864 Method of obviating 
could so construct the blocks on which the ship rests, that 
the weight of the ship might be applied to assist in the 
operation, he could accomplish this very desirable end. 
In September, 1800, the shoring and lifting the San Jo- 
sef, a large Spanish first-rate, then in dock at Plymouth, 
was committed to his directions ; to perform which, the 
assistance of the principal part of the artificers of the 
yard was requisite. In conducting this business, the 
plan, which will be hereafter described, occurred to his 
mind ; and from that time, he, by various experiments, 
proved his theory to be correct : the blocks, constructed 
by him, upon which the ship rests, being so contrived, 
that the facility in removing them, is proportionate to the 
quantity of pressure ; and this circumstance is always 
absolutely under command, by increasing or diminishing 
the angle of three wedges, which constitute one of the 
blocks ; two of which are horizontal, and one vertical. 
By enlarging the angle of the horizontal wedges, the 
vertical wedge becomes of consequence more acute ; and 
its power may be so increased, that it shall have a great 
tendency to displace the horizontal wedges, as was 
proved by a model, which accompanied the statement to 
the society ; where the power of the screw is used as a 
substitute for the pressure of the ship. 
Mr. Seppings caused three blocks to be made of hard 
wood agreeable to his invention, and the wedges of va- 
rious angles. The horizontal wedges of the first block 
were nine degrees ; of the second, seven ; and of the 
third, five ; of course, the angle of the vertical wedge of 
the first block was 16& degrees ; of the second, 166 ; 
and of the third, 170. These blocks, or wedges, were 
well executed, and rubbed over with soft soap for the 
purpose of experiment. They were then placed in a 
dock, in his majesty’s yard, at Plymouth, in which a 
sloop of war was to be docked : an examining them af~ 
