NATURE 



[October 24, 1912 



MM. Fayet and Schaumasse find the elements of the 

 orbit of this object to be almost identical with those 

 of Tuttle's comet. 



Comet 1912a (Gale). — The following set of elements 

 for the orbit of comet 1912a, from which he derived 

 the corrected ephemeris we gave last week, is pub- 

 lished by Dr. Ebell in No. 4604 of the Astronomische 

 Nachrichten ; it is based on observations made on 

 September S, 17, and 26 : — 



T = 1912 October 4-95917 M.T. Berlin. 



"- = 25' 3.3' 37-9"] 

 a =297 2 53-3 ^1912-0 

 I = 79 5r IO-2 J 

 loR<7 = 9-854958 



A further extract from the ephemeris is given 

 below : — 



Ephemeris 12/1. M.T. Berlin. 



>(,me) 



S(lrue) 



S(lrue) 



During the period covered by this ephemeris the 

 calculated decrease in magnitude is o'5. 



Measuring the Angular Diameters of Stars. — In 

 No. 2, vol. xxxvi., of The Astrophysical Journal, Dr. 

 Pokrowsky suggests a method whereby it should 

 become possible to measure the angular diameters of 

 stellar objects, a result which, if obtained directly, 

 would greativ widen our knowledge of stellar physics. 

 The method is too technical in detail to be given here, 

 but it depends upon the consideration that if two rays 

 emanate from different points on the surface of a 

 distant light-source, such as a star, there will be a 

 difference of phase depending upon the distance be- 

 tween the two points. These two systems of rays 

 after polarisation form two images of different in- 

 tensities in the focus of a telescope, and Dr. Pokrow- 

 sky shows that by measuring the difference of intensity 

 the angular diameter of the star may be derived ; thus 

 the problem is reduced to one of stellar photometry, 

 and it is calculated that for bright stars, such as 

 Arcturus, Canopus, Capella (average magnitude, say, 

 = o'o), angular diameters of o'oo3i" might be dis- 

 covered. As the method would be very sensitive, 

 atmospheric conditions would greatly interfere, and 

 the apparatus could only produce positive results at a 

 mountain observatory. 



The Perseids of August 12, 1912. — Some interest- 

 ing data concerning the meteor shower of .\ugust 

 last are given by Prof. Zammarclii, in No. 10, vol. i. 

 (2nd series), of the Meinorie delta Societa degli Spettro- 

 scopisti Italiani. The observations were made at the 

 meteorological observatory attached to the seminary 

 at Brescia, and in a total of i3'6 hours, spread over 

 the nights of August 10, 11, 13, and 14, six observers 

 recorded 170 meteors. The greatest horary rate 

 occurred on August 11, w-hen 93 meteors were seen in 

 four hours; on August 12 the sky was covered and 

 observations impossible. For each meteor the time, 

 the magnitude, and the appearance are given, and in 

 many cases the position of the beginning and end of 

 the path. 



The Physical Cause of the s-Term in Latitude 

 Variation. — A possible cause producing the s-term 

 in latitude variation is suggested by Mr. S. Shinjo in 

 a paper of which we have received a reprint from the 

 TflkvS Sugaku-Buturigakkwai Kizi (second series, 

 vol. vi., No. 16), published by the Tokio Mathematico- 

 Physical Society. Putting on one side, as unlikely, the 

 possibility of its being due to systematic error in the 



NO. 2243, VOL. go] 



observations and the suggestion that it is due to real 

 changes in the earth, Mr. Shinjo reverts to the prob- 

 ability that the c-term is introduced by the action of 

 anomalous refraction. But no such inclination of the 

 atmospheric strata as is necessary to produce the 

 anomalous refraction has been observed over any large 

 area. Mr. Shinjo, however, inquires into the purely 

 local conditions appertaining to and immediately sur- 

 rounding the observing station, and suggests that in 

 these very localised areas the atmospheric gradient is 

 frequently sufficiently sharp ; for example, the differ- 

 ence in temperature between the sun side and the 

 shade side of the observing hut might produce a 

 pressure-gradient sufficient to produce the s-term. 

 He concludes that the greater part of the term is prob- 

 ably produced by this cause, about one-fourth as a 

 consequence of the daily variation of the pole, as 

 remarked by Sitter, and a small part may possibly 

 be due to real change in the earth. 



THE BECOUEREL MEMORIAL LECTURE 

 OF THE CHEMICAL SOCIETY. 



A N extra meeting of the Chemical Society was held 

 ■^~*- on Thursday, October 17, when Sir Oliver 

 Lodge, F.R.S., delivered a memorial lecture in honour 

 of Antoine Henri Becquerel, late honorary and foreign 

 member of the Chemical Society. Prof. Percy F. 

 Frankland, F.R.S., president of the society, occupied 

 the chair. 



Sir Oliver Lodge referred to the changes that of 

 recent years have come over physical science. Not 

 many years back its progress appeared to be placid, 

 along well-worn channels, and based upon the sub- 

 stantial knowledge of the past. To-day it is charac- 

 terised by intense speculative activity on the one hand, 

 and, on the other, by exceptional scepticism. 



Discoveries are of two chief kinds : the discovery of 

 law and the discovery of fact. The discovery of law 

 often leads to the discovery of new facts, and the dis- 

 covery of new facts to either the formulation of new 

 laws or new modes of statement, or to the resuscita- 

 tion of discarded ones. As examples of the discovery 

 of law may be instanced Newton's gravitational theory 

 of astronomy. Maxwell's electro-magnetic theory of 

 light, the atomic theory of chemistry, and the con- 

 servation of energy. As examples of the discovery of 

 fact may be quoted the prehistoric discovery of flame, 

 the discovery of static electrification, of the electric 

 current, of magneto-electricity, of the electron, and of 

 spontaneous radio-activity. 



Of the scientific discoveries made during the past 

 fifty years, that of the Rontgen X-rays perhaps created 

 the most widespread interest; but even more striking 

 and revolutionary was Becquerel's discovery of the 

 spontaneous radio-activity of matter, for the spon- 

 taneous splitting up of atoms and the consequent ex- 

 pulsion of constituent fragments was not provided 

 for on any theory. 



A discovery of essential novelty cannot be made by 

 following up a train of prediction. It is often made 

 during the process of following a clue, but the clue 

 does not logically lead to it. A really new fact comes 

 as a side issue — something unexpected and that might 

 have been overlooked. The discovery which has been 

 pointed to by theory is of great value, but it is usually 

 the outcome of a long and fruitful period ; whereas 

 the discovery which comes as a surprise generally 

 marks a fresh epoch, and opens a new chapter in 

 science. 



So with the discovery of spontaneous radio-activity. 

 IJecquerel was looking for the possible emission of 

 Rontgen rays bv a fluorescent substance. It was a 

 reasonable thing to look for, and had it been found 



