442 



NATURE 



{Sept. 26, 1872 



niELA 'S COMET 



TV/TR. J. R. HIND has addressed the following ktter to 

 ■'-'•'■ the BitUetin of the Association Sciciitifique de 

 France : — 



You will prolmljly think me rather sanguine in 'suppc^ing 

 for a moment that there is a chance of re-discovering either 

 nucleus of Biela's comet this year, when in the ordinary course 

 of things a perihelion p:issige would be due. I look at 

 the matter in this light. We know that in February 1846 a very 

 remarkable alternation of brilliancy took place : that the second 

 nucleus, barely discernible at first, so greatly increased its light as 

 to surpass what I will teiTn the parent-nucleus, ami continued tluis 

 several days, when it gradually faded. Again in September 

 1S52, M. Otto Struve's drawnigs show the same remarkable in- 

 terchange of light between the 20th and 25th. Whatever the 

 cause may be, fach nucleus appears to have a re-vivifying power, 

 so to term it, and I think it is just possible this may be exerci-^ed 

 at one tim? or other to such an extent as to bring the comet again 

 within our grasp, though its condition in 1865-1S66 may have 

 been such as to render it quite invisible from the earth. In this 

 idea of the subject, I have prepared swce]3ing ephemerides for 

 September and October, part of which (that applying to next 

 absence of moonlight and longer) I now do myself the ho nour 

 to send you. The mean motion inDr. Michez's orbit from 1S66 

 would bring the comet into perihelion 1872, October 6 '4, and I 

 have calculated places on this supposition, also with variations of 

 ± S'' in perihelion passage. Clausen carried forward the per- 

 turbations of both nuclei in 1866, and his elements for that year 

 would indicate (of course, neglecting perturbation 1866-1872) the 

 following times of perihelion passage. 



Nucleus I . . 1872 Oct. 4776 Greenwich 

 Nucleus II . . ,, Oct. 7'256 ,, 

 and hence these differences of R. A. and N. P. D. between the 

 two nuclei, which, if one is only found, might be useful in bring- 

 ing to licht the other. 



Perhaps there may yet be time to interest some of your many 

 correspondents in a search for Biela during the first ten days of 

 October. Here the weather has been exceedingly unfavourable, 

 and, though I have watched assiduously, there has not be-"n a 

 single opportunity of examining the eastern heavens in the morn- 

 ing during the last period of absence of moonlight. 



I remain, etc. 



J. R. IIIXD 

 Observatory, Twickenham, near London, Sept. 17 



SVVEEPIMG El'HEMKRIDES FOR BiELA's CoMET 



Perihelit 

 Septcmlier 



Pe.iI.elion. 

 October 6,4. 



Mr. Jlind, in a letter w!th which he has favoured us, 

 states that M. Stephan, the Director of the Observatory 



of Marseilles, will employ the large Foucault mirror of 

 that establishment in a search for the comet. 



AMERICAN ASSOCIATION FOR THE AD- 

 VANCEMENT OF SCIENCE 



■^^HE session of this Association opened at Dii- 

 ■*• buque, Iowa, on August 21. At the end of last 

 year's meeting it was expected that the Association would 

 meet this year at San Francisco, which place it was hop;d 

 I'rof. Agassiz would have reached in the Hasslcr by the 

 time of the opening, and added an unusual brilliancy to the 

 proceedings by an account of some of his discoveries in 

 the Southern seas, f he great naturalist, however, as we 

 know, has not yet reached the Californian coast ; and 

 partly on this account, but mainly, we believe, on account 

 of the great expense to most of the members of a journey 

 to San Francisco, that city has not this year been 

 honoured with the presence of the associated savans of 

 the United States. Indeed, if we may Judge by the some- 

 what diminished attendance, and the unusually small 

 number of papers read, even Dubuque seems to be too far 

 away from the homes of many of the members. Some of 

 the prominent members of the American Association were 

 absent this year, the many, however, who did attend, 

 met with a very liberal reception from the citizens of 

 Dubuque. 



The retiring president of the la^t year. Prof. Asi Gray, of 

 Cambridge, Ma^s., made, as is the custom, a valedictory address. 

 He took the opportunity to sketch his recent experience at the 

 West as a botanist, for, strange to say, un'il the present summer 

 he had not seen the Mississippi nor set foot upon a prairie. Prof 

 Gray touched lightly upon the history of the Sequoias ; that 

 their age must be count.'d by hundreds of years we cannot doubt ; 

 but also we cannot doubt that they did not anteda'e the glaciers 

 whose icy expanses have left their in''isputable evidences every- 

 where around. The main porticm of Prof Gray's address was de- 

 voted to showing the probability that cerlain trees of the present 

 day, the Sequoias of Califor.iia, the Taxoiiiiim, or Bald Cypress 

 of the Atlantic, and the Glyptostrolnis, a Chinese tree, the only 

 ones of their tribe at present existing, were not only closely allied 

 in structure and general characteristics, but were the lineal suc- 

 cessors by gradual modification of the fossil trees of geological 

 ages ; and that all our existing vegetation was a continuation of 

 that of the Tertiary period. Tnree hypotheses are open to 

 account for their present existence : either they were created 

 in the detached regions where they are now found ; or they 

 are the first members ol a new and incre'sing race ; or 

 they are nearly the last representatives of a once powerful and 

 widely-spread trUie. After discussing the first two alternatives. 

 Prof Gray gives liis reasons, which are supported by pala2onto- 

 logical evidence, for believing that the " big trees " of Cahfornia 

 are the last of their race, and that a little further drying up of the 

 climate, which is now in progress, will speedily precipitate their 

 doom. The oldest of the trees now standing he considers to 

 possess an antiquity of about 2,000 years. 



A paper was read by Prof E. S. Morse "On the Oviducts of 

 the Brachiopods." He brought forward for the firs* time a.few 

 facts regarding the development of a species of Brachiopod from 

 the coast of Maine. The various stages in the'r development, he 

 believed, fully supported the position he maintained, that the 

 Brachiopods were true wovms and not molluscs. 



Prof Benjamin Peirce, Superintendent of the United S a^ s 

 Coast Survey, gave an exceedingly interesting account of tl:e 

 measures taken by that Bureau with reference to stations for 

 astronomical observations at great Ifigh's, such as Sherman, on 

 the Rocky Mountains. Prof Young, of Dartmouth College, has 

 been appointed to eximine and give an opinion as to the effect 

 of taking observations from the Rocky Mountains and Sierra 

 Nevadas. Prof Peirce's opinion was that observatories should 

 be placed on the summits of both, if not permanently at least 

 temporarily, the Rocky Mountains being favourable to some, the 

 SierraNevadasmorefavourablefor other observations. In a higher 

 position you get rid of absorption of light by gcttingtidof half the 



