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coke furnaces. This shows the necessity of economy at every point. When one stove of a set, with 10,000 cubic feet capacity per minute, is heated up, it contains 127,631,000 F. calories, and the blast abstracts from it in 14 hours 19,890,000 calories, or about one-sixth of the total amount of heat stored. The regenerator alone contains 63,223,200 calories when heated up, and not more than one-half its capacity will be exhausted, when clean, to give the blast the desired temperature. An excess of capacity is required in all stoves to allow for dust and the obtaining of higher temperatures in case of need. There are but five valves to operate, which is less than are used on other stoves. There being but one flame flue or combustion chamber, perfect combustion is secured with but one valve to admit air in place of a greater number on other stoves. The hot-blast valve is cooled by a small current of cold air. The absence of water in all of the valves is a strong point in their favor. By the use of two simple dust-catchers in the down flue, and by blowing through the ovens once a week, the Ebbw Vale works found their stoves to be as efficient at the end of two years as when started.

Mr. Cowper has found that the vibration caused in the passing current by firing a common gun into the stove while the blast is on is an efficient means for cleaning off the dust. The most effectual cleaning is done with a steel brush, weighted and attached to a small wire-rope, by dropping it down through each hole. By attaching the rope to proper pulleys with an index, the brush can be worked from the top without going inside. The projection of the brick in the regenerator cells affords a good opportunity for the collection of dust, and, as this point is objected to by the leading iron men who have examined the drawings, we propose bevelling off these corners. The thin walls of the regenerator offer to the gas and air five-sixths of their surface, while a brick built in a nine-inch wall offers only one-sixth of its surface. It is the dividing up of the air by the cells, bringing it into immediate contact with the heating surfaces that so effectually heats the blast. By the use of high stoves the currents are made more rapid, and thus much dust deposit is prevented.

No air-receiver is required where these stoves are used. As a variation occurs in temperature, owing to the changing of stoves, we propose using an automatic valve, by which a certain amount of cold air will be automatically mixed with the excess of hot air to bring it to the required temperature. By this means the excess of heat is retained in the stoves, and it acts over a longer time.

The cost of these stoves complete, when No. 1 fire-brick are $34

ON THE SOUTHERN LIMIT OF THE LAST GLACIAL DRIFT, ETC. 467

per thousand, is about $3 per cubic foot of air required per minute, and, if built to run only at 1100° F., they can be made at the same cost as iron stoves, and are more durable.

A furnace, when in a good condition, will take through per day a given number of tons of material. By increasing the hot blast coal can be taken off, while ore and limestone to the same extent can be added. This increases the yield, and decreases the amount of coal used. If a hotter blast is used, coal must be taken off proportionally, or it is wasted in the zone of reduction, escaping as gas, and not reaching the hearth.

Mr. Cochrane, of Dudley, England, writes that, after trials of from nine to eleven months, he finds the following results: "At a furnace 23 by 76 feet, with 20,000 cubic feet capacity, with the blast at 900° F., one ton of iron requires 25 cwt. of coke; at 1100° F., 221⁄2 cwt. of coke; at 1300° F., 20% cwt.; and at 1500° F., 20 cwt. of coke; and in larger furnaces they get the consumption of coke even lower."

ON THE SOUTHERN LIMIT OF THE LAST GLACIAL DRIFT ACROSS NEW JERSEY, AND THE ADJACENT PARTS OF NEW YORK AND PENNSYLVANIA.

BY PROF. GEORGE H. COOK, STATE GEOLOGIST OF NEW JERSEY, NEW BRUNSWICK, N. J.

(Read at the Wilkes-Barre Meeting, May, 1877.)

AT first sight this subject seems to belong to pure theoretical geology, but examination will soon show that it has important practical and economic interest to the mining engineer. The conclusion that all the northern portions of our country, as well as of the eastern continent, have, in the later periods of geological history, been covered with a thick bed of ice, is now accepted by geologists. This bed of ice, except in its greater magnitude, was like the modern glaciers of the Alps, and other mountains which extend above the line of perpetual snow. The marks it has left upon the surface show that it was comparatively thin on its southern edge, but that its thickness was much greater a little further north, and that it was several thousand feet thick at its heaviest parts. This variation of its surface would give it a descending slope towards the south, and cause the mass of ice, like a semifluid substance, to move in that direction.

The effect of such an immense weight of ice moving over the surface is to produce the common and well-known phenomena of glacial action, in cutting and grinding away softer rocks, leaving the harder rock, with its worn and scored surface, underneath. The debris of the worn rock became, as it was carried forward by the moving glacier, the boulders, gravel, sand, and clay, which now cover so much of the surface of the continent north of 40° N. And the material which was shoved forward in front of the mass of ice, and which stopped when the melting of the glacier equalled its rate of movement, was left as the terminal moraine to mark the southern edge of this great continental glacier.

This terminal moraine, in the form of uneven hillocks of clay, sand, gravel, and boulders in great variety, still stands out wellmarked, and as easily recognized as if only a few years' old. The failure to recognize it earlier has probably been owing to the occurrence of boulders on the surface south of it, and to the deposits of gravel, quartz, boulders, etc., considerably to the south of this line.

The line marking the southern limit of the drift may be traced across the State of New Jersey from east to west, beginning on the north side of the Raritan River, at Perth Amboy. The southern border of the belt of Short Hills, which extends from the last-named place to the First Mountain, marks this limit. It may be traced on the map just north of Metuchen, Plainfield, and Scotch Plains. It crosses the First Mountain and the valley between that and the Second Mountain, and then across the latter mountain a half mile or less south of Summit Station, on the Delaware, Lackawanna, and Western Railroad. From thence onwards across Passaic River, Long Hill, and, by Chatham and Madison, to Morristown, it continues to hold about the same distance to the south of the railroad. From Morristown onwards to Dover the line is more difficult to trace across the high grounds; but it can be seen on Morris Plains, near the State Lunatic Asylum, across the outlet of Shougum Pond, on Den Brook, and across the valley of Mill Brook, two miles southeast of Dover. At Dover it can be seen south of the main street and the railroad, on the side hill, and extending across the plain south of the Catholic church. It can be traced from there onwards south of Port Oram, and across the divide which separates Rockaway River from the head of Black River; and thence a little north of McCainsville and Drakeville, and across the hilly country just north of Budd's Lake, and so onwards to the Musconetcong Valley, which it crosses about a mile northeast of Hackettstown. It is marked by its hil

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