281.—Staff Level.—This is a small circular level, shown at Fig. 109, the upper surface of which is formed of a glass worked slightly concave and fixed into a short cylindrical box. The glass is hermetically sealed after being nearly filled with spirit. The circular level is mounted on a plate with a dovetail fitting which fits in a slot in the holding plate attached to the back of the staff. In use the staff holder has to observe when the bubble under the concave glass is in its centre. A very little practice is required to hold the staff vertically by means of this little contrivance, which only weighs, about 2 oz.
Fig. 109.—Staff level, ½ scale.
Fig. 110.—Staff-holder, 1/10 scale.
Larger image
282.—Staff-holder.—This implement, shown Fig. 110, striding a staff, is very generally used in Germany and other parts of the Continent. The staff is sunk into one side of a hardwood block. The block is turned at one end to form a handle. A second similar handle is cut with a strong screw and screwed into the end of the block. This screw handle by turning brings up a following piece, shown inside next the staff, which is covered with leather. When it is screwed up, the staff may be held firmly by the handles only, without the risk of the fingers coming in front. With this accessory it is also held more easily and truly vertical. It is a comfort in use in cold weather.
283.—Practice of Levelling with the Staff.—This subject can be followed here only so far as to exemplify the uses of the instruments and of accessories connected with such instruments. For practical levelling we have the standard original works of Simms, Ainsley, and others, with many modern works.[10]
284.—For Holding the Staff, Mr. Holloway, in the work referred to in the last note, gives instructions in such concise form that they may be quoted with advantage. He says:—"I generally enter into confidential chat with my staff holder, in which I explain to him the vast importance of his duties, i.e., I endeavour to make him a man of importance in his way, and I never fail to get those duties properly performed. My instructions to him are seven in number:—
"1. Draw out the slides of the staff, and be sure the joints are properly locked. Draw out one length only unless signalled to do otherwise.
"2. When the staff is once on a point never move it unless signalled to do so.