September if, 1890] 



NATURE 



487 



communicating with the earth, behave, beyond 120°, as dielectrics 

 of zero inductive power. With prolonged heating, the con- 

 ductivity along the axis quite disappears. Water plays a capital 

 r6le in the conductivity of a great many dielectrics (possibly in 

 all). With plates of baked porcelain kept moist the various 

 types of conductivity could be reproduced. The electromotive 

 forces of polarization of moist porous bodies may attain several 

 hundred volts. 



Prairie dogs, it appears from a recent letter by Dr. Wilder 

 to Science, lack the sense of distance. At Cornell University, 

 several individuals walked ofif chairs, tables, and window-sills 

 unhesitatingly. This is thought to be due to the nature of their 

 usual habitat, a plain, with no sharper inequalities than burrows 

 and mounds. One adult female seemed to have wonderful im- 

 munity from the ill-effects of falls : it once fell from the top of 

 an elevator 21 feet high, and another time from a window-sill, 

 about as high, on a granite pavement, but soon recovered. 

 These animals respond to sudden sound by erecting the body 

 and barking, and the nervous mechanism involved seems to be 

 largely reflex, rapidly exhausted, but nearly or quite uncon- 

 trollable ; indeed, one of those falls seems to have been due to 

 an unguarded erection of the body on hearing a large clock 

 strike. 



The additions to the Zoological Society's Gardens during the 

 past week include a Rhesus Monkey {Macacus rhesus i ) from 

 India, presented by Mr. Jesser Coope, F.Z.S. ; a Nightingale 

 (Daulias litscinia), British, presented by Mr. J. Young, F.Z.S. ; 

 two Green Doves (C/ialcop/iaps indicd) from Ceylon, presented 

 by Mrs. Thompson ; a Common Chameleon {Chameleon vul- 

 garis) from North Africa, presented by Master E. S. Forwood ; 

 two Short-tailed Wallabys {Halmaturus brachyurus) from Aus- 

 tralia, received in exchange; a Brown Capuchin {Cebus fatu- 

 ellus 6) from Brazil, a Squirrel Monkey {Chrysothrix sciurea) 

 from Guiana, a Banksian Cockatoo {Calyptorhynchus banksii) 

 from New South Wales, deposited ; two Red-vented Bulbuls 

 {Pycnonotus hcBmoj-rhotts), bred in the Gardens. 



OUR ASTRONOMICAL COLUMN. 

 Objects for the Spectroscope. 



Sidereal Time at Greenwich at 10 p.m. on September 11 

 2ih. 24m. 28s. 



(i) In the General Catalogue this nebula is described as "a 

 very remarkable object ; pretty bright ; considerably large ; 

 extremely irregular figure ; k Cygni involved." The spectrum, 

 as observed by Dr. Huggins, is a continuous one with a sus- 

 picion of an unusual brightness in the region beyond F. The 

 excess of blue light is probably due to the radiation of some 

 substahce, most likely carbon, added to a dim and short con- 

 tinuous spectrum. The green flutings would in that case be 

 masked by continuous spectrum, and the result would be a 

 spectrum apparently continuous in the green and discontinuous 

 in the blue. This discontinuity should be looked for in the 

 nebula spectrum, and comparisons made with the carbon 

 flutings. 



(2) This star has a spectrum of Group II. " of extraordinary 

 beauty," all the bands 1-9 being very wide and very dark 



NO. 1089, VOL. 42] 



(Duner). It is probably a star of mean condensation, and the 

 bright carbon flutings should therefore be well seen. 



(3) The spectrum of this star may advantageously be studied in 

 connection with the observations of stars which have a spectrum 

 hitherto described as of the solar type. It is one of a very late 

 stage of Group II., the distinctive dark bands being very narrow, 

 so that the spectrum approaches one of Group III. The lines 

 which are seen at this stage will in all probability be continued 

 to Group III. stars, and will therefore serve as criteria for 

 distinguishing between stars of Group III. and stars of 

 Group V. 



(4) Vogel writes the spectrum of this star as W.a (I.a), which 

 means that the star is either at a late stage of Group III., or an 

 early one of Group V. Its precise position on the " tempera- 

 ture-curve " may be determined by reference lo the criteria 

 mentioned in the note on (3). 



(5) The spectrum of this star is one of Group IV. 



(6) Although this star is far from being a faint one compared 

 with many other stars of Group VI., very few details have been 

 observed in its spectrum, either by Secchi or Duner. Duncr 

 simply states that the spectrum consists of three zones, the blue 

 being very weak. The intensity of band 6 (A. 564) relatively to 

 band 9 (A. 517), and other details, should be noted. 



(7) This is a variable of Group II, of very small range and 

 short period. The mean magnitude at maximum is about 8 '85, 

 and that at minimum 9 95. The mean period is about 67-8 

 days, and the increase to maximum is much more rapid than the 

 decrease to minimum, the former occupying 20'6 days, and the 

 latter 47-2. According to Duner, the spectrum is only feebly 

 developed, and this is exactly what it should be if Mr. Lockyer's 

 view as to the constitution of this class of bodies be correct. 

 The central swarm being well advanced in condensation, only 

 revolving swarms of short period will be effective in producing 

 changes of light, because long period swarms will pass clear of 

 the central swarm at periastron. It is only to be expected, 

 therefore, that a well advanced, or "feebly-developed spec- 

 trum should be associated with a short period in variables of 

 Group II. Under these circumstances it is not likely that 

 bright hydrogen lines will appear at maximum, but an observa- 

 tion of their absence will be of value, and other variations may 

 occur. There will be a maximum about September 15. 



A. Fowler. 



Observations of the Companions to Brook's Comet 

 (V. 1889). — Mr. E. E. Barnard, in Astronomische Nachrichten,. 

 No. 2988, gives the physical and micrometrical observations of 

 the companions to this comet made with the 12-inch and 36-inrh 

 refractors of the Lick Observatory, and those made elsewhere. 

 It will be remembered that Mr. Barnard discovered two com- 

 panions to Brook's comet on August 2, 1889, and two others on 

 August 5. His remarks on the appearance of the companions, 

 and the physical changes which they underwent from the date of 

 discovery, until they disappeared from sight, are very im- 

 portant. Two of the companions seemed to undergo the same 

 process of disintegration. Beginning with a nucleus and a tail, 

 each became enlarged, diffused, and fainter, until it had dissi 

 pated into space. In some concluding remarks Mr. Barnard 

 writes : " I have no doubt but that the great telescope would 

 readily reveal more unknown nebulce than the entire number 

 now contained in the latest catalogue of Dreyes," and the 

 number of unknown nebulce incidentally found by him during 

 these observations supports this assertion. 



Parallax of /3 Orionis. — In the Observatory for Septem- 

 ber, Dr. Gill has a note on the parallax of ^ Orionis. The star 

 is situated near one corner of the nebulous area encircled by 

 a Orionis, Lalande 1 1382, Lalande 1 1329, « Orionis, (^ Orionis, 

 and ;3 Eridani, and the observations show that it has a negative 

 parallax of about o"*l7 relative to the near parallax of the stars 

 D.M. - 7° 997 and -8° 1078, and therefore belongs to a more 

 distant system. It also results from the calculations that the 

 former star and 8 Orionis are members of an immensely more 

 remote system than the latter one. The reductions were sug- 

 gested by an examination of a photograph of the region about 

 the Orion nebula taken under the direction of Prof. E. C, 

 PickeriDg. 



Carl Frederik Fearnley.— The death of this eminent 

 Norwegian astronomer occurred on the 23rd ult. at Christiania. 

 He was born at Frederikshald on December 19, 1818. In 1844 

 he became attached to the Observatory of Christiania Univer- 

 sity as an assistant, and since 1861 has been the Director. He 

 was made a Professor of Astronomy in 1857. 



