388 REPORT OF OFFICE OF EXPERIMENT STATIONS. 



observed with due care, good results may be expected. It is quite 

 important to have the face of the abutment both true and smooth 

 in order that the gates may set properly. This can be secured by 

 having the forms in perfect alignment and |)lastering the face with a 

 fine mortar. The abutment should be level on top when completed, 

 so it may be floored over and used as a bridge for crossing the channel. 



HEAD BEAM. 



In case of the wooden abutment, the head beam to which the gates 

 are hung is formed by bolting a piece of timber to the cap of the bent, 

 but on the stone or concrete abutment a head beam of 10-inch steel 

 channel weighing 20 pounds per linear foot, from which the gates are 

 hung, should be secured to the face of the abutment, as shown on the 

 drawing. Cast-iron fillers of a suitable pattern may be used at the 

 points of attachment to hold the channel out from the face of the wall 

 the thickness of the gates. 



SWINGING GATES. 



The essential features of a good tide gate are durability, tight 

 closing, and easy movement. They are made, as shown on the draw- 

 ing, of two thicknesses of material, the pieces of each layer being at 

 right angles to those of the other. Between the two is placed a sheet 

 of 8-ounce cotton duck, painted on each side with a heavy coat of 

 white lead and oil. The boards in each layer should be drawn up 

 tight with a clamp and securely bolted at each intersection with two 

 machine bolts with wrought washer under both head and nut. To 

 resist the action of the salt water, the bolts and washers should be 

 galvanized. If the workmanship is not of a high class so as to form 

 tight joints, the vertical seams, being the outside of the gate, may 

 be calked with three threads of cotton to j^revent leaking. In case 

 creosoted lumber can not be obtained, otlier lumber may be used, 

 but it should be thoroughly soaked by immersing it in water several 

 days before using. A suitable seat is formed by fitting to the inner 

 side near the edge a piece of 6-ply rul)ber belting 2^ inches wide. Tliis 

 can be secured to the wood with brass screws IJ inches long, with 

 heads sunk well ))elow the surface of the rubber. The gates should 

 be hung to the head piece by a doulde joint or link hinge, as shown on 

 the drawing. Such a hinge allows the gate to adjust itself to the face 

 of the abutment in closing, so as to form a tight joint on all sides, per- 

 mitting the water to rise above the top of the gate without leaking. 

 A suitable hinge probably can not be purchased in stock, but can be 

 made in any machine shop from the detail drawing furnished herewith. 

 The holes should be true and accurately bored and the bolts turned 

 and neatly fitted, so as to insure free movement. To withstand the 

 action of the salt water, it is desirable to make the hinges of hard 

 brass, or if iron is used it should be kept well painted and the bolts 



