Sf.pt.. 1905.] 



KNOWLEDGE & SCIENTIFIC NEWS. 



227 



ASTR.ONOMICAL. 



Charles P. Butler, A.R.C.Sc. (Lond.), F.R.P.S. 



Star Streams. 



The Times correspondent with the British Association tele- 

 graphs from Cape Town on Angust 17th: — "In the mathe- 

 matical section the most important contribntion was made by 

 Professor Kapteyn, Director of the Astronomical Laboratory 

 of the L'niversity of Groningen, Holland, who read a paper 

 entitled ' On Star Streaming.' Professor Kapteyn explained 

 that he had been working for many years in making investiga- 

 tions into the structure of the stellar universe, and he had 

 arrived at the remarkable conclusion that the proper motions 

 of the stars are not distributed at random in space, but that a 

 great part of the brighter stars belong to one or other of two 

 great streams of stars moving in the plane of the Milky Way 

 and meeting one another in space. This discovery opened up 

 so many questions of the greatest interest that he had asked 

 some of the most important observatories in the world to 

 co-operate in several lines of research which must be carried 

 through before the problem could be completely solved. Pro- 

 fessor Kapteyn stated that he required in particular the deter- 

 mination by the spectroscope of the motion in line of sight of 

 a great number of stars down to the eighth magnitude, and he 

 hoped that the Royal Observatory would furnish him with 

 much precious material of this kind." 



Algol VaLriaLbles. 



On the iSth he reports : " In the Mathematical Section 

 something of the nature of a sensation was created by a 

 remarkable paper by Mr. Jeans, of Trinity College, Cambridge, 

 on the theory of argol (? Algol) variables, which excited the 

 enthusiastic interest of Professor Darwin, Sir David Gill, and 

 other astronomers. 



Recent Observa.tlons of Jupiter's Sixth 

 Satellite. 



In a telegraphic despatch from the Lick Observatory it is 

 stated that Professor Albrecht has observed the new sixth 

 satellite of Jupiter with the Crossley reflector, the following 

 being the determined positions: — 



The North Pola-r Cap of Ma.rs. 



From November, 1904, to May, 1905, Mr. Lampland was 

 successful in obtaining a big series of determinations of the 

 various features of the north polar cap of Mars. In a sum- 

 mary of the results tabulated, he gives the various aspects pre- 

 sented on various dates during the above period. On Janu- 

 ary 13, 1905, the cap was shrouded by an extensive veil of dull 

 white ; this was eventually pierced by the cap, showing as a 

 brilliant spot about 4^ in diameter, and then as a contoured 

 patch some g'^'j across. The veil was of the same nature as 

 had been obscuring the cap since October 30, and appeared 

 to consist of haze or cloud. From this time onwards many 

 measures of the diameter of the polar cap are given. 



On January ig, subsidiary snow patches began to appear 

 from under the veil. 



During April no signs of the surrounding white collar were 

 visible, and from a close study of the epochs of its appearance 



and disappearance, it is thought that it may be something like 

 a spring mist, surrounding the cap during the hotter months 

 of its melting, and this view is supported by the feature of its 

 indefinite boundary. The snow cap proper is girdled during 

 its contraction by a blue belt, due undoubtedly to the material 

 formed by its melting, which can be none other than water 

 from among all the substances we know, whilst the collar lost 

 itself unedged in the surrounding ochre, thus exhibiting the 

 indefiniteness of cloud. 



When the white collar disappeared, subsidiary outlying snow 

 patches stood revealed, flanking the true cap about. Of these, 

 the first to show was the great patch in longitude 206". This 

 was first seen by Schiaparelli in 1888; it was independently 

 discovered at Flagstaff in 1901, and re-observed there in 1903 

 and 1905. 



In 1905, the next most prominent subsidiary patch lay in 

 longitude +'^10, just east of the Mare Acidalium, and a third 

 set was found in about longitude 311'. 



Proposed Ma-gnetic Survey of the North 

 Pacific Ocean. 



The rapid development of commercial activity in the Pacific 

 region during recent years has rendered necessary the institu- 

 tion of a definite scheme for determining more reliable values 

 of the magnetic elements for those navigating these waters. 

 Except for data from occasional special expeditions, and such 

 as were acquired in wooden vessels many years ago, the pre- 

 sent magnetic charts in use depend largely upon observations 

 made on islands and along the coasts. It is evident, however, 

 that such determinations are rarely representative of the true 

 values on account of prevalent local disturbances. 



The present plan is to be started under the patronage of the 

 Carnegie Institution, from which an initial allotment of ^^5000 

 has been obtained to cover expenses during 1905. The scheme 

 provides for the chartering of a wood-built, non-magnetic 

 sailing vessel of about 600 tons, which, after starting from San 

 Francisco, will pursue a clockwise spiral course, embracing 

 the entire North Pacific Ocean. The total length of the pro- 

 posed cruise is about 70,000 knots, and it is estimated that the 

 work will occupy about three years. 



It is fortunate that the region under consideration contains 

 magnetic observatories in suflicient number and proper dis- 

 tribution for furnishing the necessary corrections to be applied 

 to the observed magnetic elements in order to reduce them to 

 a common epoch. For this purpose, continuous records of the 

 magnetic variations will be available from Sitka (Alaska), 

 Mexico, Honolulu (Hawaiian Islands), Manila (Philippines), 

 Shanghai (China), Tokio (Japan). In addition, it is hoped 

 that a station will soon be started in California, and that the 

 German Government will continue its magnetic observatory 

 at Apia throughout the period of the survey. 



Monochromatic Photographs of the Orion 

 Nebula. 



Professor J. Hartmann, in the course of a series of experi- 

 mental trials of a small quartz spectrograph, has recently ob- 

 tained photographs of the Orion nebula, which show important 

 differences in the composition of its several parts, indicating 

 that different parts of the nebula emit light of difterent com- 

 position, and that extensive areas of characteristic form shine 

 almost solely with ultra violet light of wave-lengths 3727. 



With this small camera the images are, of course, small ; 

 I mm. on the plate corresponds to an angle of about 10', but 

 this was found quite sufficient to permit the recognition of the 

 various parts of the nebulous areas. It was found advisable, 

 however, to be able to utilise apparatus of higher power, and 

 this was done by the use of suitably stained colour screens. 

 The most useful of these are : (i) Pici-ic acid, which transmits 

 the longer wave-length, especially the nebular lines Ni, N.,, and 

 H(3, and absorbs all wave-lengths shorter than 4800 ; (2) 

 (Juininc cobalt, which transmits only the rays between 3880 and 

 3740; (3) iV!<roso_/i/(f;-, the absorption of which begins at 5050, 

 but dies oft" again near 4000, and 3727 is easily transmitted. 

 By suitable combinations of these, photographs have been ob- 

 tained with a Steinheil mirror of 24 cm. aperture and 90 cm. 

 focus. 



The chief result is the remarkable intensity of the 3727 

 radiation in all parts of the nebula. 



