August 21, 1890] 



NATURE 



391 



and the author of the nol ice referred to is therefore invited to 

 furnish a parallel calculation, based upon the theories which 

 have hitherto received general support. This invitation the 

 writer must decline, simply because two far abler hands than 

 his have already investigated this problem on the lines which 

 he would have pursued ; and he could add nothing to the 

 authority that accompanies the utterances of Dr. J. R. Hind, 

 the Superintendent of the English " Nautical Almanac," and 

 Prof. Simon Newcomb, the Superintendent of the American. 



The following is Mr. Page's communication : — 



" Herodotus speaks of the eclipse of Thales as follows : — ' A 

 war commenced between the I.ydiansand theMedes, . . . which 

 continued five years ; and it is remarkable that one of their en- 

 gagements took place in the night. In the sixth year, when 

 they were carrying on the war with nearly equal success, on the 

 occasion of an engagement, it happened that in the heat of 

 battle day was suddenly turned into night '(Herodotus, b. i., s. 74). 



" This battle was fought on the morning of the (Julian) July 8, 

 org days after the solstice ; consequently in the time of longest 

 days and hottest weather. It would seem from the above account 

 that it commenced in the night, and .was not ended until the 

 time of the eclipse, or 5.24 a.m. ; when the armies ceased 

 fighting on account of their fears. 



"From Ptolemy's canon we.leam that Cyaxares, King of 

 Media, began to reign B.C. 634, and reigned 40 years, during 28 of 

 which the Scythians ruled over Asia. In B.C. 606 the Scythian 

 power was broken, and the Medes and Babylonians conquered 

 Assyria. Soon afterwards {i.e. in B.C. 603) that war broke out 

 between Lydia and Media which was terminated by mutual fears 

 of this eclipse. As the King of Media reigned 40 years from 

 B.C. 634, he must have died B.C. 594, which is the latest date 

 that can be fixed for the eclipse ; and as he was 28 years subject 

 to the Scythians, he must have reigned 12 years after the defeat 

 of the Scythians in B.C. 606 ; and as his war with the Lydians 

 could not have taken place for several years after this, and as the 

 eclipse was in the sixth year of the war, the date of the eclipse 

 cannot possibly be placed earlier than B.C. 600 : consequently 

 we are compelled to look for it some time between B.C. 6o3 and 

 B.C. 594." 



Appended to this communication is a calculation by Mr. 

 Page of the time of new moon in B.C. 597. This calculation is 

 founded upon Ferguson's tables, to which some corrections 

 have been applied by the computer. The calculation cannot 

 be given here in detail; but the result to 1 which Mr. Page 

 is led is July 8, 5h. 24m. lis., as that at which the so-called 

 eclipse of Thales occurred. This date differs some twelve years 

 from that which has been assigned by the two authorities just 

 mentioned, viz. B.C. 585 — a date, too, which accords with that 

 mentioned by Pliny, reckoned by Olympiads. But those who 

 find Mr. Page's arguments sufficient will agree with him ; my 

 regret is rather that he has chosen to build his theory on 

 absolute tables, and to ignore all that the ablest astronomers 

 and mathematicians have recently been able to accomplish in 

 this direction. William E. Plummer, 



The Rotation of Mercury, 



Ixyourissue for January 16 (xli. p. 257), Schiaparelli's observa- 

 tions on the planet Mercury are stated to lead that astronomer to 

 the conclusion that "Mercury revolves around the sun in the 

 same manner that the moon revolves round the earth, always 

 presenting to it the same hemisphere." 



Permit me to recall the fact that, as a matter of deductive 

 reasoning, I recorded this opinion in 1883 : " The powerful 

 tidal action experienced by Mercury has greatly retarded its 

 primitive axial motion, and increased its distance from the sun. 

 .\o surprise would be occasioned by the proof that the planet 

 has already attained to synchronistic motions" (" World- Life," 

 p. 425). This opinion was accompanied by calculations of the 

 solar tidal efficiency on Mercury. 



Alexander Winchell. 



Ann Arbor, Michigan, U.S.A., August 4. 



Wet and Dry Bulb Thermometers. 



It may, perhaps, interest you to know that on Friday last the 

 difference between the wet and dry bulb thermometers, on 

 board this ship in Grimsby roads, amounted to 1 2 J" ; the dry 

 bulb showing 66°, and the wet bulb 53°"S; Wind west ; force, 



7 to 8 by Beaufort's scale. This is the greatest difference I have 

 recorded in this country for ten years. T. H. Tizard. 



H.M.S. Triton, Grimsby, August 17. 



Experiment in Subjective Colours. 



The following experiment does not seem to be widely known : 

 it is not easy to make a clear explanation of the lenses. 



Take a number of the Graphic and a piece of thin paper, 

 which, if put upon the ordinary print, allows it to be seen 

 through, as black. Now put the paper over some of the larg-e 

 black letters on the apple-green outer cover : seen through the 

 paper, they appear as bright red, W. B, Croft. 



Winchester College, August 18, 



THE SCIENCE AND ART MUSEUM, DUBLIN, 



AND THE NA TIONAL LIBRAR Y OF 



IRELAND. 



IN the year 1877 the Natural History Museum and the 

 Library of the Royal Dublin Society, which, though 

 mainly supported for many years by Parliamentary grants, 

 had been directly managed by the Society, were, by Act of 

 Parliament, transferred to the Science and Art Depart- 

 ment, a large sum of money having been at the same 

 time paid by Government to the Society for ceding its 

 rights and property. 



Soon afterwards steps were taken by the Science and 

 Art Department for providing suitable accommodation 

 for an art and industrial addition to the Museum. Into 

 a consideration of the various causes which delayed the 

 carrying out of this project we need not enter here ; they 

 will be found described in the Reports of the Science and 

 Art Department. 



At length, in 1884, a final competition between rival 

 architects' designs for the new buildings was arrived at, 

 and those by Messrs. Deane and Son, of Dublin, were 

 chosen by the representative committee, which was 

 specially appointed for the purpose of selection. 



The sites for these buildings, which were adopted after 

 much discussion, are at right angles to Leinster Houseon 

 its Kildare Street or western side. The facades of both 

 buildings, which face one another, are about 200 feet long, 

 and are similar, consisting of two rotundas with colon- 

 nades, and pavilions at the sides. In the centre of the 

 Museum building is a large court about 125 feet by 75 

 feet. Opening from it there are in all 24 galleries or 

 rooms, which are devoted to exhibiting purposes. 



The foundations were laid by His Royal Highness the 

 Prince of Wales on April 10, 1885, the ceremony con- 

 nected therewith being the most important presided over 

 by His Royal Highness during his last visit to Ireland, 



The tender for the erection of the buildings by Messrs. 

 Beckett Brothers, of Dublin, was accepted on November 3, 

 and by the 1 7th operations had commenced. In four years, 

 or by November 1889, the Museum building was com- 

 pleted, and was handed over to the Science and Art De- 

 partment, and the transfer to the new galleries of the 

 collections which had accumulated in the temporary pre- 

 mises during twelve years was at once proceeded with. 



It was not until June of the present year that the sister 

 building, for the reception of the National Library of 

 Ireland, was completed. During the month of July the 

 transfer of the books, consisting of about 100,000 volumes, 

 from the old Library in Leinster House, has been satisfac- 

 torily accomplished. 



Both institutions are about to be opened on the 29th of 

 the present month by His Excellency the Lord-Lieutenant, 

 after which they will continue to remain open and free to 

 the public. 



It may be of interest to add some details as to the 

 principal contents and system of arfangement in the two 

 institutions respectively. In order to describe the Museum 



NO. 1086, VOL. 42] 



