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Deductions from preceding Tables.

Spectrum 0 Maximum in white, gradually decreasing to pale yellow.

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A

also

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(practically 79 per cent.). The whitest stars.

but less wh. and more yelsh. wh. than B.

yelsh. white, but the pale yellow not far behind.

between yelsh. wh. and pale yel.--the latter slightly in excess.

in pale yellow-very pronounced.

between pale yel. and yellow-nearly equal.

pretty evenly distributed between yel., pale or., and orange. in orange, but pale orange not far behind.

orange red-very pronounced.

The sequence of colours corresponding to the sequence of the spectra is thus unmistakably indicated. But in the A class there is a definite number of pale yellow stars; their occurrence is too frequent and regular to be accidental; they show an increase in frequency in the regions where coloured stars are predominant. Likewise there is a still larger fraction of white stars in the F class-contrary to the normal. This serves to emphasise the fact that in some cases two stars of exactly the same colour visually are of different spectral types-some noteworthy examples of which have come to light during the present investigation. And, conversely, some stars of identical spectra differ very perceptibly in colour-whatever the cause of such discrepancy may be. But perhaps these exceptions, which after all are not very numerous, merely point the rule which governs the relation between colour and spectrum in the great majority of cases. If I have succeeded in establishing this connection, it may be also a plea that star colour observations do possess some value; and I shall consider that these thousands of independent estimates, which have so long lain dormant, were not altogether made in vain.

Uxbridge: 1908 August 12.

Note on Y Cephei. By Rev. J. G. Hagen, S.J.

(Communicated in a letter to the Astronomer Royal.)

"The advance prints of your Astrographic Plates 3619 and 6983, which you kindly sent me for the examination of Y Cephei and its surroundings, have enabled me to measure the additional stars to the Atlas Chart of this variable which were invisible in the 12-inch refractor. They will be recorded in the Catalogue sheet No. 188 of series vi., with due acknowledgment.

"Since the magnitudes of this series are all reduced to the Harvard scale, it is well to put the magnitudes of Y Cephei, as shown on your plates, on record for future corrections of the elements of variation. The following extract from the Catalogue will designate four comparison stars :—

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Your plates give the following estimates, which anyone can verify

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"The provisional elements of variation give the following corresponding epochs of maxima :

Max. 1897 Sept. 24 = Plate 3619 + 15 days.

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"The first plate agrees well with the computed maximum and with the remark of Ceraski (A.N. 3644) that the brightness of Y was diminishing in October 1897. The second plate, however, will probably demand a correction to the assumed elements (A.N. 3744 and V.J.S. 41, page 317), as it is unlikely that the star should have diminished in brightness by 4 magnitudes in 47 days."

Rome: July 22, 1908.

Corrections to Professor Turner's paper on Correlation,—

(M.N., p. 551).

An unfortunate slip on p. 551 has been kindly pointed out by Mr. J. B. Dale.

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Both σα and should have been divided by 3, the square root of the number of observations; so that

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The correlation between A and B is therefore by no means negligible as stated on p. 552, and again on p. 545. The two "regression lines" are

or

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(B-7)=r.

σβ

(A − 7) = r.o1 (B-7) and (B− 7) = r.°3 (A − 7)

(A-7)=r.

(A-7)=2(B-7) and (B-7)=(A-7)

which are the two solutions mentioned on p. 545 obtained by grouping according to B and to A respectively.

The example was subsidiary, and the slip does not affect the main argument; but it is not easy to understand how so gross an error passed undetected.

H. H. T.

Errata in Mr. J. M. Baldwin's paper on Neptune.

p. 618, line 26, for include read exclude.

p. 620, line 4, for showing in read showing an.

LIST OF ADDITIONS

TO THE LIBRARY

OF THE SOCIETY

JUNE 1907 TO JUNE 1908.

An asterisk (*) indicates that the work is an excerpt.

Abbadia, Observatoire :

Observations faites au cercle méridien en 1905-6. Tome
Publiées par A. Verschaffel.

5, 6.

(Observatory.)

4to. Hendaye, 1907

Acta Mathematica. Zeitschrift, herausgegeben von G. Mittag

Leffler. Band 31, pt. 1-3.

(Turnor and Horrox Fund.)

4to. Stockholm, 1907-1908

Adelaide, Government Observatory:

Meteorological Observations made at the Adelaide Observa-
tory and other places in South Australia and the Northern
Territory during the year 1905, under the direction of Sir
Charles Todd.

(Observatory.)

Algiers, Observatoire :

fol. Adelaide, 1907

: Carte photographique du Ciel. Zone - 1°, +1°, +3°, +4°. (35 charts.)

(French Minister of Public Instruction.)

Allegheny Observatory:

: *Miscellaneous scientific papers; new series, No. 18-20. By Frank Schlesinger, Director.

(Observatory.)

: Publications.
(Observatory.)

8vo. Northfield, Minn., 1906-1907

Vol. I, No. 1-5.

4to. 1908

American Academy of Arts and Sciences: see Boston.

American Journal of Mathematics. Edited by T. Craig and
S. Newcomb. Published under the auspices of the Johns
Hopkins University. Vol. 29, No. 3-Vol. 30, No. 2.
4to. Baltimore, 1907-1908

(Editors.)

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