SLIPWAYS. 313 



examined, and full advantage taken of daylight, which in 

 winter-time is of some importance. There being perfect 

 ventilation all round, a ship's sides are soon dry. 



Amongst the disadvantages to be taken into consideration 

 are, the wear and tear on the carriage, road, and hauling-gear is 

 considerable ; and when the road-timbers project far into the 

 water, they are very liable to injury from passing vessels. 



Slipways which project far into the channel beyond low- 

 water mark may deflect the current, and thereby lead to the 

 formation of shoals to the detriment of navigation. 



An objection to the adoption of a slipway for ships of great 

 tonnage would be the great length required under water in any 

 locality where the rise and fall of tide is not considerable. 

 This objection would have still greater force where the range of 

 tide is practically nil, or where it might be necessary to take up 

 a ship at dead low water. 



In some localities, such as on the shores of narrow rivers, 

 slips arranged for hauling up ships of moderate dimensions, 

 broadside on, may be adopted with advantage. 1 



For long ships, steamers especially, the objections to a slip 

 appear to be serious, inasmuch as the head would be fixed, and 

 begin to lift whilst the remainder of the vessel would be more 

 or less afloat, and the hauling would continue for some time 

 before the whole length would be taken up and be supported by 

 the cradles. In the mean time, the vessel would be subjected to 

 very serious strains. 



For the purpose of storing small vessels, such as gunboats, 

 torpedo-boats, steam-launches, or yachts, which could be more 

 efficiently examined and kept in a better state of repair on 

 shore than afloat, slipways are well adapted. The arrangements 

 should be such that a large storage area may be served by one 

 slipway, so that the cradle, after drawing up and depositing one 

 vessel, may be speedily returned for another. 



The inclination of the ways can generally be determined at 

 once by a consideration of the amount and value of land 

 available, by the depth of water it is necessary to provide over 

 the carriage or cradle when at its lowest position, and by the 

 natural slope of the ground. 



As a rule, gradients of 1 in 13 to 1 in 22 have been adopted ; 

 1 in 19 being a suitable slope for a large slipway ; 2 but these 

 1 M.P.I.C.E., vol. Ixxii. p. 157. * Ibid. t p. 137. 



