46 



NATURE 



{Nov. 15, 1877 



ratus is considerable, the corks by which these tubes are fixed 

 must fit very tightly. 



In using the arrangement the bottle is filled with water, the 

 jet is then closed with the finger, and the fiinnel, which should 

 be supported on the ring of a retort stand, is filled with mercury ; 

 on removing the finger firom the jet the mercury falls into the 

 bottle, expelling the water which rises in a fountain to a height 

 depending upon that of the column of mercury, but rather less 

 than is theoretically possible, the height of the fountain being 

 ten or eleven times that of the fall of mercury. By employing 

 mercury as the falling liquid in Hero's fountain a similar increase 

 of effect may be obtained with that apparatus. 



W. A. Shenstone 



Fownes' "Manual of Chemistry" 



In my review of Fownes' "Manual of Chemistry" are two 

 mistakes which I beg to correct. On page 25, line i, read 

 improbable instead of improvable ; and line 6, dimorphides 

 instead of isomorphides. The Reviewer 



OUR ASTRONOMICAL COLUMN 



The Transit of Mercury, May 6, 1878.— The 

 transit of Mercury, which will occur on May 6 in the 

 ensuing year, is the last during the present century in 

 which the planet can be observed upon the sun's disc for 

 any length of time in this country, and on that occasion 

 the nearest approach of centres will take place only half 

 an hour before sunset ; owing, however, to the long dura- 

 tion of the transit, 7h. 35m. geocentric, Mercury will have 

 been upon the disc more than four hours and a quarter 

 when the sun sets. Reducing to Greenwich by the 

 Nautical Almanac data it appears the first external 

 contact will occur at 3h. lom. 58s. mean time, and the 

 first internal contact at 3h. 14m. 4s., or the planet will be 

 3m. 6s. in wholly entering upon the d'sc. The least 

 distance of centres will occur at 7h. om., and sun-set at 

 7h. 29m. The duration of the transit is longer than in 

 any other of this century, or indeed than in any one that 

 has occurred since the year 1756. 



Up to the present year twenty-four transits of Mercury 

 have been more or less observed ; in this number are 

 included that of 1631, November 7, predicted by Kepler, 

 when the planet was seen upon the sun's disc for the first 

 time by Gassendi, at Paris, who observed on the dark- 

 chamber method — by allowing the sun's light to pass into 

 the room through a small aperture in the window, and 

 throwing his image upon a white screen ; that of 165 1, 

 November 3, imperfectly seen by Shakerley at Surat, and 

 that of 1707, May 6, which was observed through clouds 

 by Roemer at Copenhagen near the egress. Of these 

 twenty-four transits it is singular that only ei^Jit have 

 taken place at the descending node or in May, as will be 

 the case next year. Two-thirds of the number have 

 therefore occurred in November, when we might have 

 expected the hindrances to observation to have operated 

 unfavourably in these latitudes. 



Of the three transits of the present century subsequent 

 to 1878, that of 1881, November 7, will be wholly invisible 

 in this country, the ingress taking place at loh. i6m. and 

 the egress at ish. 37m. ; in the transit of 1891, May 10, 

 the egress occurs soon after sun-rise ; and in that of 

 1894, November 10, it occurs near sun-set. The reader 

 who is curious respecting the transits of Mercury in the 

 next century may consult a communication from the Rev. 

 S. J. Johnson to the Royal Astronomical Society in the 

 Monthly Notices, vol. xxxvii. p. 425 ; and for an account 

 of Gassendi's long watch for the transit of 163 1, and his 

 successful observation of it, he may be referred to Prof. 

 Grant's classical work, the " History of Physical Astro- 

 nomy." 



Nova Cygni, 1876.— Prof. Julius Schmidt mentions 

 that the star which he first remarked on November 24, 

 1876 (and which is not found in the Durchmusterung) 



diminished very regularly from JiUnuary to August ot 

 the present year ; it exhibited none of the slight oscilla- 

 tions in brightness which are still seen in T Coronae, and 

 we may add in other " Novas." With the Athens re- 

 fractor he has observed three small stars near the 

 variable, with the following differences of right ascension 

 and declination : — 



It will be remembered that this star suddenly shone out of 

 3'4 magnitude, and had diminished to the limit of naked- 

 eye vision soon after the middle of December. Its mean 

 place for i88o'o is in R.A. 2ih. 36m. 59'9S., N.P.D. 

 47° 42' 16". 



Comet 1873, IV. — M. Raoul Gautier has worked out 

 definitive elements of the comet discovered by M. Borrelly 

 on August 20, 1873, and finds the observations best repre- 

 sented by an ellipse with a period of 3,27 7§ years, the 

 probable errors of perihelion distance and eccentricity 

 limiting the period between 3,012 and 3,585 years. This 

 comet, however, was observed for one month only, or 

 through an orbital arc of only 58°, and such results of 

 calculation in the present case are not perhaps to be 

 allowed any great weight. There are many other comets 

 which we imagine would better have repaid the labour 

 expended by M. Gautier upon Comet 1873, IV. Express- 

 ing his best paf-abolic elements in the manner adopted 

 in catalogues of comet-orbits, we have the following 

 figures : — 



Perihelion Passage, 1873, September 1083679 M.T. at Berlin, 



Longitude of perihelion 36 48 40 ) „ ^ j, 



„ ascending node ... 230 38 4 J ^^-^^^ '*73 o 

 ,, inclination 84 o 50 



Log. perihelion distance 9 '899956 



Motion — retrograde. 



Minor Planets. — A remark in this column some time 

 since upon the probability of several discoveries of so- 

 called new planets proving to be observations of bodies 

 previously detected, appears to be justified by recent 

 experience. Thus the object announced as a new planet 

 by Prof. Watson and M. Borrelly in August last was 

 shown by Herr Knorre, of Berlin, to be identical with 

 No. 141, detected by M. Paul Henry at Paris, on January 

 13, 1875, and it is now stated that the small planet 

 remarked by Herr Palisa at Pola on October 2 is reaUy 

 No. 161, which was discovered by Prof. Watson on 

 April 18, 1876, and received the name Athor. As was to 

 be expected from the rapidity with which discoveries of 

 small planets have succeeded one another of late years, 

 calculation is now considerably behind observation, and 

 we are still without published elements of a number of 

 the bodies lately brought to light. — Prof. Peters states 

 that he has proposed the name Idunna for the planet 

 discovered by him on October 14, which is No. 175, a 

 name which he says will be understood by those members 

 of the " Astronomische Gesellschaft " who, at their late 

 meeting at Stockholm, participated in the hospitality of 

 " Ydun." — There is now a strange confusion of mytho- 

 logies and systems of nomenclature in the minor-planet 

 group, a state of things that at one time might have been 

 readily avoided. 



THE ROYAL DUBLIN SOCIETY 



A SCHEME for the reorganisation of this society as 

 ■^*- a branch of the National Museum of Science and 

 Art established by the Government has been under con- 

 sideration for some time, and a report of the council on 

 the subject was submitted to the society at its meeting 

 on November 8. The scheme includes a recommenda- 



