it will have to be compressed in order to get it in; it will then tend to cling about the rod and wear a long time with good usage.

Let the beginner not be discouraged at the first trial if he does not succeed, for the process is, in reality, a simple one, and inexperienced persons have made gaskets from these drawings at the first trial. The gasket should be laid up while reading this description, and we hope all points are made clear and simple, so that a little practice will, as in a other cases, render the braiding of a square gasket as easy as one of three strands.

TO TURN AN ELBOW.

If we attempt to bend an elbow in a brass or copper pipe, unfilled with resin, it bulges out at

the sides and is dented in the middle, resulting in an unsightly piece of work. A very neat elbow can be made in a small pipe by cutting out a portion in the centre, bending the pipe over and soldering the parts, as shown in the previous engravings. If desired, a gusset can be put underneath the pipe, so as to make it stronger.

Where

This is, of course, best adapted for light work, but it is at the same time quite strong. gas fitters' elbows cannot be readily obtained, it is an expeditious method of turning an elbow. For some purposes, also, pipes look better to have square corners. With this plan they are easily made so.

FLY-WHEELS FOR LONG SHAFTING.

Long lines of shafting that communicate power to machines at a distance from the prime motor, spring and buckle greatly where the work is variable. The torsional or twisting strain, tending to wrench the shaft asunder, causes back-ash in the machinery driven, so that it runs fast and slow, or unevenly; this is often a source of great loss. The remedy is to put a moderately heavy fly-wheel on the extremity of the shaft, close to the hanger. This wheel takes up the strain and gives it out, or, in other words, equalizes the power, so that no change is perceptible. It is

practiced in some of the Eastern cotton factories, and is found of great benefit.

VELOCITY OF MECHANISM.

Fan blowers are frequently run with a velocity of 3,000 turns per minute, while the usual velocity of cotton spindles is between 6,000 and 7,000 turns per minute. These are the highest rotary velocities with which we are acquainted in ordinary mechanism, but M. Arago, in measuring the difference in the velocity of light while passing through air and through water, wished to give a revolving mirror a velocity of 8,000 rotations per second. This he was unable to do. With the most delicate and perfect arrangement of cog wheels he was able to impart only 1,000 revolutions per second to his mirror. M. Foucault, by substituting for cog wheels a delicate turbine acted on by a steam jet, raised the velocity to 1,500 turns per second. M. Arago, by removing the mirror and turning the spindle alone, achieved a velocity even by means of cog wheels, of 8,000 turns per second-equal to 480,000 turns per minute.

That spindle, therefore, turned 80 times, while an ordinary cotton spindle is turning once! This is the highest rotary velocity of which we have any account.

CHAPTER XLII.

VARIOUS USEFUL ITEMS.

RADIUS OF THE LINK MOTION.-The radius of the link in link motion for slide valves is struck from the centre of the shaft. The lead is supposed to remain the same, but it is generally increased slightly in cutting off shorter.

WATERPROOF.-The

HOW CLOTH IS MADE method of making cloth waterproof consists in dissolving one ounce of alum and an equal quantity of the sugar of lead in one gailon of water and then allowing the sediment to fall to the bottom of the vessel. Now take the clear liquid, warm it, immerse the cloth in it, and hang it up to dry, after which it will repel water, but air will pass through it freely. It is not so perfectly water-proof as an india-rubber composition.

WEIGHT OF A CUBIC FOOT OF VARIOUS METALS. -A cubic foot of cast-iron weighs 450.55 pounds, of wrought iron 486.65, brass, 537.75 and fresh water 62.5.

A TIN VESSEL to hold one gallon beer measure should measure as follows:-Diameter of top 3, of the bottom 8 inches, height 7 inches.

DOUBLE

THREADED SCREWS.-A double threaded screw runs no faster through a nut than a single threaded one of the same pitch. Double or triple thread screws are the only means of cutting extraordinarily quick pitches on small rods or shafts.

GOLD POWDER.-A gold powder, according to Cooley," is made by rubbing gold leaf with sulphate of potassa in crystals, the latter is afterward washed out. Another gold powder can be made by rubbing gold leaf on a marble slab with honey or molasses, and afterward washing out the molasses when the gold will sink to the bottom.

ARTIFICIAL GRINDSTONES.-An artificial grindstone can be made by the following formulæ, although the natural one is cheaper and better; washed silicious sand 3 parts, shellac 1 part, melt the lac and mould in the sand while warm. Emery may be substituted for sand. Used for razors and fine cutlery.

TO CLEAN BRASS CASTINGS.-A bath composed of one part of hydrochloric acid to ten of water, will answer for cleaning brass castings. They should be dipped into an alkaline solution after being put into the acid, and washed and dried before being lacquered.

TO MAKE INDIAN INK.-Indian ink is a mixture of lamp-black and glue, with the addition of