About three years ago, I received from my friend Dr Watt of West Coast, Demerara, specimens of the bark of a tree, native of British Guiana, which had been found by Mr Rodie, late surgeon R.N., to contain a vegetable alkali, and to possess some value as a remedy in the intermittent fevers of that colony. Mr Rodie made known his discovery by means of a letter which he published in the year 1834. I made some experiments with the piece of bark, at that time in my possession; but the conclusions at which I then arrived did not appear to be worthy of being published. It was obvious to me, however, from the results which I obtained, that Mr Rodie's statement was so far correct, that the bark did contain a bitter matter, having all the general characters of a vegetable alkali, and capable of forming neutral compounds with acids. The exhaustion of my original little store of materials prevented me from proceeding farther, till last year, when,through the kindness of Dr Watt, I received a barrel of the bark, and likewise of the fruit of the plant.