40 THE IMPROVEMENT OF RIVERS. 



the stone. Where the gauge is to be utilized as a walk the stones are usually from 

 six to ten inches thick and three feet to four feet wide. The figures are cut at one 

 side so as to avoid wear from travel. Where the gauge is not to be used other than as 

 a gauge the stones are generally about six inches thick by two feet wide, and are set 

 on their edges, projecting above the ground a few inches only. Gauges of this kind 

 should be located at points where they will not be covered by the settlement of sand, 

 mud, or debris. They are expensive, and are ordinarily not resorted to where vertical 

 objects can be obtained for fastening other forms. Wooden gauges placed on slopes 

 in the same manner are also in use. 



Wall Gauges. A very common method on improved rivers is to cut the gauges 

 on the lock-wall masonry. A strip of wall about a foot in width is made smooth and 

 slightly countersunk behind the general face of the wall. In this are cut V-shaped 

 division lines and figures, the latter being usually Roman characters, about one-half 

 inch deep at their center lines. The lines and figures are painted black and the face 

 of the recess or strip white, and the result gives a very distinct gauge. It is, however, 

 like most gauges, open to the objection of being difficult to keep clean and bright, 

 besides which, the paint comes off more easily than from wood. 



Tile. A new kind of gauge has come into use within the last few years which bids 

 fair to be more satisfactory than those heretofore employed. It is composed of vitrified 

 tile blocks, six inches square, and from one-half to three-quarters of an inch in thickness 

 inlaid in different colors to represent the scale and numbers. The blocks are sized with 

 care, and if set against a masonry wall with Portland cement will adhere firmly. As 

 they are impervious to moisture, the faces can easily be kept clean, and the colors will 

 not fade or scale off. Where used on locks, they are set in a recess in the wall, the face 

 of the tile being brought out nearly to the face-line of the wall. 



