382 



STATE BOAKD OF AGRICULTURE. 



B, and C. These, I think, will be understood without explanation. The 

 clamp B is formed by merely sawing a slot in the cross-bar, in which slip 

 the upright stake ; two bolts are put through, one to prevent splitting ; the 

 other to tighten by means of a wrench or a thumb-screw. The common quilt- 

 ing frame clamps would answer very nicely. If a survey has been previously 

 made, and the depth at each point is given, the cross-bars are set by measur- 

 ing up from the surface so as to be a uniform distance from the bottom. They 

 should be seven or eight feet above bottom of ditch, where they will not interfere 

 with tile laying. Over the center of the ditch on the cross-bars pull the line : with 

 a stick whose length is equal the higlit of the line above the bottom, say seven 

 or eight feet as the case may be, the bottom can be readily tested. 



If no survey has been previously made, we can use these to determine the 

 fall and the grade line. For instance, at 1 in Fig. 10, we set our first cross- 

 bar and stakes, say so as to give a depth of four feet. 



At the farthest distance that can be seen we set another cross-bar and stakes. 



Fig. 10. 



so as to give us the required depth at that point, say three feet. To find the 

 fall between these two, we have only to sight over a level of any construction, 

 from over first cross-bar to our last, and measure the distance of the intersec- 

 tion of this sight line to our cross-bar ; this last method is a rough one, and 

 will only serve to show whether we have any fall or not. After we find there 

 is sufficient fall between the two cross-bars, any number of intermediate ones 

 can be set by sighting, and accurately too. Leave these in until the tiles 

 are laid under any given one, and you will find your work done with all the 

 accuracy needed, and in very much less time than if you had attempted any 

 method which depended on leveling the bottom itself. This method will sub- 

 stitute certainty for uncertainty, and give you success, where by laying tile by 

 the eye or running water you would be likely to fail. 



Fig. IL 



