October 2, 1890] 



NATURE 



545 



(5) A fifth set of verifying facts are such links of relationship 

 between the various Aryan languages as geographically spoken 

 in historical times, such links of relationship as appear to 

 postulate a common speech in that very area above indicated, and 

 where an ancient Aryan language still survives along with 

 primitive Aryan customs. For such a common speech would 

 have one class of differentiations on the Asiatic, and another on 

 the European side, caused by the diverse linguistic reactions of 

 conquered non-Aryan tribes on primitive Aryan speech, or the 

 dialects of it already developed in those great river-partitioned 

 plains. 



(6) A further set of verifying facts are to be found in those 

 which lead us more and more to a theory of the derivative origin 

 of the classic civilizations, both of the Western and of the Eastern 

 Aryans. Just as, between the Dnieper and the Carpathians, 

 and between the Oxus and the Himalayas, there were such 

 conditions as must have both compelled and invited to pass 

 from the pastoral into a partially agricultural stage ; so, in 

 passing southward from each of these regions, the Aryans would 

 come into contact with conditions at once compelling and in- 

 viting to pass into a yet higher stage of civilization. And in 

 support of this all the facts may be adduced which are more 

 and more compelling scholars to acknowledge that in pre- 

 existing Oriental civilizations the sources are to be found, not 

 only of the Hellenic and the Italic, but of the Iranian and the 

 Indian civilizations. 



(7) Finally, if the Hellenic civilization and mythology is 

 thus to be mainly derived from a pre-existing Oriental or 

 " Pelasgian " civilization, it is either from such pre-existing 

 civilizations, or from Aryans such as the Kelto-Italiots, migrating 

 northward and southward from Pelasgian Thrace, that the 

 civilization of Western and Northern Europe would, on this 

 hypothesis, be traced : and a vast number of facts appear to 

 make it more probable that the earlier civilization of Northern 

 Europe was derived from the south than that the earlier 

 civilization of Southern Europe was derived from the north. 



The three conditions of a true solution of the problem either 

 of Semitic or of Aryan origins appear to be these. First, the 

 locality must be one in which such a new race could have ethno- 

 logically, and secondly philologically, arisen as a variety of the 

 Archaian stock of white races ; and thirdly, it must be such 

 as to make easily possible the historical facts of dispersion 

 and early civilization. And I venture to submit the above sets 

 of facts as not inadequately, perhaps, supporting the South 

 Russian "speculation as to the origin and home of the Aryan 

 family." J. S. Stuart Glennie. 



The Shealing, Wimbledon Common, September 22. 



Mr, Dixon's Mode of Observing the Phenomena of 

 Earthquakes. 



Mr. Harold Dixon's letter in Nature of Sept. 18 (p. 491) 

 is exceedingly interesting to seismologists. On two occasions 

 he was able to make the only kind of observation which is of 

 any value unless seismographs are actually employed ; he has 

 been able to make these in England, where earthquakes are rare, 

 and I know of no record of such definite information being 

 given by any of the trained observers in Japan, where earthquakes 

 are so numerous. It requires great coolness to make such 

 observations at such a time. 



Seismographic records show that even in destructive Japanese 

 earthquakes the vertical displacement of the ground is usually 

 less than one millimetre, so that the mere dij^erence in vertical 

 displacement observed by Mr. Dixon between two points in the 

 same room must have approached five hundred times the greatest 

 absolute vertical displacement in Japan. Mr. Dixon truly says 

 that, if the displacement observed by him had been due to the 

 movement of the hill itself, it must have meant a good deal, for 

 it would have meant some hundreds of thousands of times the 

 greatest vertical earth movement recorded by any seismograph. 



When I say that VI r. Dixon's letter is interesting, I make the 

 assumption that what he observed was not merely what 

 anybody observes who raises his head when looking at a distant 

 hill through a window. John Perry. 



31 Brunswick Square, W.C., September 24. 



Butterflies Bathing. 

 In Nature of August 21 (p. 402) is a note taken from 

 the Victorian Naturali^ describing an observation made by 



NO. 1092, VOL. 42] 



Mr. G. Lyell, Jun., of Melbourne. He states that several 

 butterflies {Paptlio macleayanus) were seen to enter the water 

 backwards, remain partly submerged for about half a minute, 

 and then fly off to the hill-sides refreshed with their bath. The 

 heat of the weather is given as the cause of their action. 



I should like to suggest that the insects were probably engaged 

 in depositing their eggs. Perhaps some one who has the oppor- 

 tunity will ascertain if the larva of this butterfly is aquatic, or 

 feeds on plants growing at the water's edge. 



G. A. Fkeeman. 



St. Olave's Grammar School, Southwark. 



Surface tension and Surface-viscosity. 



If an oiled needle be placed on the surface of pure water, it 

 will be supported, but if it be washed in a solution of potash, it 

 will sink. In the first case the effect cahnot be due to the sur- 

 face-tension, which is much diminished by the oil. Has the 

 viscosity of the oil anything to do with it ? Also in the case of 

 a soap-bubble, is the effect due to viscosity, and not to surface- 

 tension ; and what is the difference between surface-tension and 

 surface-viscosity? They are both, no doubt, due to cohesion, but 

 it is difficult to form definite conceptions of the two properties. 

 Would any of your readers kindly answer the above questions, 

 and give references to any workg bearing thereo'n ? Maxwell's 

 " Theory of Heat," on capillarity and viscosity, does not seem to 

 throw any light on the matter. W. P. O. 



Leicester, September 25. 



I 



ON STELLAR VARIABILITY> 



n. 



HAVE before stated that the variability phenomena 

 observed in stars of the Groups I. and II. and 

 VI. are produced by the same cause ; all differences in 

 the details of the effects being due to the different physical 

 nature of the central body. In Groups I. and II. it is a 

 swarm of meteorites with which we have to deal ; in 

 Group VI, it is a condensed star of low radiation sur- 

 roimded by a dense atmosphere containing carbon in 

 some combination. 



In both cases the bodies are normally dim ; in Groups 

 I. and II. they are so because the meteorites when un- 

 disturbed are relatively free from collisions ; in Group VI. 

 they are so for the reason stated above, the star being on 

 the verge of extinction. 



I insist upon this dimness, because the dimmer the 

 central body the more important becomes the luminosity 

 caused by, or set up in, secondary swarms. Further, 

 such variability as we are now considering is unknown in 

 the case of the hotter stars. 



It is clear that phenomena produced in either group 

 by the action of two swarms should strongly resemble 

 each other, and that if it be found that this explanation 

 holds good in one case it should be found to hold equally 

 good in the other. It is to be expected then that pheno- 

 mena observed in each may throw light upon the other, 

 and that the view advanced may be tested by the differ- 

 ences observed. 



Let us consider two hypothetical cases, to start with, in 

 Groups I. and VI. 



In Group I. we have a condensing nebula the light of 

 which when undisturbed is say 6 mag. Round this there 

 revolves a cometary swarm say in six time units. At perias- 

 tron collisions occur which raise the light of the combined 

 swarms to 3 mag. There is also another similar swarm 

 revolving in say twelve time units. The conditions are 

 such that this second swarm produces a smaller disturb- 

 ance which only raises the light to 4^ mag. We will 

 assume the periods to be exactly commensurable, and the 

 apastra to occur together. It is obvious that alternate 

 minima will be raised by this second revolving swarm, 

 but the maxima will be constant. 



In order to put results of this nature into diagrammatic 

 form \ye must consider that we are dealing with certain 



Continued from p. 419. 



