In former times Trinidad certainly was, and I believe still is, the most unhealthy of all our West Indian possessions. In certain situations, and in many of the other islands in particular districts, disease may be more prevalent, and the mortality comparatively greater; but in no other are the effects of the malaria so generally diffused, or so constantly experienced, as in this island. The atmospheric temperature is seldom above the average range common in these latitudes. In the plain in which Port of Spain is situated, it is about 86° of Fahrenheit; but the range between the highest and the lowest degree, during twenty-four hours, is greater here than in any of the other colonies that I am aware of: the nights actually feel cold. It is not, however, any great difference of the temperature that renders the island unhealthy; it is that great extent of uncultivated land, and more especially of that land which is not fit for cultivation, which still exists, and constitutes by far the largest portion of the island. The poisoned vapour constantly hangs as a dense cloud over these savannahs, and from thence penetrates into every valley, and finds a speedy passage to every hill-top. Under certain circumstances, this Miasm, or marsh-poison, becomes greatly augmented in quantity, and more virulent in its quality; and then it is that we find the fevers more frequent, and the symptoms greatly aggravated.