root, oz. Another renovating polish is-pale linseed oil, 2 pints; strong distilled vinegar, pint; spirit of turpentine, pint; muriatic acid, 1 oz. Stains for Wood.-Red.-Brazil wood, 11 parts; alum, 4 parts. Boil. Blue.-Logwood, 7 parts; blue vitriol, 1 part; water, 22 parts Boil. Black.-Logwood, 9 parts; sulphate of iron, I part; water, 25 parts. Green.-Verdigris, I part; vinegar, 3 parts. Dissolve. berries, 7 parts; water, 10 parts; alum, 1 part. Boil. 11 parts; alum, 3 parts; water, 29 parts. Boil.

Boil. Yellow.-French Purple.-Logwood,

Walnut Stain.-Boil 2 quarts of water, add 3 oz. washing soda, and then, by a little at a time, add 5 oz. vandyke brown; when the foaming ceases, add oz. bichromate of potash.

Brown Stain.-Dissolve permanganate of potash in water.

Rosewood Stain.—Alcohol, 2 gallons; camwood, 3 lb.; red sanders, 1 lb.; aquafortis, lb. Apply 3 coats: rub with sandpaper; grain with iron rust; shade with asphaltum, thinned with turpentine. In staining wood, depth of colour may be obtained by giving several coats of stain; rub down with fine sandpaper, and give two coats of size before varnishing. For dark wood-varnish with French polish, I part; brown hard varnish, 2 parts. For light wood-varnish with 2 parts white French polish, and parts white hard varnish.

3

Staining Floors.-Oak Stain. American potash, 2 oz. ; pearlash, 2 oz. ; water, I quart. Mahogany Stain.-Madder, 8 oz.; logwood chips, 2 oz.; boil in 1 gallon water, and apply hot. When dry, paint it over with a solution of-water, I quart; pearlash, 2 drachms; next, size and polish.

Polishing Stained Floors.-After sizing, apply the following polish, viz. white wax, 4 parts; yellow wax, 8 parts; castile soap, I part; soft water, 20 parts; turpentine, 20 parts; the soap to be melted in the water, the wax to be dissolved in the turpentine. Mix the whole, brush it on the floor, and well rub with a cloth pad.

To Darken Mahogany.-Apply a solution of bichromate of potash. Green Varnish for Metals.-Bronze green-strong vinegar, 2 quarts; mineral green, 1 oz.; raw umber, 1 oz.; salammoniac, 1 oz.; gum arabic, 4 oz.; French berries, I oz.; copperas. 1 oz.; dissolve with gentle heat, cool, and filter.

Green Transparent Varnish.-Chinese blue, 1 oz.; powdered chromate of potassa, 2 oz.; well ground and mixed; add a sufficient quantity of copal varnish and thin with turpentine.

Waterproof Varnish.-Dissolve guttapercha, 4 oz., resin, 2 oz., in bisulphide of carbon, and add 2 lb. hot linseed oil varnish.

Pattern Makers' Varnish.—Methylated spirit, I gallon; shellac, lb.; plumbago, lb.; dissolve and frequently stir.

Varnish for Drawings.-Dissolve by gentle heat, 8 oz. sandarac in 32 oz. alcohol. Another is-Dissolve 2 lb. mastic and 2 lb. dammar in I gallon turpentine, without heat. The drawing to be first sized, with a strong solution of isinglass and hot water.

Gravity. To find the velocity in feet per second acquired by a falling body-Rule: Multiply the time in seconds by 322.

To find the height of the fall in feet.-Rule: Multiply the square of the time in seconds by 16°1.

To find the time in falling in seconds.-Rule: Divide the velocity in feet per second by 32.2.

To find the velocity in feet per second for a given height.-Rule: Multiply the height of the fall in feet by 64'4, and take the square root of the product.

Work accumulated in a Moving Body.—To find the force acquired by a weight in falling freely from a given height.-Rule: Multiply the weight in lbs. by the square of the velocity in feet per second, and divide by 644. The result is the accumulated work in foot pounds. Or another rule for the same is: Multiply the weight in lbs. by the height in feet of free fall. The product is the accumulated work in foot pounds, or the force that would raise a similar weight to a similar height.

The following examples of accumulated work show the application of

these rules:

= 338 feet.

To find the distance in feet a ball will traverse before coming to a state of rest, say, on a bowling green, at a velocity of 50 feet per second; weight of ball, 20 lbs., and the frictional resistance to its motion being th the 502 velocity × 20 lbs. weight weight of the ball; then 2 lbs. frictional resistance × 64'4 To find the distance in feet a train will move on a level rail, whose frictional resistance is 8 lbs. per ton, and supposing that there is no other resistance; the weight of the train being, say, 100 tons, and its velocity when the steam is shut off, 50 feet per second; 502 velocity × 100 tons weight of train × 2,240 lbs.

then

100 tons weight x 8 lbs. per ton frictional resistance × 64'4 10869.5 feet before coming to rest.

=

Punching and Shearing Iron, &c., Plates.-Punching.-The resistance of a wrought-iron plate to punching is about the same as its resistance to tearing. Taking the maximum resistance at 25 tons per square inch, and the resistance to the punch being the area of the metal separated, or the circumference of the hole multiplied by the thickness of the plate, the force in tons required to punch a plate of wrought-iron is circumference of the hole x its depth x 25. And a simple rule to find the force required to punch a plate is :-Multiply the diameter of the hole in 16ths of an inch by the thickness of plate in 16ths, and divide the product by 10; which result multiply by 31 for wrought iron plates; by 4'5 for steel plates; and by 2.5 for copper plates. The final product will be the required force in tons.

The compressive strength of a hardened steel punch is 100 tons per square inch, or four times greater than the maximum tensile strength of wrought-iron plates. The smallest size of hole that can be punched, is that of which the diameter is equal to the thickness of the plate.

Shearing. The resistance of a wrought-iron plate to shearing is 20 per

cent. less than its ultimate tensile strength; and the power required in tons to shear wrought-iron plates and bars may be found by the following rule: Multiply the square of the thickness of plate in 16ths of an inch by 8, and divide by 100.

Contraction of Metal in Casting.-Allowance per foot in length of pattern :

Inch.

Depreciation of Machinery.-Amount to be deducted annually, commencing from the prime cost:

Lathes and Machine tools, first class .

Engines, shafting, gearing, and millwork

Lathes and machine tools, second class
Machinery in general

Per cent.

5

Boilers

Leather belting

Depreciation of Factories.-Amount to be deducted annually, commencing from the original cost, of well built and well cared-for factories and workshops :

Factories, stone or brick built, without machinery

Per cent.

2

Factories, wooden buildings, or light iron buildings, without
machinery

Factories, wooden buildings, or light iron buildings, with
machinery

Foundries, stone or brick built

· 5

7

7

Forges

ΙΟ

When renewals are made to the carcase of the building, due to ordinary wear and tear, their cost should be added to the capital value at the date of the said renewal, and the same rate of depreciation should be continued.