This occurred in latitude 25-1/2 deg.

N., where, according to our inexperienced conception of these singular winds, we ought to have found a regular breeze from the very opposite quarter! Nor was it till long afterwards that I learned how much the force and direction of the Trade-winds are liable to modification by the particular position which the sun occupies in the heavens; or how far the rotatory motion of the earth, combined with the power which the sun possesses of heating certain portions of the circumambient air, are the regulating causes of the Trades, Monsoons, and, indeed, of all the other winds by which we are driven about.

It is by no means an easy problem in meteorology to show how these causes act in every case; and perhaps it is one which will never be so fully solved as to admit of very popular enunciation applicable to all climates.

In the most important and useful class of these aerial currents, called, _par excellence_, and with so much picturesque truth, "the Trade-winds," the explanation is not difficult.

But before entering on this curious and copious theme, I feel anxious to carry our convoy fairly across the tropical regions; after which an account of the Trades will be better understood.
I have just mentioned that the changes of temperature, on a voyage to India, are most remarkable.