the Jenissei; an expedition was despatched to the spot by the Imperial Academy of Sciences in the summer of 1866, and the result of that expedition, it is considered, will be the disclosure of some interesting facts in the natural history of a former creation.--_Mr. Lumley's Report on Russian Trade._ ------------------ VELOCITY OF ELECTRICITY. One of our most profound electricians is reported to have exclaimed, "Give me but an unlimited length of wire, with a small battery, and I will girdle the universe with a sentence in forty minutes." Yet this is no vain boast; for so rapid is the transit of the electric current along the lines of the telegraph wire, that, supposing it were possible to carry the wires eight times round the earth, it would but occupy _one second of time_. The immense velocity of electricity makes it impossible to calculate it by direct observation; it would require to be many thousands of leagues long before the result could be expressed in the fractions of a second. Yet Professor Wheatstone devised some apparatus for this purpose, among which was a double metallic mirror, to which he gave a velocity of eight hundred revolutions in a second of time. The Professor concluded, from his experiments with this apparatus, that the velocity of electricity through a copper wire, one-fifteenth of an inch thick, exceeds the velocity of light across the planetary spaces; that it is at least 288,000 miles per second. The Professor adds, that the light of electricity, in a state of great intensity, does not last the millionth part of a second; but that the eye is capable of distinctly perceiving objects which present themselves for this short space of time. ------------------ MONOCHROMATIC PAINTING. A very delicate experiment, yet a very natural one, which Buffon appears to have first noticed, led in all probability to the invention of the monochromatic mode of painting, or painting with a single colour. If, at the moment which precedes sunset, at the close of a cloudless day, a body is placed near a wall, or against another polished body, or on a smooth chalky soil, the shadow carried by this body is blue, instead of being black or colourless. This effect is produced by the light of the sun being so weakened, that the blue rays which are reflected from the sky--which has always this colour on a clear day--fall, and are again driven back or reflected on that part of the wall which the dying light of the sun cannot strike; for even at its last moment, the light which falls straight and direct, is sufficiently strong to destroy that of the heavens, which is only reflected, wherever they meet. ------------------ THE MARINER'S COMPASS.