The subject which I have the honor to bring shortly before your notice this evening is one that formed the basis of some instructive remarks by Dr. Redwood in November, 1855, and also of a paper by Dr. Hassall, read before the Society in London in January, 1856, which latter gave rise to an animated discussion. The work detailed below was well in hand when Mr. MacEwan drew my attention to these and kindly supplied me with the volume containing reports of them. Unfortunately, they deal principally with the adulterations, while I was more particularly desirous to learn the composition in a general way, and especially the percentage of coloring resin, the important constituent in commercial annatto. Within the last few years it was one of the articles in considerable demand in this part of the country; now it is seldom inquired for. This, certainly, is not because butter coloring has ceased to be employed, and hence the reason for regretting that the percentage of resin was not dealt with in the articles referred to, so that a comparison could have been made between the commercial annatto of that period and that which exists now. In case some may not be in possession of literature bearing on it--which, by the way, is very meager--it may not be out of place to quote some short details as to its source, the processes for obtaining it, the composition of the raw material, and then the method followed in the present inquiry will be given, together with the results of the examination of ten samples; and though the subject doubtless has more interest for the country than for the town druggist, still, I trust it will have points of interest for both. Annatto is the coloring matter derived from the seeds of an evergreen plant, _Bixa Orellana_, which grows in the East and West Indian Islands and South America, in the latter of which it is principally prepared. Two kinds are imported, Spanish annatto, made in Brazil, and flag or French, made mostly in Cayenne. These differ considerably in characters and properties, the latter having a disagreeable putrescent odor, while the Spanish is rather agreeable when fresh and good. It is, however, inferior to the flag as a coloring or dyeing agent. The seeds from which the substance is obtained are red on the outside, and two methods are followed in order to obtain it. One is to rub or wash off the coloring matter with water, allow it to subside, and to expose it to spontaneous evaporation till it acquires a pasty consistence. The other is to bruise the seeds, mix them with water, and allow fermentation to set in, during which the coloring matter collects at the bottom, from which it is subsequently removed and brought to the proper consistence by spontaneous evaporation. These particulars, culled from Dr. Redwood's remarks, may suffice to show its source and the methods for obtaining it.