Page:Science vol. 5.djvu/376

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��It gives almost at the atari a short tre&tmeiit, tsucliBhortei'tban Darnell's, of eimple harmonic motions ; and it devotes several pages to the idea aod theorems of potential. The eubject of air-pumps, and with it much that is wont to make the student miserable, is dismissed after a treatment of four pages. In the chapters devoted to heat we miss the faniiliai' names of Uulong and Petit, and the other pre-R^nault investigators of the phenomena of expansion. The steam-engine occupies one page, without an illustration. Carnot's cycle, with related matters. Alls ten pages.

The book is written with great care. Its language is clear and judicious. There are, of course, etigbt inaccuracies. Foriustance; the first sentence of article 28 rends as if a point could be located by means of its distance from any one plane. Again : on p. 209 we find it stated as having been demonstrated ex- perimentally by Joule, that, " when a gap expands without performing external work, it is not cooled ; " the later experiment of Joule and Thomson, which led to a different conclu- sion, not being mentioned.

From beginning to end, this volume of Anthony and Brackett grapples with difficult principles boldly and in good faith, as if the authors expected their whole book to be read and mastered. Trigonometry is freely used, and occasionally something that borders ou the calculus. The long experience of the authors as teachers encourages the hope that they have not over-estimated the capacity of college classes ; but, excellent as is the matter and the manner of the book, one fears that the ordinary student will And portions of it for- m)dal)le.

I'erhaps it should not be otherwise. Cer- tainly the exliaoniinary student, who ci-avea strong meat, will find it here, and of the best. So small a book cannot teach all there is to learn: it is not intended to do so. It does not show the whole, of physics, but it shows physics as a whole.

���NOTES AND NEWS.

��Dumsa the oppoiitton of Ncptitne just pa!>seil, Profesaor Pickering conliiiueU the observation of Ibis pluiet's magnitude with the meridian photuiuet«r of the Harvard-college observatory lu the same method as previously eniplored. Kine series of observations extend from Dec. 16, 1884, to Jan. 21, ISSii, the doal result from which, when corrected for atmospheric abiorptlon, instrument*! error, and reduction to mean opponition, becomes 7.63. Tbe residual difference for iiiily one series Is as great as tivg-tenlhs of a mag-

���nitude. The correiponding results for two prevU seasons are 7. 71 and 7.77. Contrary to ihe i ence of Mr. Maxwell Hall of Jamaica, who evidence for a rotali on -period of Neptune in variations of the plnnel's tight according to his oi obseriatloDs, Professor Pickering regards U probable that there is any variation In the light of Neptune of a strictly periodic character, and further calls attention to the influence, much neglected by observers, upon the observed brightneaa of objects wlien seen east and west of the meridian on the same night. This has to im taken account of la the observations of maxima and minima of man]' variable stars, and may t'> some extent account lor the variations of Neptune's light delected by Mr, Hall.

— Prof. Chariei E. Beasey writes to the Amerieami naturalini that fifteen years ago there were no dande- lions in the Ames flora (in central Iowa): now Ihey are very abundant, and Lave been for half a doien years. Then there were no mulleins: now there are afew. Then the low and evil-smelling Dysodiachry»- anthemoides grew by the roailside in great abui»< dance: now it is scarcely lo be found, and Is repli

by the introduced 'dog-fennel' (AKthemis ciitutal Tbeu the small fleabane (Brlgeron divaricatuinl abounded on dry soils: now it Is rnpldly disapprarinit Then no squlrrcl-tall gras« (Hordeum jubatiim) grew [u the flora: now it is very abundant, and hav beea for ten years. Then there was no burr-grast in the flora; now It Is frequently f.iniid, and appears to be rapidly increasing. Bnih of these grasses have apparently cnuie in from ihe west and north-west. Fifteen years ago the low amaranth (Amarantu* blltuldes) wa« rather rarely found: now it is abundant, and has iritgrateU fully a hundred and fifty milM north-eastward. This plant has certainly come iDIO Che Ames flora from the south-west within Iha tast twenty ye-iis. Old settlers say that there have bMB notable migrations of plants within The past twentj or thirty year*. The buffalo gra-ses of various ktuds were fonuerly abundant In the eastern part of the state; now they have retreated a hundred to a hun- dred and fifty miles, and have been followed up bj the bhie-siems (Andropogon and Chrysopogon). The blue-stems now grow In great luxuriance all ovef great tracts of the plains of eastern Nebraska, wheM, twenty years ago the ground was practically being but thinly covered by buffalo graasea, Dakota It Is the same: ibe blue-stems are maiclil across the plains, and turning what were o Utile better than deserts iiito grassy pralrlci.

— A prlncipla that may generally be Wisely to by reviewers Is that notices of books appearing numbers should not be hosed on the first nombtc' Issued; but this can he safely departed from In an- nouncing the preparation of a new (/unrth) edition of Meyer's ' Konveraations leilkon,' of which the Brst part appears with imprint of 1885. Sixty-four pages carry it to ' Absteigung.' Abyssinia is allowed six and a halt pages, which include liberal refereHM to sources o( Information, an essential in all good encyclopaedias. Among the illustrations there aak

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