252 



KNOWLEDGE. 



[November 1, 1899. 



primitive types .... cannot of themselves be any test of 

 age. They represent no sequences, but only an incipient 

 growth permanently arrested and by adverse conditions 

 prevented from attaining its normal development. Where 

 there is no change there is no standard by which to 

 measure time. Hence the mistake made, especially by 

 some American ethnologists, who have assigned a con- 

 siderable antiquity to certain native cultures, solely on the 

 ground of the rude implements with which they appeared 

 to be associated. Certain objects, such as flint flakes or 

 chippings, if found on or near the surface, or under other 

 circumstances not necessarily involving great age, might 

 have been made at any time, and are now still made by 

 many peoples not yet brought under higher influences." 

 Hence readers of the " Ethnology ' understand quite well 

 that the expressions in question are used in " Man ; Past 

 and Present" not in an absolute, but only in a relative 

 sense, implying time sequence not universally, but only in 

 the culture areas. 



Farther on the reviewer criticises the use of the term 

 " cornea " as applied to the yellowish sclerotic of the 

 negro peoples. Here, also, a reference to the " Ethnology " 

 (" sclerotic "in the European whitish, in the negro yellowish, 

 pp. 186-7) shows that I am speaking, not of the Comen 

 vellucida over the iris, which, of course, is transparent and 

 colourless, but of the C. opaca round the iris, the colour of 

 which varies racially. The two books are intended to be 

 read together, and I may here add that they form parts 

 only of an ethnological treatise which I hope to complete 

 in a third volume. Then many things which now seem 

 strange, and have laid me open to criticism, especially by 

 specialists, will be made clear. A. K. Keane. 



TREE STEUCZ BY LIGHTNINa. 

 To the Editors of Knowledge. 



Sirs, — I have read with much interest Baron Kaulbars' 

 letter in your issue of this month, as a parallel case to 

 those he mentions occurred in 1852 to a large old oak tree in 

 Westwood Park, near Droitwich. The tree was completely 

 uprooted, and the trunk shivered into three parts, the 

 remains of which are still lying where they fell. The 

 boughs were rent and scattered in all directions, some to 

 a distance of many feet. Such a result of lightning was, 

 I think, then considered to be unique, and Faraday was 

 asked his opinion as to the cause. He held that the 

 lightning must have got down the hollow stem, and, 

 meeting with damp at the bottom, generated steam, and 

 so caused an explosion. After reading Baron Kaulbars' 

 letter, I have no doubt it was the true explanation. It is 

 possible this case may still be unique as an efiect of 

 lightning on a tree, as the only precisely parallel case 

 Baron Kaulbars gives is the very curious one of the 

 monumental column in Gatchina. Hampton. 



Waresley Court. 



<■♦ » ■■■— - 



SUSPECTED VARIABLE STARS. 

 To the Editors of Knowledge. 



Sirs, — I object to convicting anything on suspicion, be 

 it man, woman, or star, and although my friend Mr. Gore's 

 suspicions would be quite suflicient to convince the Home 

 Office in the case of a convict, they do not convince me. 



With regard to photometric measures, the Pole Star has 

 been always (I think) adopted as the standard. But what 

 if the Pole Star varies in its light ? I have not as yet 

 seen the details of the alleged discovery made in relation 

 to it at the Lick Observatory ; but with a binary or ternary 

 system of very short period there must always be a con- 

 siderable risk of one of the members of the system over- 

 lapping another and thus diminishing the light. If this 



occurs with the Pole Star, its variations may cause other 

 stars to be erroneously suspected. 



Then, as to stars whose light is of different colours, it 

 is probable, as Mr. Backhouse remarks, that different 

 observers will rate them differently, owing to the peculi- 

 arities of their sight. One eye may be more sensitive to 

 white light and another to light with a reddish tint. And 

 very possibly there may be a systematic difference on this 

 point between the Oxford and Harvard photometries in 

 which the methods of estimating star-magnitudes are 

 different. I would lay very little stress on one observer 

 describing Vega as brighter than Arcturus, while another 

 described Arcturus as brighter than Vega. Nor is this 

 difficulty surmounted by photometry. The ultimate com- 

 parison is made by the eye, and the colour of the stars may 

 affect this. We must have the same observer in order to 

 prove the variation, unless the amount is large. And even 

 with the same observer the result is open to question. 

 The stars are probably not at the same altitude, and a 

 larger proportion of the light of the star is absorbed when 

 the star is at a low altitude than when it is at a high one. 

 But we have further a proof every moonlight night of how 

 much the visibility and brightness of a star depends on the 

 condition of the surrounding portion of the sky. Indeed, 

 but for this, all the stars would be seen in the day time. 

 Hence a star which lies pretty low in the west will look 

 faint a''ter sunset, as one which lies pretty low in the east 

 will look faint before sun-rise. And on a moonlight night 

 a star near the moon will look fainter than one remote 

 from it. We may, perhaps, even underrate the magnitude 

 of a star in or near the Milky Way owing to the compara- 

 tive brightness of the surrounding portion of the sky. 



As to star-magnitudes, it is only very recently that any 

 scientific scale was adopted for measuring them. Even 

 Sir J. Herschel seemed to conclude that we could not go 

 beyond 0, and thus crowded an undue number of stars into 

 the interval between and 1. The chief value of magni- 

 tudes determined without the guidance of any fixed scale 

 seems to consist in showing which of two stars was 

 regarded as the brighter by a person who observed both. 

 Double stars often aff'ord examples of the defects of eye- 

 estimates not guided by principle. Take for example 

 Castor and y Leonis. Eeferring to the Handbook of the 

 Double Starti (ed. 1879), I find the components of Castor 

 given as .3-0 and 3-5 (in the catalogue 3 and 4) and those 

 of y Leonis at 2-0 and 3'5 (in the catalogue 2 and 3). 

 Webb (ed. 1881) gives for Castor 27 and 3-7, and for 

 y Leonis 2-0 and 3' 5. According to these estimates y Leonis 

 would of course be the brighter star. I find similar 

 estimates given as late as the last edition of Mr. Chambers' 

 Descriptive Astronomy — and Prof. Pickering published an 

 elaborate computation based on them as well as the 

 supposed orbits. But it is beyond question that Castor is 

 brighter than y Leonis by at least half a magnitude, and 

 consequently the estimated magnitudes of the components 

 must be seriously in error. Even as regards Algol the old 

 estimate of the reduction of the Ught by two magnitudes 

 seems to be generally current, notwithstanding the photo- 

 metric measures of Prof. Pickering, which make it almost 

 exactly one magnitude. 



That some of Mr. Gore's " suspects " are really guilty I 

 can quite believe, but I think we require a further investi- 

 gation into the causes of variation in observers' estimates. 

 I have an idea, too, that an examination of the spectrum 

 of a star would often tend to confirm or remove the 

 suspicion. A good determination of the spectra of all 

 known variable stars would, I believe, form a very useful 

 guide to the examination of auspicious objects. 



W. H. S. MoNCK. 



