May i8, 1876] 



NATURE 



49 



aad dictionary of all the principal Malayo-Polynesian dialects, 

 and am trying to reduce the whole to a uniform system of ortho- 

 graphy. S. J. Whitmee 

 Samoa, Jan. 3 



The Visible Horizon 



A POINT of some scientific interest has just been argued in the 

 High Court of Justice. It was contended by the Solicitor- 

 General that the three miles' limit of territorial waters was of 

 mo'iern origin, and by Sir R. Phillimore that it was due to that 

 being the distance a cannon ball would reach from the shore. 

 There can, however, be no doubt that the limit was recognised 

 long before the invention of gunpowder. 



Three miles is the distance of the offing or visible horizon to a 

 person six feet in height standing on the shore. It is natural to 

 suppose that the early maritime peoples of Europe would lay 

 claim to the sea as far as the eye could reach. This distance 

 they would find by experience was just three miles, and it can be 

 proved mathematically to be correct. Measured by this standard 

 — a tall man, usually taken as six feet high — the distance is 

 invariable for all time, places, and peoples ; measured by a 

 cannon ball, it is constantly varying, and now ought to be five 

 miles rather than three. The fact that the distance depends on 

 both ocular and mathematical demonstration, and is not subject 

 to improvement in gunnery, is the best explanation of its origin 

 and application. B. G. Jenkins 



Dulwich, May 8 



Lunar Maps 



Lohrman's complete map, three feet in diameter, four sections 

 of which were published in 1824, has been recently engraved by 

 J. A. Earth, of Leipzig, under the supervision of Dr. Schmidt, 

 director of the Athens Observatory, who has contributed a 

 descriptive letterpress. 



Schmidt's own map of six French feet diameter, will be issued 

 before the end of the present year, from the atelier of the Royal 

 Prussian Staff, the Prussian Government having, with great 

 credit to itself, purchased that incomparable work. It is the 

 result of thirty-four years' labour, and contains about 34,000 

 craters and an equal number of hills, besides over 350 rills and 

 other objects. The difficulty of noting and correctly mapping 

 this amazing number of lunar formations will be understood by 

 anyone at all acquainted with the subject ; and it wiU be seen 

 that Dr. Schmidt has completed an achievement not surpassed 

 in scientific capability and perseverance. A written text will 

 accompany the map. 



It were to be wished that our own countryman, Mr, Birt, 

 could look forward to a similar recognition of his services. His 

 great lunar map, of which we have heard nothing for some 

 time, is on a plan quite different from Schmidt's, to which it 

 would be found, if completed, an invaluable accompaniment by 

 observers of the lunar surface ; and it will speak but little for 

 the scientific taste of our country if Mr. Birt's work is allowed 

 finally to collapse for want of appreciation and encouragement. 



Miilbrook, Tuam, Ireland J. Birmingham 



OUR ASTRONOMICAL CULUMN 



The Star-Lalande 27095 (Bootes).— Olbers, writing 

 to Bode in July, 1804, respecting his observations of the 

 comet of tiiAt year, remarks of Lalande 27095, near the 

 place of which star the comet was situated on March 22 : 

 " 1st nicht luehr am Himmel zu finden." It was observed 

 by Lalande as a seventh magnitude, 1795, May 25 (" His- 

 toire Celeste," p. 164), centre wire at I4h. 42m. los. 



The star was observed by Bessel, 1828, May 24, as a 

 9th magnitude, and is No. 976 of Hour xiv, in Weis' u's 

 second catalogue. In the " Durchmusterung " it i^ 9*0. 

 There is evidently reason for supposing the star to be 

 variable. 



It follows the sixth-magnitude-star B.A.C. 4906, 19s., and 

 is 6' 37" north of it, the position for the beginning of the 

 present year being R.A. I4h. 45m. 56s., N.P.D. 52° 6'-5. 



The First Comet of 1743.— Notwithstanding the 

 very marked deviation of the orbit of this comet from a 

 parabola, it does not appear that any attempt has yet 

 been made to determine, directly from the observations, 



the true form of the orbit, or at any rate to work out 

 elements which will satisfy the observations within their 

 probable limits of error. It is true that these obser- 

 vations, with one or two exceptions, are by no means 

 exact, and Olbers, who examined the question in 1823, 

 was of opinion that, from their general uncertainty, an 

 investigation into the nature of the conic section described 

 was hardly worth the trouble it would involve. Notwith- 

 standing this expression of opinion from so high an autho- 

 rity, it may be remarked that there are a sufficient num- 

 ber of observations in our possession which cannot fairly 

 be supposed liable to serious errors to justify an attempt 

 to deduce more satisfactory elements than those hitherto 

 calculated. 



The comet appears to have been first observed by 

 Grischow or Grisso, at Berlin, on February 10, and his 

 observation on the evening of that day was considered by 

 Olbers to be the most certain of any he made upon this 

 comet, and not liable to a greater error than 2' or 3'. 

 On February 14, 15, 16 and 19, Grischow, observing ap- 

 parently with Margareta Kirch, also gives particulars 

 from which probably fair positions might be deduced. 

 And we have an observation by Father Frantz, of Vienna, 

 on February 21, given in proper form in the "Philo- 

 sophical Transactions " of the Royal Society. Also a 

 good observation by Maraldi at Paris on February 13, 

 and one by Cassini on February 17, which last, however, 

 is open to some doubt, not only for a reason pointed out 

 by Olbers, but from an error as to the comparison star. 

 Zanotti's observations at Bologna, form the longest series, 

 and extend from February 12 to 28, but they are only 

 published (in Memoires de VAcademie, 1743) in longi- 

 tude and latitude to minutes of arc, without further 

 detail, and were not given by Zanotti as having any pre- 

 tensions to accuracy. The parabolic orbit with which 

 Olbers was content to discontinue ^his computations was 

 the following : — 

 Perihelion Passage, 1743, Jan. 10, at 2oh. 29m, 37s. Paris M.T- 



Longitude of perihelion. 



,, „ ascending node 

 Inclination to ecliptic 



Perihelion distance 



••• 925751 

 ... 67 3X 57 

 ... 2 16 16 



"■sjS'siSL'""" 



These elements agree well, according to Olbers, with the 

 positions observed on Feb. 10 and 28, and with the longi- 

 tudes on Feb. 13 and 21, but the latitudes on these days 

 differ by 14' and 10' respectively, which is precisely the 

 kind of discordance, which we might expect to find, if the 

 true orbit of the comet were an ellipse of short period. 

 It will be remembered that Clausen considered this comet 

 identical with that of November 1819, detected by Blan- 

 pain at Marseilles, with a period of 673 years before 1758 

 and 5 "60 years after 181 7, and that at the suggestion of 

 Olbers the perturbations were calculated at the CoUegio 

 Romano to the year 1836, when the comet had been ex- 

 pected to re appear. The orbit of short period which 

 appears in catalogues with Clausen's name, was calcu- 

 lated from Zanotti's observations of Feb. 12, 20, and 28, 

 with a pre-supposition as to the length of the major-axis. 

 As already remarked, no attempt, so far as we know, has 

 yet been made to deduce elements direct from the obser- 

 vations, which shall represent them with smaller errors 

 than the parabohc orbits of Lacailie, Olbers, and 

 Struyck. 



Grischow records that on the evening of Feb. 11, 1743, 

 the apparent diameter of the comet was 18', that it ap- 

 peared like a greyish-white cloud, but with close atten- 

 tion, " ein kleines helles Piinctlein in der Mitte gewahr." 

 We find by calculation that the comet at this time was 

 distant from the earth only 0*051 of the earth's mean 

 distance from the sun, and are reminded that such an 

 object would have afforded an opportunity of the kind to 

 which Mr. Marth has lately adverted, for a determination 

 of the amount of solar parallax. A similar opportunity 



