January 12, 1922] 



NATURE 



55 



resistance in the horn type was very detrimental, that 



I the electrolytic type was very efficient, but that its 

 fclpense limited its use, and that the multigap type 

 ftas an efficient and cheap type of lightning arrester, 

 r. Messrs. Longmans and Co. have in the press 

 ?* Modern Practice in Heat Engines," by T. Petrie, 

 phich is intended to form a companion to the late 

 pr. Inchley's "Theory of Heat Engines." It deals 

 With the subject of power from heat engines as a 

 whole, and attempts to show how far theory may be 

 applied to the design of modern types. The book is 

 divided into three sections, steam boilers, steam prime 

 movers, and internal-combustion engines, each section 

 containing a descriptive chapter on the latest types 

 with sectional 'illustrations which, in many cases, 

 i>proximate to working drawings. Another book an- 

 •unced by the same publishers is a translation, by 

 Dr. J. S. Thomas, of Prof. A. Smits's "The Theory 

 of Allotropy. " 



Mr. F. Edwards, 83 High Street, Marylebone, 

 W.I, has just issued a Hand-list (No. 422) of Bio- 

 graphies, .Autobiographies, Diaries, Journals, Corre- 



spondence, etc., of Famous Men and Women. Many 

 men of science are represented in the catalogue. 



.Mr. E. Marsden, one of the authors of " Geography 

 for Junior Classes," of which a short notice appeared 

 in Nature of December 22 last, writes to point out 

 that the phrase "lines and belts of equal heat," which 

 the reviewer remarked "is bad anywhere," occurs 

 also in Geikie's "Elementary Lessons in Physical 

 Geography " and in the revised edition of Huxley's 

 "Physiography." The use of the phrase in other 

 books does not, however, alter the reviewer's objection 

 to it. 



In an article entitled " Fisheries Biology " in 

 Nature of December 2q, p. 585, it is stated that "the 

 spur-dog and nurse-hound are viviparous." Mr. E. 

 Ford writes to inform us that the term "nurse- 

 hound " is applied at Plymouth to Scyliorhintis stel- 

 laris, which is not viviparous. We understand from 

 the writer of our article that confusion has arisen 

 from the fact that the name "nurse-hound" is also 

 used by fishermen in his district to refer to Musiehus 

 vulgaris, which is viviparous. 



Our Astronomical Column. 



The Shower of January Meteors. — A rather 

 abundant display of these objects was observed on 

 the night following January 3. Mr. W. F. Denning 

 writes as follows : — .'\t Bristol the early part of the 

 evening was clear, and between 5.40 and 6.50 p.m. 

 meteors app>eared at the rate of thirty per hour. 

 Clouds, wind, and sleet "then interrupted watching 

 until about q p.m., when the atmosphere again 

 cleared, and the remainder of the night was splendidly 

 favourable for observation. The shower, however, 

 declined in numbers strikinglv, for in the two or 

 three hours preceding midnight the hourly rate of 

 apparition was only twelve, and there was a further 

 falling off as the night progressed. The radiant point 

 was at 232°+ 53°. Large meteors were frequent, and 

 a number of them have been recorded at several 

 'Stations. Miss A. Grace Cook witnessed the event 

 from Stowmarket and saw a considerable number of 

 meteors on the two nights January 2 and 3. She 

 registered a fair proportion of large ones, and found 

 the maximum intensitv occurred in the early part of 

 January 3. The radiant was at 23i°+53°. 



.Spectral Evidence of a Persistent -Aurora. — 

 Bulletin No. 76 (vol. 3, No. i) of the Lowell Ob- 

 servatory, contains an interesting account by Mr. V. .\1. 

 -Slipher of his successful attempts to show that the 

 aurora is always present in the night sky. Working 

 on the fact that the spectrum of the aurora consists 

 of certain emissions, of which one in the yellow- 

 green is so intense relativelv as to contain a con- 

 siderable portion of the total auroral light, he finds 

 :' it possible to record this line with an exposure of 

 ^ only a few hours, even if there be moonlight. The in- 

 f strumen^ he emplovs is a spectrograph with a 66 

 il^ degree flint glass prism, and a Dallmeyer lens of f/iq 

 ratio, the photographic plates being of the Cramer 

 i-orhromatic brand. This spectrograph was usuallv 

 -implv pointed to the skv, but in some cases a small 

 objective was placed in front of it. All the exposures 

 he made showed the characteristic auroral line, thus 

 proving the existence of auroral illumination, per- 



NO. 2724, VOL. 109] 



sistent or permanent at least over the period covered 

 by his series of plates, which commenced in the vear 

 iqi5. The two plates which accompany his paper 

 show the auroral line dearly on both moonlight and 

 moonless nights. 



Movements in Spiral Nebl'l.^.— Dr. Jeans ex- 

 hibited at the November meeting of the Roval Astro- 

 nomical Society some slides sent by Dr. Van 

 Maanen, showing movements in the spirals M loi and 

 M 33. He demonstrated that the only tenable motions 

 that would conserve the equiangular spiral forms were 

 compounded of pure rotation and motion along the 

 arms. The latter type greatly predominates in these 

 nebulae, and the indicated times of revolution round 

 the nucleus are 85,000 years and 160,000 years re- 

 spectively. Since only two whorls of nebulosity can 

 be traced, implying a duration of a third of a million . 

 years, it was conjectured that the outer whorls may 

 have become invisible, just as the puffs of steam from 

 a locomotive soon dissipate. By the combination of 

 observed shifts with line-of-sight velocilies, a distance 

 of 2000 parsecs was deduced for M 33. This would 

 be fatal to the island-universe hypothesis, since it 

 would place the object well within the confines of the 

 galaxy. There have been fairly regular oscillations 

 of opinion on the hypothesis, the prevailing view at 

 the Roval Astronomical Society's meeting being hos- 

 tile to it. 



A Bright Fireball. — Mr. G. E. Sutcliffe writes 

 from Shahpur, Ahmedabad, India, that on Novem- 

 ber 22 last, at about 6 a.m., when gazing towards the 

 Southern Cross, he saw a large fireball emerging 

 from the horizon. The object appeared to be ap- 

 proaching him and to move more slowly than ordinary 

 shooting stars. It became intensely brilliant. Its 

 motion was directed nearly from south to north, and 

 it passed a little to the east of his zenith. During 

 the early part of its track the fireball was globular in 

 shape, and it had a distinct tail like a comet. 



