Surveying and Levelling Instruments, Theoretically and Practically Described. / For construction, qualities, selection, preservation, adjustments, and uses; with other apparatus and appliances used by civil engineers and surveyors in the field.

by William Ford Stanley

275—Papering or Repapering a Sopwith Staff.—The staff, if new, is painted with three coats of rather flat, thin white-lead paint on the face, and left to season till the paint is quite hard. It is then washed thoroughly with a sponge dipped in stout, until this adheres without beading, and is again left to dry. For repapering an old staff, this is soaked with hot water in which there is some washing soda, and rubbed until the old paper is brought off. After the staff is in either of the states described above, it has to be made warm and coated with one or two coats of size. The size may be made of a piece of glue left in water for a night, and then melted in a jam-pot placed in a saucepan of water over a slow fire. When the staff is sized and dry, if ordinary papers be used, it has to be divided carefully into foot lengths, which are marked with a set square in pencil across the face of the staff. The foot lengths may be set off accurately from an engine-divided chain scale, or by beam compasses. The papers, which are printed short, are then pasted over, preferably with paste made of starch with boiling water, but not afterwards boiled. As the lengths of paper are pasted they are laid aside, pasted side upon pasted side, to thoroughly absorb the paste for a few minutes, the time varying according to the increased length required above that of the original printed paper. While still wet, the upper paper of the two is lifted up and cut with scissors, at the same time fitting to the boundary lines. This wet cutting ensures the paste being equally distributed quite up to the edges. The foot length of pasted paper is then laid by setting the upper edge exact to the upper foot line, and gradually bringing the paper down from this by dabbing with a clean cloth or straight hat-brush. If the paper does not reach the foot mark when laid, it is again lifted, and a little more pressure used in laying it the second time, which will lengthen it out as required. Other lengths are laid in the same manner. The skilled workman requires no lap to the joins of the papers, but brings them up edge to edge; with the amateur a lap of 1/8 inch is advisable.

To avoid the trouble of marking off and stretching each foot, the author has introduced jointless levelling staff papers, so that the entire length of each section may be put on in one piece. These are of special paper, and it is only necessary to paste the face of the staff well and smoothly, and lay the paper unpasted down in position upon it.

After the papers are thoroughly dry they require two coats of thin isinglass size, and then a coat or two of varnish. Paper varnish can be bought; but in defect a varnish may be made of Canada balsam dissolved in oil of turpentine. This should be laid on with a flat bristle brush (varnish brush), and set in a warm room to dry for a day or two.

276.—Preservation of the Levelling Staff in Use.—Where two staves are used they may be placed face to face for carrying, and be strapped together, and will take little harm with moderate care. Where one only is used it is generally strapped to the tripod. A strip of wood is sometimes used to protect the face of the staff.

Fig. 106.—Pad for holding a staff and tripod.

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277.—For carrying the staff with the tripod, a convenient plan is to have two pads formed of stout ox-hide butt, each pierced with two slots near their ends at the exact distance apart of the width of the staff, Fig. 106. The strap of calf leather is passed from one slot round the staff into the other slot, and then passed round the tripod and pulled up tightly and buckled. The pad of course protects the front of the staff from grazing by the friction of the tripod against it.

There is a certain amount of risk, under any circumstances, of the cylindrical tripod pressing against the front of the staff and splitting it. To avoid this the author has lately made the pads with a mahogany bridge piece, so that the pressure is distributed, coming upon the edges of the front where the staff is strongest to resist it. This is shown, Fig. 107.

278.—For the entire protection of the staff a leather-bound sailcloth case is very generally used. This may be divided into two compartments for the staff and the tripod, with pads between. The whole case has a neat appearance, and forms a protection from slight bruises and dirt, either in travelling or when set up in an office corner for future use.