BOLLARDS AND WHARF MOORINGS. 



405 



vessels, general merchandise, or coal trade, or passenger traffic. 

 Each will have its characteristic requirements. Generally the 

 term comprises all those appliances necessary for the expeditious 

 handling of ships, the materials and stores used in their con- 

 struction, the rapid manipulation of merchandise of all descrip- 

 tions, or for the comfort and convenience of a large number of 

 travellers. These appliances comprise shops and manufactories 

 of every description, storehouses, cranes, capstans, moorings, 

 coal-hoists, railways, lighting, water service, drainage, etc. 



Bollards and Wharf Moorings. Timber is objectionable for 

 this purpose on account of its liability to decay, and to be cut 

 and worn by the friction of ropes and chains. 



Granite, when well-proportioned and dressed, presents an 

 excellent appearance, and is well calculated from its hardness 

 to resist the wear of chains and hawsers. It is, however, com- 

 paratively deficient in transverse strength, and on this account 

 is not well fitted to resist the sudden and severe strains to 

 which bollards are occasionally sub- 

 jected, therefore the dimensions re- 

 quired to provide sufficient strength 

 are such as to render a mooring bollard 

 of this kind inconveniently large and 

 obstructive. 



Wrought-iron rings to act as moor- 

 ings are, under favourable conditions, 

 fixed in the face of the wharf wall, 

 secured by massive eye-bolts or staples 

 passing through the wall, and secured 

 with large washers and nuts at the rear. Such moorings are 

 useful when they can be approached from the water, and when 

 properly recessed into the wall face present little obstruction. The 

 rings and staples are usually made from bar iron, 3 to 6 inches 

 in diameter, the internal diameter of the rings varying from 

 15 inches to 24 inches in diameter. Mooring-rings should be 

 hung so that the plane of the ring is vertical in all positions, 

 that is, the axis of the hole in the eye-bolt should be vertical, 

 not horizontal. 



Hollow bollards of cast iron possess the greatest advantages. 

 Such a bollard is cheap, durable, and comparatively light, and 

 occupies but little space. 



To arrive at a practical estimate of the strains to be provided 



FIG. 354. 



