When true ground cinnamon and cassias are examined microscopically with polarized light, differences are revealed at once which are characteristic enough to distinguish the specimens, as shown in Figs. 41 and 23, Chap. III. But of the proximate chemical composition of any of the barks but little is known. Numerous determinations and analyses of the ash have been made with a view to detecting peculiarities or the addition of mineral matter. The percentage of ash is extremely variable, depending on the age and quality of the bark. Saigon chips have been known to have 8.23 per cent., while unknown cassia bark has been found with but 1.75 per cent. Cinnamon bark will be likely to average less than cassia. Fiber-like ash is very variable, Saigon yielding 26.29 per cent., true cinnamon 33.08 per cent., while unknown cassia gives 14.20; that containing the least fiber contains the smallest amount of lime. The albuminoids are also variable; the Batavia and Saigon barks appear to contain the most. The presence of over 4 per cent. is an indication of an inferior quality. The amount of the tannin runs extremely small, any addition of which can be readily detected. One-fourth of the ash of cinnamon is soluble in water, but less of “Cassia Vera,” and less yet of cassia lignea. Little has been learned which would form a sound basis for distinguishing these barks. The presence of manganese cannot be considered as indicating that substance an essential element of the ash, nor is the fact one from which such definite conclusions could be drawn as to serve as the basis of legal testimony, but it is what gives to the different barks their different colors. True cinnamon contains less than 1 per cent. of oxide of manganese; “Cassia Vera” more than 1 per cent., and cassia lignea as high as 5 per cent. The essential oil is but 0.5 to 1 per cent. of the bark of cinnamon and much less in inferior cassia. We also find the presence of mucilage, coloring matter, resin, acid, starch, and lignea as well as volatile oil. Aside from the determination of volatile oil upon which the properties of cassia bark depends, chemical analysis seems to be of little value; the principal dependence must, with our present knowledge, be placed on the mechanical and microscopic examination. To detect the adulteration of oil of cassia by oil of cloves, a drop of the oil should be heated on a watch glass. Genuine cassia evolves a fragrant vapor possessing but a little acridity. When, however, clove oil is present, the vapor is very acrid and excites coughing. With fuming nitric acid, cassia merely crystallizes; but if cloves be present it swells up, evolves a large quantity of red vapor and yields a thick reddish-brown oil. Pure cassia oil solidifies with concentrated potash but will not when mixed with clove oil.