=;i8 



NA TURE 



[September 19, 1907 



roinid and say : " ^'cs, but uur stars were selected because 

 they had big proper motions." They thereby screen 

 entirely the (act that the fundamental hypothesis that the 

 brighter stars are much the nearer as yet awaits statistical 

 demonstration. Miss Gibson worked on the seventy-two 

 stars given by Nevvcomb, as of fairly well-ascertained 

 parallax. Mr. Hinks says that the peaks in Miss Gibson's 

 parallax-magnitude curve are in two out ol three cases 

 due to selection of certain stars because of their excep- 

 tional proper motion. Now this naturally leads us to 

 inquire why the stars with magnitudes about 2 and again 

 about 6 were not selected by their proper motions, but 

 those about 4 and 5 and again those about 7 to g were. 

 Further, there is a fundamental point which Mr. Hinks 

 has to meet. Statistically to produce large effect on the 

 correlation of two quantities by selection, the character 

 used for selection must have high correlation with both. 

 In other words, if the selection of stars by proper motion 

 is to pull down the assumed high relationship between 

 magnitude and paralla.x to a low value, not only must 

 magnitude and proper motion be highly correlated, but 

 proper motion and parallax. Now these correlations have 

 been carefully investigated, and we know what they are — 

 they are such as to influence, but not very much influence, 

 any relation between parallax and magnitude. Now 1 

 think the circular process of the reasoning I have referred 

 to will be visible. It runs as follows : — 



There is a high relationship between parallax and 

 magnitude ; it is not statistically evident, because the 

 parallax stars have been chosen on account of proper 

 motion ; this involves a very high correlation between 

 proper motion and magnitude ; a very moderate correlation, 

 but not a high correlation, does exist. Shall we say that 

 these stars have been selected by reason of something else ? 



Surely the hypotheses of high relationshJps between 

 magnitude and parallax and proper motion are of 

 sufficient importance to deserve proof, rather than to be 

 taken as axiomatic? If the reader will examine Table III. 

 of vol. ii. of the Yale Observatory Memoirs (p. 202), 

 which has reached me since Miss Gibson's memoir 

 appeared, he will find the parallaxes of 163 stars, differ- 

 ing widely from Newcomb's series, dealt with, but the 

 correlation ratio (0-28) is even less than that (0-40) found 

 for Newcomb's material. The specious appearance of 

 descending magnitude wnth the paralla.x groups is almost 

 wholly due to the first group of large negative parallaxes, 

 which seems merely to signify that large errors of parallax 

 are more common with faint stars. I take it that 

 035 is an excessive value for the relationship between 

 proper motion and magnitude.' Against these merely 

 moderate relationships I would place those connecting 

 spectral class and magnitude, which can be as high as 

 0'6q, and, again, the fact that colour and magnitude arc 

 related at least as closely as parallax or proper motion 

 and magnitude; and I would venture to ask whether it 

 may not be that the mass, the chemical constitution, and 

 the life-history of a star, as evidenced in its spectroscopic 

 character, have sensibly more to do with the magnitude 

 than its mere distance? After all, almost any theory of 

 distribution of stellar mass, position, and motion would 

 lead us to expect a relatively small correlation between 

 proper motion and distance, sensible, indeed, on the 

 average of great numbers, but as ineffectual for the pur- 

 pose of selecting an individual as choosing an able 

 assistant by a preliminary measurement of his head. 



K.ARL Pf-.arson. 



Biometric Laboratory, University College, London. 



Plague Prevention in India. 

 His Majesty's recent letter on this subject to the 

 Government of India was well designed to stimulate the 

 Government to more active efforts against the disease, but 

 has been followed by pronouncements from it which do not 

 suggest any strong 'hope that that object will be attained. 

 In these pronouncements the Government of India issues 

 advice to the heads of local administrations regarding the 

 methods of dealing with plague— a familiar matter ; but, 



1 Dr. A. Lee has worked out for me the correlation ratio for more than 

 330 northern and 303 southern stars in Bo«'s catalogue. For the southern 

 stars the correlation of magnitude and proper motion is insignificant, for the 

 northern stars it is much less than in the above cases, and would be in- 

 sienificant but for a group of four stars with maEnitude less than 1 -5. These 

 points will be brought out in a forthcoming memoir. 



NO. 1977, VOL. 76] 



as the Pioneer Mail of August 23 remarks : — " Nothing 

 is said about finding the money for the proper carrying 

 out of these recommendations." There is, moreover, 

 another defect which suggests further doubts. The whole 

 of the edict is filled with injunctions to avoid " any action 

 which excites the opposition of the people." Now as 

 almost every sanitary action, from cleansing the back- 

 yard upwards, does excite the opposition of a large per- 

 centage of the people, this policy means, I fear, not the 

 advancement, but the abandonment of any large-scale 

 operations against plague in India. 



Obviously, in epidemics as in war, the superstitions, 

 fancies, and trifling objections of the individual must give 

 way to the public interest. The only alternative is wide- 

 spread death. To use compulsion may be unpleasant to 

 a Government, but it is a duty to use it. If a Govern- 

 ment does not use compulsion it must be held responsible 

 for the fatal results. In my experience, popular opposi- 

 tion to sanitary measures is not really a serious matter. 

 The strength of it is in inverse proportion to the capacity 

 and resolution of the authorities. What opposition has 

 occurred in this case has, I think, been created largely 

 by the original weakness which gave in to it. It is useful 

 to coinpare the despotic and successful sanitary methods 

 of the Americans with the feeble and futile system adopted 

 in India. 



It is difficult to see the object of this pronouncement of 

 the Government of India, which will apparently tend only 

 to hamper executive officers in the performance of their 

 duties. We must infer that the recommendations were 

 made chiefly with a view to please the numerous pseudo- 

 philanthropists w'ho e.xert so much evil influence in the 

 councils of the great empire of Letspretendia. 



Those who wish to ascertain w'hat is really being done 

 against plague in India, compared with statements in 

 Parliament, should consult Prof. Simpson's recent lecture 

 in the Lancet, especially that of July 27. According to 

 him, the Government has spent only about 1,500,000!. on 

 plague prevention, against 17,000,000!. on famine relief, and 

 this in spite of the fact that 20,000,000?. surplus revenue 

 has been collected during the same period (since 1896). 



I have not seen any complete discussion of the actual 

 measures which should now be taken against plague in 

 India, but think that the following will be approved of 

 by most hygienists who have considered the matter : — 



(i) The whole of the plague administration should be 

 centralised, removed from the hands of the civilians who 

 have hitherto obtained such poor results, and put in those 

 of experts, on the .American system. This administration 

 should allot the expenditure, indicate the researches, direct 

 the practical measures, publish monthly reports showing 

 exactly what it is doing, and be held responsible for the 

 results of its work. 



(2) The expenditure on plague research should be in- 

 creased ten-fold. The present commission is doing excel- 

 lent work, but the investigations can be obviously enlarged 

 so as to include many new fields, such, for instance, as the 

 search for a specific therapeutic agent, on the lines of work 

 now being done in connection with sleeping sickness. 



In the message of the Government of India there is no 

 sufficient statement on either of these important points. 

 We may rest assured that if they are not included the 

 plague measures w'ill remain as ineffective as before. 



Ronald Ross. 



The University, Liverpool, September 16. 

 Root-action and Bacteria. 



In Nature of July 18 (p. 270) I mentioned that I had 

 proved the excretion from plant roots of a toxic substance. 

 This substance proves to be alkaloidal in nature, and is 

 precipitated, in addition to the usual alkaloidal reagents, 

 by most of the substances in use as artificial manure. 

 Potassium sulphate and chloride appear to be the most 

 complete precipitants of all the reagents so far tried. 

 They appear to precipitate the substance in the form of a 

 base — a white amorphous powder. The amount excreted 

 is by no means negligible, and Sesamiim indicum, indeed, 

 in its early stages at least, appears to excrete more solid 

 matter than it builds up in its own substance. 



Details are given in a Memoir of the Agricultural Depart- 

 ment of India. F. Fletcher. 



Ghizeh, Egypt, August 22. 



