Aug. 17. 1876] 



NATURE 



337 



OUR ASTRONOMICAL COLUMN 



The Double-Star B.A.C. 1972.— Capt. Jacob, review- 

 ing the measures of this object, first registered double by 

 Dunlop with his 9-feet reflector at Paramatta (No. 23 of 

 the Catalogue of 253 stars), remarked of it in 1858 : "the 

 angle is, on the whole, evidently advancing, and the dis- 

 tance decreasing, but the measures are strangely wild, 

 considering the easiness of the object, and seem to indi- 

 cate the presence of some perturbing body." For com- 

 parison the following may be selected : — 



Dunlop ... 1826 'GO Position 329 o Distance 3'oo 



Herschel ... 1835 02 „ 342-5 „ 3 86 



Jacob ... 184694 „ 3485 „ 3-22 



... 185273 „ 3507 „ 2-8i 



... 185817 „ 3547 ,, 2-i8 



Jacob's measures of 1858 are the last we find ; he con- 

 sidered an appulse would take place about 1875. 



Dunlop says of the results in his catalogue similar to 

 the above, the " positions and distances are only estima- 

 tions while passing through the field of the 9-feet tele- 

 scope," and no great stress, therefore, need be placed 

 upon them. If we assume that the change of angle and 

 distance is the effect of proper motion, a comparison of 

 Sir John Herschel's measures of 1835, with the later ones 

 at Madras, leads to the following formulas : — 



A o = — 07876 + [8-80975] (t — 1850) 

 A 3 = + 2-6926 - [88 1 900] {t - 1850) 



Whence we find for 187675, position 34°-4, distance i""i3, 

 showing a considerable change since the last published 

 measures, which should render it easy for one of our 

 southern readers to decide upon the cause of the apparent 

 motion. In the case of rectilinear motion the nearest 

 approach would fall in 1881 or 1882, on an angle of from 

 5o°-55°, and in 1891 the component which we are taking 

 tor the companion (though the stars appear of equal 

 magnitude — the seventh) would be upon the parallel fol- 

 lowing i"-2. So much is to be gathered from the data at 

 present in our possession. The position of the star for 

 1876 is in R.A. 6h. im. 35s., N.P.D. 138° 27'.— It should 

 be added that the above formulae give an angle of position 

 for 18260, differing 11° from Dunlop's estimation and the 

 distance greater by 2\ seconds. 



The Second Comet of 1844. — The period of revolu- 

 tion assigned to this comet by Prof. Plantamour, of 

 Geneva, after a most minute discussion of the observa- 

 tions, is upwards of a thousand centuries, with a probable 

 error cf about thirty centuries ! Such a result may be 

 regarded with suspicion by many, but let us see upon 

 what grounds it has been founded. 



The second comet of 1844 was independently discovered 

 by Mauvais, at Paris, on July 7, and two nights later by 

 D'Arrest, at Eerlin. It was observed before the con- 

 junction with the sun and perihelion passage until 

 September 7, and was found at the Royal Observatory, 

 Cape of Good Hope, on October 27, and observed with 

 great precision on forty-eight days at that establishment 

 until March 10, 1845, when it was distant from the earth 

 2-9, and from the sun 2-4. The later European observa- 

 tions are those taken at the Royal Observatory, Green- 

 wich, on March 4, and at Berlin on March 6. 545 

 observations of position were available for the deter- 

 mination of the orbit, and are discussed in the Mhnoire 

 S7ir la Comete Mauvais de Vajwee, 1844, by Prof. Plai.t- 

 amour. He started with the parabolic elements of Nicolai, 

 which had led to the re-discovery of the comet in Europe 

 after the perihelion passage, on January 27, 1845. The i 

 perturbations due to the action of Venus, the Earth, \ 

 Jupiter, and Saturn, during the whole interval of obser- ; 

 vation, were rigorously determined and taken into account, ; 

 and after a double solution of equations of condition ^ 

 founded upon normal positions, thus freed from the 

 slight distortions due to planetary attraction, the devia- j 



tion of the eccentricity from unity was found, with a 

 probable error of only j'jjth part of the amount of this 

 deviation. The resulting definitive orbit is an ellipse 

 with a semi-axis major = 2183-8 ; the corresponding 

 period is 102,050 years ± 3,090. This value of the time 

 of revolution is founded upon an arc of the comet's orbit, 

 extending to 204^, described in eight months. 



The aphelion distance of the comet is 4,366 times the 

 earth's mean distance from the sun, a space which light 

 would require twenty-five days to traverse, and yet little 

 more than a fiftieth part of that of the nearest fixed star 

 according to our present knowledge, a suggestive fact 

 when the visits of comets to other systems are under 

 discussion. 



New Nebul.^. — M. Stdphan, Director of the Observa- 

 tory at Marseilles, has communicated to the Paris 

 Academy a list of twenty-three new nebulae detected with 

 the Foucault telescope of o-8o m. aperture, which raises 

 the number of such discoveries, so far published, to 120 ; 

 but M. St^phan mentions that he has approximate posi- 

 tions of about 400 new nebulze, between 45° and 100° 

 N.P.D., and hopes yet to considerably increase this 

 number. As might be expected, the twenty-three new 

 nebulae are mostly very faint ; one only is called " pretty 

 bright— very small — round" in R.A., I7h. 6m. 47s.; 

 N.P.D., 48° ii'-7, for 18760. 



THE NORWEGIAN NORTH ATLANTIC 

 EXPEDITION 



Reikiavik, July 27 

 T N continuation of our last account we hear that the ex- 

 •*■ pedition has been not at all favoured by the weather. 

 Since it left Christiansund, June 27, it has met with no 

 less than five storms (wind velocity, forty- five miles an 

 hour) ; two in the' " Lightning " Channel early in July, 

 one at Thorshaven, one north of Faroe, and one at the 

 Westman Islands (off the south coast of Iceland). It 

 has been only in the short intervals between these storms 

 that any deep-sea work has been done. The last days of 

 June were fine, so the expedition sounded, dredged, and 

 trawled off Christiansund on the bank called " Storeg- 

 gen." Here the fauna was quite Atlantic ; on the outer 

 edge of the bank the water deepened to 300, 400, and 500 

 fathoms, and the ice-cold water was met with, yielding an 

 Arctic fauna. Two large specimens of Umbellularia (the 

 same as earlier) were found, with a new star- fish and an 

 animal which is quite new to the naturalists on board. 

 Of smaller organisms there were also several new ones. 



In lat. 63" 10' N., long, i" 30' W., a sounding in 1,050 

 fathoms gave a temperature under 32° below 300 fathoms. 

 The Voringeti had to leave this station to refit, as a sea 

 had carried away the two fore-hatches. The course was 

 shaped for Thorshaven, where the expedition stayed 

 eight days to refit (July 8-15). The stay there was very 

 interesting, especially for the geologists. The formation 

 of caverns at sea-level was an operation visible in all 

 stages of progress. In the zoohte caverns of Naalso a 

 rich harvest of minerals was secured. 



The inhabitants of Thorshaven received the expe- 

 dition very hospitably, and remembered, with great plea- 

 sure, the stay of the Lightning and Porcupine. 



After a trip round the main island to Westmanhaven, 

 the Voringen left Faroe, July 16, and steered for its last 

 station. Bad weather brought work here to a speedy 

 conclusion ; however, a series of temperatures were ob- 

 tained, indicating ice-cold water at a depth of 300 or 400 

 fathoms. On the north-eastern corner of the Faroe bank 

 the depth increases very rapidly. In lat. 63° 22' N., long. 

 3° 30' W., soundings gave 1,180 fathoms. A series of 

 temperatures gave 32" -4 in 400 fathoms, 3i°*8 in 500 

 fathoms, and the bottom temperature was 29°-8. In lat. 

 63° 55' N., long 7° 10' W., 30°-2 in 677 fathoms ; in lat. 

 63'' 3' N., long. 10° 15' W., 37°'2 in 256 fathoms. Further 



