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456 It has attracted much attention. It is manifestly produced in the upper regions of the atmosphere; for It is best seen from elevated mountains, where it continually visible in clear weather. It is often hidden at low stations by the plentiful reflected skylight that comes from the coarser dust of the lower atmosphere, even though the sky seem tolerably clear. It ban been astonishingly distinct here in Cambridge through the past winter, on the clear anti-cyclonic days, with north-west winds, following the withdrawal of the cyclone cloud-disk; and it attains its greatest visibility between clouds, because much of the lower dusty air he then in shadow, and does not outshine the delicate colors of the ring. On some recent cloudless but slightly hazy days it has been entirely invisible.

I have not observed the connection between the viability of the ring and the changes of temperature and formation of clouds noted by Professor Stone, and should be gled to learn more details as to date of observations, and no to closeness of the connection in point of time. A comparison of observations on these questions made at Colorado Springs (where I presume Professor Stone made his records) and on the summit of Pike's Peak would be very instructive in this respect.

The most remarkable point in connection with the ring is its persistence long after the cessation of the brilliant twilights with which it began. How is the volcanic dust or the ice dust that causes it supported so long? It seems incredible that dust could simply float for a year and a half in so thin a medium as the atmosphere at a height of ten or more miles. Electrical repulsion has been suggested as a supporting force, and it may be somewhat effective above the level of storm-circulation; but, besides this, it seems possible that the peculiar properties of water-vapor may give some aid. Wollaston long ago speculated on the limitation of the atmosphere at an altitude where its gases were frozen. The solid particles would there fall till evaporated, when the gases thus formed would rise again till frozen once more by the cold of expansion. Ritter and others have recently reconsidered this process. Whether the theory in applicable or not to oxygen and nitrogen, it certainly is of importance when water-vapor is considered: for, as is well known, the elasticity and condensibility of this constituent of the atmosphere are mutually antagonistic. The vapor tends to diffuse itself to altitudes where the cold caused by its expansion would require the condensation of a part of it; and, although such perfect diffusion is prevented in the lower atmosphere by the friction that the vapor suffers in passing through the air, it does not seem unreasonable to believe it may obtain at great altltudes where a normal distribution of vapor must be more nearly attained, and especially so at times when an extra apply of both vapor and dust is shot high Out of volcanic craters. We may therefore believe that at some high level the atmosphere is 'saturated' with vapor: above this there will be continual condenaation, supplying a delicate shower of the minutest Ice particles; and, if these really need a solid nucleus to freeze upon, the nuclei may be sustained by the continuous upward diffusion of the vapor that rises to take the place of that which has been condensed, only to be condensed itself in its turn. Klessling's discussion of the diffractive action of particles suspended at considerable altitudes fully accounts for the twilights and the solar ring; and the close agreement In date of occurrence of several great volcanic explosions, and subsequent brilliant twilight displays, naturally leads to the acceptance of the volcano as the source of the diffracting matter. Perhaps the Wollastonlan Idea may aid in explaining the remaining difficulty: namely, the long-continued suspension of some of the diffracting matter in the upper atmosphere.

W. M. Davis,

Cambridge, May 84.

In the brief abstract in Science (May 8, p. 890) of my address on 'Life," at the celebration of the semi-centennial anniversary of the Lyceum of natural history of Williams college, I am credited with the following statement: "Kick a stone and a dog: the difference in the result is caused by education."

The words are printed in quotation-marks as if they were my own; and, as a friend tells me that they seem to him to imply a belief that life has been produced by the education of dead matter, and that a stone might be educated into a dog, I hope you will give me space to say that the words are not mine.

Beyond the quotation, with approval, of Huxley's statement,—that "for us, at least, the distinction between living bodies, and those which do not live, is an ultimate fact,"—the address contained no opinions regarding the origin or cause of life. It was devoted to the presentation of a definition; and I tried to show, first, that education makes us acquainted with the order of nature, and thus enables us to use one events as the sign of another which is to follow, and to regulate our actions according to the laws of nature; and secondly, that, since all living thing respond to the order of nature in the same way, they also are educated; and that education, or the ability to make such responses, is life.

The writer of the abstract in Science had no opportunity to consult my manuscript, but I believe that the sentence which I have quoted is from his notes on a passage which reads as follows: "The actions of the dog are significant. They stand in relation to the external world, and their meaning could never be learned from the study of the dog's body, but must be sought in his environment, and that of his ancestors. The real difference between living and dead matter lies in this significance of the action of living things. This is what we really mean when we say that the dog is alive, while the stone is not."

W. K. Brooks.

EBENEZER EMMONS.

Professor Ebenezer Emmons was born at Middlefield, Mass., May 16, 1800, and died at his plantation, Brunswick county. N.C., on the 1st of October, 1863. He was prepared for college at Plainfield, Mass., under the Rev. Mr. Halleck, entered Williams college at the age of sixteen, and was graduated in the class of 1820.

As a surgeon, Dr. Emmons ranked high in his profession, and for fifteen years was the most eminent practitioner in Berkshire county. He was appointed professor of chemistry at

he always stated to his children that he was born in 1800.
 * r1 His birth has been variously stated as in 1790 and 1;99; bu