172 



NATURE 



[April 26, 19 17 



difficult to prevent interference of traces when three 

 elements are included in a single sheet. Only great 

 care and resourcefulness could have dealt .with the 

 difficulties as satisfactorily as has been done in the 

 present case. 



In addition to the high prices and short quantities 

 of printing paper ilow available, strawboard, which is 

 necessary for the binding of books, has risen enor- 

 mously in price, whilst a famine in that commodity 

 threatens soon to deprive the publishing trade alto- 

 gether of the power to bind books in cloth. At no 

 distant date, therefore, it is probable that we shall 

 see English books issued with paper covers, a state 

 of things which may continue indefinitely, def>ending 

 not so much upon the cost of this essential material 

 as the length of time which must elapse, even after 

 the war, before there are again sufficient supplies 

 available. It is clear that in the very near future 

 publishers, binders, and booksellers will have, in re- 

 gard to the majority of books, to adapt themselves to 

 a new order of things, and the public will have to 

 be satisfied with books issued, as is so widely the 

 custom on the Continent, in paper covers. 



Mr. John Murray's new list of announcements con- 

 tains, among others, " Collected Essays and Ad- 

 dresses," by Sir F. Darwin (some of the subjects 

 dealt with are "Sir Francis Galton," "Sir George 

 Darwin," "The Movements of Plants," "The Educa- 

 tion of a Man of Science," and "The Teaching of 

 Science ") ; a new and revised edition of " The Book 

 of the Rothamsted Experiments," edited by Dr. E. J. 

 Russell, containing a chapter by A. D. Hall on the 

 secondary effects of manures on the soil, and one by 

 Dr. Russell on the production of plant food in the 

 soil; and "A Regimental Surgeon in War and 

 Prison," by Capt. R. V. Dolbey. 



OUR ASTRONOMICAL COLUMN. 



A New Comet. — In a message to the Times of 

 April 20, dated April 19, it is stated that a comet of 

 marked brilliancy had been observed at Sydney. It 

 was seen in the eastern sky at dawn, and Prof. Cooke 

 is said to have described it as a new comet. The 

 position of the comet had not been determined. 



Comet b 1916 (Wolf). — ^The following continued 

 ephemeris, for Greenwich midnight, is given by Prof. 

 Crawford in Lick Observatory Bulletin No. 289: — 



1917 R.A. Dec). Log ^ Bright- 



fa. m. s. „ , ness 



April 26 20 21 28 -i-ii 12-2 01994 2-8l 



27 23 55 29-0 



28 26 22 II 459 01943 



29 28 49 12 2-8 



30 31 16 19-6 01892 301 



May I 33 43 364 



2 36 9 12 53-2 01841 



3 38 36 13 9-9 



4 41 2 266 01 79 1 3-21 



5 43 28 43-2 



6 45 55 13 59-8 01742 



7 48 21 14 16-4 



8 50 47 32-9 0-1694 342 



9 53 13 14 49-3 



10 55 38 . 15 5-7 o 1646 



11 20 58 4 219 



12 21 o 29 38- 1 01599 363 



The unit of brightness ii that on March 5, and the 

 figures given in the last column should be multiplied 

 by 17 to reduce to the unit of brightness on 1916 

 May 10. 



The path of the comet during the above period is 



NO. 2478, VOL. 99I 



through the constellation Delphinus. On May i the 

 comet rises about 10.45 p.m. G.M.T. It is now an 

 interesting object in the telescope, but it has been 

 disappointingly faint, and it does not seem very prob- 

 able that it will become visible to the naked eye. 



The distance of the comet from the earth on 

 April 30 will be 144,000,000 miles, and on May 10 

 136,000,000 miles. 



The April Lyrids. — These meteors appear to have 

 been more active than usual this year, and the maxi- 

 mum occurred on April 21. On April 20 Mr. Denning 

 watched a beautifully clear sky at Bristol, and recorded 

 twenty-one meteors in three and a quarter hours; of 

 these, six were Lyrids. On April 21 the sky was over- 

 cast at Bristol, but Mrs. F. Wilson reports from 

 Totteridge that the firmament cleared at about 11 p.m. 

 G.M.T., and that thirty-five meteors, chiefly Lyrids, 

 were observed in the two and a half hours up to 

 13.30 G.M.T. Others must have been missed while 

 the paths of the brighter objects were being registered. 

 The radiant point was at 272° -f 34°, and precisely the 

 same as found independently at Bristol on the previous 

 night. One fireball was observed at Totteridge, and 

 the Lyrids were recorded as very swift and as usually 

 leaving streaks. 



On April 22 the weather at Bristol was very favour- 

 able after 9.30 G.M.T., but a watch for meteors main- 

 tained for about two and a quarter hours yielded only 

 six, half of which were Lyrids. 



The conclusion that this important meteoric stream 

 recurs under a very plentiful aspect at periods of about 

 sixteen years is confirmed by this year's observations. 



Stellar Spectra of Class R. — The second volume 

 of the publications of the Detroit Observatory, which 

 has recently been issued by Prof. Hussey, furnishes 

 further-evidence of the energy- and thoroughness with 

 which astrophysical investigations are carried on in 

 America. The chief subjects dealt with are stellar 

 spectra of type B containing emission lines, by R. H. 

 Curtiss; observations of stars of class Md, by P. W. 

 Merrill ; the spectrum of ^ Ursae Majoris, by L. Had- 

 ley; and the spectra of stars of class R, by W. C. 

 Rufus. In each case a review of previous work is a 

 valuable feature, and the volume is enriched by 

 numerous beautiful reproductions of spectra. While 

 all the contributions add considerably to previous 

 knowledge, that on the stars of class R calls for 

 special notice, as there has been much doubt as to 

 the place of these stars in the' stellar sequence. The 

 peculiarity of class R spectra is that they include 

 rays of shorter wave-length than is the case with the 

 ordinary fourth type (N) stars. Ten of the sixty-six 

 known members of the class have been studied in 

 great detail^ and six spectra of class N were also 

 photographed for comparison. Mr. Rufus finds that 

 the strength of carbon absorption is not a distinguish- 

 ing feature between classes R and N, and that the real 

 criterion for differentiating them is the intensity of 

 the continuous absorption in the violet. The out- 

 come of the discussion is to suggest that stars of 

 class R form a connecting-link" between the solar type 

 and class N, and that the evolutionary sequence 

 divides at the solar type, classes K and M forming 

 one branch, and classes R and N constituting the 

 other. The alternative possibility that classes M and 

 K may belong to an ascending branch of the tempera- 

 ture curve, as would be the case in Lockyer's classi- 

 fication, does not appear to have been considered. 



The radial velocities of the ten class R stars range 

 from —49 to +25 km. per second, and give an 

 average of 14-9 km. when corrected for the solar 

 motion. The average colour-index is 1-7, as compared 

 with 2-5 for class N. 



