142 TIDE-GAUGE DESCRIBED. \0dober, 



previously well secured, a good spar was lashed to tins 

 rope, and a fair strain kept on it for some days. The 

 rope thus became frozen like a solid wire ; the upper 

 end of this pole was connected by an iron clasp, with a 

 flat moulding or clock-chain formed of oak and copper. 

 To ensure its being at all times perpendicular, as in 

 pump-work in mines, etc., the radius pieces b b were at- 

 tached with channels for the chain to work in. This 

 balance-beam acted in a metal-formed crutch, with pin, 

 and was attached at the inner end by a similar chain 

 to the gauge-rod, which alone was sufficiently ballasted 

 to preserve a steady and even strain for the descent of 

 the gauge. Externally, to keep the pole steady to its 

 work and at a constant tension, an additional lever- 

 balance was employed, with a strain equal to 56 Ibs. 

 It is clear, then, that the bottom weight being too 

 heavy to be moved by any ordinary force, that the rise 

 of the ice, or ship, must draw up the index-bar; and, 

 being of itself considerably heavier than the outer pole, 

 etc., the descent of the ship must cause it to fall. All 

 this being covered by the housing iu-board, was pro- 

 tected from snow or any other inconvenience, and the 

 gauge occupied on the quarter-deck the position of the 

 wheel unshipped for the winter. Beside it, was a tem- 

 porary table and a lantern, illuminating the graduation, 

 and enabling the person watching to register it. But 

 our mode of registry, by equal altitudes, requiring the 

 time at each inch of rise or fall, a ratchet, or notched 

 edge, was cut on one side of the movable slide, which 

 acting on a one-toothed wheel, caused it to draw from its 

 perpendicular a plane board, at the lower end of which a 



