£49 
a Ship's Approacli to Land. 
The thermometrical journal from which the subsequent tabie- 
is extracted, was commenced at New Orleans on the 15th August 
1818, but I had previously kept memoranda of the greatest 
rise and fall of the mercury for some days. Its greatest alti^ 
tude in the air was 96° in the shade a few days prior to that 
date ; but having lost these memoranda, I do not recollect 
the day, and it never fell, even during the night, lower than 
85°. While we lay for some days at Balize, waiting for wind 
and tide to get over the bar, the average heat of the air at noon 
v/as 89°5 and the thermometer in the water stood regularly at 
88 °, even when sunk to the depth of about four fathoms. 
In making the experiments, the utmost care was taken 
that they should be accurately performed. The air and water 
thermometers had been attentively compared, and found exact- 
ly to agree when placed together ; and a tin case, loaded with 
lead, was fitted to the instrument used for ascertaining the tem- 
perature of the water, for the double purpose of avoiding sur- 
face water, which might be supposed to be in some degree af- 
fected by the intensely hot solar rays, and of retaining water 
at the same heat round the tube, until stich time as the instru- 
ment could be hauled on board, and the height of the mercu- 
ry read off from the scale. The experiments were regularly re- 
peated once in every watch, or four hours, but in particu- 
lar situations they were made much oftener. The annexed 
table will shew that (at least at that particular season of the 
year), the nearness of land^ or soundings, in the Gulf of Mexi- 
co, and in the strait between Cuba and the Tortugas, and 
Martyr’s Reefs, had no effect on the thermometer ; but that as 
soon as we passed Cape Florida, the very first opportunity we 
had of making a satisfactory experiment, viz. on the 11th Sep- 
tember at 8 P. M, when conscious of our proximity to the 
shore to the southward of Cape Canaveral, it will be perceiv- 
ed how faithful a monitor it proved ; and the same held good 
along the coast of America, as far as the 36th degree of lati- 
tude. Indeed, after the first two days subsequent to our quit- 
ting the strait, I had acquired such confidence in this valu- 
able instrument, that when confined below by fever (being to- 
tally unable to keep the deck), I caused the thermometer to be 
regularly examined every two hours, and somctiipes much of- 
3 , 
