January 12, 1893] 



NATURE 



257 



swarm lying in its track, and it is quite possible that the bright- 

 ening of the comet at the lime of the discovery was very sudden, 

 thus explaining why the comet was not detected earlier. 



The Rev. E. M. Searle {Astronomical Jourtial, No. 283) 

 has deduced a period fifteen days shorter than that of Mr. 

 Boss. 



M. Schulhof, of Paris, finds a period of 6-909 years. He 

 also points out that among the known periodic comets that of 

 De Vico shows the greatest orbital similarity to Holmes's comet, 

 and he considers that they may possibly have a common origin. 



Mr. Roberts, of the Nautical Almanac Office, accepting as 

 real the supposed impression of the comet obtained by Mr. 

 Schorling in a photograph of the region taken on October 18, 

 found a period of fifteen years, but the general agreement of the 

 latest CO uputations seems to indicate that the image in question 

 could not be that of the comet. 



The comet is now so dim that it is not considered necessary 

 to continue the ephemeris. 



Ephemeris of Comet Brooks (November 20, 1892). — The 

 following ephemeris of Comet Brooks (Berlin, midnight) is 

 given in Ast. Nach., No. 3140, by Kreutz : — 



Date. R A. Decl. (app.) Log r. Log A, 



h. m. s. o / 



Jan. 12 ...21 40 18 ... + 5941 ••■ 00786 ... 9"89i5 

 13... 56 4 ... 58 8-1 ... 00791 ... 9-9012 

 14 ...22 953... 56 33 '6 ••• 00797 ••• 9'9ii4 

 15... 22 3... 54 59'! •■• 0-0803 ... 99220 

 16... 3247... 53257 •• 0-0810 ... 99330 

 17... 4218... 51 54'2 ••• 0-0818 ... 9'9442 

 18... 5047 ... 5025-2 ... 00826 ... 99556 

 19 ... 22 58 23 ... 4859*3 ••• 0-0835 ••• 9*9670 

 The Meteor Shower of November 23, 1892. — Further 

 observations of this fine display of shooting stars are recorded 

 in Astronomical Journal, No. 283. Prof. J. K, Rees counted 

 165 meteors in half an hour, and noted some as bright as Mars ; 

 all of them were very swift. The Rev. J. G. Hagen estimated 

 that one observer, with a clear view to the west would have 

 seen 250 meteors in half an hour, and notes that some were as 

 bright as Jupiter. Mr. Sawyer estimated the maximum fre- 

 quency as about 300 per hour, and, strangely enough, describes 

 them as "slow-moving, generally quite bright, although none 

 were observed as bright as the planets Mars and Jupiter." Both 

 Prof. Rees and Mr. Sawyer note that the meteors appeared in 

 clusters, four or five fallmg almost at the same instant, while for 

 a few minutes none were seen. The radiant was near 7 

 Andronaedse, and there is little doubt that the shower was that 

 due to Biela's comet. 



GEOGRAPHICAL NOTES. 



In M. Dybowski's journey from the Mobangi to the Shari, 

 as described at a recent meeting of the Paris Geographical 

 Society, he encountered one of the most systematically cannibal 

 tribes which has yet been described. This tribe, known as 

 the Bonjos, have only one object of purchase— slaves to be 

 eaten. They refuse to sell food or any other products of their 

 country for anything else, and the surrounding tribes capture 

 and export can >eloads of slaves for this purpose. The French 

 expedition experienced great difficulty in obtaining food amongst 

 a people who had no desire for ordinary articles of trade. 



The boundaries of the republics of South and Central 

 America are certainly the least definite lines on the political 

 map of the world so far as civilized lands are concerned. The 

 que>tion of delimitation is never at rest. Dr. H. Polakowsky 

 gives in the last number of Pelermaun' s Mitteilungen a brief 

 account of the negotiations and surveys relating to the frontier 

 of Costa Rica and Nicaragua from 1858 to 1890. The difficulty 

 in this case lies in the fact that the mouth of the San Juan 

 river, a certain point of which was fixed on in 1858 as the coast 

 frontier, is continually changing, and a breakwater belonging 

 to the harbour and canal entrance of Greytown, in Nicaragua, 

 now stands in what was formerly the territory of Costa Rica. 

 On the Pacific coast years of diplomacy were required to fix 

 the centre of Salinas Bay, but it is satisfactory to know that 

 permanent boundary stones have now been erected at both 

 ends of the line. 



Mr. Coles delivered his second lecture to young people 

 under the auspices of the Royal Geographical Society, on 



NO. 12 1 T. VOL. 47] 



Friday evening, when a large audience of both young and old 

 enjoyed his spirited descriptions of Iceland and British Columbia, 

 illuminated by many anecdotes of pers mal adventure. 



The defective condition of the charts, even of the coast of 

 Europe, was strikingly brought out by the recent court-martial 

 on the stranding of H.M.S. Howe in Ferrol Channel. The 

 chart used on board was drawn from soundings made about a 

 hundred years ago, with a few substquent corrections, which 

 failed altogether to indicate the rock on which the Howe struck. 

 The Spanish authorities are reported 10 have refused permission 

 for the new chart surveyed by the officers of the Channel 

 Squadron to be published, and meanwhile the Hydrographic 

 Office has cancelled the old chart. 



A NEW SEISMOGRAPH. 



"DEFORE speaking of this memoir, let me enter a protest 

 -*-' against the method of publishing these " Annali " iii such 

 a way as to convey the impression that the papers composing it 

 were written three years before their actual date. All readers 

 are warned that when the volume is bound up, and the paper 

 covers are removed, they must post-date the papers by three 

 years. 



The seismograph described in the present paper is intended for 

 stations of the second class. The objects in view in its con- 

 struction were amplification of the record in a pendulum seis- 

 mograph, and improvement of the warning apparatus in the 

 form of a style seismoscope of the Milne type which the author 

 finds frequently fails. 



The amplifying lever is composed of fine placfont tubes arranged 

 girder-like in the form of a short hollow triangular prism, sur- 

 mounted by an acute triangular pyramid, which points downwards, 

 and carries at its apex the writing style. The pendulum bob is a 

 flattened cylinder, supported by a placfont wire I 50 m. long. 

 The amplilying lever at the junction of the three pyramidal and 

 the prismatic tubes supports three radial arms meeting in the 

 centre, as it were, of the pyramid base, and support a ball-and- 

 socket joint of agate, the cup part of which is at the end of an 

 arm projecting from the supporting wall. Immediately above 

 this centre, and occupying the prism space of the lever, is the 

 cylindrical box, the wire supporting which passes through a 

 small hole in the centre of the base of the prism. We thus 

 have a simple lever of the first order of light girder work. It is 

 prevented from rotating in azimuth by including some steel wire 

 permanently magnetized. 



The style has been modified by lightening it and making it 

 more rigid and non-oxidizable, which is done by using a capil- 

 lary glass tube. 



The registering apparatus is a smoked glass plate, supported 

 over a clock, started at the moment of the earthquake by a 

 seismoscope. To prevent the complex figures of the ordinary 

 registration in a pendulum seiNmograph, the author has arranged 

 so that the plate shall rotate through a segment of a circle every 

 three seconds, so as to bring a fresh surface of smoked glass 

 beneath the style. 



Some modifications are then described. The principal one is 

 making the bob annular, carrying a suitable aperture, in which 

 is engaged the short end of a lever. This lever is composed of 

 three very thin brass tubes, graduating away smaller from the 

 fulcrum, which is a gimbal joint such as suggested by the 

 reviewer some years since in Nature. This lever carries at its 

 lower and longer end the style which records on the glass 

 plate as in the original one described in this memoir. 



Another modification is a combination of the triple and single 

 suspension of the pendulum bob, that is, the bob ring is first 

 suspended by triple wires to a button which in its turn hangs 

 at the end of a single wire. 



The details of these seismographs are fairly well worked out, 

 but the employment of aluminium in many of the parts has been 

 neglected. Likewise, no arrangement has been made for the 

 oblique play of the engaged pinion in the newer lever. The 

 only new point about this seismograph is the interrupted rotatiori 

 of the recording plate. This has a decided advantage in giving 

 a dissected record, but is part counterblanced by the fact that 

 important movements that may be taking place at the moment 



« G - Agamennone, " Sopra un Niiovo Pendolo Sismografico." Annali 

 dcW Ufficio Ccntrale Meteor, e Geodinamico, ser. sec, pt. 3, vol. xi., 1889. 

 (Roma, 1892 ) 



