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STUDIES OF VORTEX-RINGS.
175

it is impossible that the multitudinous species of animals and plants may have been produced one separately from the other by spontaneous generation, nor that it is impossible that they should have been independently originated by an endless succession of miraculous creative acts. But I must confess that both these hypotheses strike me as so astoundingly improbable, so devoid of a shred of either scientific or traditional support, that even if there were no other evidence than that of paleontology in its favor, I should feel compelled to adopt the hypothesis of evolution. Happily, the future of paleontology is independent of all hypothetical considerations. Fifty years hence, whoever undertakes to record the progress of paleontology will note the present time as the epoch in which the law of succession of the forms of the higher animals was determined by the observation of paleontological facts. He will point out that, just as Steno and as Cuvier were enabled from their knowledge of the empirical laws of coexistence of the parts of animals to conclude from a part to the whole, so the knowledge of the law of succession of forms empowered their successors to conclude, from one or two terms of such a succession, to the whole series, and thus to divine the existence of forms of life, of which, perhaps, no trace remains, at epochs of inconceivable remoteness in the past.

STUDIES OF VORTEX-RINGS.

By ADRIEN GUÉBHARD.

A FAKING skip-rings in the water, and gazing at the vapors in the air, furnish common expressions for complete inactivity and vacuity. Yet, in these occupations may be found subjects of profound and worthy studies. Nothing is vulgar to one who knows how to see, nothing indifferent to one who knows how to observe; and the fall of a drop of water, insignificant as we may regard it, may bring us into the neighborhood of the ultimate mysteries of those regions to which the fall of an apple once transported the immortal genius of Newton. As profitable subjects for study may be found in those common rings, simple wrinkles on the surface of the water, in which the physicist sees many things and the clown few; or, in those turbid clouds of smoke which every day float toward the sky from our fires here below. Everybody has seen some adroit smoker throw from his mouth or his pipe pretty, white wreaths, whose whirling vapors it was a pleasure to follow in the air.[1] It is a fact of daily observation that

  1. Fig. 1 has been designed after the celebrated picture of Brauwer in the Lacaze Gallery of the Louvre. In the original, the picture only represents a spiral of smoke. But the form of the mouth and the convergence of the eyes sufficiently indicate the helpless effort of the drunken man. The subject seems to have been a favorite one with the