FIRST.—_To find the height of the apparent level above the true, at any distance._—If the given distance be contained in the table, the correction of level is found in the same line with it; but if the exact distance be not found in the table, then multiply the square of the distance in yards, by 2.57, and divide by 1,000,000, or cut off 6 places on the right, for decimals; the rest are inches: or multiply the square of the distance in miles, by 66 feet 4 inches, and divide by 100. SECOND.—_To find the extent of the visible horizon, or how far can be seen from any given height, on a horizontal plane, as at sea_, &c.—The height of the observer’s eye above the horizon being known, the extent of his visible horizon is found in the column opposite, under the word _Distances_. THIRD.—_To find the distance of any object when it first comes in sight, its height being, known._—For the distance of any object will be the extent of the visible horizon of the observer, added to the visible horizon of the point he observes. It is necessary in this case for the observer to know only the height of that part of the object which is kept from his view, by the curvilinear figure of the globe.—Knowing the distance of an object, its height may be found in the same manner. If the height or distance exceed the limits in the table; then, first, if the distance be given, divide it by 2, 3 or 4, till the quotient comes within the distances in the table; then take out the height answering to the quotient, and multiply it by the square of the divisor for the height required. But when the height is given, divide it by one of these square numbers, 4, 9, 16, 25, &c. till the quotient come within the limits of the table, and multiply the quotient by the square root of the divisor. _LOAD._—Artillery carriages, or waggons, are frequently loaded with 14 cwt. for 3 horses, and 20 cwt. for 4 horses. This, however it may answer on an English road, is a great deal too much for general service. No doubt a carriage of one construction will travel easier than of another, with the same weight; and where the mechanical advantage thus gained is greatest, the heaviest weight may be put, with the same number of horses; but in the carriages usually made for the service of artillery, 4 cwt. _per_ horse, beside the weight of the carriage, is the utmost they ought to be allowed to draw. The French ammunition waggons, which are drawn by 4 horses, are always charged with 1200 pounds only. The regulations for home service in 1798 state the load for a bread waggon at 2400 lbs. and for a cart of entrenching tools at 400 lbs. Men used to bear loads, such as porters, will carry from 150 to 250 pounds. A horse will carry about 300 lbs. and a mule about 250 lbs.—See also the word _Horses_.