Jan. 13, 1887] 



NA TURE 



257 



articles likely to be interesting and useful both to beginners in 

 ])hotography and to advanced practitioners. 



The Severn Fishery Board has issued an Almanac for the 

 year 1887, which is intended to show the law as to fishing in the 

 Severn fishery district, and to indicate to water-bailiffs, fisher- 

 men, and others interested in fishing, what they may look for in 

 different months of the year. The information on which the 

 statements in the Almanac are based was collected by the 

 Board's officers. 



The seventh volume of the Transactions of the Sanitary Insti- 

 tute of Great Britain, 1885-86, presents a full report of the pro- 

 ceedings of the Congress of the Institute held at Leicester from 

 September 22 to 26, i38s. The papers read at the Congress 

 were divided into three sections — (l) Sanitary Science and Pre- 

 ventive Medicine ; (2) Engineering and Architecture ; (3) 

 Chemistry, Meteorology, and Geology. Mr. John F. J. Sykes, 

 Honorary Secretary for the first section, recommends that a 

 special day, or part of a day, should be devoted to the considera- 

 tion of domestic sanitation and ambulance. In both of these 

 subjects ladies take great interest, and Mr. Sykes is of opinion 

 that his suggestion, if adopted, would add immensely to the suc- 

 cess of future Congresses. 



The amount of the rainfall at Ben Nevis Observatory during 

 1886 was I07'85 inches, the greatest monthly fall being 1457 

 inches in November, and the least 2 '84 inches in February. In 

 1885 the annual rainfall was (see vol. x.xxiii. p. 347) I4'5'50 

 inches, the largest monthly fall being 24*33 inches, and the least 

 4 '97 inches, the rainfall of 1886 being thus very much less. 



We understand that complaints have been made to the 

 Fishery Board for Scotland that steam-vessels have been 

 recently prosecuting beam-trawling overnight in the waters 

 closed by the Board's by-law against this mode of fishing. 

 Some time since the Board instituted legal proceedings against 

 parties who had infringed the by-law, some of whom were 

 fined, and they also posted placards at the different harbours and 

 creeks in the prescribed waters giving notice of the terms of the 

 by-law, and it was hoped that the illegal practice would have 

 been thereafter discontinued. The Board's cruiser Vigilant has 

 done what she could to protect these waters, but owing to her 

 being a sailing-vessel she cannot do this so effectively as a 

 vessel with steam power. In the circumstances the Board have 

 instructed H.M.S. Jackal, at present cruising on the west coast, 

 at once to proceed to the east coast and protect the inclosed 

 areas there, as well as to take a general superintendence of the 

 fisheries. The prescribed waters include the Firth of Forth, 

 St. Andrews Bay, and Aberdeen Bay. The present Jackal is 

 a new, powerful, and swift vessel, and is provided with the 

 electric light, which will enable her to sight vessels at a con- 

 siderable distance on dark nights. The Board's cruiser Vigilant 

 will at once proceed to the west coast and take up fishery duty 

 there, assisted by H.M.C. Daisy tender. 



The Report of the Swiss Commission for the Keform of 

 Gymnasial Instruction has just been issued. The Commission 

 recommend that the teaching of Latin shall begin in the fifth 

 class, and shall be continued, for five hours weekly, up to the 

 highest class ; that instruction in Greek shall depend upon the 

 expressed desire of parents or guardians, and shall begin in the 

 fourth class ; and that all scholars who do not learn Greek shall 

 learn either English or Italian. Two spare hours gained by 

 pupils in English or Italian are to be spent in the study of natural 

 science and mathematics. 



Mr. Edison, the electrician, of New York, is reported to be 

 seriously ill. 



The additions to the Zoological Society's Gardens during 

 the past week include two Barn Owls (Sirix flammea) from 



South Africa, presented by Mr. E. Hume ; a Black-headed 

 Gull {Larus lidibundus), British, presented by Mr. W. S. 

 Rawlinson ; two Eyed Lizards (Lacerta ocellala), European, de- 

 posited ; four Bramblings {Fringilla moiitifringilla), British, 

 purchased. 



OUR AS TRONOMICA L COL UMN 



The Si.x Inner Satellites of Saturn. — Appendix I. to 

 the volume of Washington Observations for 18S3 contains an 

 important memoir by Prof Asaph Hall on the orbits of the six 

 inner satellites of Saturn. Of these, the two innermost have 

 been known to us about 100 years, but the other four for more 

 than 200. Owing, however, to the difficulty of making accurate 

 observations of them, their orbits were but rough approximations 

 until the publication of Bessel's work on the orbit of Titan, 

 which appeared in vols. ix. and xi. of the Astronomische Nach- 

 richtsn, and from which that value of the mass of Saturn was 

 derived which has been generally used up to the present time in 

 computing the perturbations produced by this planet. Bessel 

 likewise commenced, but did not live to complete, a memoir on 

 the " Theorie des Saturns Systems," of which Prof. Hall justly 

 remarks that it " is still the most comprehensive investigation we 

 have of the differential equations of this system, and of the 

 various forms of the perturbative function arising from the figure 

 of the planet, the ring, the action of the satellites on each other, 

 and the action of the sun." M. Tisserand has shown, however, 

 in a short but important paper, " Sur le mouvement des absides 

 des satellites de Saturne et sur la determination de la masse de 

 I'anneau," that Bessel's determination of the mass of the ring 

 from the motion of the line of apsides of the orbit of Titan was 

 seriously in error, since he neglected the influence of the 

 figure of the planet. We were, therefore, ignorant of the 

 true value of the mass of the ring, but if the inner satellites 

 moved in orbits which were decidedly eccentric, so that the 

 motions of the lines of apsides could be accurately deter- 

 mined, the mass of the ring and figure of the planet could 

 be deduced. It was therefore a matter of great interest to 

 determine these orbits as accurately as possible ; and Prof. 

 Hall therefore undertook the observation of those satellites 

 with the great refractor of the Naval Observatory, Washington. 

 The observations of Titan, given in Prof. Hall's paper, were 

 made at Washington during the eleven years, 1874 (in which 

 year Prof. Newcomb observed the satellite) to 1S84. During the 

 years 1S75, 1876, and 1877, Prof Hall observed differences of 

 R. A. and declination of Saturn and Titan at the same time and in 

 the same manner as he observed lapetus, to which satellite he 

 found the method well adapted. Rhea, Dione, and Tethys were 

 observed by Prof Newcomb in 1874 and by Prof. Hall in 1875, 

 whilst for Mimas and Enceladus observations extending over the 

 years from 1874 to 1879 have been used. In the reduction of 

 the observations of Rhea, Dione, and Tethys, the observed 

 ])lace5 have been compared with places computed from the 

 elements for these satellites given by Dr. W. Meyer, of Geneva, 

 and corrections to his elements are deduced therefrom. The 

 corrected orbits show in each case a practically insensible eccen- 

 tricity, and the observations of Mimas and Enceladus also can be 

 satisfied within the limits of their probable errors by circular 

 elements. Prof Hall, however, draws attention to the fact that 

 for the three innermost satellites the eccentricity of the orbit, 

 and consequently the position of the line of apsides, cannot be 

 determined with any certainty from the observations at his 

 disposal. Some more accurate method of observation than that 

 of the filar micrometer should be adopted ; possibly observing 

 the conjunctions of the satellites with the ends of the ring, the 

 Cassinian division, and with the sides of the ball, might prove 

 more efficient. A heliometer, if one existed of sufficient 

 aperture, would probably furnish the most satisfactory means 

 of all. 



The orbits of the five inner satelHtes being thus sensibly 

 circular, any consideration of the motions of their lines of apsides 

 is placed out of the question. These five satellites also appear to 

 move in the plane of the ring. It is therefore easy to furnish 

 tables of their motions, and Prof. Hall supplies them for the 

 period 1875-1950, together with the elements of the ring, at the 

 close of his paper. For the mass of Saturn, from the motions of 

 Titan, Rhea, Dione, and Tethys, he finds the reciprocal to 

 be 34787 ± fio. The best previous determinations have been 



