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fore the Academy, with models and drawings to illustrate; 

 it. The inventor first gave a rapid description of the 

 several methods of taking ships out of water for repair, 

 which have been in use from the earliest times to the present 

 day, viz., by — 



1. Stranding on bilge ways. 



2. Careening. 



3. The machine called the Camel, invented about 1680. 



4. The graving dock. 



5. Morton's patent slip. 



^ rrii 11 r Both comparatively recent Ame- 



b. 1 he screw dock. \ . . ^ . "^ , , , 



- mi 1 1 1. , 1 s vican inventions, and only used 



7. Thehydraulicdock. i , j j . 



8. The floating dock of the River Tyne, used at New- 

 castle. 



He then pointed out the several disadvantages to which 

 each of these is severally liable. 



These are briefly, in the first case, costliness, tedious- 

 ness, straining of the ship, and imperfect access to the hull. 

 In the second, great danger and imperfect access to the hull. 

 The Royal George was sunk by careening her. In the 

 third case, want of access to the ship — impossibility of ex- 

 posing the whole hull — straining of the framing, and danger. 

 In the fourth or graving dock, great original outlay ; great 

 labour and loss of time in pumping out water where rise of 

 tide is small ; loss of two or three hours of daylight every 

 day by the sunken position of the ship, and awkwardness in 

 handling long spars or timber ; difiiculty of inspection, and 

 unhealthiness of situation to workmen ; and, lastly, dotting 

 of timbers, from the constant damp atmosphere of a sunk 

 or graving dock. 



Morton's slip overcomes most of these evils, but has 

 some peculiar to itself. Ships can only come on and go 

 off the slip at high and low water ; hence, in large ves- 

 sels, the loss of one tide is often the loss of a fortnight ; 



