March 30, 1893] 



NATURE 



519 



ture our cirrus clouds. Where this veil occurs in denser masses 

 there are the belts, and the phenomena of white spots is nothing 

 less than holes in this veil itself exposing the uniform white 

 layer below. During this period of observation the great red 

 spot was extremely faint and seemed to belong to the white 

 portion beneath, being apparently seen through a hole in the 

 gauzy structure. Since October 8 last, when Prof. Pickering 

 . commenced a series of measures with the 13-inch telescope of 

 the diameters of the satellites, some most interesting results 

 have been forthcoming. It was on that day also that he ob- 

 served one of these small bodies first as an elliptical figure, and 

 then afterwards as a circular one, and later he had the good 

 fortune to watch and observe the disc as it gradually began to 

 assume the elliptical form. After this observation it was found 

 that the other three satellites had at some time been reported 

 as representing an elliptical disc, the shortening taking place 

 equatorially, thus they would seem to revolve about their minor 

 axes. To make quite sure that this was the case and not the 

 result of some optical delusion, Prof. Pickering seems to have 

 instituted various experiments, but the elongations, as he says, 

 " nevertheless remained persistent in the same direction." The 

 first satellite then is a prolate ellipsoid revolving about one of 

 its minor axes in a period of I3h. 3m., while the other three 

 assume at regular intervals the form of ellipses, these periodic 

 -changes being produced by the rotation upon their axes. 



With respect to the second satellite, the shape of which, by 

 the way, is put down as that of an ellipsoid of three unequal 

 axes revolving about the middle one, and whose period of 

 rotation is 4ih. 24m., a curious observation was made in 

 December last. Just about the time of occultation, the equa- 

 torial diameter being "decidedly shortened," the satellite 

 retained its shape until almost in contact with the limb, when 

 suddenly "the major axis of its ellipse changed its position 

 angle through thirty degrees, becoming parallel to the limb of 

 the planet." With regard to the other two satellites 

 Prof. Pickering mentions many new facts relating to colour, size, 

 rotation, &c., too numerous to refer to here, but we may say 

 that he has been led to the conclusion that all the four satellites 

 are nothing more than condensed swarms of metorites, like 

 Saturn's ring. In the case of each-satellite he gives an ephemeris 

 which indicates the time at which each presents its maximum 

 elliptical phase. 



The Horizontal Pendulum.— In a volume of 216 pages 

 entitled "Das Horizontal Pendel und seine Anwendung zur 

 Beobachtung der absoluten und relativen Richtungs - Aen- 

 derungen der Lothlinie," Dr. E. von Rebeur-Paschwitz brings 

 together all his observations made in the years 18S9-92 at the 

 observatories at Wilhelmshaven and Potsdam, and also in 

 Puerto- Orotava on Teneritfe. Besides containing a long dis- 

 cussion on the observations themselves, a very useful collection 

 with short notes of the literature on this subject is added. The 

 pendulum, which was of an isoceles triangle shape, carried a 

 small mirror at the middle part of the shortest side, the move- 

 ments of which were photographically recorded with the help of 

 sensitised paper and an oil lamp. In addition to numerous 

 seismical appearances, three distinct periodic pulsations were 

 recorded. The first he says is with great probability due to 

 the different positions of the moon, and after supplying the 

 terms containing lunar factors he finds a close agreement 

 between the observed and calculated values — the observations 

 indicating the existence of a tide with a coefficient of o"'or. 

 With regard to the daily period, he finds that these movements 

 are by no means local, but quite general over the earth's sur- 

 face ; the real cause of these motions do not seem to have been 

 fully brought home, as the magnitudes of the amplitudes seemed 

 to differ considerably locally ; but in a note Dr. Paschwitz 

 mentions that the action of the moon on the daily period is in 

 all cases of great importance. The third and last movement, 

 that of the motion of the zero-point, seems to be totally de- 

 pendent on meteorological conditions. 



The Rising and Settings ok Stars.— At the present 

 day there are many who are interested in the calculation of star 

 places, times of rising of stars, &c., for times very remote, 

 such as, for instance, in the solution of such problems that have 

 arisen with regard to the orientation of temples, occultations, 

 eclipses, &c. Where we now use the meridian, our early 

 ancestors adopted the horizon, and it was to this plane that 

 they referred many of their astronomical measurements. The 

 heliacal rising and setting, and the cosmical rising and setting 



NO. 12 22, VOL. 47] 



are only some of the expressions that were in use to define 

 different relations between heavenly bodies and the horizon at 

 a given time, and only quite recently has the importance of 

 such terms as these been pointed out. In a late publication of 

 ihe Aitronomischen Gesellschaft,Bd. xx. Dr. Walter F.Wislicenus 

 has worked out a set of tables for the computation of the yearly 

 risings and settings of stars, and the special problems which can 

 more easily with their help be solved may be stated as: (i) 

 Given <p, e, o, S the latitude, obliquity of ecliptic and coordinates 

 of a certain star for a certain year to find the longitude of the 

 sun at the time of the heliacal rising. (2) Given <p, e, for a 

 certain date, and A for the heliacal rising of an unknown star to 

 find a and 5. (3) Given 6, a, 5, for a certain date and also the 

 value of \ at the time of the heliacal rising to find (p the place of 

 observation. 



GEOGRAPHICAL NOTES. 



French exploration towards Lake Chad is being carried on 

 steadily and successfully. The latest results have been obtained 

 by M. Maistre, who set out from the Mobangi in July, 1892, 

 traversed the south of Bagirmi through the Shari valley, and 

 entered Adamawa by a route never before traversed by Euro- 

 peans, ultimately descending the Niger, where the expedition 

 reached Akassa on March 25. The health of the expedition 

 was good, and in the earlier part of their work friendly relations 

 were kept up with the natives. In Adamawa, however, there 

 were hostile encounters. 



Mr. Mackinder concluded his course of educational lectures 

 for the Royal Geographical Society last week by a masterly 

 discussion of some of the geographical aspects of British history. 

 The effect of the position of the British Isles on their history 

 was summarised concisely in the statement that Britain stands 

 out of the continental world, yet looks into it through its south- 

 east window, and looks not merely into the world, but into the 

 great historic avenue of the world's life. Naturally, therefore, 

 the centre of Britain's national and commercial life has been 

 drawn eccentrically to the south-east corner. This accounts for 

 the inevitable position of London. The configuration of the 

 country, with its natural zones of highlands and lowlands, led 

 with equal clearness to the distribution of peoples and inter- 

 ests, which caused the historic opposition of England and 

 Scotland. 



Mr. and Mrs.Theodore Bent, aftersome delayat Massowa, 

 on account of tribal wars, reached Adowa on the way to Aksum 

 in the middle of February. At Adowa there are Himyaritic 

 ruins of some importance, which Mr. Bent proposes to study 

 before going on to Aksum, where he hopes to have several weeks 

 of active archaeological research. 



In a recent report on the Iriangulation of the north-west por- 

 tion of South Australia, published by the Government of that 

 colony, the work of the surveyors during the last few years is 

 briefly summarised. From 1888 to 1890 16,000 square miles 

 were surveyed in the form of a belt, about fifty miles wide, 

 stretching from the Anthony Range to the western boundary of 

 the province, a distance of 320 miles. Up to the end of the 

 1892 season 11,300 square miles of additional land were sur- 

 veyed. The work in many places was extremely arduous on 

 account of want of water, a supply for the camels having some- 

 times to be carried for more than forty miles, and for more than 

 a year no rain whatever fell. 



THE INSTITUTION OF NA VAL 

 ARCHITECTS. 

 "T^HE annual spring meeting of this Institution was held last 

 -'- week in the hall of the Society of Arts on Wednesday, 

 Thursday, and Friday, March 22, 23, and 24. There was a fair 

 number of papers on the 'agenda, of which the following is a 

 list :— 



On the present position of the cruiser in warfare, by Rear- 

 Admiral S. Long. Merchant cruisers considered with reference 

 to the policy of maintaining a reserve of vessels by annual sub- 

 ventions to shipowners, by Lord Brassey. Some considerations 

 relating to the strength of bulkheads, by Dr. F. Elgar, On the 

 measurement of wake currents, by George A. Calvert. On the 

 new Afonasieffs formulae for solving approximately various 



