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NATURE 



[August 31, 1893 



of the professors of mathematics here with whom I have come 

 in contact have taken the trouble of solving it, ani therefore it 

 is that I am appealing in this strain to the mithimiticians who 

 have any interest in the chronology of India. 



Many interested scholars have expressed their desire for the 

 solution of this problem. Thus says Prof. Schlegel : "I leave 

 to astronomers to examine whether the parts of the description 

 agree with one another, and if this be the case, thence to 

 deduce the date. The Indians place the nativity of Rima in 

 theconfines of the second age (Treta) and the third (D.vapara) ; 

 but it seems that this should be taken in an allegorical sense. 

 .... We may consider that the poet had an eye to the time 

 in which, immediately before his own age, the aspects of the 

 heavenly bodies were such as he has described." 



Besides the positions of the planets at the birth of Rama, I 

 have a few more data concerning the Hindu system of the 

 division of heavens, which I shall be glad to communicate 

 to any gentleman who is acquainted with that system, and ex- 

 presses a desire for the same. 



Kanhaiyalal. 



Lahore, August 8. 



Arrangements for Work of Chemical Section of the 

 British Association. 



Many of your readers will be interested to know that 

 M. Moissan has kindly arranged for a demonstration of the 

 properties of fluorine, and his method of isolating the element, at 

 a meeting of the Chemical Section of the British Association 

 at Nottingham, in September. M. Moissan will also exhibit 

 some specimens of the diamonds he has artifically produced. 



We also hope to have at least two discussions, one on Bac- 

 teriology and its related chemical problem--, which Prof Percy 

 Frankland has been so good as to promise to open, and another 

 on explosions in coal mines, with special reference to the "dust 

 theory." This, Piof Harold Dixon has kindly consented to 

 introduce. 



Permit me to remind authors that they will greatly facilitate 

 the arrangements for the satisfactory grouping of papers at the 

 sectional meeting, if they will communicate as early as possible 

 with the Secretaries, Burlington House. 



J. Emerson Reynolds. 



University of Dublin, Trinity College, August 21. 



The Bacchus Marsh Boulder Beds. 



Your issue of August 10 contains an interesting communica- 

 tion by Messrs. Ofticer and Balfour on the glacial boulder beds 

 of Bacchus Marsh in Victoria, in which they are referred to as 

 triassic. May I be permitted to point out that this is erroneous ? 

 It is true that the late Dr. O. Feistmantel in his earlier de- 

 scriptions of, and references to, the flora of these beds, regarded 

 them as triassic, but this was the natural consequence of their 

 correlation with the Talchir group of India, which he then 

 ascribed to the trias. In 1886 it was shown by Dr. Wagner and 

 myself sumultaneously that the true correlation of the Talchir 

 group was with the marine beds below the Newcastle coal 

 measures of New South Wales ; the Bacchus Marsh boulder 

 beds are consequently upper carboniferous, and form part of 

 the traces of the upper carboniferous glacial period which have 

 been recognised in Australia, Africa and Asia. The matter 

 will be found fully dealt with in pages 120-123 ^""^ 191-214 

 of the second edition of the " Manual of the Geology of India," 

 just published by the Indian Geological Survey. 



S.S.i?wa, August 19. R. D. Oldham. 



Old and New Astronomy. 



While thanking you and your reviewer for your very courteous 

 and appreciative notice of the " Old and New Astronomy," I 

 should like to be permitted to point out that the chapter on the 

 sun's surroundings was printed and was in the hands of the 

 public before my connection with the work commenced. Your 

 reviewer suggests that I ought to have corrected certain state- 

 ments in this earlier part of the volume, but I felt that it was 

 sufficient to mention in the preface that I did not agree with all 

 Mr. Proctor's conclusions, and it must be obvious that it would 

 neither have been an easy nor a gracious task to have attempted 

 in the latter part of a book to criticise the statements and theories 

 of the deceased author of the earlier chapters. 



NO T244, VOT,. 48] 



Your reviewer suggests that the proof I give of the very small 

 density of the Orion Nebula is "vitiated by the fact that it is 

 impossible to estimate the gravitational effect of the dark matter 

 in interstellar space." I conclude that he does not refer to dark 

 matter within the area of the nebula, for this would only add to 

 the mass of the nebula and to the observed velocities of the stars 

 in its neighbourhood. That dark matter evenly distributed in 

 space around would not interfere with the gravitational effect of 

 the nebula will be evident to those who remember that the 

 attraction of a hollow spherical shell on a body within it may 

 be neglected, since the attractions in all directions balance 

 whatever is the position of the body within the spherical shell. 

 The stars around the nebula seem to be distributed in all 

 directions, and it cannot be supposed that in each case there is 

 a gravitating dark mass on the side away from the nebula which 

 counterbalances the attraction of nebulous matter. 



Your reviewer cannot, I think, have seen Dr. Huggins's photo- 

 graph of the spectrum of the Orion Nebula and the stars in- 

 volved in it, or he would not suggest that the bright lines in the 

 spectra of the stars could be due to the overlapping by tremors 

 and atmospheric disturbances of the spectrum of the nebular 

 matter. The bright nebula lines distinctly widen and brighten 

 in the neighbourhood of the stars. One is therefore forced to 

 conclude that the bright lines when they cross the stellar spectra 

 belong to the stars. A. C. Ran YARD. 



August 19. 



There is nothing in my review that implies the desirability 

 of Mr. Ranyard having modified any of Mr. Proctor's conclu- 

 sions in the chapter on the sun's surroundings ; I simply pointed 

 out an error of date that should have been corrected. 



I do not see any reason for supposing that the quantity of 

 matter in the area we call the Orion Nebula is greater than 

 that in any other arbitrarily selected equal area in space, and 

 the evidence seems conclusive that the whole of interstellar 

 space is a meteoric plenum. This being so, there is no reason 

 why stars in the neighbourhood of the nebula should have their 

 velocities in any way affected by it. Mr. Ranyard proves that 

 there is no great difference in density, but does not touch the 

 question of the absolute quantity of matter involved. 



I have not seen Dr. Huggins's original photographs of the 

 spectrum of the Orion NebuLa, and the stars involved, nor have 

 I seen direct copies of them, but I have examined other photo- 

 graphs in which the star and nebula spectra appear, and lave 

 also visually examined the spectra, and am iiy no means con- 

 vinced that the nebula lines are brighter and wider in the stars. 



The Reviewer. 



An Old Device Resuscitated, 



I.N' the Astronomical Column of the current number of 

 Nature a description is given from V Astronomic, of .M. Jar- 

 son's method of giving equatorial motion to a telescope mounted 

 on an ordinary altazimuth stand. This method will be found 

 figured and described by Lord Lindsay, now Earl Crawford, 

 in the Monthly Notices of the Royal Astronomical Society, 

 xxxvii. I, Nov. to, 1876. Moreover, in a note appended to 

 the paper. Lord Lindsay says that since writing it his attention 

 had been drawn to the fact that this principle of mounting had 

 been described by Sir George Airy in Monthly Notices, xv. 



F. W. Levander. 



30, North Villas, Camden Square, N.W., August 28. 



Laws of Error in Drawing. 



I SHOULD be obliged if you allow me to state in the next 

 issue of Nature, to prevent any misconception of the extent of 

 those " compulsory errors " alluded to in my article printed in 

 the current number, that I am able to specify such, with equal 

 particularity, as they occur in the following additional figures, 

 viz. : — The cylinder, the ringed cylinder, the oblong, the 

 octagon, cone, hexagonal pyramid, octagonal pyramid, triangle 

 (solid). Also in those figures framed of square-sectioned 

 woodwork that have the following shapes, viz. square, cross, 

 triangle, arch, hexagon, pentagon, circle. Again, that they 

 are observable in all forms which are complexities of the 

 primal forms above given ; and, moreover, I have traced them 

 clearly in the draughtsmanship of Orientals, and even in the 

 drawing of the greatest painters. Arthur L. Haddon. 



Glenavon, Cornwallis Avenue, Clifton Vale, Bristol, 

 August 25. 



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