590 



NA TURE 



[April 23, 1908 



and rendered less sharp, but certain lines are unaltered 

 in wave-length, while others increase by amounts of the 

 order of a few hundredths of an Angstrom unit per atmo- 

 sphere increase of pressure. There seems to be no con- 

 nection between the influence of pressure on the wave- 

 length and the Zeeman effect in the case of bromine, 

 although there may possibly be such a connection in the 

 case of nitrogen peroxide. 



Solutions of the examples in " .\ Sequel to Elementary 

 Geometry," by Mr. J. W. Russell, which was reviewed 

 in the issue of Nature for February 6 last (vol. l.xxvii., 

 p. 315), have been prepared by the author, and published 

 at the Clarendon Press, Oxford. The price of this key is 

 35. 6cl net. 



OVR ASTRONOMICAL COLUMN. 



Structure of the Coron'a. — In Nu. iq, vol. ii., of the 

 Mitteilun^eii der Xikolai-Hanptstemu'tiitc zii Pulkowo, 

 Prof. Hansky discusses the results derived from a study 

 of the photographs of the corona taken by the Pulkowa 

 expedition at .'Mcocebre (Spain) during the total solar eclipse 

 of August, 1905. The principal aim of the photographs 

 was to determine the velocity of the propagation of coronal 

 matter in space, and the eight exposures were therefore 

 arranged symmetrically about mid-eclipse, and given 

 approximately equal times. 



Each streamer and prominence shown on the photo- 

 graphs is discussed very fully, and Prof. Hansky finally 

 ciraws the following conclusions. The corona of 1905 was 

 of the " maximum '" type, and was divided into eight 

 groups of streamers, arranged symmetrically about the 

 sun's axis. It appears probable that the forms and direc- 

 tions of the coronal streamers depend upon the forms and 

 directions of the prominences above which they are found. 

 In this conclusion Prof. Hansky's result agrees with that 

 recently published by Dr. W. J. S. Lockyer (see Nature, 

 No. 2005, p. 514). The centres of emission of the 

 streamers, though often near spots, do not coincide with 

 them. Those streamers which occur over great promin- 

 ences are readily distinguishable by their forms. The jets 

 of prominences resemble jets of matter, the observed 

 velocity of which approximates to 200 km. per sec. Any 

 movement of coronal clouds above prominences is shown 

 to be very slow, its velocity not exceeding 30 km. per sec. ; 

 this is so small that any such movement during the three 

 minutes of totality would not produce a change of position 

 sufficiently great to exceed the limits of observational 

 errors. 



Spectroscopic Binaries now under Observation. — 

 With the view of assisting in the prevention of unnecessary 

 duplication in the observation of spectroscopic binaries, 

 Prof. Frost, director of the Yerkes Observatory, recently 

 addressed a circular letter to the principal observers in 

 this work asking them to furnish him, for publication in 

 the Astrophysical Journal, with a list of the objects now 

 under observation at the several institutions. The various 

 replies appear in No. 2, vol. xxvii., of the journal (p. 161), 

 and show that duplicate observations are already in pro- 

 gress. Prof. Hartmann points out, whilst furnishing a 

 list of stars, that duplication is not necessarily an evil, 

 for, with the determination of radial velocities still in a 

 state of evolution, such duplication serves as an independent 

 check on the various results. Prof. Pickering suggests 

 several pieces of work where cooperation would probably 

 lead to useful results, and points out that, even with an 

 objective-prism spectrograph, the star f Ursae Majoris 

 shows marked irregularities in its spectrum which have 

 not yet been accounted for. 



The Relation between the Colours and Periods of 

 V'arwble St.vrs. — In an interesting paper which appears 

 in No. 4238 of the Astronomische Nachrichten (p. 209, 

 March 9), Herr S. Beljawsky, Gottingen, discusses at 

 some length the relation found to exist between the colours 

 and the periods of variable stars. From the tables and 

 curves given in the paper it is seen that in general the 



XO. 2008, VOL. 77] 



I'ariablc stars of long period are much redder than the 

 ihort-period variables. Regarding the amplitudes of the 

 typical light-curves, it is found that up to periods of 200 

 days the amplitude increases with the period, beyond 200 

 days it appears to remain constant. 



A. Field Method of determining Longitudes. — Paper 

 No. s of the Egyptian Survey Department is devoted to 

 an explanation, by Mr. E. B. H. Wade, of an instrument 

 designed by him for making field determinations of longi- 

 tude by observations of the moon. By a system of mirrors 

 placed at the object-glass end of a small 2j-inch tele- 

 scope, Mr. Wade successively brings the images of two 

 stars in contact, tangentially, with the limb of the moon, 

 thus finding the times of equal lunar distance. The 

 apparatus is ingeniously designed, and is readily portable. 

 Full explanations of the instrument and the method are 

 given in the paper, which is illustrated by a number of 

 diagrams and curves. 



Observations of Eros. — The results of ten measures of 

 the position of Eros, made with the 15-inch refractor of 

 the Uccle Observatory during the period September 25 to 

 October 19, 1907, are published, in No. 4240 of the Aslro- 

 notnische Nachrichten (p. 252, March 23) by Herr G. 

 Van Biesbroeck. Comparing the positions thus determined 

 with those given in the ephemeris published in Ihf 

 " Berliner Jahrbuch " for igog, it is seen that the mean 

 corrections to the latter are — i-ios. in R.-A. and — 8''-o 

 in declination. 



Vari.4ble Radul Velocity of r\ Virginis. — \ note in 

 No. 2, vol. xxvii., of the Astrophysical Journal (p. iho, 

 March) gives the provisional elements of the orbit of th.f 

 brighter component of ri Virginis, as determined at the 

 Ottawa Observatory by Mr. W. E. Harper. The period 

 is found to be 71-9 days, the velocity of the system 4-2-2 

 km. per sec, the eccentricity of the orbit 0-4, and the 

 length of the semi-major axis 25,750,000 km. The 

 velocity-curve shows a variation from —40 km. to 

 4-20 km. 



AGRICULTURAL EXPERIMENTS AND 

 REPORTS. 



"T^HE eighth report of the Woburn Experimental Fruit 

 Farm contains a very valuable investigation of the 

 washes commonly used for spraying fruit trees. They 

 have hitherto been made up in rather a haphazard way, 

 without much reference to the chemical changes involved, 

 and Mr. Pickering is to be congratulated on having re- 

 duced them to a scientific basis. He shows that Bordeaux 

 mixture (obtained by precipitating copper sulphate solution 

 with lime) made in the ordinary way consists of 



ioCuO,S03,4CaO,S03, 

 but this is not so economical as another precipitate, 

 4Cu0,S03, for obtaining which full instructions are given. 

 An investigation of the " Woburn wash " (paraffin 

 emulsion and caustic soda) led to a very important ex- 

 amination of emulsions in general, which has enabled Mr. 

 Pickering to state the conditions under which they may 

 be expected to form. When oil is churned with water it 

 is broken up into very minute particles ; if still smaller 

 particles of an insoluble substance are present they coat 

 the oil drops and prevent them from coalescing ; an 

 emulsion is therefore formed. During the progress of 

 this work Mr. Pickering discovered a new emulsion which 

 promises to be of great service to the fruit-grower. Basic 

 copper sulphate (obtained by adding lime to ordinary 

 copper sulphate) was churned with oil and water, and gave 

 a perfect emulsion to which caustic soda could be added 

 without any adverse effect. The result is a wash contain- 

 ing the three things which have to be used in winter and 

 spring ; the grower can therefore get them all on in one 

 operation instead of in three as hitherto. The insecticidal 

 and fungicidal action of these and other washes was also 

 investigated, and there is a discussion of the nature of 

 the action of insecticides. 



Of late years molasses has been increasingly used as 

 cattle food, and. various agricultural stations have investi- 

 gated its digestibility and nutritive value. .\ Bulletin 



