and air. This was done with the view of assisting to provide authentic
data, collected from all parts of the world, and ready for the use of
future labourers, whenever some accidental discovery, or the direction of
some powerful mind, should happily rescue that science from its present
neglected state. But those hours of entry greatly interfere with the
employments of such officers as are capable of registering those
instruments with the precision and delicacy which alone can render
meteorologic data useful, and their future utility is at present so
uncertain, that it does not appear necessary that you should do more than
record, twice a day, the height of the former, as well as the extremes of
the thermometer, unless, from some unforeseen cause, you should be long
detained in any one port, when a system of these observations might then
be advantageously undertaken. There are, however, some occasional
observations, which cannot fail of being extensively useful in future
investigations:

1. During the approach of the periodic changes of wind and weather, and
then the hygrometer, also, should find a place in the journal.

2. The mean temperature of the sea at the equator, or, perhaps, under a
vertical sun. These observations should be repeated whenever the ship is
in either of those situations, as well in the Atlantic as in the Pacific;
they should be made far away from the influence of the land, and at
certain constant depths, suppose fifty and ten fathoms, and at the
surface also; and this last ought to be again observed at the
corresponding hour of the night.

3. A collection of good observations, systematically continued, for the
purpose of connecting the isothermal lines of the globe, and made, as
above, at certain uniform depths.