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Rh phenomena into consideration, and, making due allowance for the weakness of his pigments, to incorporate the apparent tints into his picture. Here, again, what Nature with her vivid colors does in an instant, the artist has to bring about more slowly; but the illusion is complete in both cases from the moment our conceptions are brought into accord with it.

There is, furthermore, something in the colors of natural objects which is distinct from the strength and clearness of the illumination, and appears peculiar to certain kinds of light. Among such peculiarities are the metallic luster, the silken sheen, and opalescence, which, although they all proceed from combinations of the spectrum-colors, have not yet been sufficiently investigated to enable us to determine all the circumstances contributing to produce them.

The colors used in painting afford little that is analogous with these lusters. Can the painter produce these effects also by contrast? They appear in pictures by the most eminent masters to be reached almost in perfection. If, however, we inquire whether the painter can reproduce the peculiarities of luster and color which we admire so much in Nature through the contrast of his colors alone, we shall have to admit that he calls other elements into play.

We have already shown how our conceptions of the relations of objects in place are influenced by our unconscious prepossessions. May not these also intrude themselves upon and modify our conceptions of the color and tone of the picture? The connoisseur who has frequently observed the shimmer of the sea, and who has followed with a finely developed perceptive power the transformations of the landscape under a changing light, and who has been in the habit of watching in an æsthetic mood the combination and grouping of the individual features of Nature, is doubtless better able to realize these peculiarities also in works of painting, than he who applies only a sharp but untrained discernment to the gradual development of the idea of the picture.

Thus art, temporarily withdrawing us from Nature by substituting her own creations for the reality, brings us back to Nature as the inexhaustible source whence all its elements are borrowed; and the imagination, also, in its own way, is able to make use of those elements for new creations.—Translated for the Popular Science Monthly from Die Natur.

and Lieutenant Cardozo last year made a successful scientific exploration of the lake-region of Africa. They made a geodetic triangulation of the country from Ibo to Lake Nyassa, whence Lieutenant Cardozo—Colonel Pinto having withdrawn on account of illness—went to Shirva and Blantyre, and by a new road to Quilimane. This is the first scientific work of the kind done in that part of Africa.