RAILWAY CONSTRUCTION. 301 



splashing over the sides when disturbed during high winds. The 

 large pipe, A, is securely bolted at the bottom of the tank, and 

 forms a shield or funnel through which the supply pipe, B, passes 

 upwards into the tank. C is an overflow, or waste pipe, to 

 carry away any surplus which may find its way into the tank 

 after the water has risen to its fixed maximum height. All the 

 contact surfaces of the cast-iron tank-plates must be accurately 

 chipped or planed, and fitted to ensure water-tight joints. Stay- 

 rods must be placed at frequent intervals, connecting the vertical 

 or outer plates to the horizontal or floor plates. When required 

 to hold more than 20,000 gallons, it is better to make the tank 

 in two parts, by placing a permanent plate petition across the 

 middle, in reality making two separate tanks, which can be 

 connected or disconnected at will. The double tank arrange- 

 ment gives additional strength, and possesses the advantage that 

 the one tank can be emptied and cleaned out while the other 

 remains in service. 



Water-tanks constructed of wrought-iron or steel plates are 

 usually made circular in form, with vertical sides. The floor- 

 plates must be either carried on small girders, as in the cast-iron 

 tank, or be strengthened internally with angle-irons, tee-irons, 

 and tie-rods. The rivetting must be well done, all joints sound 

 and watertight. This class of tank must be kept well painted, 

 or oxidization will take place very rapidly. The arrangement 

 of inlet, waste-pipe, and delivery pipe may be the same as for the 

 cast-iron tank. Although frequently seen abroad, these circular 

 wrought-iron tanks are not often adopted at home. By many 

 the appearance of the circular tank is considered inferior to one 

 of neat rectangular shape, and the form of the round tower does 

 not lend itself so conveniently for use as a pump-room or store. 



There may be no practical difficulty in constructing a large 

 circular wooden vat or water-tank, but there cannot be any 

 great actual economy, except in those countries where suitable 

 timber is very cheap, and iron very dear. The wooden tank 

 must be made of selected materials, and by skilled workmen ; 

 but however carefully constructed it, cannot be expected to last 

 so long as an iron tank. In many parts of the United States of 

 America there are excellent examples of the circular wooden 

 tank, strongly put together, and covered with a light ornamental 

 roof. Numbers of these wooden tanks have been erected there 

 in places where the cost of carriage alone of an iron tank would 



