544 



NATURE 



{Oct. 2, 1879 



The following works of scientific interest will be published by 

 Messrs. Macmillan and Co., during the coming season :—" A 

 Treatise on Comparative Embryology," by Mr- F. M. Balfour, 

 F.R.S. ; the second part of the second volumeof Professors Roscoe 

 and Schorlemmer's " Treatise on Chemistry " ; this, which is 

 just ready, completes the " Inorganic Chemistry ; " Prof. Boyd 

 Dawkins' "Early Man in Britain"; Prof. Gamgee's "Text- 

 Book of the Physiological Chemistry of the Animal Body ; " 

 " Pharmacology and Therapeutics " and " Natural History in 

 the Bible," by Dr. Lauder Brunton, F.R.S. ; "A Manual of 

 Geology," by Prof. Geikie, F.R.S. ; " Structural Botany on the 

 Basis of Morphology," by Prof. Asa - Gray ; " Blowpipe 

 Analysis," from the German of J. Landauer, by Messrs. James 

 Taylor and W. E. Kay ; " Questions on Chemistry," by Mr. 

 Francis Jones; "Easy Lessons on Heat," by Miss C. A. 

 Martineau ; " Easy Lessons on Light," by Mrs. F. E. Avdry ; 

 "A Handbook of Double Stars," with a Catalogue of 1,200 

 Double Stars and Extensive Lists of Measures for the Use of 

 Amateurs, by Edward Crossley, F.R.A.S., Joseph Gledhill, 

 F.R.A.S., and James M. Wilson, F.R.A.S., with Illustrations ; 

 and a new and thoroughly revised edition of "Pharmacographia," 

 by Messrs. FlUckiger and Hanbury. Prof. Huxley's "Intro- 

 ductory " to the Science Primers, has already been announced. 



The additions to the Zoological Society's Gardens during the 

 past week include a Vervet Monkey (Cercofilhecus lalandii) 

 rom South Africa, presented by Mr. E. Meyerstein ; a Black 

 Rat (Mus rattus) from Rangoon, presented by Mr. R. M. 

 Middleton ; a Norwegian Lemming {Myodes lemmus) from Nor- 

 way, presented by Mr. James Shuter, F.R.C.S. ; a Bonelli's 

 Eagle {Nisaetus fasciatus) from Mogador, presented by Capt. W. 

 P. Forwood ; a King Parrakeet (^Aprosmichis scafulatus) from 

 New South Wales, presented by General Blake ; a White- 

 backed Piping Crow (Gymnorhina leuconota) from South Aus- 

 tralia, presented by Mrs. Buchanan ; a Silky Marmoset {Midas 

 rosalia) from Brazil, a Malbrouck Monkey (Ctrcopithecus cyno- 

 sums) from West Africa, deposited ; a Red-billed Tree Duck 

 (Deudrocyena autumnalis) from South America, purchased ; a 

 Brown Bear ( Ursus arcios) from Russia, received in exchange. 



MOUNT ETNA 



C HORTLY after the eruption of Mount Etna in May and June 

 "^ last M.H.de Saussure visited the mountain, and made a minute 

 exploration of the region abont the sources of the eruption. The 

 results of this examination he describes in a series of letters in 

 the yournal de Geneve from June 17 to July 4, copies of which 

 M. de Saussure has sent us, along with a note containing additional 

 observations. On his first ascent he and his guide had to spend 

 the night on Monte Temperossa in rather critical circumstances 

 and with the scantiest supply of food and drink. Indeed, it 

 seems to have taken a day or two after reaching a supply of 

 water below ere M. de Saussure's thirst could be quenched. He 

 had observed large patches of a deep black attached to the rocks, 

 and had been puzzled to know what they were. His thirst, how- 

 ever, quickened his perception, and on scratching aw ay about a 

 centimetre of ashes he found underneath what he had half ex- 

 pected, beautiful white snow. The failure of this first excursion 

 determined M. de Saussure to choose another point of departure 

 than Lingugrossa, and to devote three days if necessary to tra- 

 verse the neighbourhood of the cone. He thus succeeded in 

 reaching the upper limits of the eruption on the north side. The 

 crevasse which has been opened on Etna has divided the volcano 

 into two parts. On the north face it extends to the valley which 

 bounds the mountain ; on the south face it seems to be arrested 

 half way. Some of the details of the eruption have already been 

 given in Nature, vol. xx. p. 198. On the north face the lai-ge 

 crevasse gave out two considerable streams, superposed in the 

 same fault. The upper stream began in the neighbourhood of 

 the cone of Etna, and was arrested to the east of Monte Pernicro. 

 Thence the crevasse is quite exposed, and gave out only eruption 

 of gas. Below Monte Pizzello there is formed a cone of ashes 

 which gave out no lava. From this point the crevasses continue 



exposed to the ravine which separates Monte Nero from Monte 

 Temperossa. Here are the sources and centres of the great lava 

 stream which extend to near Mojo. M. de Sau-ssure describes 

 in detail the upper stream, which appears not to have been 

 previously visited. 



This eruption first appears at a height of about 2,700 metres, at 

 the foot of the slopes of the upper plateau which supports the 

 principal cone (Monte Morigibello). A violent explosion has here 

 opened the side of the mountain, throwing out a mass of rocks, 

 and forming a steep gulf in which the northern crevasse seems 

 to terminate. Below this point of explosion the lava was thrown 

 out in great abundance, and formed a current at first narrow, 

 which afterwards inundated the slopes of a high plateau spread- 

 ing over a distance of several kilometres. At the point of 

 departure was formed a sugar-loaf cone of small height, which, 

 on June 13, was still very active, and whence escaped with a 

 hissing sound a thick smoke of vapours, mixed occasionally with 

 great flames resulting from the combustion of gas. The lava 

 was spread over a vast inclined plateau, flowing over very rough 

 streams of recent lava, on which it is broken up to an infinite 

 extent as far as the foot of a mountain with three craters (Monte 

 Pernicio) which turns it to the east. 



An important fact observed by M. de Saussure is that these 

 lavas flowed over the snow, and that at the time of his visit even 

 they rested on a thick bed of that substance. In fact, in all the 

 faults of the lava, in all the openings, at the bottom of all the 

 ravines resulting from the sinking of the lavas, snow was found, 

 often several metres in thickness. Nothing proves better, M. 

 de Saussure thinks, how bad a conductor of heat the eruptive 

 matter is. The terminal end, as it rolls down, carpets the 

 ground with blocks resulting from the continual rupture of the 

 already solidified envelope, and thus forms a base on which 

 afterwards flows the viscous current. At the same time a large 

 mass of snow must have been melted. M. de Saussure saw 

 traces of a large number of streams loaded with ashes which 

 had been precipitated from all the rocks and washed the slopes 

 of the snows, which extend much lower than the lava stream. 

 One result of this eruption over snow is that the lava is mixed 

 with a mass of mud, the melting snow diluting the dnst resulting 

 from the porphyrisation of the blocks at the same time as the 

 shower of ashes from the great crater falls on the surface of the 

 current. The fire and water ceaselessly intermingling by the 

 mechanical action of the burning gravel, produced a sort of muddy 

 marmalade, which, rapidly fusing by the persistent heat of the 

 lavas, gave rise to clouds of vapour and left all the stream, all its 

 blocks, all its pebbles, covered with a layer of dry mud, which 

 turns into dust and gives to the new lavas a grey colour which 

 prevents them from being distinguished at a distance from old 

 lavas. 



Below the upper lavas the slopes which extend in the direc- 

 tion of Monte Nero are covered with vast fields of hard and deep 

 snow. Their surface is all strewn with yellow spots, so that at 

 a distance they seem covered with sulphur. This appearance is 

 due to the abundant efflorescence of ferrous chloride which con- 

 denses on the surface of the snow, and which has formed small 

 mound-like masses, mixed to a small extent with agglutinated 

 ashes. The whole of the snow is, moreover, covered with 

 patches of hardened mud of the size of a plate, and even much 

 larger, also ornamented with yellow efilorescence, and mostly 

 cracked like dried mud or split from bottom to top by a push 

 which has raised them and broken them into a star-like shape. 

 M. de Saussure thinks that these singular accidents are due to 

 deep emanations, and seem to show that under the snow the 

 ground is riddled with crevasses in direct communication with 

 the volcanic centre. The acid vapours reaching the lower surface 

 of the- snow are there condensed by the cold ; but gradually they 

 reach the surface, and have then formed an infinite number of 

 small sources, which are charged with mud because the ashes of 

 the old subjacent lavas have been diluted with water resulting 

 from the condensation of vapour against the under surface of the 

 snow, increased by the snow melted by the heat of these same 

 vapours. After quitting the snows, an immense area of sand-hills 

 is met with covered with blocks from the crater of Etna. 



M. de Saussure paid a visit to the great cone of Etna in com- 

 pany with an English and an American tourist. As they were 

 walking over the lower slopes of the cone of ashes, he observed 

 a small crack in the fine sand which covered the ground. This 

 soon ceased to be visible, and suddenly M. de Saussure saw a 

 much larger crevasse open under his feet, and he felt at the same 

 time the ground begin to glide down the steep slope. He fled 



