In such an extensive and distant survey, numerous subjects of inquiry, though not strictly nautical, will suggest themselves to your active mind; and though, from your transient stay at any other place, you will often experience the mortification of leaving them incomplete, yet that should not discourage you in the collection of every useful fact within your reach.  Your example in this respect will stimulate the efforts of the younger officers under your command, and through them may even have a beneficial influence on the future character of the navy.

It has been suggested by some geologists, that the coral insect, instead of raising its superstructure directly from the bottom of the sea, works only on the summits of submarine mountains, which have been projected upwards by volcanic action.  They account, therefore, for the basin-like form so generally observed in coral islands, by supposing that they exist on the circular lip of extinct volcanic craters; and as much of your work will lie among islands and cays of coral formation, you should collect every fact which can throw any light on the subject.

Hitherto it has been made a part of the duty of all the surveying vessels to keep an exact register of the height of the barometer, at its two maxima of 9, and its two minima of 3 o’clock, as well as that of the thermometer at the above periods, and at its own day and night maximum and minimum, as well as the continual comparative temperature of the sea 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.