To make them.—The pickets are first to be fixed in the ground in a circle, the size of the bottom of the intended gabion; then a few twigs are to be wove through the upper ends, to keep them from flying out; afterwards the work must be begun at the bottom and continued upwards; and the whole being well driven down with a mallet, the edges must be secured by twigs, wattled up and down. The twigs of willow, birch, hazle, alder, poplar, and beech are proper for this purpose. The top of the gabion must be made very even, because that becomes the bottom when finished. Four men are usually employed on each gabion, with a billhook, a mallet, a spade, and two axes. Two collect the wood, while the other two form the gabion. A 3 foot gabion ought to be made in half an hour.
GIN Triangle.—Length of arms of the gin 16 feet 4½ inches. Roller, 6 feet long. Tackle fall, 78 feet of 3 inch white rope. Sling, 6 inch white rope.
For the different exercises of the gin, see the word [Exercise].
GRAVITY.—Table of the Specific Gravity of several Solid and Fluid Bodies.
| Platina | 23400 | Nitre | 1900 |
| Fine gold | 19640 | Ivory | 1825 |
| Standard gold | 18888 | Brimstone | 1810 |
| Quicksilver | 11325 | Solid gunpowder | 1745 |
| Fine silver | 11091 | Sand | 1520 |
| Standard silver | 10535 | Coal | 1250 |
| Copper | 9000 | Boxwood | 1030 |
| Copper halfpence | 8915 | Sea water | 1030 |
| Gun metal | 8784 | Common water | 1000 |
| Cast brass | 8000 | Oak | 925 |
| Steel | 7850 | Gunpowder, close stacken | 937 |
| Iron | 7645 | ”in loose heap | 836 |
| Cast iron | 7425 | Ash | 800 |
| Tin | 7320 | Maple | 755 |
| Crystal glass | 3150 | Elm | 600 |
| Marble | 2700 | Fir | 550 |
| Common green glass | 2600 | Charcoal | |
| Flint | 2570 | Cork | 240 |
| Common stone | 2520 | Air | 1.232 |
| Clay | 2160 | Brick | 2000 |
| Common earth | 1984 | ||
The several sorts of wood are supposed dry.
This table also contains the weight of a cubic foot of each body in avoirdupois ounces; from whence results the following rules:
1. To find the Magnitude of any Body from its Weight.
As the tabular specific gravity of the body Is to its weight in avoirdupois ounces, So is one cubic foot, or 1728 cubic inches, To its content in feet or inches respectively.
2. To find the Weight of a Body from its Magnitude.