436 



NATURE 



[June 3, 1920 



Our Astronomical Column. 



Return of Tempel's Comet. — Tempel's second 

 I>eriodic comet, discovered in 1873, was detected by 

 Mr. Kudara at Kyoto, Japan, on May 25d. yh. lom. 

 G.M.T., in R.A. 2oh. 55m. 7s., S. decl. 4° 53'. The 

 approximate time of perihelion passage is 1920 July 

 10-36. The other elements are approximately as 

 follows : — o) 186° 38' 43", ^ 120° 37' 59", i 12° 45' 17", 

 ^ 33° 54' 21", /i 685-881". The following ephemeris 

 has been computed for midnight : 



K.A. S. Decl. Log r Lo^ ^ 



h. m. s. n , 



June 4 ... 21 28 o 434 0-1402 9-8077 

 12 ... 215428 441 0-1330 9-7739 

 20 ... 22 21 44 57 0-1274 97440 

 28 ... 224840 558 0-1236 9-7166 



July 6 ... 23 15 20 7 15 0-1216 9-6950 

 The comet is probably faint, but as it is approaching 

 both sun and earth its brightness should increase per- 

 ceptibly. It rises half an hour before midnight, and 

 is fairly well placed for observation just before dawn. 



Double Stars. — Since its erection in 1894, the 28-in. 

 equatorial at Greenwich has been mainly used for the 

 observation of double stars ; the list included many 

 of special difficulty owing to faintness or close 

 proximity. Mr. J. Jackson has discussed the observa- 

 tions made at Greenwich and elsewhere in Monthly 

 Notices for March, and publishes twenty revised 

 orbits. One of the stars is Struve 2525, for which very 

 discordant values of the period have been found. 

 The new value, 354-9 years, is larger than those 

 previously found, which range from 138 to 307 years. 

 The semi-axis major is i-i" and the eccentricity 0-93, 

 so that at the time of periastron, 1887-3, the star could 

 not be separated. 



The star Struve 2055 had given much trouble to 

 computers ; two observations by Sir William Herschel 

 in 1783 and 1802 were mutually inconsistent. Mr. 

 Jackson has unearthed a note that the micrometer 

 reading was not written down at the time, and that 

 the reading entered may be wrong. The quadrant 

 noted is shown to have been correct, and Herschel 's 

 other observation in 1802 is well satisfied. The period 

 assigned is no years and the eccentricity o-86. 



With respect to notation, he directs attention to 

 diversity in the method of reckoning the angle w, and 

 recommends the general adoption of the system used 

 by Campbell, Aitken, and Hussey, in which it is 

 measured in the direction of motion in the orbit plane. 



Diffraction Image of a Disc. — Mr. H. Nagaoka 

 contributes a useful article on this subject to the 

 Astrophysical Journal for March. Diagrams of 

 the " isophotes " are given, and it is shown that the 

 results explain the black drop observed in transits of 

 Venus, and the projection of bright stars upon the 

 moon's disc that has often been observed in occulta- 

 tions at the illuminated limb. A striking case of this 

 phenomenon has lately been noted in the reappearance 

 of the star Leipzig I 4091 from behind Saturn on 

 March 22 last. Messrs. Reid, Dutton, and Mclntyre, 

 observing in South Africa, saw the star reappear within 

 the limb of the planet, its conspicuous orange colour 

 facilitating its detection. They give the explanation 

 that the outer portion of Saturn is composed of trans- 

 parent clouds, but it would seem that the expansion of 

 the disc by diffraction is sufficient to account for it. 

 (B..A.A. Journal, April.) 



It is of interest to note that in South Africa the 

 star at disappearance passed behind the ring, while 

 in Europe, owing to parallapc, it did not. It 



was clearly visible through the ring, showing that the 

 separate particles composing the ring are not very 

 densely massed. 



NO. 2640, VOL. 105] 



N 



Monument to Charles Gerhardt. 



OW that Alsace is once more united to France, 

 it is peculiarly fitting that Strasbourg, his native 

 place and where he lies buried, should be the site 

 of the long-delayed monument it is proposed to erect 

 to the memory of Charles Gerhardt. British chemists 

 who are at all familiar with the history of their 

 science scarcely need to be reminded of the part 

 played by Gerhardt in its development, or of the 

 influence which his writings exercised in the search 

 for rnethods of elucidating the structure and con- 

 stitution of chemical compounds. 



His "Traits de Chimie organique " may be said to 

 mark an epoch ; it was a significant feature of a 

 niovement which characterises the middle of the 

 nineteenth century, and which the book itself greatly 

 accelerated. Although much of its teaching, as the 

 systematised expression of the facts of organic 

 chemistry, is obsolete, the work is, and will remain, 

 a classic, for it forms the basis upon which the super- 

 structure of modern chemistry is erected. Gerhardt, 

 however, was not only a speculative philosopher of 

 the highest type; he was also an experimentalist of 

 uncommon power and insight who framed his 

 theoretical conceptions in the light of his own ascer- 

 tained facts, and tested them by further investigations 

 designed either to substantiate or to disprove them. 

 His name is associated with the discovery of many 

 new substances, some of which, like the acid 

 anhydrides, are of the greatest theoretical and prac- 

 tical importance. It may be claimed for him that, 

 together with Dalton and Berzelius, he was one of 

 the principal founders of the atomic theory and the 

 originator of the notation which immediately flows 

 from it. 



An influential committee has now been formed to 

 discharge the debt — long overdue — which the chemical 

 world owes to Gerhardt's memory. It comprises the 

 names of some of the most eminent of French men of 

 science and of those of Allied countries, under the presi- 

 dency of M. Armand Gautier, member of the Institute, 

 with an executive consisting of M. Haller, member 

 of the Institute, as chairman; M. Chenal, treasurer 

 of the French Chemical Society, as treasurer; and 

 M. Tiffeneau, assistant professor of the Faculty of 

 Medicine, as secretary. The object is well worthy 

 of the consideration of British chemists, and may 

 be speciallv commended to the notice of the Chemical 

 Societv and the Society of Chemical Industry if these* 

 bodies have not already responded to the aopeal.* 



T, E. Thorpe. 



Biological Papers from Bengal. 



THE publications of the .'\siatic Society of Bengal 

 during the years 1916 to 1919, which we have 

 lately received for review, contain a large number of 

 contributions to biology, showing an activity in this 

 department that has liot been surpassed before. ^ If 

 we consider also the publications issued by the Indian 

 Museum, the Calcutta Botanic Gardens, and the 

 flourishing Bombay Natural History Society, we have 

 reason to rejoice over the prosperous state of this 

 branch of knowledge in our Indian Empire. .Allusion 

 should be made also to the enterprise of Dr. N. 

 Annandale, who, alone or with other members of_ the 

 Zoological Survey of India, of which he is^ the direc- 

 tor, has in the' last seven years investigated the 



1 A circular signed by Sir James J. Dobbie, presidpnt of theChemical 

 Society, has just been issued inviting fellows of the society to contribute to 

 the memorial fund. Such contributions should be sent to the Treasurer, 

 Chemical Society, Burlington House, London, W.i.— Ed. Nature. 



