Page:Popular Science Monthly Volume 20.djvu/189

Rh Nature herself sometimes produces this phenomenon without any human intervention, and shows us the vortices of the ignis fatuus, to which the middle ages attached so many poetical legends, rising on summer evenings from the stagnant waters of marshes. The craters of volcanoes also frequently give off smoke in the form of magnificent ring-clouds.

Huygens observed, with one of the first telescopes, the annular form of those curious satellites of Saturn, the singular equilibrium of which is still a subject of discussion. The periodical November meteors form a real ring of planetary fragments around the earth; everything seems to prove that the milky way is nothing but a gigantic ring of cosmic dust, of which our sun and its satellites are only a few grains; the question of the form of the zodiacal light is hardly doubtful; and, finally, among the infant worlds that we call nebula?, the annular figure recurs with such frequency that it can no longer be considered exceptional; and the inspiration of genius which caused Laplace to see in the fracture of such a ring the whole origin of our solar system is reflected in the broken rings which are found among some of these nebulæ.

The laws of nature, however, frequently reveal themselves best in the infinitely little; and I have made my first observations toward a new study in watching the filiform currents produced during the osmotic interchange of two liquids through the pores of a membrane.

While intimately regarding the curious phenomena with which Ducrochet sought to connect all the laws of life, I devised a way to observe the current of osmose, if I may so speak, in the act. This is not easily done with alcohol or water, but, by carefully taking advantage of the refracting and magnifying properties of cylindrical glasses, I succeeded, at last, in distinguishing before either very dark or very light grounds, slight, thin trains indicative of movement; and it was really a curious phenomenon to see two liquids of so strong affinities for each other, brought into intimate contact through a permeable membrane, obeying the laws of gravity almost without mixing, and taking their course across each other in the form of distinct threads, which presented at the same time the sharpness and the apparent fixity of a fiber of pure glass. The figure of these threads is not constantly stationary, but is subject to a regular movement, in which periodically, while still preserving its individuality, it seems to undergo alternate swellings and attenuations that give it the appearance from a certain distance of shafts of columns put one upon the other, of larger and larger capitals, or of pointed parasols, or Chinese hats with several crowns. If we look at them from above, we may perceive, in these spirals and expansions, the profiles of real circular rings, slightly attached by an invisible cord to a central stalk which bears them