May 8, 1879J 



NATURE 



37 



then move the cylinder so that the multiplier is at the 

 fixed index. The product is read off at one of the movable 

 indices, bearing in mind that the number of figures in the 

 product is the algebraic sum of the number of figures in the 

 multiplier and multiplicand, if it is not read upon the same 

 index as the latter, but it is one less than that sum if read 

 upon the same index. The use of the scales n and m is 

 shown by the following : « being read from the lowest 

 line of the top spiral and pi from the vertical edge of the 

 former. To find the value of 5^^ : on placing c to 500 

 scale n reads '68, and scale m '01897, which gives '69897 

 for the logarithm of 5. '69897 X 13 = 908661. Next 

 placing the cylinder so that it reads '08661 on scales m 

 and « the index c reads 12207, hence the required power 

 is 1220700000 consisting of ten figures as required by the 

 logarithm above. Where a considerable degree of accu- 

 racy is required we believe this slide rule will be found of 

 much service, but it cannot compete on the one hand, 

 on account of its somewhat cumbrous nature, with the 

 ordinary patterns of slide rule for rough and ready work, 

 or on the other with a table of logarithms for calculations 

 requiring close approximation. 



OUR ASTRONOMICAL COLUMN 



A New Nebula. — Dr. Tempel, of the Observatory of 

 Arcetri, Florence, notifies his discovery of a nebula on 

 March 14 in a part of the heavens which has been most 

 rigorously scrutinised in searching for these objects. For 

 this reason it was at first supposed to be a faint comet, 

 and was compared with the seventh magnitude following, 

 W.B. XI. 305 ; but on March 16 its place was found to 

 be imchanged. Dr. Tempel says it is properly a double 

 nebula, with two small but distinct nuclei, distant from 

 15" to 20", and he adds the nebula Herschel II. 32, which 

 is in the vicinity, was on both evenings much smaller and 

 fainter than the new one. Herschel' s nebula is caught at 

 once in slow sweeping with a 6 or 7-inch refractor, so that 

 an object to be very decidedly more conspicuous, must be 

 within reach of ordinary telescopes, and it is hardly 

 credible that its appearance can have long been as,' Dr. 

 Tempel now describes it, without its being previously de- 

 tected. Mr. Lassell's Catalogue of 600 new nebula: dis- 

 covered at Malta contains several in the immediate 

 neighbourhood, so that the observer, Mr. Marth, could 

 hardly have failed to have his attention called to the ob- 

 ject in question, if then as visible as at present. Dr. 

 Temper s nebula is obviously worthy of immediate and 

 continued observation; its position for 1879 is in R.A. 

 lih. iSrn. 55., N.P.D. 86° i''4, or it precedes the seventh 

 magnitude above named im. 27s., nearly on the parallel. 

 Chacornac, in his Chart No. 34, has a star I2'l3mag. 

 within about 3' from the above position, but shows no 

 nebulosity ; this circumstance is of itself sufficient proof 

 that the nebula was not visible twenty-five years since. 

 We would suggest that the position of this object relatively 

 _ to the stars near it should be determined with all possible 

 accuracy ; it will be remembered that the centre of con- 

 densation in the variable nebula in Taurus has appeared 

 to oscillate about the point where it was first remarked in 

 October, 1852; or, to speak perhaps more correctly, 

 nebulosity has at times been quite imperceptible in the 

 original place, though apparent at a very short distance 

 from it 



Brorsen's Comet. — In No. 2,254 of the Astronomische 

 ^ Nachrichten Dr. Armin Wittstein of Leipsic has given an 

 orbit and ephemeris for this comet, founded upon a cor- 

 rection of the elements of Prof. Schulze by means of 

 observations at Leipsic on March 19 and 26. There 

 appears, however, to be error in the work ; the new 

 elements differing much from an observation on April 14, 

 and so far as we can see, it is probable that the ephe- 

 meris for May, which has appeared in Nature, will be 

 much nearer the truth than Dr. Wittstein' s figures ; at 



the same time it is to be remarked that the predicted 

 elements require sensible correction, though not to such 

 an extent as his calculations would indicate. Were it 

 considered worth while, an orbit might be deduced from 

 the observations already made at the present appearance, 

 which would afford the means of following the comet 

 closely during the remainder of its visibility, but the pre- 

 dicted elements with a correction to the time of perihelion 

 passage, will doubtless suffice for finding the comet 

 readily, as long as it is within reach. 



Re-observation of Tempel's Comet, 1867 II.— In 

 a communication to the Paris Academy it is announced 

 that the comet of short period discovered by Dr. Tempel 

 in 1867, and observed again at its return to perihelion in 

 1873 after experiencing heavy perturbation from the 

 action of Jupiter, was found once more by its original 

 discoverer, at the Arcetri Observatory on April 24. At 

 I4h. 30m. Florence mean time, its R.A. was i6h. 50m. 59s. 

 and its declination 13° 32' south, so that its position 

 corresponds nearly with that given in the first of M. Raoul 

 Gautier's three ephemerides in Astron. Nach., No. 2,242, 

 in which the perihelion passage is assumed May 6'94i6 

 Berlin M.T. Dr. Tempel says he had searched for it in 

 vain during the rarely fine nights of February and March. 

 The comet is faint and diffused, with a granulated appear- 

 ance about the centre, and 2' in diameter. This granular 

 characteristic of comets, by the way, is one which has 

 been frequently noted by Dr. Tempel, and which other 

 observers do not appear to recognise so often. He 

 directed particular attention to it when announcing his 

 discovery of the comet of the November meteors, 1866 I. 

 If the perihelion passage of the comet 1867 II. be 

 assumed to take place, 1879, May 69537 M.T. at Green- 

 wich, and the mean diurnal motion = 593"' 184, with the 

 other predicted elements of M. Raoul Gautier, it is 

 probable that the comet's position will be given very 

 nearly during its present appearance. The co-ordinate 

 constants in his orbit, for apparent equinox of June i, 

 are :— o / 



x^r [9'99389L sin. {v + 328 2-4), 

 y = ''[9'95727], sin. {v + 242 33-4), 

 z = ?-[9'65727], sin. (v + 2i8 41'7). 



GEOGRAPHICAL NOTES 

 The steamer Nordenskj'dld, Capt. Sengstake, belong- 

 ing to Herr A. Sibiriakoff, is almost ready to sail from 

 Gothenburg for Behring Straits, viA the Suez Canal, to 

 search for the Vega, along with the Jeanette, belonging 

 to Mr. Bennett, of the New York Herald. Herr Grego- 

 rieff,oftheSt. Petersburg Geographical Society, sails with 

 the Nordenskj'dld. Herr Sibiriakoff is sending off two coast 

 searching parties to Behring Straits, one from Nischni 

 Kolymsk and the other from the mouth of the Anadyr. 



The current number of the Royal Geographical So- 

 ciety's monthly periodical contains ample evidence of the 

 good work which is being done by our missionaries 

 towards making geography. Dr. James Stewart con- 

 tributes an account of the second circumnavigation of 

 Lake Nyassa, Dr. Laws a report of his journey along 

 part of the west side of that lake, and Mr. G. Blencowe 

 notes on the physical geography of Zululand and its 

 borders, based on nineteen years' experience on the 

 Natal and Transvaal frontiers. The geographical notes 

 are fairly good, the more important being those which 

 describe a new route from the Caspian to Kungrad, and 

 recent explorations in Persia and Central Australia, but 

 we cannot refrain from expressing our surprise that m a 

 periodical, which ought to be the leading authority on 

 geography, more space is not devoted to this department, 

 the most important of all, for therein should be recorded 

 brief accounts of all that is being done m the way of 

 travel and exploration throughout the world. It will m- 

 terest many of our readers to learn that the full text of 



