Marcu 5, I1914| 
NATURE 
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17 
C—O eee. ee EE EEE 
previous knowledge of the science for granted, the 
elementary facts upon which the chief everyday appli- 
cations of electricity are based. The volume on wild 
flowers contains two hundred black and white illus- 
trations of common flowers, and descriptions of these 
and others arranged in chapters according to their 
colours. Thus we have chapters on white, yellow, 
red, blue, flowers, and so on. The price of each 
volume in the series is 6d. net. 
OUR ASTRONOMICAL COLUMN. 
STARS WITH VARIABLE RapiaL VELOcITIES.—In the 
Astrophysical Journal for January (vol. xxxix., No. 1, 
p- 39) Mr. Oliver J. Lee contributes numerous 
measures of variable radial velocities of stars deter- 
mined in the course of measuring Bruce spectrograms. 
Of the twenty-eight stars to which reference is made, 
eighteen have been previously announced as spectro- 
scopic binaries, but the remaining ten are new. The 
following table is abstracted from the information 
given in the paper, and indicates the star in question, 
position, magnitude, and class :— 
Star ae Dec. Mag. Class 
Bens awh, 
89/ Piscium ib hig +3 5 Bes IN 
Were Celine 228 +8 I 4°3 A 
125 Tauri ... 5 34 +25 50 50 Be 
40 Aurige... 6 0 +38 30 He A 
2anCanss Viennese. 3.30 +49 32 4°6 As 
33 Bootis ... 14 35 +44 50 5°4 A 
27 B Libreze 15 12 - 9 1 2°77 Bg 
BD 25°4165 20 II +25 17 4°8 B, 
332 Aquarii DI —I4 21 4°4 Bg 
18 A Piscium 22037, + I 14 AvOn As 
SUN-SPOTS : THEIR INTERNAL MOTION AND SHORT- 
PERIOD VARIATIONS.—The fifth volume of the Publika- 
tionen der Sternwarte des Eidg. Polytechnikums zu 
Zurich contains two contributions, the first by William 
Brunner, on the investigation of the internal motions 
in sun-spots, and the second by Elsa Frenkel, on 
short-period variations in the frequency of sun-spots. 
The former is a detailed research, carried out in a 
systematic manner, on the internal motions, chiefly 
divergent. The chief result leads the author to asso- 
ciate this divergent motion with the origin and 
development phases of spot groups. The data em- 
ployed were those of the period between January 1, 
1887, and January 1, 1905, and were the result of 
observations made with the refractor of the Zurich 
Observatory. Numerous plates accompany the text. 
The second paper involves the discussion of the Zurich 
observations made during the period 1876-1911. 
Readers must refer to the original publication for the 
detailed account of the research, but the chief con- 
clusions may be stated briefly as follows. The 
author finds a probable period of 200 days, but this 
is not apparent during the last three eleven-year 
periods, when the spot activity went below a certain 
limit. The length is not constant, but varies about a 
mean value of 150 to 200 days. The ordinate of the 
periodigram is about 100 times smaller than the 
eleven-year period, and the amplitude about ten times 
smaller than that of the eleven-year period. Another 
period of 68-5 days was indicated, but this will be 
investigated again at a later date. Attention is 
directed to the lengths of these two periods, namely 
200 and 68-5 days, and the sidereal times of revolution 
of the two inner planets, namely Mercury, 87-9 days, 
and Venus, 224-7 days. The text is accompanied by 
a large number of plates showing the observed and 
smoothed curves of the daily relative numbers. 
NOV 82314, VOL. 93 | 
| 1913, x1. 
DETERMINATIONS OF GRAVITY IN EGYPT AND THE 
Supan.—Survey Department Paper No. 18 (Cairo) 
contains details of the determination of ‘‘ g”’ at eight 
stations in Egypt and the Sudan, carried out by Mr. 
P. A. Curry, in connection with the geodetic survey. 
Almost the whole of the observations and the whole 
of the computational work have been done by Mr. 
Curry himself. The stations range from Helwan to 
Khartoum, nearly 15° of latitude, and the height 
above sea-level varies from 42 to 383 metres, but the 
topographical correction has been nil for each of the 
stations. The Stuckrath pendulum apparatus em- 
ployed was borrowed from the South Kensington 
Museum, where it had been deposited after the return 
of Captain Scott’s first Antarctic Expedition. This 
instrument provides essentially for the determination 
of the time of oscillation of each of a number of in- 
variable pendulums swinging in separate cells of a 
vacuum chamber. Besides the correction due to the 
rate of the chronometer, four instrumental corrections 
need to be determined, namely, for temperature, pres- 
sure, amplitude of vibration, and flexure of pillar. 
Kew was taken as the base and Helwan was made 
the primary Egyptian station. 981-201 cm./sec.? 
(based on the Potsdam system) was adopted as the 
value of ‘‘g’”’ at Kew, and from a discussion of ninety- 
eight separate determinations 979:295 cm./sec.? was 
obtained as the final value of this constant at Helw4n, 
the probable error being +0-0027. The values obtained 
for each of the stations have been reduced to sea-level 
and compared with the theoretical value for the lati- 
tude of the station given by Helmert’s formula (1901). 
Remarkably close agreement obtains, ranging only 
between +0009 and —o-013, whence it is concluded 
that there is nothing very abnormal about the values 
of gravity at these eight stations. 
THE COBAR COPPER FIELD: 
OBAR, on the western plains of New South Wales, 
464 miles by railway from Sydney, is one of the 
most important, though not most profitable, of the 
copper fields in Australia; .it yielded 6500 tons of 
copper in 1911,- and has produced more than 90,000 
tons since its discovery in 1869. The development of 
the field was hampered by its remote position and its 
semi-arid climate, for with a rainfall of only 15 in. 
it is surrounded in dry seasons by a wide, waterless 
tract. In its early days, however, the export of ore 
was once stopped by floods, which inundated the plains 
beside the Darling River for a width of fifty miles. 
Another. trouble was an invasion in 1890 by millions 
of rabbits, which destroyed the vegetation by devour- 
ing the shrubs and ring-barking the trees. 
The rocks of the mining field belong to three main 
divisions.‘ The oldest is the Cobar Series, which 
comprises semi-metamorphic sediments of perhaps pre- 
Silurian age; its most important member consists of 
thick beds of chert, which Mr. Andrews regards as 
a recrystallised organic precipitate. The account of 
these beds suggests theic resemblance to the Heath- 
cotian Series of Victoria, which are of Cambrian age. 
The middle division, the Mallee Tank beds, includes 
fossiliferous limestones, and its age is certainly Silu- 
rian. The upper division is Devonian, and includes 
a varied series of quartzites, shales, and claystones. 
The rocks of all three divisions have been disturbed 
by intense compression due to earth movements at the 
beginning and at the end of the Devonian period. 
The pressure was so powerful that the minimum dip 
observed in the Silurian rocks is 30°, and the Devonian 
1 E. C. Andrews: Report on the Cobar Copper and Gold-field. Part i. 
(Department of Mines, New South Wales, Mineral Resources, No. 17). 
Pp. 207:+-xlv plates++-19 maps in separate portfolio. 
