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.

Toothed wheels

Depreciation of Machinery.-Amount to be deducted annually, com

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

unusual amount of vibration
Factories, wooden buildings, or light iron buildings, without

machinery

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

subjected to

5

5

7

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.

Table 160.-PROPERTIES OF SATURATED STEAM.

(An extract from a table in the "Encyclopædia Britannica," by Mr. D. K.

Clark.)

Table 160 continued.-PROPERTIES OF SATURATED STEAM.

One atmosphere 14'706 lbs. pressure per square inch = 29'92 inches of mercury; each lb. pressure per square inch is equal to a column of mercury 2.035 inches, or 1018 rise in a syphon gauge.

To convert degrees Fahrenheit into Centigrade.-Rule: Subtract 32 and divide the remainder by 1.8.

To convert degrees Centigrade into Fahrenheit.-Rule: Multiply by 18 and add 32 to the product.

To convert degrees Fahrenheit into Reaumur.-Rule: Subtract 32 and divide the remainder by 2.25.

To convert degrees Reaumur into Fahrenheit.-Rule: Multiply by 2.25 and add 32 to the product.

EFFECT OF SHOT ON IRON PLATES.

Power of Shot and Shell.-Captain C. O. Brown, R.A., of Woolwich, in a paper read before the Institution of Mechanical Engineers, gave the following equation as the one used in the department of the Director of Artillery for calculating problems of shot :

K = a certain constant whose value depends on the

quality of the plate, &c.

The left hand side of the equation represents the power of the shot at the moment of striking. The following particulars of experiments with guns. are extracted from the same paper.

་

"The 38-ton gun, whose calibre is 125 in., was fired with a charge of 130 lb. and a projectile of 812 lb. weight at a structure known as 'No. 40 target,' consisting of three layers of 6 in. of iron with 5 in. of teak between each, making a total of 19 in. of iron and 10 in. of teak. The projectile had a striking velocity of 1,420 feet per second. Using the expression above to obtain the penetration b, and writing K as 253, which is so taken as to give 6 in inches, we get b = 19:41. This means that the shot would just penetrate through a solid iron plate 1941 in. thick. It ought, therefore, to pierce the three 6 in. plates and teak, with something to spare. It did actually pass through, excepting that a portion of the base was left in the target.

"The 38-ton gun was afterwards chambered, so as to enable it to take a charge of 200 lb.; and was fired at the same structure (No. 40 target) strengthened by the addition of a front plate of 6 in. and 5 in. additional teak. The striking velocity of the shot was now 1,525 feet per second, which gives a power to penetrate a solid plate 21 in. thick. As, however, the structure contained 26 in. of iron, the problem becomes one of partial penetration. It is a very different thing to penetrate. completely through a plate 21 in. thick, and to enter 21 in. into armour 26 in. thick; because in the latter case the extra metal is backing up and adding to the strength of what might otherwise be pierced. Hence the shot's point only attained to a depth of about 20 in. of iron in all. In these two experiments it may be said that the plate-upon-plate system did well.

“The trial of the 80-ton gun closely resembles the above; this gun was fired, while in its unchambered condition. Its calibre was 16 in., diameter of projectile 15'92 in., weight of projectile 1,700 lb., firing charge 370 lb. With this its striking velocity at 120 yards was 1,496 feet per second. The target, known as 'No. 41,' consisted of four 8 in. plates, giving a total of 32 in. of iron, sandwiched with 4 in. layers of teak. The penetration under these conditions will be found to be 28 in.; that is to say, the shot ought just to penetrate completely through a solid plate whose total thickness was 28 in. As it was fired against 32 in. of iron, it would not penetrate so far; and 25 in., which was the amount of iron the points did actually go through, is not far from what might be expected.

"The 80-ton gun, after chambering, was fired at the same target with a charge of 425 lb., the projectile, &c., being as before. The striking velocity was now 1,585 feet per second. The projectile might therefore penetrate completely a solid plate 30 in. thick. Its point got to a depth of about 27 in., the back of the target bending back nearly 14 in., and opening in a star crack, 2 in. wide, through which the point was visible."

THE NEW PATENT LAW ACT, 1883.

An application for a patent must be made in the prescribed form, signed by the appplicant, and must be limited to one invention.

The application may be made by the actual inventor or inventors, either alone or in conjunction with others, but the declaration must state which of the applicants is the inventor.

If an inventor dies without applying for a patent, a patent may be granted for his invention to his legal representative, if application be made. within six months of the inventor's death.

If an applicant for a patent dies, the patent may be granted to his legal representative, and be sealed any time within twelve months after the death of the applicant.

In applying for a patent, the inventor must lodge at the patent office a combined declaration and petition, and a provisional specification, describing the nature of the invention, accompanied by drawings, if required, or a complete specification may be lodged in place of the provisional specification, particularly describing the nature of the invention, and in what manner it is to be performed, and accompanied by drawings, if required.

A specification, whether provisional or complete, must commence with the title, and a complete specification must end with a distinct statement of the invention claimed.