uti

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��it bu auraciei much attcntinii. It Is manifestly

firoduced in the upper regiaiiB id the ntmosphcre; for t Is best Been from elevuted raouiiUilns. where it is continual); visible in clear weather. It is nden hid' den at low sUillons by tlie plentiful reflected .-kylighl th»t comes from the courser dust of the loirer atmos-

E here, even though (he sk^ Beem tolerably clear. It Bs been ^tonlshingly distinct here in Cambrldce through the past iriiil«r. on the clear anti-cyclonic days, with north-west wlnde, following the withdrawal of the cjiclonic cloud-disk; and it attains ils greatest visibility between clouds, tiecause moch of tlie lower dusty air is tlien in (shadow, and does not ontHbine thedelicatecoloraof the ring. On some recent cloud- less but slightly haiy days it has been entirely Invisi- ble.

I have not observed the connection between the visi- bility of the ring and the changes of temperature and fomation of clouds noted by Profei^sor Stone, and should be glad lo learn more details as to date of obaervatloTis, and as to closeness of the oonnectlon in point ot lime. A comnarMnn of obserratfons on thcae questions made at Colorado Springs (where I preiutne Professor Stone made his records) and on the summit of Pike's Peak would be very instructive in this respect. Tbe most remarkable poir ' ' ' ' ~

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��t twilights with which it began. How is tbe volcanic dust nr the ice dust that causes it sup- ported to long? It seems incredible tiiat dust could iimply float for a year and a half in so thin amedium M the atmosphere at a height of ten or more miles. Electrical repulsion lias been suggested as a tupjiort- ing force, and it may he somewhat effective above the level of stonii-circulatlon ; but,besidee this, it seems po»<9ibIe thai the peculiar properties of water- rapor may give some aid. AVollaston long ago spec- ulated on the limitation o( the atmosphere at an altitude where lis gases were fmxen. The solid parti- clen would tberefall tUl evajwrated, when the gases thus formed would rise again till frozen once more by tbu cold of expansion, Ritler and others have recently recoinlilered this process, Wbetlier the theory is applicable or not to oxygen and nitrogen, it eerlaiuly Is of Importance when water-vapor is con- sidered : for, as 1b well known, the elasticity and cun- deoslbillty of this constituent of the atmosphere are mutually ant^onistlc. The vapor tends to diffuse Itself to altitudes where the cold caused by its eipan- alon 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 alti- tudes where a normal distribution of vapnr must be more nearly attained, and especially so at times when an extra snpiily of both vapor and dust is nhot 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 con- densation, BUpplylngadelicateshowerof the minutest ice particles ; and, if these really need a solid nucleus to Ireeie upon, the nuclei mav be sustained by the continuous upward diffusion ol the vapor that rises to lake the place of that which has been condensed, only to t>e condensed Itself In Ils turn. Elessling's discuaiion ot the diffractive action of particles sus- pended at considerable altitudes fully accounts for the twilights and the solar ring ; and the close agree- ment ill date of occurrence ot several great volcanic explosions, and aubaequFint brilliant twilight displays, naturally leads U) the acceptance of the volcano us

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��the source of the diftracting matter. Perhaps tba Wollasionian idea may aid in explaining tbe remain- ing difflcuily; namely, the long-ci>ntinued sus]ieiirion ot some of the diSracLlng matter in the upper atmos- phere. W, M. Davxb.

Cambridge t May 24.

Life.

In the brief abstract in Science (May 8, p. 386) of my address on ' Life,' at tbe celebration ot the seml- centennia! anniversary of the Lyceum of natural hi toiy ot Williams collpge, I am credited with following statement: "Kick a stone and a d(^: difference In the result in couieii by education.'

The words are printed in quolation-marks. as , they were my own ; and. an a friend lella me that tfaey seem to bim U) Imply a belief that life has been pro- duced 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 tbe quotation, with approval, of Huxley's statement, — that "for us, at least, the distinction between living iMidies, and those which do not live. Is an ultimate fact," — the address contained no opinions regarding the origin or cause of life. It wa« devotad to the presentation of a definition; and I triad to show, first, that education make^ us acquainted «rith the order of nature, and thus enables us to ttss on« event a; the sign of anotber which is to follair, and to regulate our actions according to the laws of nature; and secondly, that, since all living thio^ respond to the order of nature in the same way, they also are educated: and that education, ot the abtU^ to make such responses, is life.

The writer of the abstract in Sefence had no op- portunity to consult my mnnnacript, but I believe that the sentence which I have quoted U from his notes on a passage which reads as follows: "The actions of the dog are significant. They aland In relnlinn to the external world, and their tneania// coutd never be learned from tbe study of the do^ body, but must be sought In his envimnmeiil, and that of Ilia ancestors. The real difference betweon living and dead matter lies in this Bi;m(fic<ince actiona of living things. This Is what we mean when we say that the dcyg is alive, while t stone is not." W. K. BaoOKr

��EBENEZER EMMONS.

Professor Ebekezer Ewstoss was born i) Middlefield, Mass., May IG, 1800,' and ( at his plantation. Branswick conntj', N.G-i the 1st of October, 186.^.

He was prepared for college at PlainfisU Mass., under the Rev. Mr. tialleck, eot« Williams college at tbe age of sixteen, i was graduated in the class of 1820.

As a surgeon, Dr. Emmons ranked h^h | his profession, and for fifteen years most eminent practitionci' in Berkshire com He was appointed professor of cliemiaiiy j

' HI* birth bu bftn virioualy aUUd u la ITM u

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