It has unhappily been, for a longtime, as difficult as it is important. If the plain and marked characteristics of the two animal species often disappear; if a skilful analysis, enlightened by direct comparison with analogous objects, can alone discover them, how can the anthropologist size between two neighbouring types, express and transmit by description, light, fleeting distinctions, some times invisible for him, who has not the habit of observing them?

Three inventions or new application, made almost simultaneously, have happily removed part of the great difficulties, and opened a new era in the natural history of man; the daguerreotype, which fixes and engraves with geometrical precision, the general shape of the body and the features of the face; the Cephalometer of Antelme M. D. which measures and sketches with a process almost as exact, the dimensions and forms of the head, and enables one to determine, as nearly as possible, the mean dimensions and typical form of the head of a people the sex and age: in fine, the perfection and happy application to anthropology of the process of moulding, performed directly, or by the aid of the ingenious physonotype of M. Sauvage; a process by which the whole head and, if necessary, the members of the body are preserved and placed before our eys.

We have the hope that, with the aid of the Daguerreotype and physionotype, the american naturalists will enrich anthropology with results of great interest. By photographic portraits, such as those presented to the Academy by M. Thiesson; by mouldings to be added to the fine collection made by M. Dumoutier, now in the museum; by colored drawnings, by descriptions and measures, they would transmit us information of extreme precision, true scientific elements, to which the committee would attach the greatest importance.

We think it our duty to direct the researches of the american naturalists, not only to the different varieties of the American race, but also to the half-breeds, yet so little known, of both, and, also, to the offspring of the crossing of the first with the Caucasian race. We request them, as soon as they shall have determined exactly the physical characteristics of these difficult varieties, to neglect no information that may enlighten us as to their intellectual capacity.

We would, likewise, entreat these gentlemen to specify exactly and express by colored drawnings done with care, the different states of the hues of the American races and half-breeds, from the moment of their birth up to the period that they arrive at the normal color of their kind.

We would desire them, besides, to collect, of these same races, their half-breeds, and the white race, more minute particulars than as yet obtained, on the duration and difficult phases and epoch of puberty.

Chemistry and agriculture.—These are the principal forms that allow the use of Caoutchouc without dissolving it and without altering the heat.

1o Straight tubes; elbowed tubes; tubes in T of different thickness and diameter;

2o Full cylinders, to be cut in France as wanted;

3o Rectangular plates, cut in France;