October i8, 1894] 



■NATURE 



607 







that the plainer canals were conspicuous, and even those of 

 average d stinc'ness could be seen without much difficulty. At 

 the date of writing (September l8) he had observed about thirty 

 (if the canals, although only about two-thirds of the pUnet's 

 face had been examined. Ganges wis seen double on August 29, 

 but not so clearly as in 1892. Gchon was also seen plainly 

 flouble on the same date. Three other canals — Eii'toslos, 

 Cvlops, and Cerberus — were found distinctly duplicated, and 

 ihe germination of Phison was suspected. The observations 

 were made almost exactly at the time of the summer solstice of 

 Mars' southern hemisphere. Mr. Williams has observed a few 

 small dark spots similar to the " lakes " detected by Prof. \V. 

 II. Pickering at Arequipa in 1892. 



The Mass OF Mercury. —M. Backlund's recent researches 

 on the mass of the planet Mercury, and the acceleration of the 

 mean movement of Encke's cimet, are described by M. Callan- 

 dreau in Coiiiples-retidus of October i. Encke's comet is in- 

 teresting not only on account of the diminution of its period of 

 revolution (about two hours from one apparition to the next), 

 but also from the fact that its movement is disturbed by Mer- 

 cury. A discussion of the seven apparitions of the comet be- 

 tween 1S71 and 1S91 has led M. Backhind to conclude that 

 Mercury has a much smaller mass than has hitherto been 

 ascribed to it. The value obtained is 



Mass of Mercury = - — 

 9,647,000 



It would, therefore, take about 9,700,000 bodies like Mercury to 



make up the mass of the sun. 



To account for the acceleration of Encke'.s comet, it has been 

 supposed that a resisting medium of some kind is uniformly dis- 

 tributed round the sun. M. Backlund, however, thinks that 

 all hypotheses of a continuous resisting medium of uniform 

 density ought to be discarded, and that the resistance is very 

 probably met only in certain regions. This idea is a very 

 plausible one, for, according to Laplace's hypothesis, in the 

 formation of the planets from the solar nebula, all the substance 

 of the rings would not be used up in the process, and some of 

 it would without doubt travel along the planetary orbits as 

 clouds of very light material. It is suggested that Encke's 

 comet passes through nebulous clouds of this kind, and that the 

 resistance they offer causes the observed acceleration of the 

 mean motion. 



Brorsen's Comet 1S51 III. — This comet first appeared in 

 the month of August 1851, moving in the constellations of 

 Bootis and Draco, On forty-one evenings observations were 

 made, besides numerous measures of position with micro- 

 meters, and many have been the attempts to deduce an accurate 

 orbit. Among these may be mentioned Kumker {Aitr. Nach., 

 No. 771), Vogel (.-/)■/■;-. Nach.. No. 774), Brorsen (Astr. Nach., 

 No. 775), and Tuttle {Astr. yourital, II.), who found parabolic 

 elements, none of which satisfied the observations sufficiently. 

 At a later date Brorsen obtained elliptical elements (Astr. Nach., 

 No. 782), which he compared with all the then known observa- 

 tions. In the communication before us, on a new determination 

 of the orbit of this comet bv Dr. Rudolf Spitaler (Ixi. Denk- 

 schriflen der Math. Nalumnss. Classc der k. Ak. iter IFisseii- 

 schaftcii),\\\e wriier makes use ofsome new observations and more 

 accurate places for the camparison stars. To limit this note we 

 will slate in a few words the result he .has obtained. The most 

 probable iiarabolic elements after two or three " verbes- 

 serungen " were 



T = 185 1 .August 26 '2523 Paris Mean Time. 



310 57 237 ^ 



9, = 223 40 21 '2 

 1= 3S 12 57-5 ) 



log,/ =9 '9933272 

 An attempt to improve thi 

 follows : — 



Eq. 1 85 10. 



led to elliptic elements as 

 T = iSjl August 26 "249997 Paris Mean Time. 



ir = 310 57 19-2 i 



« = 223 40 33-9 Eq. 1851-0. 



/ = 38 12 52-9) 



log? = 99933235 

 e --- 0-9999151 



Both the.se elements give ephemerides which agree well with 

 the observations, and can he looked upon as accurate within Ihe 

 limit of error of the observations. 



MO. 1303. VOL. 50] 



M. PAPAVASIUORE ON THE GREEK EARTH- 

 QUAKES OF APRIL, 1894.' 



'T'HE earthquake series to which this abstract refers consisted 

 of two principal shocks and a large number of minor 

 ones, the former felt throughout all Greece and farbeyoni, 

 but chiefly affecting the north. east region of continental 

 Greece, and especially the province of Lo:ris. 



The first great shock occurred on April 20, and was registered 

 by a seismoscope at the observatory of Athens at 6h. 52m. 

 p.m., Athens mean time. The region in which much damage 

 was done may be divided into three principal zones. (I The 

 epicentral zone, comprising the peninsula of y-K'olymion (west 

 of Cape Theologos). Three villages were completely destroyed ; 

 iSo persons were killed, and 27 wounded. (2) The zone in 

 which nearly all the buildings were overthrown. This is in 

 the form of an ellipse whose major axis is 28 km. long, and 

 extends in a south-east and north-west direction from the Bay 

 of Larymne to near Cape .-Vrkiizi ; the minor axis is 8 to 9 km. 

 in length. Nine villages were affected ; 44 persons were killed, 

 and 20 wounded. (3) The zone in which houses were much 

 damaged or partially fell, also in the form of an ellipse. The 

 major axis is 90 km. in length, directed south-east and north- 

 west, and reaches from Driiza to near Molos. The minor axis 

 is 65 km. long, and extends from Levadia to Mantoudi in the 

 Island of Euboea. 



During the night of April 20-2 r, the ground in the first and 

 second of these zones was in a state of almost incessant dis- 

 turbance, interrupted often by stronger shocks, for three 

 days shocks were very frequent throughout all three zones ; then 

 they became more and more rare un'il, on April 27, a second 

 great shock occurred, more violent than the first, and registered 

 at the Athens Observatory at 9h. 21m. 6s. p.m., Athens mean 

 time. The sacne continual disturbance of the ground followed 

 as before. 



This second shock disturbed a greater area than the first. 

 The major axis of the second zone is 30 km. longer, especially 

 towards the north-west ; it reaches from the Bay of Scroponeri 

 to St. Constantin. The major axis of the third zone is length- 

 ened by about 22 km. to the town of Lamia. The minor axes 

 of these zones are also several kilometres longer, especially on 

 the south-west side. The same villages suffered, but the amount 

 of damage was greater. 



This ear;hquake was a remarkable one in several ways. At 

 the moment of the shock, the sea ro.se in a wave which sub- 

 merged the whole coast from the Bay of St. Theologos to St. 

 Constantin. The water afterwards retired, except in the Plain 

 of Atalante, where the greater part of the coast is now submerged 

 for a distance of some metres. Several springs have ceased to 

 run, while others have increased their flow. New thermal 

 spiings have started up at .Edipsos, near pre-existing ones, and 

 similar in nature. Numerous fissures, occasionally some kilo- 

 metres in length, have been formed. 



But the most remarkable phenomenon of all is the produc- 

 tion of agreat fissureabout 55 km. long. Its breadth varies from 

 a lew centimetres to three metres, according 10 the nature of the 

 ground, being on an average aliout half a metre. It extends in 

 a constant east-south-east and west -north-west direction from 

 the Bay of Scroponeri through Atalante, until it disappears near 

 St. Constantin. This fissure appears to be a fault, on account 

 of (l) its extraordinary length and its parallelism to the Gulf 

 of Euboea; (2) the constancy of its direction and its inde- 

 pendence of geological structure ; and (3) the existence of both 

 a throw and horizontal displacement along the fissure, causing 

 a lowering of the Plain of Atalante and a slight shift towards 

 the northwest. The throw is generally very small, often zero 

 on Cretaceous ground, reaching several centime! res on the 

 Tertiary formations, and as much as ij metres on the alluvial 

 beds of the Plain of Atalante. 



M. Papavasiliore regards this fault as one of the series which, 

 at the end of Terti.iry or beginning of <J.iateriiary times, gave 

 rise to the Gulf of Euboea, and the recent earthquakes as due 

 to otogenic movements by which the width of the gulf may in 

 future be still further increased. 



C. Daviso.n. 



1 Abstract of two papers by M. S. .A. P.ip:ivasiIiorc : (c) *'Sur le tremble- 

 ment de tcrre de Locride (tirccc) du niois d-avril 1694 '- : (?) '- Svir l.i nature 

 de la grandc crcv.nssc produile ii la suite du dernier iremblc-nent de lerre dc 

 Locride.- — C.^iriptes-rcHJifs, \-o\. 119, 1894, pp. 113-114, 3^o-;!fi. 



