70 Temperature of the Curibbean Sea. 



holes in the top and bottom, admitted free access of the water 

 to a second thermometer, of similar construction to the first. 

 The opportunity was very favourable for the object, the 

 weather being fine, with light airs and but little swell : the 

 1230 fathoms run out in rather more than 25 minutes, 

 at the expiration of which time the line was fairly on the 

 quarter, the ship's drift having been bodily to leeward, with- 

 out her having had either head or stern way ; there was con- 

 sequently much less stray line than had been anticipated. 

 The best practical judgement which Captain Clavering could 

 form on the spot was, that the depth to which the thermo- 

 meters had actually attained must have exceeded a thousand 

 fathoms, as an allowance of the remaining 230 fathoms for 

 stray line would certainly be more than ample, if no bight of 

 consequence existed in the rope, which, from the appearance, 

 and from the rapidity with which the weight drew out the 

 line, might be judged the case : 230 fathoms would equal a 

 drift to leeward of iths of a mile in 25 minutes, whereas that 

 of the ship did not exceed \ a mile an hour; it is more than 

 probable, therefore, that the depth is underrated when it is 

 estimated at 1000 fathoms, or 6000 feet. The line was hauled 

 in in 53 minutes, and the thermometers came up in good or- 

 der ; the one in the cylinder to which the water had free ac- 

 cess had registered 4?5°'5 ; the attempt to exclude the water 

 from the other cylinder did not in this instance altogether 

 succeed, in consequence of the top not having been screwed 

 down sufficiently close upon the leather; this thermometer 

 had registered 49 0, 5 ; the difference of 4° may be attributed, 

 perhaps, partly to the latter not having been so long in con- 

 tact with the cold water as the other thermometer, as the wa- 

 ter appeared to have had great difficulty, and was probably 

 some time in forcing its way into the interior of the closed 

 cylinder ; and partly to the heat which so great a thickness 

 of metal would retain for a considerable time; the surface 

 water was from 82 0, 5 to 83°*2 in the course of the afternoon ; 

 the difference of temperature between the surface, and a depth 

 exceeding 1000 fathoms, was therefore 33°-3 by one ther- 

 mometer, and 37 0, 3 by the other, the indication of the latter 

 being entitled to the most reliance. 



" It may be reasonably inferred, that one or two hundred 

 fathoms more line would have caused the thermometer to have 

 descended into water at its maximum of density, as depends 

 on heat, below which, consequently, no further diminution of 

 temperature would take place; this inference being on the 

 presumption that the greatest density of salt water occurs, as 

 is the case in fresh water, at several degrees above its freez- 

 ing point." 



