r. 2. What is the best method of
polishing steel? A. The usual method is to grind first on a coarse
wet stone, then on a fine wet stone, then on a lead lap supplied
with fine emery and oil, and finally polish on a buff wheel supplied
with dry crocus and revolving rather slowly.

(2) R. L. J. asks how to make copying black and red inks. A. 1.
Bruised Aleppo nutgalls, 2 lb.; water, 1 gallon; boil in a copper
vessel for an hour, adding water to make up for that lost by
evaporation; strain and again boil the galls with a gallon of water
and strain; mix the liquors, and add immediately 10 oz. of copperas
in coarse powder and 8 oz. of gum arabic; agitate until solution of
these latter is effected, add a few drops of solution of potassium
permanganate, strain through a piece of hair cloth, and after
permitting to settle, bottle. The addition of a little extract of
logwood will render the ink blacker when first written with. Half an
ounce of sugar to the gallon will render it a good copying ink. 2.
Shellac, 4 oz.; borax, 2 oz.; water, 1 quart; boil till dissolved,
and add 2 oz. of gum arabic dissolved in a little hot water; boil
and add enough of a well triturated mixture of equal parts indigo
and lampblack to produce the proper color; after standing several
hours draw off and bottle. 3. Half a drachm of powdered drop lake
and 18 grains of powdered gum arabic dissolved in 3 oz. of ammonia
water constitute one of the finest red or carmine inks.

(3) X. inquires: What is the rule for making a counterbalanced face
wheel for engines? A. It is a common practice to place the counter
weight directly opposite the crank, with its center of gravity at
the same distance from the center of the shaft as the center of the
crank pin, making its weight equal to weight of piston, piston rod,
crosshead, and crank pin, plus half the weight of the connecting
rod.

(4) A. R. asks: What is the best way to remove cinders from the eye?
A. A small camel's hair brush dipped in water and passed over the
ball of the eye on raising the lid. The operation requires no skill,
takes but a moment, and instantly removes any cinder or particle of
dust or dirt without inflaming the eye.

(5) D. F. H. asks: Can I move a piston in a half inch glass tube by
the expansion of mercury? A. Yes, but you will require a long tube
to get any appreciable motion of the piston.

(6) J. W. asks: What size of a bore and what length of a stroke I
would want for a rocking va