on to meet; but an all-pervading influence which overwhelms like the sea, and against which, in the mass, individual effort stands paralyzed and helpless.  When the doctor is summoned the mischief has at least commenced, and, it may be, is so far over that treatment by mere medicines sinks into secondary significance.  Then he, true minister of health, candid enough to bow humbly before the great and inevitable truth, and professing no specific cure by nostrum or symbol, can only try to avert further danger by teaching elementary principles, and by making the unlearned the participators in his own learning.—­The Asclepiad.

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THE TREATMENT OF GLAUCOMA.

As this disease is so fatal to vision, any remedy that may be suggested to diminish the frequency of its termination in blindness cannot fail to be read of with interest.  M. Nicati, in the Revue generate de clinique et de therapeutique, has had marked success in the treatment of glaucoma by drainage of the posterior chamber, either by sclerotomy or by sclero-iritomy, as the conditions of the individual case may require.—­N.Y.  Med.  Jour.

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A TWIN SCREW LAUNCH RUN BY A COMPOUND ENGINE.

[Illustration:  TWIN SCREW STEAM LAUNCH GEMINI.]

The launch shown in our illustration was built in New Westminster, British Columbia, Canada.  She is 42 ft. keel and 7 ft. beam, and has 4 ft. depth of hold.  She has an improved Clarke compound engine, also shown in an accompanying illustration, with a high pressure piston four inches in diameter, and a low pressure piston eight inches in diameter, the stroke being six inches, and the engine driving two twenty-six inch screws.  With 130 pounds of steam, and making 275 revolutions per minute, the launch attains a speed of nine miles per hour, thus fully demonstrating the adaptability of this engine to the successful working of twin screws.

[Illustration:  THE CLARKE COMPOUND TWIN-SCREW OPERATING ENGINE.]

In the Clarke engine, the exhaust pipe from the high pressure cylinder leads to the steam chest of the low pressure cylinder, while the piston in the upper cylinder is secured on a piston rod extending downward and connected with a piston operating in the lower cylinder, the exhaust pipe from the latter leading to the outside.  On the piston rod common to both cylinders is secured a crosshead pivotally connected by two pitmen with opposite crank arms on crank shafts mounted to turn in suitable bearings on the base, which also supports a frame carrying the low pressure cylinder, on top of which is a frame supporting the high pressure cylinder.  The valves in the two steam chests are connected with each other by a valve rod connected at its lower end in the usual manner with the reversing link, operated from eccentrics secured on one of the crank shafts.