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pearance; but from behind it is observed to be nought but a skeleton, with its wooden framework covered with canvas and round the lower part protected with sheet iron. At the windows are arranged dummy heads, which are raised and lowered at different intervals, representing the defenders reconnoitering and firing over the surrounding country from time to time. Through the open doorway extends a narrow railroad track upon which runs the effigy of the inn proprietor, who is also armed with a rifle. Behind the building, in a bomb-proof shelter, are disposed the men operating the various mechanisms of this property inn; while safely concealed behind the iron walls lie the beleaguered force, who maintain a spirited defensive fire.

In the operation of this piece a large squad of men are required, since some forty or fifty wires, many of which are electric, extend from the operating pit. At first, only a desultory fire is opened, as the attacking force stealthily approaches from cover to cover. As they near the inn, dummies suddenly assert themselves among the scrub, being actuated by mechanism from the operating pit; and these at first become the aim of the attackers, the besieged in the inn maintaining an intermittent fire which rapidly increases in intensity. The effect of the marksmanship of the attacking force upon the dummies, is forcibly indicated, each bullet that hits showing a white mark. Simultaneously the faces appear at the windows; and in a few minutes the fight becomes fast and furious, as the besiegers gain excellent positions near the inn. In the midst of the fusillade, the inn-keeper, armed with his weapon, appears in the doorway for an instant and disappears, the object of such movements being to train the marksmen in the task of instantaneously taking aim with fatal effect. Finally, when the inn is almost surrounded, fullsized dummies are observed momentarily appearing and disappearing on all sides. in the scrub and undergrowth flanking the inn; these represent fugitives making their escape from a position which has been rendered untenable.

That such a method of training soldiers possesses many valuable features, is shown by the effect of the rifle fire main

tained by the marksmen upon the dummies, despite the fact that they are only momentarily exposed. All the hits are indicated by white marks, and invariably, at the conclusion of operations,the effigies are found to be absolutely riddled with bullets. The infusion of realism into the work also exercises a direct influence upon the forces under training, especially in regard to the expediency of advancing stealthily from cover to cover individually in isolated units, and in regard to individual initiative, sinc the soldier, being unaware of when or where the dummies will appear, has to be on the qui vive the whole time, ready for instant action.

To

In regard to artillery training, similar tactics are followed, live shells being employed. Dummy field-pieces, comprising pieces of wood shaped like cannon, are carried on wheel-pieces and trunnions and concealed in the brushwood. these dummies, firecrackers are attached. In a bomb-proof shelter close by, are stationed the officers who record the result of the artillery fire and manipulate the dummies. At the critical moment, the crackers are ignited and thereby the presence of the concealed force is betrayed to the advancing artillery. Immediately a terrific fire is opened upon the position with real shell, and the hillside is torn and seared by the fierce explosions. By the time the "Cease Fire" is sounded, the battery of dummy guns are reduced to a mass of splinters; and such a hot fire as is maintained would be sufficient to wipe out in real hostilities the whole of the concealed force and weapons. By this system the artillery have become highly efficient, and display great accuracy in picking up the range at the first discharge an all-important factor in artillery warfare. Nine times out of ten the dummy guns will be struck by the first shells and reduced to matchwood, which marksmanship, considering the fact that the firecrackers do not give vent to a very loud concussion, nor raise an appreciable amount of smoke, testifies in a striking manner to the efficiency of the method of training that has been adopted.

In this mimic realistic warfare, it is possible to reproduce to a large extent conditions similar to those that prevail

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Salt Mined Without Human

Effort

By James Cooke Mills

HIRTEEN hundred barrels every twentyfour hours of fine salt-mined, purified, and crystallized, packed ready for the table, without the touch of a hand or the lifting of an arm—this is the last achievement in salt-making, the final round in reduced cost of production.

It is of considerable importance and interest in the great salt industry-not so much, perhaps, because of increased. profits to salt-makers, as because of the remarkable advance it shows in mechanics along these lines. Only through many difficulties, failures, and disappointments has inventive genius succeeded in producing a barrel of salt at a cost of only a few cents.

The three factors that permit. this economy of production, are solid, reinforced concrete; waste exhaust steam; and automatic machinery. That these factors should be combined in Saginaw valley, the center of the great salt-producing section of Michigan, is particularly striking, inasmuch as the second factor, the utilization of waste exhaust steam, has here been the main feature in salt manufacture for many years.

The Lower Peninsula of Michigan is almost entirely underlaid with a stratum of rock-salt, averaging in thickness about 300 feet, and varying in depth from 600 to 1,200 feet. This bed of salt-rock is saturated with brine to a degree of strength 84 to 90 per cent. It is practically

inexhaustible, caused by a large area of rock-salt outcropping in the bottom of Lake Huron, the process of seep supplying hundreds of salt wells with thousands of barrels of brine pumped out daily.

In the city of Saginaw, there has just been completed and put in operation the most modern salt plant in America, since advantage has been taken of all new devices, machinery, and methods of handling the product, tending to economy in salt-making. These factors, and that of utilizing the waste steam from the Saginaw Plate Glass Company, of which the salt plant is an adjunct, have reduced the cost of producing salt to a figure surprising to all salt experts. Automatic machinery has so supplanted labor in every process, that from the rock-salt to the barrel loaded in the car for shipment, no hand has touched a crystal. Only the master salt-maker, W. J. Mason, a wellknown salt expert, and a few helpers, are required to watch the machinery and keep it in perfect running order.

The rock-salt is mined and brought to

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SALT PILED IN STORAGE HOUSE.

About 5,000 barrels is here shown-the product of four days' evaporation.

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TWO OF THE SIX CONCRETE SETTLING-TANKS. Showing filter (at right), with brine flowing from trough into partly filled tank; also drill-house in center background.

the surface in the form of brine, through five wells placed from 150 to 200 yards apart. These wells are 779 feet deep, encased with heavy tubing; and in the center runs a one-inch pipe down into the rock-salt bed. Through this pipe is this pipe is forced under great pressure a jet of pure water, which at the bottom takes on a strong saturation of the rock-salt and is forced back to the surface through the tubing by the pressure of the downward rush of water at the bottom.

The drill-houses, with high towers placed over the wells, enclose the pumping machinery, which is operated by 71⁄2horse-power electric motors, the power being furnished by generators in the power plant of the Plate Glass Company.

From the drill-houses, the brine, 98 per cent strong, is pumped to an elevated circular tank of 200 barrels' capacity.

All brine is more or less impregnated with iron and other impurities; and to free it from these, the brine is drawn from the elevated receiving tank to a filter 16 feet square by 20 feet high, placed on top and at the end of one of six settling tanks. The filter consists of a series of open trays, set one over another

about one foot apart, on which are placed scraps of metal of various shapes.

The brine overflows the supply pipe at the top, and percolates through the mass of filtering material into wood troughs below, being aërated and purified in the process.

The six settling-tanks are built up from the ground, of solid concrete, each 170 feet long by 20 feet wide and 72 feet deep; and are of the most substantial construction, reinforced by embedded iron bonds of long, corrugated rods of iron. Every alternate dividing wall is provided with a narrow plank walk to facilitate the examination of the brine.

From the filter troughs, the brine runs into a series of troughs along the top end of the settling-tanks, where it is further aërated, and by a simple arrangement of gates allowed to flow freely into any of the six tanks desired.

In these settling-tanks, the brine is treated to a solution of lime, which precipitates the remaining impurities, leaving the brine as blue as any ocean expanse, as pure and clear, but far more salty. The purifying of the crude brine through the agencies of the sun, air, and

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chemical action having been fully accomplished, the clear brine is ready for the next important operation of converting it into crystals of salt-by far the most interesting part of salt-making.

The clear brine is now pumped into the salt block, a wood building 180 feet square, and conveyed to two concrete pre-heaters, where it is heated by steam pipes and prepared for the "grainers."

These grainers, ten in number, are the crowning feature of the whole works. They are the only ones ever constructed of solid concrete; and in this departure from the old method of using wood planks, calked, the builders have achieved a remarkable advance in salt-making, the secret of which will be shown further on. In order to make clear the process of crystallizing the brine, it is necessary to give a full description of the construction of the grainers.

They are long, shallow tanks of solid, reinforced concrete, each 150 feet long, 12 feet wide, and 20 inches deep. The sides and bottom vary in thickness from six to ten inches. The banks are built up from a firm earth foundation, and so

constructed that expansion and contraction are effected without any damage from cracking.

Through the entire length of each grainer, are ten four-inch steam pipes running through truss-bars suspended about eight inches from the floor of the grainer by means of wire cables secured to heavy beams above.

All the engines in the large plate glass works exhaust into an elevated main 22 inches in diameter, connecting the works with the salt block. with the salt block. This main is protected with asbestos covering, and the steam is conserved far beyond all the requirements of the salt-making. The main enters the salt block at the rear, extending across the ends of the grainers and at right angles to them. At intervals of fifteen feet along the main, smaller feed-pipes run up and over the passageway, and downward on the right through the floor, being then connected to the steam pipes in the grainers—in such a way that there is equal distribution of steam to all, so that all the ten grainers are in operation at the same time.

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Showing method of hanging pipes that carry steam to heat the brine; also the automatic rakes beneath. When
grainer is filled to within two inches of top, pipes are entirely submerged. Steam rising from
grainer escapes through open cupola in roof.

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