438 



NATURE 



[December i6, 1915 



In the Aiii dei Lined, vol. xxiv., No. 2, Prof. P. 

 Pizzotti studies the relative central orbit of a pair of 

 bodies attracting, according to the Newtonian law, 

 but of variable mass. The investigation appears to be 

 based on the assumption that the impressed force is 

 equal to the product of the mass and acceleration, and 

 not to the rate of change of momentum, the effect of 

 variable mass thus being equivalent to a, variation in 

 the gravitational constant. The method would thus 

 appear to be strictly applicable to the motion of two 

 elextrified bodies with variable charges,- or attracting 

 bodies parting with their substance by evaporation, 

 but not to cases of bodies accumulating matter from 

 without. 



A RECENT number of Scientia contains an interesting 

 article by Signer Aldo Mieli on Greek science and the 

 characteristics of its development. He directs atten- 

 tion to the fact that while mathematicians hold in high 

 esteem the achievements of Euclid and the investiga- 

 tions of Archimedes, and while the physician finds 

 much to admire in the works attributed to Hippo- 

 crates, the chemist and the biologist are disposed to 

 regard Greek speculation on their respective subjects 

 as fruitless. These diverse judgments are due, he 

 thinks, not to any different attitude of the Greek 

 intellect towards one subject as compared with another, 

 but rather to the special characters of the subjects 

 themselves. The aim of Greek thought was the 

 unification of disconnected knowledge. This laid the 

 foundation of true science, but carried with it the 

 tendency to reduce natural phenomena to a rigid geo- 

 metrical or logical system. The culmination of Greek 

 science was reached by Hippocrates, Aristotle, and 

 Euclid. Hippocrates brought his generalisations to 

 the test of observation ; Aristotle in great measure did 

 the same, the value of his results depending largely 

 on the opportunities he possessed for checking them 

 by observation and experiment. Euclid laid a solid 

 foundation in the region of pure mathematics. The 

 successors of the two former long delayed the pro- 

 gress of knowledge by an undue reliance on the dicta 

 of their masters, but the "granitic" fabric of Euclid 

 made possible the w^ork of ApoUonius on conic sec- 

 tions, and even the conception of the infinitesimal 

 calculus reached by Archimedes. 



Mr. J. H. Gardner, writing with reference to the 

 note in Nature of December 9 (p. 407) relating to the 

 Archives of Radiology and Electro-therapy, in which 

 the statement was made that "it is the only English 

 periodical dealing with the subject of X-rays In all its 

 bearings," reminds us that the Journal of the Rontgen 

 Society, of which he is the editor, has for a much 

 longer period dealt fully with this subject. The latter 

 important and excellent journal, to which reference has 

 frequently been made in Nature, is, however, almost 

 exclusively devoted to printing the Proceedings of the 

 Rontgen Society, and therefore does not come within 

 the same category as one dependent for its existence 

 upon the conditions that apply to any other public 

 periodical. For the same reason, we should not con- 

 fuse the Electrician, or a new periodical on electrical 

 engineering, with the Journal of the Institution of 

 Electrical Engineers. This was the distinction we had 

 in mind when referring to the new publication on 

 radiology in all its branches. 



NO. 2d.07. VOL. q61 



Under the title Archives Russes d'Anatomie, d'His- 

 tologie et d'Entbryologie, Prof. A. Dogiel, professor 

 of anatomy and physiology in the University of Petro- 

 grad, has commenced the issue of a new periodical 

 intended to make Russian workers in the three 

 branches of biology embraced by it independent of 

 German mediums of publication. All articles will be 

 published in the Russian language, but they will be 

 accompanied by translations into French or English, 

 or summaries, which in no case will be less than three 

 parts the length of the original paper. Three fascicules 

 are to form a volume of about forty-five sheets of 

 Russian text, illustrated by plates produced by the best 

 engravers in Petrograd. The annual subscription will 

 vary according to the number and nature of the plates, 

 but will not exceed 12 roubles (255.) for each fascicule. 

 Subscriptions should be addressed to Prof. A. Dogiel, 

 P^trograde, Vasili Ostrov, 3^ LIgne, Malson 4, loge- 

 ment 16, or to the publisher, K. Ricker, P6trograde, 

 Rue Morskaia, 17. 



OUR ASTRONOMICAL COLUMN. 



Comet 19155 (Taylor). — This comet has been ob- 

 served at the Naval Observatory, Washington, by Mr. 

 H. E. Burton. On December 6, iih. 33-5m., its posi- 

 tion was R.A. 5h. 22m. 42-95., declination 0° i' 36", 

 quite close to 8 Orlonls. Its magnitude is not stated. 



Spectroscopic Orbit of 12 Lacert^. — ^^Orbital 

 elements have been obtained for this binary system 

 by Mr. R. K. Young from a series of spectrograms 

 secured at Ottawa. It presents technical difficulties 

 owing to its extremely short period and faint mag- 

 nitude. Its period remained In doubt until quite 

 recently, and proved to be only 4h. 38m. 3s. The 

 range of velocity is 35 km., the velocity of the sys- 

 tem — 14-23 km., the projected semi-major axis has 

 the very small value =46600 km., and the mass 

 function = 0-0001. The spectrum Is of type B2 (Crucian 

 level). The system bears close resemblance to that of 

 13 Cephei. 



The Use of the Blink-Microscope. ^ — Further series 

 of stellar proper motions found and measured by 

 means of the blink-microscope are given in Circular 

 No. 28 of the Union Observatory, South Africa. On 

 twelve pairs of catalogue plates thirty-five stars with 

 annual proper motions exceeding o-i" have been fourd. 

 Of these seventeen were brighter than the loth mzg;- 

 nitude. Mr. Innes points out that observations of 

 wide double stars justify the assumption that the vast 

 majority of the stars on the plates is relatively "fixed" 

 (i.e. moving as a group). Thus after picking out the 

 proper-motion stars it would suffice for astrographic 

 chart purposes to measure a mere dozen or so stars 

 per plate, a proceeding which would cut down the 

 vast programme of the Carte du del Comity to 

 ioo,ooo stars. 



The Structure of the Spectrum of the Solar 

 Corona. — The recent brilliant application of Planck's 

 quantum theory to the explanation of some celestial 

 spectra by Prof. J. W. Nicholson demonstrated that 

 vibrations of a hypothetical dynamical system — the 

 so-called protofluorlne atom — should be capable of 

 giving rise to the majority, but not all, of the then 

 known lines in the spectrum of the solar corona. 

 Among those not so picked up were three prominent 

 lines, one of these being the well-known A 5303, the 

 others having wave-lengths 43159 and 3534 A. Prof. 

 Nicholson stated that the cube-roots of the wave- 

 lengths of these lines differed by a constant quantity, 



