90 



NATURE 



[November 28, 1907 



SATL'RN'h Rings. — Further observations of the invisibility 

 of Saturn's rings during the recent passage of the earth 

 through the piano containing them are recorded in No 

 4215 tp. 249, November 17) of the Asironomische Nach- 

 richtcii. According to the calculations of Prof. B. Peter, 

 of Leipzig, the second disappearance should have taken 

 place on October 4. M. Schaer, of Geneva, saw the rings 

 as a luminous line without any difficulty on October 2, 

 using a reflector of 140 mm. aperture. On October 3 the 

 weather was unfavourable, but the rings were still visible, 

 with a reflector of too mm. aperture, at 6h. 4Sm. on 

 October 4. At yh. 30m., however, the last trace of the 

 bright line had disappeared. Continuing the observations 

 with a refractor of 34 cm. aperture, at yh. 45m. the rings 

 could be seen momentarily, but were totally invisible at 

 8h. Bands of a brownish tint were several times seen on 

 each side of the trace of the rings. 



Dr. Hassenstein made observations with the 13-incli re- 

 fractor at KiJnigsberg on October 1 and 3. At 8h. 

 (G.M.T.) on the former date the rings were undoubtedly 

 visible, but at sh. (G.M.T.) on October 3 they were in- 

 visible; at loh. the rings could not be seen, but dark 

 streaks and the shadow of the rings were visible. Dr. 

 Hassenstein concludes that the passage of the earth 

 through the plane of the rings took place at oh. (G.M.T.) 

 on October 3. 



Photographs ok Jupiter. — The November number of 

 the Biillclin de la Socicti' astronomique de France (p. 481) 

 contains a reproduction from a photograph of Jupiter 

 taken by M. Qu^nisset at the Juvisy Observatory on 

 March 2. The instrument employed was the \"iennet 

 objective of o-i6 m. (6-3 inches) aperture and 2-9 m. 

 (114 inches) focal length, and about 100 exposures were 

 made. The resulting images show many details, and some 

 of them are remarkably well defined, presenting nearly all 

 the details seen with the 240 mm. equatorial at the same 

 time. On some of the photographs the Great Red Spot is 

 ■even more apparent than in the visual observation. A 

 reproduction from a drawing made forty minutes earlier 

 shows how well the details are registered on the photo- 

 graph. 



The same journal contains reproductions from Prof. 

 Lowell's photographs of Mars taken on July 11 and 2S 

 respectively. 



Final Designations of recently discovered Vari- 

 ables. — No. 4212 of the Astrouomischc Nachrichtcn 

 (p. 181, November 7) contains a table giving the final 

 designations of recently discovered variable stars allotted 

 by the commission of the .'\.G. catalogue for variable 

 stars. The list gives the provisional and final designa- 

 tions, the position for iqoo, the precession, the chart place, 

 and the range of magnitude for each variable, and includes 

 twenty-four variable stars of long period, eleven irregular 

 and twenty-five short-period objects, and thirteen variables 

 of the Algol type. 



A Large Eruptive Prominence. — Four excellent photo- 

 graphs of a large eruptive prominence, taken by Mr. Fox 

 on May 21 with the Rumford spectroheliograph of the 

 Yerkes Observatory, are reproduced in No. 3, vol. xxvi., 

 of the Astrophysical Journal (October, p. 155). On the 

 first photograph the prominence was seen strongly attached 

 to the sun's limb, but on the succeeding plates it is shown 

 as greatly altered in form and considerably weakened in 

 its lower parts. Thirteen plates were exposed, using the 

 H line, between 4h. 2m. and sh. sqm., and during that 

 period the height of the prominence, as measured on the 

 photographs, varied as shown in thn following table : — 



Surveys of Nebula. — Future workers on rhe possible 

 changes in ncbulse or in the stars involved in such masses 

 will find the exhaustive survevs of the Andromeda, the 

 ^ Persei, and the 12 Monocerotis nebula, recently carried 



NO. 1987, VOL. yy] 



out at the .Astrophysical Institute, Konigstuhl-Heidelberg, 

 of invaluable assistance. 



The results of these surveys are published at length in 

 the Publikationen of the institute, No. i, vol. iii., con- 

 taining those obtained by Herr P. Golz from his researches 

 on the .Andromeda nebula, and No. 11, vol. ii., embody- 

 ing Herr Lohnert's results concerning the star-densities 

 of the nebula; near | Persei and 12 Monocerotis re- 

 spectively. The former treats of 1259 stars involved in 

 the great spiral nebula;, and gives the position and magni- 

 tude of each star for the equinox of 1900 ; then follows a 

 catalogue of fifty-four recognisable points in the nebula 

 which have been measured, and of which the positions 

 (1900) are given. The treatise concludes with a detailed 

 description of the nebula, a discussion of the relation of 

 the star-density to the form and brightness of the gaseous 

 mass in various parts, and the results of a statistical in- 

 vestigation of the distribution of the stars. .Among other 

 results, Herr Gotz finds that all the stars concerned are 

 fainter than the ninth, whilst sixty-four are fainter than 

 the sixteenth, magnitude. The greatest number, taken in 

 magnitudes, are between magnitude 14-0 and 15-0, there 

 being 316 of this class. 



Herr Lohnert's work deals similarly with the distribu- 

 tion of the stars in the other two nebulse named, the results 

 being given in tables and also shown diagrammatically, as 

 are those appertaining to the Andromeda research. 



NEW 



GEOLOGICAL SURVEY 

 MEMOIRS.'^ 



MAPS AND 



(l) "T^HE Geological Survey is making rapid progress in 

 the publication of its re-survey of Cornwall ; the 

 memoir on the geology of Falmouth and Truro (Sheet 352) 

 has already been reviewed in Nature, and that on the 

 Newquay district was described in the issue for May 16. 

 Now we have the Penzance sheet of the map (adjoining 

 that of Falmouth), and an explanation thereof. 



This area includes not only the "Land's End dis- 

 trict," including Penzance and St. Ives, but also the neck 

 of land which unites it to the rest of Cornwall. The 

 district possesses several interesting physical features, for 

 the granite areas up to a height of about 420 feet above 

 the sea exhibit smooth and undulating contours, the 

 ground forming a dissected plateau and rising gently to 

 the foot of a well-marked bluff, which is an ancient sea- 

 cliff. The age of this plateau cannot be fixed for certain, 

 and though Mr. Reid seems inclined to refer it to early 

 Pliocene time, he admits that it may be much older 

 (? Eocene), and may only have been re-modelled and 

 graded in Pliocene times. The low-lying neck of land 

 which lies between Mounts Bay and St. Ives Bay has 

 also an interesting history : originally it may have been 

 part of an Eocene river-valley, but in Pliocene times it 

 was a strait, and the Land's End district was then an 

 island. 



The most important rock-masses delineated on the 

 colour-printed map and described in the memoir are : — 

 (i) the three members of the Lower Palaeozoic system, 

 which are probablv of Ordovician age, but have received 

 local names in Cornwall — the Mylor series, the Falmouth 

 series, and the Portscatho scries ; (2) the masses of 

 intrusive igneous rock — granite and greenstone — which 

 have been thrust through these ancient strata. 



The contact-alterations produced by these successive in- 

 trusions are fully explained. The greenstones (diabasic 

 rocks) are earlier than the granite, and their effects are 

 different from those produced by the latter. Each area 

 of granite is surrounded bv an aureole or belt of altered 

 rock, and the border of the granite itself has been con- 

 verted into schorl-rock (quartz and tourmaline). It is in 

 these altered belts and in the adjacent parts of the granite 

 that the principal mineral wealth of the country has been 

 foimd. 



There is a chapter on the elvans or dyke; of quartz- 



1 (0 "The Geologv or the Lands End District." Ry Clement Reid, 

 F.R.S.. and Dr. J. S. Flett, with contributions bv Messrs. Wilkinson. 

 Dixon. Pollard, and MacAlister. Pp. viii-l-isS ; with six plates. (London: 

 H.M .Stationery Office, 1007.1 Price of memoir v- M-. of map is-. 6d. 



(2) "The Geologv of the Country around Hungerford and Newbury." 

 By H. ]. Osborne White. Pp iv+iso; illustrated. 



Stationery Offic 



-.) Prl 



;of 



2s. 6ti., of map 1 



. 6,r. 



