428 



NATURE 



[August 28, 1890 



Countless swarms of rats periodically make their appearance 

 in the bush country of the South Island, New Zealand. They 

 invariably come in the spring, and apparently periods of about 

 four years intervene between their visits. In a paper published 

 in the new volume of the Transactions and Proceedings of the 

 New Zealand Institute, Mr, Joseph Rutland brings together 

 some interesting notes on the bush rat {Mus maorium). In size 

 and general appearance it differs much from the common brown 

 rat. The average weight of full-grown specimens is about 2 

 ounces. The fur on the upper portions of the body is dark 

 brown, inclining to black ; on the lower portions white or 

 greyish-white. The head is shorter, the snout less sharp, and 

 the countenance less fierce than in the brown species. On the 

 open ground bush rats move comparatively slowly, evidently 

 finding much difficulty in surmounting clods and other impedi- 

 ments ; hence they are easily taken and destroyed. In running 

 they do not arch the back as much as the brown rat. This 

 awkwardness on the ground is at once exchanged for extreme 

 activity when they climb trees, These they ascend with the 

 nimbleness of flies, running out to the very extremities of the 

 branches with amazing quickness ; hence, when pursued, they 

 invariably make for trees if any are within reach. The instinct 

 which impels them to seek safety by leaving the ground is 

 evidently strong. A rat, on being disturbed by a plough, ran 

 for a while before the moving implement, and then up the horse - 

 reins, which were dragging along the ground. Another 

 peculiarity of these animals is that when suddenly startled or 

 pursued they cry out with fear, thus betraying their whereabouts, 

 an indiscretion of which the common rat is never guilty. 



In a paper recently read before the Vienna Academy, Herren 

 Elster and Geitel give the results of a year and a half's observa- 

 tions of atmospheric electricity on the north side of Wolfenbiittel 

 (bordering an extensive meadow). They used a stand carry- 

 ing a petroleum flame and connected by insulated wire with an 

 electroscope. A marked difference was found in the phenomena 

 of spring, summer, and autumn, on the one hand, and winter 

 on the other. In the former the daily variation of the fall of 

 potential showed a distinct maximum between 8 and 9 a.m., as 

 Exner found at St. Gilgen, and a distinct minimum between 

 5 and 6 p.m., whereas Exner found a maximum about 6. 

 In winter there is great irregularity ; but a weak minimum 

 occurs about II a.m., and a more decided maximum about 

 7 p.m. It appears to the authors that other factors than 

 humidity, with which Exner seeks to explain the variations, are 

 concerned in the case. When the temperature goes below zero, 

 cold mist being then generally present, there is often rather a sharp 

 rise in the values, the aqueous vapour having then less action. 

 Rainfall in a neighbouring region lowers the fall of potential 

 both in winter and summer, and a disturbance of the normal 

 course will announce a coming change in places still unclouded. 

 Snow, it seems, rather raises the values. It has been shown by 

 Linss that the course of the fall of potential is inversely as the 

 coefficient of dispersion of the air for electricity ; which, again, 

 depends not only on the dust and aqueous vapour present, but 

 also, according to Arrhenius's theory, on a sort of electrolytic or 

 dissociative action of the sun's rays on the atmosphere (thus it 

 has been shown that electricity escapes from a conductor under 

 the influence of ultra-violet rays). The authors find their results 

 support this latter view. They consider that the electric pro- 

 cesses during formation of precipitates are the chief cause of 

 the disturbance of the normal condition. 



The additions to the Zoological Society's Gardens during the 

 past week include a Rhesus Monkey (Macacus rhesus) from 

 India, presented by Miss "White ; a Common Fox {Cams vtclpes), 



British Isles, presented by Mr. H. Fane Gladwin ; a • Fox 



[Canis ) from Buenos Ayres, presented by Mr. J, R. Bell ; 



NO. 1087, VOL. 42] 



a Common Otter (Lutra vulgaris), British Isles, presented by 

 Mr. W. Corbet ; a Punjab Wild Sheep [Ovis cycloceros) from 

 India, presented by Dr. W. King ; two European Scops Owls 

 {Scops gui) from Austria, presented by Mr. Edward R. Divett ; 

 six Prussian Carp (Carassius vulgaris), British fresh waters, 

 presented by Mr. G. S. Godden ; three Pochards {Fuligula 

 ferina), Europe, purchased ; a Yak {Poephagus grunniens), a 

 Yellow-footed Rock Kangaroo {Petrogale xanthopus), and three 

 Cambayan Turtle-doves {Turtur senegalensis), bred in the 

 Gardens. 



OUR ASTRONOMICAL COLUMN. 



Objects for the Spectroscope. 



Sidereal Time at Greenwich at 10 p.m. on August 28 

 2oh. 28m. i6s. 



(i)G.C. 4572 ... . 



(2) P Cygni 



(3)D.M. -I- 17° 4370 



(4) e Delphini ... , 



(5) a Delphini 



(6) 228 Schj . 



(7) X Ophiuchi ... , 



Mag. 



R.A. 1890. Decl, 



Var. Yellow. 



Reddish-yellow. 



4 1 Yellowish-white. 



3 5 • White. 



7 Reddish-yellow. 



Var. Red. 



h. m. s. 



20 17 28 

 20 13 44 

 20 33 4 

 20 28 o 

 20 34 30 

 19 28 I 

 18 33 7 



+ 19 45 

 +37 41 

 + 17 S3 

 + 10 56 

 + 15 31 

 -1634 

 + 8 44 



Remarks^ 

 (i) This is a fine though small planetary nebula, with four 

 minute stars in close proximity. Lord Rosse described it as "a 

 beautiful little spiral." In 1866 Dr. Huggins observed the 

 spectrum of the nebula, and recorded : — " The spectrum of this 

 nebula consisted of one bright nebulous line of the same re- 

 frangibility as the brightest of the lines of nitrogen. No other 

 line was certainly seen." It is evident that this observation has 

 an important bearing on the character of the chief line of the 

 nebula spectrum, and it would be well if some other observer 

 would take the trouble to reobserve it. It should be noted also 

 whether the nebulosity is limited to one side of the line, or is 

 equally visible on both sides. 



(2) In i6co, this appeared as a bright star, but it has since 

 been comparatively faint. It is especially interesting from the 

 fact that its spectrum contains bright lines, chief amongst these 

 being the lines of hydrogen and D3. The Henry Draper 

 Memorial photograph, however, shows in addition a very bright 

 line near A. 447, which Mr. Lockyer suggests, from its association 

 with Dg, is Lorenzoni's/of the chromosphere spectrum. It will 

 be remembered that this line occurs also in the spectrum of the 

 Orion nebula. Hence, the lines in the visible part of the spectrum 

 which are common to P Cygni and the Orion nebula are 

 hydrogen (F and G), Dg, and 447 (/) ; another bright line in the 

 violet is also common to the photographs of the two spectra. 

 This similarity is evidently in favour of the view that stars with 

 bright line spectra are similar in constitution to nebulae, though 

 they are probably more condensed. It will be an interesting 

 inquiry to see if P Cygni has anything more in common with 

 nebulae in the visible spectrum. 



(3) According to the records of the spectrum of this star, it is 

 one of the finest of Group II. Duner calls it superb, all the 

 bands 2-9 being extremely wide and dark. It affords a good 

 opportunity for further observations of the pecuKarities of this 

 class of spectrum. 



(4) Gothard states the spectrum of this star as ? W.a, whilst 

 Vogel writes it \,a (Group IV.). My own observations confirm 

 Vogel's statement, the spectrum being almost like that of a 

 Lyras. 



(5) A star of Group IV. 



(6) This is a star of Group VI., showing the secondary bands 

 2, 3, 4, and 5 (all in the red and yellow) in addition to the bands 

 of carbon. The star is not so red as most of the members of the 

 group, and this is no doubt due to the absorption of red light by 

 the secondary bands. Other details should be looked for. 



(7) This Group II. star will reach a maximum about September 

 5, and the appearance of bright lines, as in other variables of the 

 same type, may be expected. The period is about 300 days, and 

 the magnitude changes from 6 "8 to 9. A. Fowler. 



