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XXI. Observations on the temperature of the ocean and atmo- 
sphere , and on the density of sea-water, made during a voyage 
to Ceylon. In a Letter to Sir Humphry Davy, LL. D 
F. R. S. By John Davy, M. D. F. R . S. 
Read May 22, 1817. 
My Dear Brother, 
According to the promise contained in a former letter, I 
proceed to give you a short account of the observations which 
I made during my late voyage from England to Ceylon. At 
present, I shall confine myself chiefly to three topics, the 
specific gravity of the water of the ocean, and its tempera- 
ture, and the temperature of the atmosphere; subjects of 
some importance in the natural history of our globe ; and 
in which, I know, you are interested. Incidentally I shall 
notice the height of the barometer, the direction of the winds, 
and the state of the weather. 
For the sake of brevity, I shall present the principal results 
of my observations in the form of a table, to which I shall 
add some explanatory notes and general remarks. 
