2. Suppose the dimensions of the adjoining chain to be as follows:-Breadth at formation level, 9 yards; depth at the end adjoining the above chain, 7-05, and breadth at top, 30.15 yards; and at the greater end, depth, 7.15, and breadth at top, 30-45 yards; what is the cubic content?

6138 77+3069.38 cub. yds.

RULE 2.-Example 3.-Required the cubic content of one chain in length of cutting, the top breadth being 31.2 yards; that at the formation level the same as in the two preceding examples, and the depth 7.4 yards?

When the surface of the ground slopes considerably in a transverse direction, as in the annexed diagram, at suitable distances, sections of the excavation must be made, or rather measured upon those taken at the commencement, (p. 55,) and the content found by measuring them in two triangles as shown on the following page.

Should an embankment, erected upon similar ground have to be measured, it is only to suppose the top and bottom of the diagram reversed.

When there is a difference between the section at each end of a chain, the foregoing rules are not strictly mathematically correct, nevertheless they are sufficiently accurate for practice, because, having found the sectional (double) area and perhaps not the most complexly-the excavation may be divided longitudinally into as short portions as we please, which will cause each result to be a very close approximation to each true cubic content.

L

CHAPTER V.

HAULAGE.

Resistance opposed to the Motion of Carriages upon level Railroads-Power, Speed, and Distance of a Horse's Day's Work-Quantity of Work performed each Day by a Horse-Weight of Earth-waggons-Specific Gravity of Earth -Expenses attending Horse Power-Expense of Conveyance, per Cubic Yard, per Mile-The Tractive Force necessary to Ascend and Descend Planes, elucidated-Tables exhibiting the Useful Effect per Day of each Horse, in Tons and Cubic Yards of Earth, drawn one Mile; and also the Expense of Haulage per Ton, and per Cubic Yard, upon various Inclinations of Ascending and Descending Planes-Examples showing how the Tabies are Calculated-Method of Calculating the Gross Load, and Useful Effect, that can be produced by any Motive Power on a Level, and on Ascending and Descending Planes.

Upon a railroad in good condition, the resistance to the motion of such carriages as are commonly used, is estimated equal to the 240th part of the insistent weight, or 9.33 lbs. per ton; that is to say, if the weight of a waggon and its load amounted to three tons, the traces of a horse drawing it would be stretched with a force equivalent to 28 lbs. An ordinary horse is considered to exert a tractive force of 150 lbs.,* when travelling at the rate of two and a half miles an hour; and the duration of his day's work at this speed is estimated at eight hours, or equal to twenty miles travelled per day. Whence we have 150×240× 20=321 tons, including carriages, transported one mile per day by each horse.

Mr. Bevan, whose results are much more entitled to confidence than those of any other experimentalist, on account of the much more extended scale of his experiments, estimates the power of a horse at 163 lbs. being the mean force exerted by each horse out of 144 at ploughing."-Hebert, p. 540.

But for temporary lines of railway, the friction must be computed at considerably more than the preceding, on account of the subsiding of the road, the quantity of extraneous matter upon the rails, and many other retardations incident to such undertakings; moreover, the wheels of earth-waggons-in order to keep the carriages low-being, in general, smaller than the wheels of other waggons, causes an additional friction; therefore, after making a reasonable allowance for these, and similar imperfections, we may, perhaps, assume correctly the resistance on the level to amount to the 150th part of the insistent weight.

The only benefit that arises by using low wheels -exclusive of the facility they afford in loadingbeing that of improving the angle of draught, is, in the present instance, rendered almost nugatory, owing to the load being conveyed in more carriages than one, which prevents any advantage resulting to the draught-line, except from the waggon immediately attached to the horse, that of the remaining part of the waggons being only horizontal.

Although twenty miles is usually assigned as the day's work of a horse when loaded, we may calculate a greater distance during the time he is employed in the transmission of excavated earth, as one-half of the space is traversed with the carriages empty. We shall, therefore, in the following disquisitions respecting horses, estimate their day's work at twenty per cent. more; equal to twelve miles travelling with the load, and twelve in drawing back the empty waggons. It may be necessary to state that even less than twenty miles is generally considered a day's work for common carting, an allowance attributable to the unavoidable loss of time in loading.

Taking the power of a horse at 150 lbs., we will then have 150× 150×12=270,000 lbs. gross, removed one mile per day, and deducting onefourth of it for the weight of the waggons, his performance per day will amount to 90-4 tons of earth transported one mile. The weight of a cubic yard of ordinary earth being about twenty-eight cwt. (19.29 cubic feet per ton, or one ton equal to five-sevenths of a cubic yard,) one horse will convey 64.57 cubic yards of soil one mile each day. Now, suppose we allow for horse-power and attendance seven shillings per day, the expense of conveyance per mile will amount to 1-3 pence per cubic yard.

There may, and probably will, be various opinions with regard to the formula we have adopted; but thus much may be said with certainty, that the sum of 13 pence per cube yard agrees very nearly with the results of our own practical experience. When the horse-power cost six shillings per day, the expense was usually about one penny per cubic yard per mile; and 6s.: 7s.:: 1d.: 1.17d., which is only 1d. less than our result.

Although we have known works of great magnitude executed at the rate of six shillings per day, for horse-power and attendance, yet, at the present time, seven shillings per day is considered nearer the actual average cost.

It may, however, be proper to remark, that the cost of conveyance is not exactly proportionate to the distance; there are certain unavoidable contingencies where the earth is loaded, and also at the place of deposit, caused by hauling the waggons to and fro, placing and replacing them, stoppages, &c., the expense of which being commonly as much for a short distance, as for one of greater length.