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Description: |
| "...we employ a 'percussion gage,' the principle upon which its action is dependent being that of the percussive action of a flat surface acting horizontally upon a port of the water, the height of which is to be gages... The form of apparatus that we have used, and which has answered the purpose perfectly well, consists of a cylinder furnished with a loosely fitting piston, that may be suddenly brought down within said cylinder without any sensible resistance from friction or steam..." |
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