CANAL CONSTRUCTION. 55 



In the Land Invention, the flume contains both 

 the headgates occupying the full width, and the sand 

 gates, which are on the lower side of the canal. There 

 are two floors above the headgates, and the flume is set 

 so that the upper floor is on the proper grade of the 

 canal. Just at the flume and for a short distance above, 

 the bottom of the canal is about two feet below the 

 grade. The sand gates, which may vary in number ac- 

 cording to the width of the canal, are on the lower side, 

 and each of these gates is connected with the canal by a 

 separate channel until it reaches the side nearest to the 

 discharge. These channels are curved and properly 

 fitted.' Each one of these forms a separate funnel, and 

 the gates are kept constantly raised because, as in the case 

 of nearly all canals, the natural stream under riparian 

 rights is entitled to the flow of some of its full tide at 

 least. The sand is pulled from the far side of the canal, 

 which is the chief advantage. The planks forming the 

 sand funnels are set edgewise and thus support the floor 

 of the main water course above. 



Waste Gates. The safety valve of a canal is its 

 waste gate, and there are many styles in use. That 

 which we will describe herewith is known as Nelson's 

 automatic waste gate and is described as follows, as well 

 as shown by sectional drawing Figure 15. 



The gate (1) is built of two-inch plank securely bolted 

 to four gate standards 2x8 inches and of length equal to 

 the depth of the canal for which it may be designed, and 

 as many gates each three to four feet wide may be placed 

 in the principal frame, termed wasteway, as the magni- 

 tude of the anticipated flood water may require. The 

 <rate is hung on substantial hinges at the top to a hori- 

 zontal beam 4x12 inches, as shown in the figure. Near 

 the bottom the gate is supported by two levers (2), 

 which are four inches square, placed between the gate 

 standard, through which a round bolt is placed, as shown 



