134 



KNOWLEDGE 



[July 1, 1893. 



condensation in the rich Sirian region (Puppis) Canis, 

 Orion, Taurus, lies off the southern border of the Galaxy 

 before cutting through it in Perseus and Cassiopivia, whilst 

 after that point the whole mass of Sirian condensation 

 passes north of the southern edge of the Galaxy, from 

 which it recedes further northward as we descend through 

 Cepheus, Cygnus, Lyra, Hercules, and Ophiuchus to 

 Scorpio, the southern limit of the Draper catalogue. 

 There is not a doubt that the completion of the Harvard 

 spectroscopic survey will show the main line of Sirian 

 condensation to be coincident with the great belt through- 

 out its course. 



Mr. Monck says that Solars seem to preponderate iu 

 Sobieski's Shield. As may be seen from the curves of 

 distribution published with the paper mentioned, there is a 

 very decided preponderance of Solars iu this region, and, 

 as I remarked at the time, this is the only point where the 

 Solars gain supremacy over the Sirians in the Galaxy, a 

 fact more remarkable still when it is remembered that this 

 rich solar group, unique in its nature, lies immediately off 

 the break, equally unique, which occurs in the great belt 

 of bright stars in its passage through Ophiuchus. If this 

 break be not physical, then it can be optically produced 

 only by the proximity of the sun to the great belt at this 

 point, causing an apparent dispersion of its constituent 

 stars ; and this solar group, I feel sure, is in some way 

 involved. I am, Sir, yours faithfully, 



Stretford, Lancashire, J. Maclair Boraston. 



June 6th, 1893. 



the 



It 

 the 



To tJu Editor of Knowledge. 



Groningen, 12th June, 1893. 



Dear Sir, — Will you allow me some space to say a 

 couple of words in answer to some remarks made by Mr. 

 Monck in the April and June numbers of Knowledge. 



In the first, he remarks that it seems as if the 

 diminishing of the difference between the photometric and 

 photographic magnitudes, as we pass outward from the 

 Galaxy, might be explained by systematic error in 

 eye estimations of the stars in the Galaxy. 



To a great extent this must doubtless be conceded. 

 can only be called iu question if the dinrtion and 

 amount of this systematic error, as determined by photo- 

 metric methods, proves sufficient to explain the divergencies 

 found. My discussion of the whole matter has been 

 published in the " Bull, du Com. intern, pour 1' ext'cut. 

 photogr. de la Carte du Ciel," tome II. (1892). 



In consulting this publication Mr. Monck will find that 

 I carefully considered this point, with the result that, as 

 the photometric observations as yet published seem to 

 make it inadmissible to attribute to the error in question 

 a value exceeding 0-2 m. or 03 m., this error is in- 

 sufficient to cover the facts. 



In regard to the letter inserted in the June number, I 

 may say at once that 1 am fully aware of the fact that 

 several points investigated by myself, in respect to the 

 distribution of stars in space, have been independently 

 suggested by Mr. Monck, and I feel very happy to find our 

 results in general mutually confirmed. This extends to 

 the remark made by him about the distinction to be 

 drawn between Capellan and Arcturian stars. Though I 

 was led to this same conclusion, even at the time of my 

 first publication, I have not as yet published anything 

 about it because I hoped to be able shortly to investigate 

 a far greater number of stars, and especially because Prof. 

 Pickering's sub-classes are less trustworthy and to a large 

 extent dependent on the magnitude. Now that attention 

 has been called to the fact it may be well to state the 

 rude results arrived at. 



Of 374 stars of the 2nd type with proper motions 

 exceeding 0"16 (Stumpe's stars) 



40 per cent, belong to Pickering's class F 

 18 ,, ,, „ ,, ,, G 



42 K 



Prof. Pickering finds for all his stars (without regard to 

 proper motion) 



22 per cent, belonging to class F 

 20 ,, ,, „ ,, G 



52 ,, ,, ,, ,, K 



So that, of the stars of the 2nd -type, those of the class 

 F seem to be especially condensed about the sun. 



I feel less inclined to agree with Mr. Monck about the 

 question of the equality of the absolute velocity of the 

 1st' and 2nd type stars, and I think he exaggerates our 

 ignorance on this point. I feel somewhat confident that, 

 after having carefully considered the proof of my Prop. X. 

 in the June number, he will agree with Miss Gierke that 

 it is difficult to contest, in the present state of knowledge, 

 the conclusion that stellar rates of ti'avel are independent 

 of spectral distinction. 



In conclusion, I may perhaps be allowed to state more 

 clearly than I have perhaps done as yet, that my paper on 

 the systematic dift'erence of photographic and visual mag- 

 nitudes in various parts of the sky, as well as those on the dis- 

 tribution of stars in space, are to be considered as jmrisidiuil 

 only — several points require a more exhaustive research, 

 partly to be based on yet more extensive materials. 



Especially the question, "Is it true that galactic and 

 extra-galactic stars have equal linear velocities, and if not, 

 in what proportion do they vary ? " seems to call for a far 

 more exhaustive investigation. Only the consideration 

 that these investigations will take of necessity a very 

 considerable time, has determined me in publishing results 

 that cannot be considered as quite definitive. 



Yours sincerely, J. C. Kapteyn. 



THE GOVERNMENTAL INQUIRY AND THE 

 FIELD-VOLES. 



By W. F. KiJtiiY, F.L.S., F.E.S., Assistant in the Zooloijicul 

 Tiepartment, British Museum (\atunil Histari/), South 

 Kensini/ton. 



BLUE-BOOKS dealing with scientific subjects are 

 more common now than formerly, and much 

 information which will be useful both to naturalists 

 and agriculturists has been brought together in 

 a convenient form, in the recently published 

 " Report of the Departmental Committee appointed by the 

 Board of Agriculture to inquire into a plague of field-voles 

 in Scotland, with minutes of evidence and appendices, and 

 a copy of the minute appointing the Committee.'' 



The field-voles are small animals resembling mice, which 

 appear from time to time in enormous numbers in various 

 countries, and cause very serious injury to the crops. 

 During 1891 and 1892, the southern counties of Scotland 

 have been devastated by the short-tailed field- vole, and, 

 according to Mr. R. F. Dudgeon's estimates, drawn up 

 early in 1892, " in Roxburghshire, 30,000 to 40,000 acres 

 had been affected, of which he considered 12,000 to 15,000 

 acres had been rendered useless ; in Dumfries-shire, 40,000 

 to .50,000 acres, and in the stewartry of Kirkcudbright, 

 10,000 to 12,000 acres were described by him as infested 

 by voles." 



So serious became the evil that a Committee of Inquiry 

 was appointed by a minute dated the 28tli May, 1H92 ; and 

 it is their report which has just been issued. In the spring 

 of 1892, Dr. Loeftier, a German bacteriologist, announced 

 that he had discovered a new bacillus, producing a disease 



