16 



K N O W LEDGE. 



[January 1, 1894. 



Wcatltfr Lore : n Cnllevtion of Proverbs, Sayintifi, and 

 Rules concerniwi the Weather. By Eiehard Inwards, 

 F.K.A.S. (London : Elliott Stock, 1893). Mr. Inwards' 

 handsome book, of nearly two hundred pages, contains an 

 interesting mine of weather lore. Many of the proverbs 

 afford evidence of keen observation, though most may be 

 said to be only of interest as they point to ancient super- 

 stitions and the universal tendency of mankind to form 

 general conclusions from a too limited observation of facts. 

 Mr. Inwards notes that a great many proverbs about the 

 weather i-ome from Scotland, and but \ery few from 

 Ireland. He has collected the " fossil wisdom " about 

 the weather from Eoman and Saxon times onward, and 

 notes that proverbs concerning particular days must, on 

 account of the reformation of the calendar, be held to refer 

 to times a little later than the dates now affixed. 



Scicncr Notts. 



Mr. Enock, in the Entomnlotjist, seems to forebode a 

 plentiful crop of Hessian fly this year. The farmers, he 

 says, are actually " sowing Hessian fly, " by spreading 

 the screenings from the threshing machine with the rough 

 manure. He suggests /Vce distribution of illustrated sheets 

 by the Board of Agriculture ; but one is tempted to ask, 

 What is the Royal Agricultural Society doing ? 

 — .-♦-* — 



Every student of astronomy has read of the luminous 

 outburst observed upon the sun by Messrs. Carrington and 

 Hodgson in 1859, and the magnetic disturbances which 

 were supposed to be caused by it or to be simultaneous 

 with it. Two brilliant objects appeared upon the sun, 

 near the edge of a simspot, and, after travelling a distance 

 of about thirty-six thousand miles across the surface in five 

 minutes, disappeared. There can be little doubt as to the 

 accuracy of the solar observation, but the statement that 

 the phenomenon was immediately followed by a magnetic 

 storm does not appear to be founded upon fact, though the 

 majority of astronomical text-books lay great stress upon 

 the connection between the two phenomena. An examina- 

 tion of the case has led Mr. W. Ellis, of Greenwich 

 Observatory, to the following conclusions : (1) The solar 

 outburst in 18.59 was seen independently by two obser\ers ; 

 the fact of its occurrence seems, therefore, undoubted. 



(2) The corresponding magnetic movement was small. 



(3) Many greater magnetic movements have since 

 occurred. (1) No corresponding solar manifestation has 

 been again seen, although the sun has since been very 

 closely watched. The erroneous impression has been long- 

 lived, but apparently it must now be abandoned. 



— I * I — 

 The probable origin of cannibalism has recently been 

 discussed by H. Henkeuius. He considers that hunger 

 was the original incentive, and that the vice was persisted 

 in from choipe. Many writers are of opinion, however, 

 that religious motives are accountable for the origin of the 

 custom, and in Polynesia and Central America it certainly 

 occurs most frequently in connection with religious cere- 

 monials. Peschel has pointed out that tribes distinguished 

 by a certain social and intellectual advance are frequently, 

 up to a certain point, more cannibalistic than their less 

 civilized neighbours ; and this would support the view 

 that one chief motive for the practice may be the rather 

 complex idea of acquiring the strength and virtues of the 

 fallen. The proceeding would certainly seem to be anta- 

 gonistic to tlie instincts of the greater number of mam- 

 malian species, and to require as a condition such a con- 

 flicting incentive to these as a strong mental persuasion 

 would supply. 



A curious statement is made in the report of the Royal 

 Commission on the Water Supply of the Metropolis. It 

 is stated that disease-generating bacteria floiurish better in 

 distilled water, or water previously sterilized, than in 

 ordinary river water where other bacteria, as for instance 

 those engaged in putrefaction, are present. There is a 

 natural antagonism between pathogenic and uon-patho- 

 geuic bacteria. Hence where we have very pure water, 

 such as is obtained from the deep chalk, an accidental 

 fouling by infective matter may be more disastrous than if 

 the supply were ordinary river water. This would tend 

 to revolutionize our conception of the necessary conditions 

 of safety in the matter of drinking water. 



11 r 1 1 r V s . 



[The Editor does not hold himself responsible for the opinions or 

 statements of correspondents.] 



COMPARISON OF STAK-PHOTOGRArHS. 

 To thf Editor of Knowledge. 



Deab Sir, — In the October and November numbers of 

 Knowledge are letters from Mr. Glew and Mr. Wilson on 

 a method of comparing different photographs of the same 

 region of the sky, for detecting changes, by superposing a 

 positive (on glass) from one of the negatives over the other 

 negative. 



I originally proposed this method in the Astronomische 

 Xachrichten (No. 3101) nearly two years ago, and have 

 used it before and since that time. 



I enclose a copy of the Nachrichten containing my note 

 on the subject, which I would thank the Editor if he would 

 kindly reproduce in Knowledge, as it seems not to have 

 reached the eyes of some readers, though it was noticed 

 by several astronomical journals when it was published in 

 the Xachrichten. 



Moimt Hamilton, California, E. E. Barnard. 



November 20th, 1893. 



A simple and rapid method of detecting changes on celestial pho- 

 tographs due to moUon or varlahiliti/ of thp celestial bodies. 

 By E. E. Barnard. 



'' Tlie general adoption of photography for the charting of the 

 heavens suggests tlie desirability of some means of facilitating 

 the comparison of photographs of any one region on different 

 dates, for the detection of change or variability. 



" The most careful inspection of such plates by the ordinary 

 methods would be laborious, and would scarcely reveal changes 

 unless they were very striking — repeated measurements of every 

 object being out of the question. 



"In thinking this matter over, it would seem that an admir- 

 able and almost in-stantaneous method is applicable where the 

 photographs have been made with the same instrument — the 

 scale remaining unaltered. 



" Suppose two such jihotogiaphs to have been made on 

 different dates. From one of these negatives, say number one, 

 make a glass contact positive. Superpose this upon negative 

 number two — film to film. Since the scale in each case is the 

 same, the superposed negative number two will completely blot 

 out every image on the positive from number one, if in the 

 meantime none of the objects has moved. If, however, any 

 change has occurred, the images of the moving olijects on the 

 positive will not be obscured, and by holding the two plates, so 

 superposed, to the light the eye will instantly detect the fact 

 by the unobscured image of the object on the positive from 

 plate number one. Now if the interval between the dates of the 

 two photographs is not so great that the moving object has left 

 the region photographed, it can be easily found on plate number 

 two by making a positive of that ])late and superposing it on 

 negative number one ; the position of the object again being 

 made evident bv the unobscured image. 



