To treat the whole body of ore from a mine, dry crushing is strongly recommended.  To accomplish this in the most efficient manner, a stone breaker which will reduce to about 1/4 in. cubes is necessary.  For subsequent crushing Kroms rolls have, up to the present time, proved most satisfactory.  They will crush with considerable evenness to a thirty mesh, which is generally sufficient.  The crushings are then roasted in the ordinary way in a reverberatory furnace and the whole of the roastings are passed through the machine we have just described.  By this it is claimed that over 90 per cent. of the gold can be extracted at very much the same cost as the processes now in general use in gold producing countries, which on the average barely return 50 per cent.  If so, the gentlemen who have brought forward these improvements deserve all the success their process promises.—­Engineering.

* * * * *

APPARATUS FOR EXERCISING THE MUSCLES.

The apparatus herewith illustrated consists of a wooden base, which may be bolted to the floor, and which supports two wooden uprights, to which is affixed the apparatus designed to exercise the legs.  The apparatus for exercising the arms is mounted upon a second frame that slides up and down the wooden supports.  It is fixed in position at any height by means of two screws.

[Illustration:  APPARATUS FOR EXERCISING THE MUSCLES.]

The apparatus for exercising the legs, as well as the one for the arms, consists essentially of a fly wheel mounted upon an axle extending to the second upright and bent into the form of a crank in the center.  The fly wheel is provided with a winch whose arm is capable of elongation in order to accommodate it to the reach of the sound limb.

The apparatus for the legs is arranged in a contrary direction, that is to say, the wheel is on the opposite side of the frame, and upon the fixed uprights.  It is really a velocipede, one of the pedals of which is movable upon the winch, and is capable of running from the axle to the extremity, as in the upper apparatus.  This pedal has the form of a shoe, and is provided with two straps to keep the foot in place and cause it to follow the pedal in its rotary motion.  A movable seat, capable of rising and descending and moving backward and forward, according to the leg that needs treatment, is fixed back of the apparatus.

The operation is as follows:  Suppose that the atrophied arm is the left one.  The invalid, facing the apparatus, grasps the movable handle on the crank with his left hand, and revolves the winch with his right.  The left hand being thus carried along, the arm is submitted to a motion that obliges it to elongate and contract alternately, and the result is an extension of the muscles which strengthens them.

The apparatus, which is as simple as it is ingenious, can, it is true, be applied only when one of the two limbs, arm or leg, is diseased, the other being always necessary to set the apparatus in motion; but, even reduced to such conditions, it is destined to render numerous services in cases of paralysis, atrophy, contusions, etc.—­Moniteur des Inventions Industrielles.