The crust of the clayish earth is covered with a reddish brown covering of about half a millimeter in thickness. This covering proves to be composed, under the microscope, of cellular filaments and various shaped bodies of various composition. They are made up of cells with densely and coarsely granulated reddish colored contents--shape, size, and composition are very variable, as shown in the figures. _The cellular bodies make up the essential organic part of the clayish substance, and, without any doubt, if anything of the organic compounds of the substance is in genetical connection with the disease, these bodies would have this role_. The structure and coloration of cell contents exhibit the closest alliance to the characteristics of the division of Chroolepideæ and of this small division of Chlorophyllaceous Algæ, nearest to Gongrosira--a genus whose five to six species are inhabitants of fresh water, mostly attached to various minute aquatic Algæ and mosses. Each cell of all the plants of this genus produces a large number of mobile cells--zoospores. Fig. 9 represents very probably one zoospore developed from these plants as figured from 10 to 16. * * * * * CARBON. M. Berthelot, in the _Journal de Pharmacie et de Chimie_ for March, states that from peculiar physical relations he is led to suspect that the true element carbon is unknown, and that diamond and graphite are substances of a different order. Elementary carbon ought to be gaseous at the ordinary temperature, and the various kinds of carbon which occur in nature are in reality polymerized products of the true element carbon. Spectrum analysis is thought to confirm this view; and it is supposed the second spectrum seen in a Geissler tube belongs to gaseous carbon. This spectrum, which has been recognized along with that of hydrogen in the light of the tails of comets, indicates a carbide, probably acetylene. * * * * * CANNED MEATS. By P. CARLES. When tinned iron serves for containing alimentary matters, it is essential that the tin employed should be free from lead. The latter metal is rapidly oxidized on the surface and is dissolved in this form in the neutral acids of vegetables, meat, etc. The most exact method of demonstrating the presence of lead consists in treating the alloy--so-called tin--with _aqua regia_ containing relatively little nitric acid. The whole dissolves; the excess of acid is driven off by evaporation at a boiling heat, and the residue, diluted with water, is saturated with hydrogen sulphide. The iron remains in solution, while the mixed lead and tin sulphides precipitated are allowed to digest for a long time in an alkaline sulphide. The tin sulphide only dissolves; it is filtered off and converted into stannic acid, while the lead sulphide is transformed into sulphate and weighed as such. * * * * *