123 



it cannot be used in foul weather, or with the tail of the slip 

 in a tideway ; the average length of the inclined plane being 

 about five hundred feet, and the rate of elevation of a ship 

 from three to five feet per minute, the time of taking a 

 ship out of water, including the removal of the cradle, oc- 

 cupies from four to six hours ; and hence, though nominally 

 cheap, this is by loss of time really a dear mode of repair to 

 the ship-owner — the ship lies on an inclined plane, which is 

 inconvenient in hoisting or lowering heavy parts, particularly 

 in steam-ships. The hull is always strained, and new cop- 

 pering is often found wrinkled, by the ship running off the 

 slip, and receiving unequal support from the water meeting 

 her at an angle to her plane of stable floatation. The vibra- 

 tion of the numerous rollers is also injurious in the same 

 way. 



The American screw and hydraulic docks have the ad- 

 vantage, in point of speed, when in use ; but are unsafe for 

 large ships, and awkward in the posture of the ship's 

 hull. 



The Newcastle- on-Tyne floating dock possesses all the 

 disadvantages (except original costliness) of the graving 

 dock, and is without the safety of the latter. 



The author then explained the nature of his own method, 

 and exhibited it in action by means of a large working 

 model ; without plates it is difficult 'to describe this com- 

 bination. The vessel to be raised, floats in over a timber 

 platform of a suitable size laying at the bottom, and by 

 means of two very powerful cabstern cranes, actuated by a 

 small steam engine, and acting on two large flat linked 

 chains, the platform is raised above the surface of the water, 

 bringing up the vessel along with it, and placing her upon 

 a suitable level for the convenience of workmen to get under 

 and round the hull, for which the platform is specially adapted. 

 The two chains spoken of lay horizontally at either side 

 of the platform, and above it, and are armed with rollers at 



