Thickness in parts of an inch.

TABLE

Of the Weight of a Superficial Foot of Plate or Sheet Iron, Copper, and Brass, in pounds.

Note.-No. 1 wire gauge equal ths of an inch.

18

4

The great variety of thicknesses into which copper is manufactured, cause in trade the weight to be named whereby to deter mine the thickness required, the unit being that of a common sheet, so designated, viz. 4 feet by 2 feet, in lbs., thus:

A 70 lb. plate is 3ths of an inch in thickness.

16

The thickness of lead is also in common determined or understood by the weight, the unit being that of a square or superficial foot; thus:

4 lbs. lead isth of an inch in thickness.

6

16
1

10

1. Suppose I have an article of plate iron, the weight of which is 728 lbs., but want the same of copper, and of similar dimensions, what will be its weight?

728 x 116 844:48 lbs.

2. A model of dry pine, weighing 32 lbs., and in which the iron for its construction forms no material portion of the weight, what may I anticipate its weight to be in cast iron ?

Note. It frequently occurs, in the formation or construction of models, that neither the quality nor condition of the timber can be properly estimated; and, in such cases, it may be a near enough approximation to reckon 15 lbs. of cast iron to each lb. of model.

SILVERING POWDER, &c., for silvering copper, covering the worn parts of plated goods, &c.1. Nitrate of silver 30 gr., common salt 30 gr., cream of tartar 34 dr. Mix. Moistened with water, and rubbed on dial plates or other copper articles, it coats them with silver.

2. Silver precipitated from its nitric solution by copper 20 gr., alum 30 gr., cream of tartar 2 dr., salt 2 dr.

3. Precipitated silveroz, common salt 2 oz., muriate of ammonia 2 oz, corrosive sublimate 1 dr. Make it into a paste with water. Copper utensils are previously boiled with tartar and alum, and rubbed with this paste, then made red hot, and afterwards polished.

4. Dissolve muriate of silver in a solution of hyposulphite of soda, and mix this with prepared hartshorn, or other suitable powder.

PLATINA FOR SPRINGS-Platinum 1 part gold 12 parts. Add the platinum to the gold in a state of fusion.

Tables by which to facilitate the Mensuration of Timber.

1. Required the number of square feet in a board or plank 161 feet in length, and 9 inches in breadth.

Opposite 94 is 8125 × 16.5 134 square feet.

2. A board 1 foot 24 inches in breadth, and 21 feet in length; what is its superficial content in square feet?

Opposite 24 is 2292, to which add the 1 foot.

Then 1·2292 × 21 = 25'8

25.8 square feet.

3. In a board 154 inches at one end, 9 inches at the other, and 14 feet in length, how many square feet?

15.5+9

2

124, or 10208; and 1·0208 × 14.5 = 14-8 square feet.

TO GIVE IRON A TEMPER TO CUT PORPHYRY.-Make your iron red hot, and plunge it into distilled water from nettles, acanthus, and pilosella, or in the very juice pounded out from these plants.

PASTE FOR CLEANING METALS.-Take oxalic acid 1 part; rottenstone 6 parts. Mix with equal parts of train oil and spirits of turpentine to a paste.

In the cubic estimation of timber, custom has established the rule of the mean girt being the side of the square considered as the cross sectional dimensions; hence, multiply the number of cubic feet per lineal foot, as in the Table of Cubic Measure, opposite the girth, and the product is the solidity of the given dimensions in cubic feet.

Suppose the mean girth of a tree 211 inches, and its length 16 feet, what are its contents in cubic feet?

3.136 × 1650-176 cubic feet.

CAST METAL CYLINDERS.

The Cylinders are solid, each 1 foot in length.

Table showing the Weight of Pipes 1 foot long, of bores from 1 inch to 12 inches in diameter, advancing by of an inch; and of thicknesses from of an inch to 11 inches, advancing by of an inch.