32 APPENDIX. 



and chopping sea; thus, 1, waves under one yard high; 2, waves under two yards high, 8cc. 

 Ch, chopping ; L, long ; R, rough cross sea ; S, smooth water ; Sw, swell. The draught of 

 water should be observed on all possible occasions. Draught or float gauges for this purpose 

 were formerly in use in the British navy, but have long since been discarded ; though it is 

 believed that all French ships of war are still fitted with them, and their use fully acknow- 

 ledged. The usual form of float gauges consisted of tubes communicating with holes 

 through the bottom ; one near the stem, another near the stern post ; the water flowing to the 

 same height in these tubes as outside the ship, and thus indicating her degree of immersion : 

 but as it is very inconvenient to increase the number of holes through the bottom, of which 

 there are unavoidably so many in steam vessels, it is recommended that two horizontal pipes 

 of small dimensions should be inserted, one in the bow, the other in the stern, about a foot 

 below the light draught water line, and at a few feet from the stem and stern post, choosing 

 some convenient spot on the round of the bow, directly over or vertical to the scarf of the 

 stem, for the foremost hole, and placing the after one over the mortice of the stern 

 post ; each of the pipes to be fitted with a cock, and communicating in some place easy of 

 access with a glass vertical tube, the tubes having graduated scales corresponding with the 

 ship's draught marks. On either cock being turned, it is evident the water will flow to the 

 same height inside as out ; and the ship's immersion may, in a tolerably smooth sea, be 

 read off with great facility and correctness, making it a rule always to stop the vessel 

 a few minutes for the observation : and when it is recollected the frequent slight stoppages 

 which a steam vessel makes on a long voyage, for the purposes of adjusting screws in the 

 machinery, paddles, &c. &c., which may always be seized as opportunities of observing 

 the immersion, the delay will hardly be objected to; 1 at all events, whether the gauge is 

 used or not, the draught of water should be observed on all possible occasions, and marked in 

 the journal, with the addition of the letters F or E, to denote the boilers being full or empty: 

 and as a very little experience will soon inculcate an adequate knowledge of the effect on 

 the ship's trim, produced by the consumption of fuel and provisions, the draught may be esti- 

 mated when it cannot be observed, and entered each day at noon in the proper column. 



This habit of continually inserting the immersion, and observing the effects pro- 

 duced as the draught varies, will draw the attention of the officer to the important 

 necessity of keeping his vessel in trim, by the judicious arrangement of coals or other 

 weights, and tend to make him familiar with her qualities; the judgment necessary to 

 be exercised, in applying the proper symbols to express the state of the wind and sea, 

 recording at the same time the rate of the engine, and the vessel's progress under every 

 variety of circumstance, will engender a large portion of useful practical knowledge ; and the 

 steam journal will become a valuable record of incalculable use, in promoting the science of 

 steam navigation. 



A table has been calculated, showing the rotary length of the path formed by the extremity, 



1 The plane of flotation of a vessel at rest, and the same vessel in rapid motion, is very different, even though the 

 sea be quite smooth ; it is consequently impossible to obtain the statical immersion of any ship when sailing or 

 steaming, either by actual observation or the use of any description of float-gauge ; though the immersion so 

 obtained, if it could be observed, would have more immediate reference to the actual resistance experienced by the 

 vessel in passing through the water. 



