LOCKS. 169 



against the masonry. The tops of the posts are fastened to a similar timber, and the 

 latter is joined to the corresponding one on the opposite side by tie-rods 10 feet or 

 more apart, so that the dump-buckets can pass between. These tie-rods, and conse- 

 quently the tops of all the posts, are then held in rigid position by wire guys on each 

 side, running to the bank or to the coffer-dam, and tightened by means of long turn- 

 buckles or eye-bolts at their ends. When the forms are removed the bolts, which 

 should be greased before being imbedded, are drawn out, and the holes closed with 

 mortar. In one example the posts were of 3" X 8" timbers 4 feet apart, and it 

 was found that for a vertical span of 10 feet between supports they were scarcely stiff 

 enough to withstand the ramming. This could be remedied by providing intermediate 

 tie-rods and sleeve-nuts. This method has been advantageously modified by using guys 

 on one side only, combined with braces. The arrangement of the longitudinal tim- 

 bers was similar to that before described (except that an intermediate course was used) 

 those opposite being joined together by f" tie-rods provided with gas-pipe sleeves 

 about 2 feet from each end. The heads of alternate posts on one side of the wall, 

 at distances of about 10 feet, were provided with eye -bolts to which wire guys were 

 attached, and just below good braces were secured to the posts. The latter were then 

 brought to place and held rigid by adjusting each guy and its brace at the same time. 

 The opposite row of posts was then adjusted by the tie-rods, which passed through 

 the horizontal timbers, light struts being used on the top ones to assist in holding 

 them apart. The final adjustment of each post, where required, was secured by 

 wedging behind it against the timbers. 



If cast-iron quoins are to be used, the sections should be bolted in place on a long 

 timber, which must be perfectly straight and true. This should be then set up in exact 

 position and thoroughly braced so as to hold the quoin plumb and rigid during the 

 concreting. Where the forms extend from bottom to top, the sections are sometimes bolted 

 directly to the lagging.* 



If the lock is to be built by contract it is preferable to have the design of the 

 forms carefully worked out, and the drawings and specifications for them made a part 

 of the agreement. Few contractors have had much experience in building concrete 

 locks, and their knowledge of what is required for satisfactory forms is consequently 

 limited; while, on the other hand, the collective experience of the Government engi- 

 neers is large and should be sufficient to permit of obtaining the best results. If the 

 design is left to the contractor he will naturally endeavor to use cheap methods and 

 materials, whereas to secure a form that will give straight surfaces and a good finish 

 to the walls a considerable expense must be incurred, and unless suitable designs are 

 exhibited to the bidders as" a part of the contract, friction and dissatisfaction will later 

 result. Nothing is more annoying in this respect, either to engineer or to contractor, 

 than to have during concreting a constant lining-in of forms and lagging which have 

 got out of place because of want of stiffness in the posts or for lack of proper bracing. 



* See paragraph on " Quoins, in this chapter, and on ' Anchor Bars and Pintles," in the chapter following 



