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reduced, and made wholly to depend upon experience, with reference to the wearing out of wheels, and the expense of renewing them.
Attention should be paid to diminishing, as much as possible, the size and weight of all wood and iron work in coaches. As all coaches are provided by contract, and as it is the interest of the contractors to make them as strong as possible, it is much more than probable that they are built much stronger, and consequently much heavier, than necessary.
Notwithstanding the roads are now no longer cut into deep ruts and holes, the coaches are all nearly as heavy as they were fifteen years ago. The Postoffice, and all coach proprietors, shoidd take care, in making their contracts with the builders, to have the weight of each coach carefully determined upon, and properly specified in the contracts.
Although science, if properly applied, will certainly lead to improvement in the construction of coaches, a series of experiments should be made, in order to determine, with complete accuracy, what is the full effect of wheels, springs, and good roads in diminishing the labour of horses.
Mr. M'Neill's invention of an instrument for trying the draught of carriages, which has been found to be perfectly fit for the purpose, now admits of such experiments being made with a certainty of leading to accurate results; and it is very important that they should be made. In point of fact, although the extracts which have been taken from works of science are quite sufficient to convince all persons who have received a scientific education that the fore wheels of a coach ought to be high, and that the greater part of the load should be placed over the hind ones, as it happens that few of those persons who are concerned in the directing of the building and in the building of coaches have ever applied themselves to scientific inquiries, so as to know either why spokes are called levers, and what the property of the lever is, or what the effects are of the friction of wheels in turning on their axles and in moving on roads, it is quite necessary that experiments should be made, so that, by showing how much work horses actually do in drawing different kinds of carriages, nothing shall be left wanting to expose the prevailing errors with respect to wheels, and the proper manner of loading coaches.
As Mr. M'Neill's instrument can be fixed to a coach, with the horses to it, what it shows is, the actual force or labour which they exert in drawing; and, therefore, the experiments made with this instrument are not liable to errors, like other experiments, where it is necessary to use a substitute for the real power.
The expense of making a proper set of experiments would amount to some hundred pounds: as, however, there exists nothing to make it worth the while of any private person to incur it, these experiments should be ordered and paid for by government. This small expenditure would soon be repaid by the saving which would be effected by diminishing the labour of horses in drawing stage-coaches, and, consequently, the expense, which now falls indirectly on the public in providing a sufficient number of them, and maintaining them.
The plan here proposed for a mail coach may be easily adapted to stage-coaches.
For a light post-coach the hind side springs should be fastened under the axle, and the hind boot made 42 inches wide; a second set of irons should be put above the door of the hind boot, and a gammon-board should be attached to the body.
For a heavy coach the perch should be made 6 inches longer; the fore boot also 6 inches longer; the fore wheel 4 feet high; and the hind wheel 4 feet 10 inches high.
In packing coaches the hind boot should be first packed, and then the hind irons. The fore boot should be used only for parcels and luggage to be dropped or taken up on the road.
APPENDIX, No. I.
DESCRIPTION OF THE ROAD INDICATOR, AN INSTRUMENT INVENTED BY MR. MACNEILL FOR THE PURPOSE OF ASCERTAINING THE DRAUGHT OF CARRIAGES, AND THE COMPARATIVE MERIT OF ROADS; WITH TABLES OF EXPERIMENTS, ETC.*
This instrument, which is described in the following pages, is capable of being applied to several very important purposes in road engineering, amongst which are the following: —
First, It affords the means of ascertaining the exact power required to draw a carriage over any line of road.
Secondly, It can be applied to compare one line of road with another, so as to determine which of them is the best, and the exact amount of the difference, as regards horse power, both for slow and fast coaches.
Thirdly, The comparative value of different road surfaces may be determined with great exactness.
Fourthly, It affords the means of keeping a registry, in a most accurate manner, from year to year, of the state of a road, showing its improvement or deterioration, and the exact parts in which such improvement or deterioration have taken place.
* This paper has been furnished by Mr. Macneill.