4.?6 SURVEY OF THE INTERTROPICAL ism. daily range of the thermometer was as much as o?. ?. 20% while the mercury on board did not rise or fall more than 3 �4 �his great difference is to be attributed to the cooling power of the dew, which was precipitated most copiously every night upon the surface of the earth: whilst the water, not being so easily affected by this nightly radiation, took so much longer to cool. In the day-time the reverse took place; for the earth being much more heated by the action of the sun's rays than the water, the temperature on shore was much greater than on the sea. We had no thermometer with us that could measure the heat of the sand upon which our tents were erected. Mr. Hunter placed his pocket-thermometer in it, but the mercury reach. ing the top of the tube, which was graduated to 130 �e was obliged to withdraw it to preserve the instrument from being damaged. On one occasion we had a hot land-wind from the S.F_,., that veered round as the day advanced to N.E., during which the thermometer stood at 96�- nerally, however, we had a fresh sea-breeze from the north-west, with dear and fine weather; but, towards the latter part of our visit, we had some very cloudy dull days, and a few showers of rain: this change hurried my departure; and we considered ourselves fortunate in embarking
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