until the staff appears in the field of view; when this is effected, the vernier plate is clamped, and the observation completed as before. In this way the survey is carried on; and the perpendiculars and rates of inclination are afterwards calculated, and the plan and section laid down in the usual way.

Spirit Levels.

Troughton's levels, which are considered the best, are usually made with very powerful telescopes and delicate ground spirit levels. These instruments are usually fourteen inches long; but some are eighteen and others twenty inches long. They cost from 12. to 18., and are so well balanced and secured, that they will not require, with proper care, for a long time, any adjust

ment.

The method of using these instruments is as follows:

When the direction of the road has been marked out, a line is measured by a chain commencing at the beginning of the new line, and terminating at that point where the inclination of the surface of the ground changes, or where the line of direction changes. This distance is carefully entered in the field book. The spirit level

is set up as nearly as possible in the middle of this line, and a levelling staff with a vane is held by assistants at each extremity of the line: the telescope is then adjusted for distinct vision, and its axis brought to be truly vertical by means of the spirit level and parallel plates. The telescope is then directed to the staff, which is placed at the commencement of the line, and the assistant is directed to lower or raise the vane until it is bisected by the cross hairs in the telescope; the height marked by the vane on the staff is then set down in the field book in the column headed (back observation). The telescope is then turned round until the staff at the termination of the line is perceived in the field of view; the necessary signals are then given to lower or raise the vane on the staff until its centre coincides with the cross hairs in the telescope: the height of the vane on the staff is then entered in the field book in the column marked for observation, and the magnetic bearing of the line is also observed and set down in another column. Sometimes only one staff is used, in which case it is removed from the first to the second station after the observation is made. When very great accuracy is required, the level is set up by measurement exactly in the centre between the two staffs, for by this means the errors of adjustment and any

slight deficiency in the instrument are compensated and mutually destroy each other.

Sextants.

The small pocket sextant is a most useful instrument in making road surveys; after a little practice, it can be used with great facility, and will be found a superior instrument to the common surveying needle, and much more accurate, besides affording the most expeditious method of making surveys of any yet known.

ROAD TOOLS.

Spades.

In some parts of the clay districts, a narrow spade, considerably curved in the blade, technically called a grafting tool (Plate VII. fig. 10.) is much used, particularly in cutting deep drains in stiff clay.

Shovels.

The best description of shovel for road work is pointed in the blade, and has a curved handle to allow the workmen to bring the blade flat to the ground without stooping. (See Plate VII. fig. 13.)

Trucks.

When metal rails can be laid down, the truck or small waggon is the best description of carriage for removing earth; a drawing of one of these is given in Plate VII. figs. 11 and 12. they usually hold a cubic yard of earth. The body is generally made of elm, the frame of oak, and the wheels and axles of iron.

Hammers.

Two descriptions of hammers, which are the most useful in road works, are represented in Plate VII. figs. 15 and 16. The handles should be flexible and made of straight grained ash; particularly those used for breaking pebbles the small hammers should have a chisel face, and the larger ones a convex one, about five-eighths of an inch in diameter. Those made of cast steel are the best; and though expensive in the first cost, they wear much better than wrought iron ones, and very seldom break at the eye.

Pronged shovels are useful for filling stones, when broken, into carts or barrows; a drawing of one is given in Plate VII. fig. 7. A man is enabled to lift stones with much greater ease and more expeditiously with one of these shovels

than with a common one; besides, he lifts them without taking up any earth with them.

Scrapers.

Scrapers are sometimes made of wood shod with iron, but those made of plate iron are preferable: they should be six inches deep, and from fourteen to eighteen inches long in the blade, according to the materials of which the road is composed; the softer and more fluid the mud, the longer the scrapers should be; they turned a little round at the ends to prevent the mud from escaping. The best scrapers are made of old saw plates, stiffened on the back by a rib of wrought iron, or by riveting the plate to a board of elm, cut to the proper width and length and about half an inch thick.

Hedging Knives.

These instruments have been long used in Scotland, where they are called plashing tools: they are made of different sizes; that represented in Plate VII. fig. 14. is the most useful. When a labourer is a little practised in the use of them, he can trim a hedge as well as a gardener with a pair of shears, and much more expeditiously. They should be made sufficiently light to enable a man to use them with one