commenced closing, while a small valve opened and allowed enough water to pass in to complete the stroke.

The largest engine erected by Mr. Darlington was similar in its general construction to that just described. It had a cylinder 35 inches in diameter; stroke 10 feet; pressure column 227 feet high. Its average speed was 80 feet per minute, and its greatest speed 140 feet per minute. The pressure of the water was 98 pounds per square inch, giving a total weight of 40 tons upon the piston. This engine was automatic, the motion was certain and regular, and the cost of maintenance was trifling.

Sir William Armstrong has made use of water pressure obtained from natural falls to produce rotary motion by means of a pair of cylinders and pistons, with slide valves, in some degree resembling those of high-pressure steam-engines, but provided also with relief valves. Water-pressure engines of this description were erected at the lead mines at Allenheads, in Northumberland, and are used for the various operations of crushing the ores, hoisting, pumping, and driving the machinery of the concentrating works. Small streams of water which flowed down the slopes of adjoining hills were conducted into reservoirs at elevations of about 200 feet, and from thence by pipes to the engines. In a mining district upon the river Allen, in England, where the fall of the water is not sufficient to work water-pressure engines, overshot wheels have been used to force water into accumulators, from which it could be conveyed in pipes to the required points.

Table showing the locality, engineers, and dimensions of some of the principal water-pressure engines.

Underground water-wheels are used in various parts of Germany. when the circumstances permit. Where a system of mines is drained through a deep adit, the water can be transferred from one mine to another, and its fall utilized by such wheels, until it finally reaches the level of the adit by which it escapes. Instances of this may be observed in the district of Freiberg, Saxony.

WATER-WORKS AT WHITE PINE

There is a very interesting exhibition of hydraulic engineering at the White Pine mines, due to the skill and enterprise of the distinguished engineer A. Von Schmidt. Water is there pumped a height of 900 feet in round numbers, in two lifts of 450 feet each. There are four large steam engines, two at each station, and each engine of 177 horse-power. The cylinders are 22 inches in diameter and they have a stroke of five feet. They can be worked together or independently. The water is forced through 12-inch pipes of boiler iron, and the capacity of the works is reported as 2,500,000 gallons daily.

CHAPTER LXXV.

RAISING AND LOWERING MINERS.

The ascent and descent of miners in the mines of the West, when of depths not exceeding 200 feet, is usually by ladders in one compartment of the hoisting shaft; but in all guided shafts where cages are used it is customary to descend and ascend in these cages. This is not only dangerous, but it interferes with the work of hoisting ore; and in all deep mines, especially in vertical shafts, it becomes important to provide some other safe and rapid means of hoisting and lowering the men.

This necessity has been met abroad, and in some of our mines upon Lake Superior, by the introduction of the man-engine, known in Germany as the Fahrkunst and in France as echelles mobiles. They are all alike in principle, and consist essentially of two strong beams or rods hung side by side in the shaft of a mine. Each beam has platforms or landings large enough for a man to stand upon placed at equal distances from the top to the bottom. Handles to be grasped by the hands of the men are attached at a convenient height above each platform.

They are not a modern invention, having been known in Germany during the last century; but they did not become generally used, and were almost forgotten, until about forty years ago. Since then they have been used extensively in Germany, Belgium, and Cornwall.

In the year 1833, when the deep George adit was opened in the mines of the Harz, two water-wheels were thrown out of work, and the idea was suggested of using the pump-rods attached to them for the ascent and descent of the miners. The experiment was tried. The rods were strengthened, stages or platforms were attached at suitable distances, and a regular alternate up-and-down motion was given to them by means of the wheels. It was a great success; the miners were relieved from most of the arduous labor of climbing, and even invalids, who before could not reach the lower parts of the mine, were enabled to resume their work.

The principle of the man-engine will be made more clear by reference to the annexed diagram. RR and RR represent portions of two heavy rods or beams, extending from the top to the bottom of a shaft, and suitably guided and supported throughout their length. To these rods, and at equal distances, small stages or platforms, A B C, and A' B'C', are securely fixed.

An alternate upward and downward movement is given to each of these rods; while the rod R, with its stages, is ascending, the opposite rod R' is descending. This movement brings the platform A on the rod

R opposite to the platform B' on rod R', and the platform B opposite the platform C'. The motion is then arrested for a moment, and is

R

E

immediately afterward reversed, and the platforms return to their original position. If miners are standing upon the platforms of R, they will all be raised by the upward movement a distance equal to half the distance between the platforms. At this point, the motion ceasing, the miners step from the platforms of the rod R to those upon the rod R', and by the next movement are again lifted, when they step across as before, and so on until the top of the shaft is reached. The descent is similarly accomplished.

In some mines only one of the rods moves, and the other remains stationary, or rather the second rod is omitted, and stages are fixed to the side of the shaft in the rock itself; in such cases the single rod has to move the whole distance between two stages instead of half that distance, as when two rods are used.

When a single rod is used in connection with fixed stages, the miners pass alternately from the stage on the rod to the stage fixed in the rock. They then wait until the half-stroke brings a fresh stage opposite to them, on which they place themselves, and so on.

The distance between two stages on the same rod generally varies from 4m.50 to 8m.00. The stroke of the apparatus with two movable rods is always half the distance between the stages, consequently it varies from 2m.25 to 4.00. There are from four to eight double strokes per minute.

The single-rod man-engine is the one most used in Cornwall. It makes three strokes of 12 feet each per minute. The rods are generally about seven or eight inches square, decreasing in size toward the bottom. The weight is counterbalanced by levers or by balance-bobs, attached at different levels.

Motion is imparted to the rods of the man-engine by means of water-wheels with cranks, steam-engines with crank-motion, or direct-acting steam-engines, the two rods being connected by balance-beams in such a way that their motion, though inverse, is equal and simultaneous. M. Warocqué substituted for the cumbrous balance-beams a column of water, contained between the pistons of two cylinders side by side, and connecting freely below the pistons, and made other improvements so important that the echelles mobiles are described in some publications as Warocquères.

The crank motion is particularly well suited to the movement of the man-engine, inasmuch as the velocity of the movement decreases gradually at the beginning and end, and becomes almost nothing as the crank passes the centre, thus giving time for the miner to step from one beam to the other, or from the beam to the stage fixed to the side of the shaft.

When direct-acting engines are used, there is a stoppage after each stroke to give the miners time to pass from one stand to the other. This stop varies from two to eight seconds, which is ample, as the passage from one stand to the other does not take more than one second. This would be a very good system if the stop were always rigorously the But all who have worked the machine with direct single action and cataract know that it is impossible to obtain this regularity. The

same.

irregularity may indeed cause accidents. The miner, relying on the normal time of the stoppage, may be surprised in the midst of the movement he is making, and as the single-action engine starts suddenly, and very quickly acquires a great velocity, he may have one leg roughly taken up while the other remains on the stage which rapidly goes down. When the man-engines receive their reciprocal motion from a crank on a revolving shaft, there is, so to speak, no stoppage. The stages which approach each other are hardly on the same level when they separate again; but by taking care to have the machines provided with regulators and heavy fly-wheels, the movement is regular, and there is no change to surprise the miner at the moment of his passage from one stage to the other.

It must not be forgotten that the movement of the machine being uniform, that of the connecting-rod which commands the man-engine is variable. It is very slow at the commencement of its stroke, is accelerated at the middle of the stroke, and becomes slow at the end. The miner, thanks to the regularity of the movement and the slowness of speed, when the stages approach the same level and separate from each other, can begin his passage from one rod to the other a little before the stroke, and continue it a little after.

Experience proves that this second method is the safest. The persons who go down for the first time on these machines do not experience any disagreeable sensation. It is not so with the single-acting machines; when, after the stoppage, the stage lifts or lowers a person suddenly who is not accustomed to them, he experiences a disagreeable sensation, (a sinking at the stomach,) which is increased by the sudden stop at the end of the stroke. This feeling is similar to that experienced when one is lowered or "dropped" suddenly in a cage; and, with some persons, produces sickness and fainting. In the Saxon mines, at Freiberg, the movement is given by water-wheels and cranks; and there is nothing about it unpleasant or awkward to any one accustomed to life underground. The writer, after watching the movement of the rods for a few moments in one of the shafts, stepped upon and used them without difficulty. There is always this advantage to one unaccustomed to them, that if, from any cause, the step from one stage to the other is not taken in time, it is perfectly safe to remain upon the rod and be lowered and hoisted again.

Man-engines worked by direct-acting engines, in order to raise the same number of men in a given time, must move more rapidly than when the motion is communicated by a crank.

Let us suppose two man-engines, worked by these different engines, having a stroke of 3m.00 and making 6 double strokes per minute. The speed per minute is equal to 3m × 12 strokes single=36m. Therefore, while the crank machine will take 60 seconds to go over these 36.00, og a mean velocity of 0.60, the single-acting engine will take 60 seconds diminished by 12 stoppages, which are generally of 23 seconds=30 seconds; its speed must then be double-1m.20. The diagrams annexed clearly indicate the difference that exists between the working of these two methods.

In these curves the abscisses represent the number of seconds from the beginning of an oscillation, and the ordinates the corresponding spaces passed over by a stage.

The machine with single action predominates in Belgium, while the crank machine is more used in Germany and England. The single-acting machines are generally placed directly over the shaft.

These engines are composed of two steam cylinders joined together;

the piston-rods are attached directly to the man-engine. The steam acts directly and alternately underneath or above one or the other of the pistons.

Course 360

Run 3.00

< Ascending.

><

Descending. >

Working curve of the stage of a Man-engine when actuated by a double-acting

engine.

>< Descending. ><

==

Stoppage. >

Working curve of the stage of a Single-acting engine.

But there is an important condition to be observed, which compli cates this arrangement a little. The platforms of the man-engines must have exactly the same velocity, and the strokes must terminate at exactly the same moment, so that both sets of platforms will be connected. This problem has been solved in two principal ways.

One method, designed by M. Hanrez, is to connect the rods by a pinion, as shown in the annexed figure.*

A strong rack is placed on each rod, and these work into opposite sides of the same pinion, steadied by an intermediate guide-rod. Uniformity of motion has thus been secured, for it is evident that when one rod descends the other must move simultaneously and equally. Every precaution has been taken by the constructor to prevent breakage. The teeth of the pinion and the racks are strong and carefully cut; and very few accidents have occurred.

The other method consists in extending the piston-rods through the upper cover of the cylinders, so that these two rods may be connected by a chain working over a pulley. They then necessarily move simultaneously. As a pulley working between the cylinders would have too

* From Plate L, Matériel des Houillères, Burat.