rally reduced by an elegant curve, concave to the eye, to a diameter less by at least one-third, and sometimes to half its original base. From thence, its taper diminishing more slowly, its sides by degrees come into a perpendicular, and for some height form a cylinder. After that, a preparation of more circumference becomes necessary, for the strong insertion and establishment of the principal boughs, which produces a swelling of its diameter. Now we can hardly doubt, but that every section of the tree is nearly of an equal strength in proportion to what it has to resist; and were we to lop off its principal boughs, and expose it in that state to a rapid current of water, we should find it as capable of resisting the action of the heavier fluid, when divested of the greater part of its clothing, as it was that of the lighter, when all its spreading ornaments were exposed to the fury of the wind: and hence we may derive an idea of what the proper shape of a column of the greatest stability ought to be, to resist the action of external vio. lence, when the quantity of matter is given of which it is to be composed."

With these views as to the proper form of the superstructure, Mr. Smeaton began the work on the 2d of April, 1757, and finished it in August 4, 1759. The rock, which slopes towards the S.W. is cut into horizontal steps, into which are dovetailed, and united by a strong cement, Portland stone and granite. The whole, to the height of thirty-five feet from the foundation, is a solid of stones, engrafted into each other, and united by every means of additional strength. The building has four rooms, one over the other, and at the top a gallery and lantern. The stone floors are flat above, but concave beneath, and are kept from pressing against the sides of the building by a chain let into the walls. It is nearly eighty feet high, and since its completion has been assaulted by the fury of the elements, without suffering the smallest injury.

We regret that we cannot with propriety trace out the progress of this great work, and shew with what skill and judgment this unparalleled engineer overcame the greatest difficulties: we, however, beg to recommend to our curious readers Mr. Smeaton's own Account of the Eddystone Light-house, not doubting that they will be highly gratified by the perusal. According to the Requisite Tables, this light-house is situated in lat. 50. 8 N. Lon. 4. 24 W. of Greenwich, or 4. 18. 23 W. of London.

CHAP. VIII.

CHRONOLGICAL TABLE OF MECHANICAL INVENTIONS,

SCIPIO Nasica's clepsydra*

Scissors invented in Africa

B. C. 159

Diophantus employed some algebraic symbols. Montucla.
Pens made from quills

Glass introduced into England

A. D. 635

674

Silk worked in Greece about

700

The Chinese canal S06 miles long, finished by 30,000 men

in 43 years

980

Paper of linen introduced about

1100

The first canal in England, from the Trent to the Witham

1134

Gunpowder used at Lyons in Brabant Wiegleb

Muskets used at the siege of Arras

1356

1414

* An instrument to measure time by the fall of water.

Many Flemish weavers were driven to England by the Duke

Bows and arrows still used in England, and artillery with

Fromantil is said to have applied pendulums to clocks in

1656

In 1787 about twenty-three million pounds of cotton were manufactured in Britain; about six were imported from the British colonies, six from the Levant, and ten from the settlements of other European nations. Half the quantity was employed in white goods, one-fourth in fustians, one fourth in hosiery, mixtures, and candle wicks; giving employment to 60,000 spinners, and

360,000 other manufacturers. In 1791, the quantity was increased from twenty-three millions to thirty-two.

The value of the wool annually manufactured in England is about three millions sterling; it employs above a million persons, who receive for their work about nine millions.

Thread has been spun so fine as to be sold for £ 4 an ounce; lace for £40.

The premiums annually proposed by the Society for the Encou ragement of Arts, enable us to form some opinion of the present state of our machinery and manufactures. Some of their objects are, a substitute for white lead paint, a red pigment, a machine for carding silk, cloth made from hop stalks, paper made from raw vegetables, transparent paper, the prevention of accidents from horses falling, cleaning turnpike roads, machines for raising coals, and for making bricks, instruments for harpooning whales; machines for reaping or mowing corn, for dibbling wheat, for thresh. ing; a family mill, a gunpowder mill, a quarry of millstones; and a mode of boring and blasting rocks 1802.

[Luckombe's Tablet of Memory. Young's Nat. Phil. Edit.