MACADAM, JOHN LOUDON, was b. in Scotland in 1756, and passed his youth in the United States. On his return, he was appointed manager of a district of roads in Ayr shire, and originated and successfully practiced the system of road-making, now known, by his name. Iu 1819, he WaS summoned to England, and was appointed by parliament to superintend the roads in the Bristol district, which were in a most deplorable con dition. In 1827 he was appointed general surveyor of the metropolitan roads; and in, reward of his exertions to render them efficient, received a g,rant of 4.30,000 from government. His system rapidly became general throughout England, and was also. introduced into France with great success. Macadam died at Moffat, in Dumfriesshire, in 1836. The priociples of his system, which is known as Macadamizing, are as follow; " For the foundation of a road, it is not necessary to lay a substratum of large stones,. pavement, etc., as it is a matter of indifference whether the substratum be hard or soft; and if any preference is due, it is to the latter. The metal for roads must consist of broken stones (granite, flint, or whinstone is by far the best); these must in no case exceed 6 oz. each in weight, and stones of from 1 to 2 oz. are to be preferred. The large stones in the road are to be loosened, and removed to the side, where they are to be broken into pieces of the regulation weight; and the road is then to be smoothed with a rake, So that the earth may settle down into the holes from which the large stones were removed. The broken metal, is then to be carefully spread over it; and as this operation is of great importance to the future quality of the road, the metal is not to be laid On in shovelfuls to the requisite depth, but to be scattered in shovelful after shovel ful, till a depth of from 6 to 10 in., according to the quality of the road, has been obtained. The road is to have a fall from the middle to the sides of about 1 ft. in 60, aud ditches are to be dug on the field-side of the fences to a depth of a few inches below the level of the road." This system, which at one time threatened to supersede every other, is calculated to form a hard and impermeable crust on the surface, thus protect ing the soft earth below from the action of water, and so preventing it from working up through the metal in the form of mud. Strange to say, it has succeeded admirably in
cases where a road had to be constructed over a bog or morass, but in some other circum stances, it has been found deficient. See 'Bonus.
McALLISTER, FORT, a strong earthwork, erected by the confederates during the war of the rebellion on Genesis point, on the right bank of the Great Ogeechee river, 6 m. from Ossabaw sound, and 12 m. s. of Savannah, Ga. It successfully resisted the fleet of monitors under commodore 1Vorden in 1863, but was taken by assault by the 2d division of the 15th corps under gen. Hazen, Dec. 13,1864, with a loss of 90 men. This WM the closing feat of Sherman's "march to the sea," and led to the surrender of Savan nah a few days later.
McALPINE, 1VILLIAm J.; b. New York. 1812; after completing his classical educa tion, Ile began engineering in 1827, under John B. Jervis, with whom he remained 12 years, during which thne he was employed upon the Delaware and Hudson canal and railroad, and upon other public works, under the direction of his chief. He was the successor of Mr. Jervis as engineer of the eastern division of the Erie canal enlargement until 1846, when lie was chosen to construct the dry-dock at the Brooklyn navy-yard. In 1852 he was elected state engineer of New York. In 1854-56 he was railroad coin missioner of the state, in which capacity he made a valuable report upon the principles and practice of railroad construction and management. Afterwards, for two years, lie was engineeer and acting president of the Ene railroad. later still, engineer of the Galena and Chicago, and of the Ohio and Mississippi railroads. Ile constructed the water-works of Chicago and Albany, and planned those for Brooklyn and 3.slew Bedford.. In 1870 he presented plans, which were accepted by the Austrian government, for the itnprovement of the cataracts of the Danube.