^248 Mr Livingston on the Thermometer as an Indkator 
to the northward of 43” 1 2', in which latitude the thermometers 
used by Mr Mason, on board the ship Eliza packet, were un- 
fortunately broken : nor have I heard of any made to the 
southward of Cape Hatteras anterior to these, of which the re- 
sults are recorded in the above mentioned journal. 
I'lie public, and mariners in particular, owe much on this 
subject to the labours of Mr Purdy, hydrographer, London, 
who, in his well arranged memoir, intended to accompany his large 
chart of the Northeni Atlantic, has treated at considerable length 
those silent, imperceptible,"’* but dangerous enemies of safe na- 
vigation, currents^ to which he has doubtless directed the 
attention of many, and put them on their guard against their 
perilous elfects. In the same work, Mr Purdy has also taken no- 
tice of the variations of temperature in the w^ater upon the coasts of 
the United States ; and I have reason to believe has induced o-? 
tilers as well as myself, to devote some attention to the subject. 
My first experiments were made in October 1817, on a voy- 
age from Philadelphia to Kingston, in Jamaica. I began them 
inside the Capes of the Delaware, (i. e. in the Delaware Bay), 
and continued them to Jamaica ; but the journal of my voy- 
age was lost on board a schooner, which upset in March 1818. 
I well recollect, however, that in the bay, the mercury in a 
Fahrenheifs thermometer stood at 60° or 61°; about ten or 
tw’eive miles outside the capes, it rose to 66°, and afterwards, when 
we entered into the limits of the gulf stream current, as it sweeps 
along the American shore, it rose to 78°, from which it did notva- 
ry until we passed to the southward of the parallel of Bermuda. 
I have heard, but upon vague authority, that some experi- 
ments made on and near the bank of soundings to the south- 
westward of Ireland, exhibited a difference of two degrees of 
Fahrenheifs scale, between the ocean water and the water on 
the bank, the latter being of a lower temperature. Many cir- 
cumstances lead me to incline to the opinion, that to the north- 
ward of the Tropic of Cancer, in the Northern Atlantic, the 
thermometer is an useful indicator of an approach to land. I 
am, however, far from recommending that implicit confidence 
should be placed in it, but shall be happy if my suggestions of 
the probability of its being useful should induce others to make 
the neccstiiiry experiments to ascertain the fact in the various 
places which may suit their convenience. 
