The arch is usually an arc of a circle.  A kiln of the size of No. 4, as constructed at the Michigan Central Iron Works, with a good burn, will yield 4,000 bushels of charcoal.

The vertical walls in the best constructions are 12 to 13 feet high, and 1-1/2 brick thick, containing from 20 to 52 bricks to the cubic foot of wall.  To insure sufficient strength to resist the expansion and contraction due to the heating and cooling, they should be provided with buttresses which are 1 brick thick and 2 wide, as at Wassaic, New York; but many of them are built without them, as at Lauton, Michigan, as shown in the engraving.  In both cases they are supported with strong braces, from 3 to 4 feet apart, made of round or hewn wood, or of cast iron, which are buried in the ground below, and are tied above and below with iron rods, as in the engraving, and the lower end passing beneath the floor of the kiln.  When made of wood they are usually 8 inches square or round, or sometimes by 8 inches placed edgewise.  They are sometimes tied at the top with wooden braces of the same size, which are securely fastened by iron rods running through the corners, as shown.  When a number of kilns are built together, as at the Michigan Central Iron Works, at Lauton, Michigan, shown in the plan view, only the end kilns are braced in this way.  The intermediate ones are supported below by wooden braces, securely fastened at the bottom.  The roof is always arched, is one brick, or eight inches, thick, and is laid in headers, fourteen being used in each superficial foot.  Many of the kilns have in the center a round hole, from sixteen to eighteen inches in diameter, which is closed by a cast iron plate.  It requires from 35 M. to 40 M. brick for a kiln of 45 cords, and 60 M. to 65 M. for one of 90 cords.

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The belief that population in the West Indies is stationary is so far from accurate that, as Sir Anthony Musgrave points out, it is increasing more rapidly than the population of the United Kingdom.  The statistics of population show an increase of 16 per cent. on the last decennial period, while the increase in the United Kingdom in the ten years preceding the last census was under 11 per cent.  This increase appears to be general, and is only slightly influenced by immigration.  “The population of the West Indies,” adds Sir A. Musgrave, “is now greater than that of any of the larger Australian colonies, and three times that of New Zealand.”

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HEAT DEVELOPED IN FORGING.