road has become worse; and by a reference to the figures in the column, it will be seen that it is defective in every part as compared with the preceding years, but more especially so near the end, where the draught in summer varies from 60 to 85 lbs., and in winter from 75 to 95 lbs. ; whereas, in 1830, two years before, the draughts in summer, over the same part of the road, varied from 35 to 38 lbs. only, and in winter from 46 to 40 lbs. The instrument, therefore, shows not only that the road has been getting generally worse, but it points out the particular parts, and the exact amount of deterioration; thus enabling the proper authorities to say that the road has become worse, the amount of the deterioration, and the exact part of the road where such deterioration has taken place.

The public advantages to be derived from such a system of road inspection would probably be very great. It would show not only where the best plan of repairing roads has been followed, and point out where there are good and bad surveyors, but it would also show if the money of the trust is improperly applied or wasted on any line of road; and it will enable trustees, who let the repairs of their roads by contract, to determine whether or not the contractors have done their duty, and kept the road in the same state of repair as at first, or whether they had improved it, or suffered it to become defective.

There are many other uses to which the instrument may be applied, but the foregoing are the principal

ones.

Mr. Telford, in his Report to the Parliamentary Commissioners of the Holyhead and Liverpool Roads, speaking of this instrument, states, "I consider Mr. Macneill's invention, for practical purposes on a large scale, one of the most valuable that has been lately given to the public."

Mr. Babbage, the Lucasian Professor of Mathematics in the University of Cambridge, in his valuable and wellknown work on the Economy of Machinery and Manufactures, in considering the injury which roads sustain from various causes, states, “As connected with this subject, and as affording most valuable information upon points in which, previous to experiment, widely different opinions have been entertained; the following extract is inserted from Mr. Telford's Report on the State of the Holyhead and Liverpool Roads. The instrument employed for the comparison was invented by Mr. Macneill, and the road between London and Shrewsbury was selected for the place of experiment. The general results, when a waggon weighing 21 cwt. was used on different sorts of roads, are as follow:

1. On well-made pavement the draught is

2. On a broken stone surface, or old flint road 3. On a gravel road

46

4. On a broken stone road, upon a rough pavement foundation

5. On a broken stone surface, upon a bottoming of concrete formed of Parker's cement and gravel 46."

Specimen of the Manner in which it is proposed to keep a Registry or Journal of the State of Repairs of any Road.

FROM LONDON TO

First Quarter of First Mile.

DESCRIPTION OF THE INSTRUMENT.

The framework is of wrought iron, about two feet six inches long, and eighteen inches wide. In this frame a dynamometer and brass cylinder are placed; the dynamometer is connected by its arm to one side of the frame, and the cylinder is secured in the frame by trunnions, which are cast on it, and which turn in a circular hoop or belt, firmly screwed to one side of the frame, and a bar running across it. The dynamometer, or weighing-machine, which forms part of the instrument, was introduced, some years ago, by Mr. Marriott; and as it is now so generally known, being used in mailcoach and other offices instead of the common steelyard, or scales requiring weights, it is needless to describe it here. On my applying the weighing-machine, in its simple form, to measure the draught of carriages, I found that the index vibrated so quickly, and over so large an arch of the circle, that it was impossible to observe the point indicating the force of draught; for a horse exerts his power by a succession of impulses, or strokes of his shoulders against the collar, at every step he makes, and not by a constant uniform pull, as is generally supposed. To remedy this inconvenience, and do away with the vibrations, I applied a piston, working in a cylinder full of oil, and connected with the dynamometer in such a manner that when any power or force is applied to it, so as to carry round the index, the piston is at the same time moved through the fluid. The connection of the dynamometer with the cylinder is by means of a lever working on a pivot; the arms of the lever are of unequal length; the tail-piece of the dynamometer is connected with the short arm, at a distance of two inches from the centre, or fulcrum, by means of a

pivot-joint at precisely the same distance from the ful crum; a flat bar of iron is connected with the longer arm, by a joint similar to that by which the tail-piece is connected with the short arm, so that any power or weight applied to the bar will produce the same effect on the index as if the power was applied directly to the tail-piece of the dynamometer; this bar passes over a friction roller, and to it the power of the horses is applied when in use, by means of traces and a bar, as in the ordinary mode of draught. At the extremity of the long arm, the piston rod is connected by a joint similar to the others; the piston-rod, after passing through a stuffing-box in the cap of the cylinder, is screwed into a piston, or circular plate of thin brass perforated with small holes; and out of one part of the circumference a square notch is cut, the use of which will be hereafter described.

By this construction the resistance of the fluid to the piston, which acts at the extremity of the long arm of the lever, prevents its turning round the fulcrum to the extent it otherwise would do when it is acted upon by any sudden impulse applied to the bar; it will, however, move over a space proportioned to the intensity of the force applied; and if the pulls follow each other in rapid succession, the piston will move slowly out, and the index will turn round steadily and uniformly, until the power is balanced by the spring of the dynamometer, at which time the index will point out on the dial very nearly the weight or power which is equivalent to the draught.

The divisions on the dial-plate of the dynamometer decrease from zero upwards, in order to compensate for the increased force which the spring exerts in propor