USEFUL PROJECTS 



871 



two of which arc horizontal and one 

 vertical. By enlarging the angle of 

 the horizonta,! wcdgt»s, the vertical 

 wedge becomes of consequence more 

 acnte ; and its power is so increa-ed, 

 that it has a greater tendency to 

 displace the horizontal wedges, a.3 

 can be proved by a model*, whore 

 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 invcuticn, and the \Vcdges of 

 ' ' various angles. The horizontal 

 wedges of the first block were nine 

 degrees, of the second seven, and 

 of the third five ; of course the an- 

 gle of the vertical wedge of the first 

 block was 162 degrees, of the second 

 1G6, and of the third I70. These 

 blocks or wedges were well exe- 

 cuted, 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 xVar was to be 

 docked ; on examining them after 

 the vessel was in, and the water gone, 

 they were all found to have kept 

 their situations, as placed before the 

 ship restt'd upon them. Shores in 

 their wake were then erected to 

 sustain the ship, prior to the said 

 blocks being taken from under the 

 keel. The process of clearing them 

 ^as by applying tlie power of bat- 

 tering-rams to the sides of the outer 

 ends of the horizontal wedges, 

 alternate blows being given fore 

 and aft, by which means they imme- 

 diately receded, and the vertical 

 wedges were disengaged. It was 

 observed, even in this small ship, 

 that the block which was formed 

 of horizontal wedges of nine de- 

 grees, came away much easier than 



those of seven, and the one of seven 

 than that of five. In removing the 

 aforesaid blocks by the pow er of the 

 battering rams, which were suspend- 

 ed in the hands of the men employ- 

 ed, by their holding ropes passed 

 through holes for that purpose, it 

 w^s remarked by Mr. Se]>pings, that 

 the operation was very laborious to 

 the people, they having to support 

 the Wfigl)t of the battering-rams, 

 as well as td set them in motion. 

 He then conceived an idea of affix- 

 ing wheels near the extremity of that 

 part of the rams which strike* 

 the wedges. This was done before 

 the blocks were again placed ; and 

 it Juts since been found fully to an- 

 swer the purpose intendedj particu- 

 larly in returning the horizontal 

 wedges to their original situations, 

 when the work is performed for 

 which they were displaced j the whceis 

 also giving a great increase of pow- 

 er to the rams, and decrease of la- 

 bour td the artificers ; besides which j 

 the blows are given with much more 

 exactness. The same blocks Avere 

 asain laid in another ddck, in whic'i 

 a two-decked shipi of the line was 

 docked. On examination, they were 

 found to be very severely pressed, 

 but were removed with great case. 

 They were again placed in another 

 dock, in which a three-decked ship 

 of the line was docked. This ship 

 having in her foremast and bowsprit, 

 the blocks were pat quite forward, 

 that being the part which presses 

 them with the greatest force. As 

 soon as the water was out of the 

 dock, it was obserred, that the ho- 

 rizontal wedges of nine and seven 

 degrees, had receded some feet from 

 their original situations. This af- 

 forded Mr. Seppings a satisfactory 

 prdof, which experience has since 

 3 K 4 demon* 



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