534 



NATURE 



\Oct. 2, 1879 



Perihelion passage, 1879, October 4'287i G.M.T. 



Longitude of perihelion 201 41 52-8 I Apparent Eq. 



,, ascending node... 8654 4-2 ( August 31. 



Inclination 76 57 38'2 



Log. perihelion distance 9*9983406 



Motion — direct. 

 Positions deduced from these elements for midnight at 

 Greenwich are :— 



Right Declination Log. distance Log.distance 



Ascension. North. from Earth. from Sun. 



h. m. o / 



Oct. 2 ... 14 ig'l ... 22 31 ... o'2044 ... 9*9985 



3 ... — 23-5 ... 21 30 



4 ... — 27*9 ... 20 30 ... 0'2072 ... 9'9985 



5 ... — 32-1 ... 19 29 



6 ... — 36'3 ... 18 28 ... o'2io6 ... 9'9987 



7 ... — 40-4 ■•• 17 28 



8 ... — 44-4 ... 16 27 ... 0-2144 ... 9-9995 



9 ••• — 48-3 •■• 15 27 



10 ... — 52-2 ... 14 28 ... 0-2187 ... 0-0008 



n ... — 55-9 ... 13 28 



12 ... 14 59-6 ... 12 30 ... 0-2234 ... 00027 

 On November 4-5 the right ascension is 242^ 40' and the 

 declination 7° 6' south, the comet setting in London two 

 and a quarter hours after the sun ; the intensity of hght 

 is then somewhat greater than at discovery, so that 

 observations may be e.xpected till about a month after the 

 perihelion passage. 



Near Approach of Comets to the Earth. — 

 Amongst the cases of close approach of comets to our 

 globe there are two in which we are able to fix the actual 

 degree of approximation with certainty, the orbits at the 

 times having been determined with great precision. The 

 first is that of the comet of 1770, treated of by Laplace in 

 the Mccanigiie Celeste. According to Clausen's elaborate 

 investigation, in which the effect of the earth's attraction 

 is included, this comet at 5h. 6m. P.ir. Greenwich time 

 on July I, was distant only 0-01509 of the earth's mean 

 distance from the sun, or 1,390,000 miles, and it is the 

 closest approach of one of these bodies of which we have 

 any certain knowledge. On this evening its apparent 

 diameter, as measured by Messier, was no less than 2|°, or 

 nearly five times the apparent diameter of the moon ; at 

 this time the comet was traversing the constellation 

 Draco. The second case is that of Biela's comet at its 

 appearance in 1805. At gh. p.m. on December 9, just 

 before it descended below the horizon in Europe, and 

 almost at the time of the last observation by Thulis at 

 Marseilles, the comet was distant 0-0366, or about 

 3,380,000 miles. There can be little doubt that the 

 comets of 568, 1366, 1472, and others passed near the 

 earth, but the elements of their orbits are not determinable 

 within anything like close limits. The first comet of 

 1743, for which Clausen assigned an eUiptical object, was 

 also near to us, but the orbit in this instance is doubtful, 

 and the actual distance in perigee cannot be deduced 

 with precision. 



There have been many instances where comets at one 

 or other node have passed much nearer to the earth's 

 orbit even than in the case of the comet of 1770, as 

 occurred with Biela's comet in 1839, but the nodal 

 passages have taken place when the earth has been far 

 removed from these points of her path. 



BIOLOGICAL NOTES 



The " Challenger " Rhizopods.— In the current 

 number of the Quarterly Journal of Microscopical Scicnee 

 Mr. H. B. Brady, F.R.S.,continueshis very interesting pre- 

 liminary report on the porcellanous and hyaline types of 

 rhizopods met with in the dredged stuff brought home by 

 the Challenger Expedition. He very justly abolishes the 

 misleading generic names of Tri- and Quiiique-loculina, 

 agreeing with Prof. Williamson to employ the modified 

 term Miliolina for the section. Quoting Decaisnella, 



M-Chalmas, as a synonym of Z><rt-/)'/o/o;-rj, P. and J., he 

 mentions that D. eruca occurs in considerable variety of 

 form, but that after the examination of a large number of 

 fresh specimens, he has never seen anything io correspond 

 to the structures figured in M-Chalmas's paper in the 

 Camples Rendus — figures curiously enough reproduced in 

 another portion of the same journal, in which Mr. Brady's 

 paper appears. The species of Lagena found supply ma- 

 terial, we are told, for five or six crowded plates, its 

 varieties embracing modifications of contour and surface 

 decoration before unknown and most remarkable for their 

 individual beauty. The rare and interesting Pavonina 

 Jlabclliformis, D'Orbig., has been taken at three of the 

 Challenger stations ; originally described imperfectly by 

 D'Orbigny from a specimen from Madagascar in 1826, it 

 remained unknown until dredged by Dr. E. Perceval 

 Wright in shallow water near the Seychelles. Two e.v- 

 cellent figures of it are given. A number of forms of 

 Globigerina are described. Ilastigerina, Wy. T., is referred 

 to Nonionina, D'Orbig. The paper closes with some 

 notes on " Pelagic Foraminifera," in which, " while with- 

 out departing from an attitude of caution in accepting 

 evidence upon a subject so beset with difficulties," the 

 author confesses that he sees no anomaly in the supposi- 

 tion that organisms so simply constituted as this group of 

 protozoa may be equally at home at the surface and .it 

 the bottom of the ocean. 



The "Challenger" Echinl— Prof. Alexander 

 Agassiz has just published a preliminary report on the 

 echini of the exploring expedition of H.M.S. Challeng.T 

 in the Proceedings of the American Academy (vol. xiv. 

 p. 190, June, 1S79). It was not Agassiz's intention to 

 pubhsh this preliminary notice, as he lioped to be able 10 

 issue the descriptions of the species with his final report 

 on the group ; he found himself, however, compelled for 

 the sake of retaining for the material of the Challenger 

 expedition the priority of discovery, to notice, however 

 briefly, the magnificent collection of sea-urchins intrusted 

 to his care by Sir Wyville Thomson. In contrasting this 

 collection with those made during the two expeditions of 

 the U.S. steamer Blake, Agassiz says that these latter 

 contain some of the most interesting forms obtained by 

 the former, often complementing more or less imperfect 

 Challenger material. Among the Cidarida?, Arbjeciadje, 

 and DiadematidK, many new species were found, and a 

 new genus allied to Astropyga. Among the Echino- 

 thuriae, a number of new species were dredged. Among 

 the Echinometradas nothing of importance was collected. 

 Among the Temnopleurida: excellent series of the species 

 of Salmacis and Temnopleurus were obtained, a Cottaldia, 

 hitherto only known from the chalk, and an e-xquisite 

 genus Prionechinus, allied to Salmacis. The most inter- 

 esting feature of the Echinidae proper, was the occurrence 

 of several northern forms in deep water in the tropic:;. 

 Not a single new species of Clypeastroids was found, and 

 the number of specimens even was quite small. They do 

 not play any important part in shaping the character cf 

 the fauna of deep water, and are, perhaps, the most 

 strictly littoral group of Echini, indicative at least, in the 

 present epoch of comparatively shallow water, inside of 

 the loo-fathom line, and probably giving us a good guide 

 as to the depth of the sea and the nature of the bottom of 

 the cretaceous and tertiary shores, where they occur in 

 such large numbers. One recent species of Catopygus is 

 interesting, as adding another of the cretaceous forms to 

 those still living. By far the most interesting group of 

 Echini is that of the Pourtalesias — the species were found 

 in abundance ; of Pourtalesia there are six species. In 

 Cystechinus there are three species, C. Wyvillii and 

 C. clypeatus have quite stout tests, while in C. vesica the 

 test is reduced to a mere film, so that even in alcohol the 

 shape of this sea urchin reminds one of the crown of an 

 old felt hat which had seen its best days. The test of all 

 the Pourtalesiffi is quite delicate, the amount of lime- 



