CHAPTER VII. 



Closing entrances Principal points to bo kept in view Gate-platform Quoins- 

 Gates Heel-post Timber gates Metal gates Form of gates Rise of 

 gates Nipping Staunchness Opening and closing gates Hydraulic rams 

 and chains Direct-acting rams Gate rollers Support to gates in rough 

 weather Stay-gates Dunkirk Dock gates Amsterdam Ship Canal gutes 

 Avonmouth Dock gates Whitehaven Dock gates Barry Dock gates San- 

 fernando Dock gates Alexandra Dock gates, Hull West India Dock gates- 

 Caissons Sliding caissons Floating caissons Floating box caissons Caisson 

 at Limekiln Dock Barry Dock caisson Kowloon Dock caisson Esquimalt 

 Dock caisson Cerro Dock caisson Garvel Dock caisson. 



Closing Entrances. The principal points to be kept in view 

 in determining the method to be adopted in closing dock and 

 lock entrances are safety in working, rapidity of manipulation, 

 and facility of inspection and keeping in repair ; local con- 

 ditions as to site will also have considerable weight. The 

 choice vests between gates and caissons. 



Where gates are adopted, the passage is constructed with 

 substantial side walls and sill against which the gates close. The 

 bottom may be in the form of an inverted arch, or as a flat floor 

 of masonry, depending somewhat upon the dimensions of the 

 entrance, the materials used, and the conditions obtaining as 

 regards the site. 



In each side wall recesses are formed of a depth sufficiently 

 great to admit of the gates, when opened, being completely 

 housed so as to be well clear of the fairway of the entrance. 



The gate-platform, or that part over which the gate travels 

 when swinging, is level, and of course below the lowest point of 

 the sill ; the step thus formed becomes the sill against which the 

 gates press. The face of the sill is vertical, and must be so truly 

 dressed as to form a perfectly water-tight joint with the gates 

 when closed. 



The end of the recess corresponding with the free end of the 

 gate is termed the square quoin, and forms a protection to the 

 gate when laid back in the recess ; they require to be of consider- 

 able strength, in order to meet the heavy blows and general hard 



