Oct. 28, 1 875 J 



NATURE 



555 



of the southern heavens have not been entirely neglected 

 of late years. The public observatories are perhaps too 

 closely occupied with other work to allow of much being 

 expected from them in a class of observation peculiarly 

 suited to the amateur astronomer, but there must be a 

 grand field of operations for private observers, in southern 

 double and variable-star astronomy. 



Capt. Jacob's last orbit of p Eridani may be written 

 thus : — 



Peri-astron passage 1819-83 



Node 110° 40' 



Node to peri-astron in directioa of motion ... 285° 50' 



Inclination 46° 36' 



Excentricity 0*323 



Semi-axis 4"'2S 



Mean annual motion, —3° "3645, or period of revolution 107 years. 

 The components are of equal brightness, and hence it is 

 to be expected some measures maybe registered 180° 

 different from others ; accordingly, to work the whole 

 series mto any supposable orbit it is necessary to add 

 180° to Sir J. Herschel's micrometrical measures (Cape 

 Obs., p. 276), and indeed it will be seen that he has so 

 recorded the angles of the 20-feet sweeps, p. 174. 

 The errors of the above orbit are, for 



1835-00 Pos. (c — 0) + 2° '5 Dist. (c - d) o"'oo 



i857'96 „ - i°-6 „ -f o"-o3 



The following are deduced from the same orbit : — 



1875-0 Pos 2i8°-9 Dist 3"-92 



76-0 „ 2i6"'-3 3"-89 



77-0 „ 2i3°-7 „ 3'-86 



As the measures of this star are, so far, scattered in 

 several volumes, they are collected here for convenience 

 of reference. Dunlop's angle was evidently registered in 

 the wrong quadrant, as is pointed out both by Sir J. 

 Herschel and Capt. Jacob ; the correct reading appears 

 to be 343° 6'. 



The place of/ Eridani for the commencement of 1876 is 

 in R.A. ih. 35m. 53., and N.P.D. 146'' 49'-5. 



(2) O. 2 387. — Between the epoch of Mr. Otto Struve's 

 measures in 1844 and Baron Dembowski's in 1868, the 

 angle in this binary has retrograded 77°, and no doubt if 

 measures are obtained this year a very considerable 

 further change will be manifested : yet the distance, if 

 we except Secchi's estimate in 1856, has been found about 

 half a second, as long as the star has been under obser- 

 vation. A first approximation to the elements may soon 

 be practicable. The place of this object for beginning of 

 1876 is R.A. I9h. 44m. 6s., and N.P.D. 55° o'-i. The 

 number applies to the Pulkova Catalogue of 1850. 



The Minor Planets.— No. 150 of the group of 

 small planets has been reached. Prof. Watson, director of 

 the Observatory of Ann Arbor, Michigan, having detected 

 another member, apparently on the night of October 18 ; 

 the place as yet doubtful, the telegrams through the 

 French and English cables being discordant. It is stated 

 to be of the 10th magnitude, and is therefore brighter 

 than the great majority of planets discovered during the 

 last few years. Considering the close scrutiny which the 

 ecliptical region of the sky is receiving at the present day, 

 we must surely soon be in a position to pronounce with 

 some degree of confidence whether any trans-Neptunian 

 planet as bright as stars of the 13th magnitude exists 



within 2^° or 3° from the ecliptic, and in the event of 

 greater inclination, the scheme of Prof. Peters, on its 

 completion, may afford an equally definitive conclusion. 

 There have been some curious alarms in this direction, 

 as in the autumn of 1850, during observations of the 

 minor planet llygeia at Washington, when an apparently 

 slow moving object was compared with the planet on 

 more than one evening ; but although sought for dili- 

 gently on the supposition of its being a distant body, was 

 not recovered, nor, we believe, has since been seen in the 

 observed place. The change of position was larger than 

 could well be attributed to casual errors in micrometric 

 observations ; but there seems to be no other explanation 

 of this case, except admitting error of observation and the 

 existence of a variable star of long period in that spot. 



NOTES FROM THE ''CHALLENGER'' 



pROF. WYVJLLE THOMSON has just sent me from 

 ^ the Challenger an account of certain results of Deep 

 Sea dredgings in the North Pacific. In these dredgings 

 was obtained a Gymnoblastic Hydroid of such colossal 

 dimensions that the largest form hitherto known sinks in 

 comparison with it into utter insignificance. Prof. Thom- 

 son has determined the Hydroid as a Monocaulus or 

 nearly allied form, and a beautiful drawing which accom- 

 panies his letter confirms this view. 



The animal itself has not yet arrived, but the letter 

 which gives an account of its capture contains so many 

 points of general interest, that the following extract will, 

 I feel sure, be acceptable to the readers of Nature :'— 

 "H.M.S. Challenger, N. Pacific, July 24, 1875. 



" On the 17th of June, in the North Pacific, lat. 34° 3/ 

 N., long. 140° 32' E., depth 1,875 fathoms, temperature at 

 bottom 1° 7 C, bottom grey mud, the trawl brought up 

 three or four examples of what seems to be a species of 

 Monocaulus, or something allied to it. The point 

 which naturally struck us most was that the hydranth in 

 a specimen measured fresh by Moseley and myself, was 

 nine inches across from tip to tip of the expanded (non- 

 retractile) tentacles, and the hydrocaulus was seven feet 

 four inches high ! On the Sth of July, lat. 37° 41' N., 

 long. 177° 4' W., depth 2,900 fathoms, with bottom tempe- 

 rature the same as before, and a bottom of red clay with 

 manganese nodules, the trawl, which was torn to pieces 

 by having taken in too great a weight of nodules of man- 

 ganese, brought up entangled in its outer netting another 

 fine specimen of this same form. It was put in weak 

 picric acid, and then into weak alcohol, and you have it 

 in the short piece of test-tube among the horsehair. This 

 specimen was not measured, but the hydranth was care- 

 fully sketched by Mr. Wild, and I enclose you the sketch. 



" These delicate things, drawn up rapidly through the 

 water from a depth of nearly four statute miles, and 

 transported into such totally different conditions of tem- 

 perature, pressure, &c., suffer greatly from the violent 

 change : they are in fact almost knocked to pieces, and 

 their finer tissues are in a nearly deliquescent state, so that 

 our great anxiety is to get them at once into some reagent 

 which will harden them somewhat. It is wretched to see 

 them melting away absolutely under one's eyes : when put 

 into any of our fluids they at once contract out of all form, 

 but that cannot be helped. I thought it best you should 

 have them as well preserved as we could manage, so I 

 only gave them a cursory glance and sent them on. 



" The hydrocaulus is enormously extensile — it is of a 

 pale pink colour, and our specimens, when distended in 

 the water, were about four feet or so long : one, as I men- 

 tioned before, which Moseley and I measured, was seven 

 feet four inches high, but that one was stretched over the 

 surface of the trawl net, and although it must of course 

 have been capable in life of cxtendmg to that degree, it 

 might not have been a normal attitude. When at what 



