ii8 



NATURE 



[June 2, 1892 



A table of contents may be found at the end. 



Appended to the various sections are the names of the authors 

 responsible. The i8o pages of text necessarily vary in character. 

 Thus, 50 pages are devoted to an almost daily record of the state 

 of the volcano during the twenty months of the eruption. For 

 not a few days we have a record of the times and degree of 

 violence of all the explosions which (February 12 and 14, 18S9) 

 might number more than 100 between 10 a.m. and 6 p.m. On 

 the other hand, we find between pp. 207 and 210, a rSsumi of 

 the chief facts observed, and the conclusions to which they 

 point. 



There are 20 pages (9-29) on the topography and geology of 

 the island of Vulcano. Details are given as to the rocks collected 

 at various localities, and the conclusion (expressed with some re- 

 serve) as to the history of the island, is very similar to the view 

 stated (Proc. Geo!. Assoc, vol. xi. pp. 395-96, 1890) by Dr. 

 Johnston-Lavis. 



The author (Mercalli) only recognizes one crater (with 

 lavas of andesitic and basaltic type) in the " Piano " district, 

 which forms the southern half of the island. The Serro di 

 Capo and Monte Lentia represent the western part of a second 

 old (north-west) crater of more "acid" type, which may have 

 had its centre almost coincident with that of the present active 

 cone, and which, judging by the weathering of the rocks, may 

 be older than the Piano crater. The author notices that the 

 straight north and south line, drawn from Vulcanello through 

 the hot springs by the " Faraglioni " and the two overlapping 

 "Forgia Vecchia"-s (on the north flank of Vulcano) to the 

 present crater (or "Fossa di Vulcano"), if continued, strikes 

 Monte Saraceno (a lateral cone on the north-west edge of the 

 Piano crater). It is then pointed out that, assuming Monte 

 Saraceno to be situated over a continuation of the crack which 

 most probably runs from Vulcano to Vulcanello, and assuming 

 the present eruptive centre to coincide with that of the old 

 north-west crater, that then the present " Fossa di Vulcano " is 

 situated on the point of meeting of two cracks, viz. a north to 

 south one from Vulcanello to Monte Saraceno, and a no th- 

 west to south-east one joining the more ancient craters. The 

 present crater would then be situated over a weak point. 

 Whether or no Monte Saraceno be situated over a crack ex- 

 tending south from Vulcano rather than over some other, there 

 is nothing at any rate in the above against the view expressed 

 in Prof, judd's "Volcanoes" (see Fig. 81), according to which 

 there is one main crack beneath the island of Vulcano, the crack 

 from Vulcano to Vulcanello being but a continuation of that on 

 which the more ancient craters lie. As to the number of craters 

 more ancient than the main modern cone, it will be seen that 

 the Report takes a view intermediate between that of Scrope 

 ["Volcanos," 2nd edit., p. 192, Fig. 47] and that of Judd 

 ["Volcanoes,'" p. 196, and Figs. 77 and 85]. 



The twenty pages (30-50) devoted to the records of previous 

 eruptions are naturally full of interest. A number of quotations 

 from older writers are given. The conclusion is that the erup- 

 tions of Vulcano in the historic period have been on the whole 

 very similar. 



As interesting dates may be noticed : — 475 B.C., Vulcano in 

 activity (Thucydides) ; 183 B.C., Vulcanello formed; about 

 1550 A.D., strait between Vulcanello and Vulcano filled up 

 by eruption of the latter ; 1727, Forgia Vecchia (on north slope 

 of Vulcano) in eruption (D'Orville) ; 1771, " Pietre Cotte" 

 obsidian stream (on north flank of Vulcano) poured out ; 1878, 

 Fumaroles still visible on Vulcanello. ^ 



From p. 53 to p. 174 is devoted to (i) detailed record of the 

 eruptions, as to which a valuable resumi is given, pp. 112-14 > 



(2) seismological and various other physical observations ; and 



(3) the description of the erupted products. 



The following epitome is based on that given by Silvestri, 

 pp. 207-208 :— 



(a) The recent activity of Vulcano lasted 20 months, viz. 

 August 3, 1888, to March 22, 1890 (with final explosions. May 17), 

 the most violent explosions (p. 113) occurring on August 4, 1888, 

 December 26, 1889, and March 15, 1890. , There had pre- 

 viously been a period of repose (1832-72), followed by minor 

 premonitory eruptions in 1873-7-8-9 and 1886. 



{b) Just as we have the " Flinian " or " Vesuvian " eruptions 

 of Vesuvius accompanied by violent outbursts of "ashes" and 

 welling out of lava, and the incessant, milder '' Strofnbolian" 



I Dr. Lavis found these practically extinct in 1887 (see Natcjre, vol. 

 xxxviii. p. 13). 



NO. I 1/9, VOL. 46] 



type of eruption, so we may distinguish a " Vulcanian " type 

 (pp. 58-59). Characteristic of this are — 



(i.) Intermittent explosions with discharge of bombs, ash, 

 dust, and vapours. Each of these explosions resembles 

 the first outburst of "Plinian" ("Vesuvian ") erup- 

 tions (p. 112). 

 (ii.) The absence of lava streams, 

 (iii. ) The absence of noteworthy earthquake shocks. 

 (c) The more violent of the explosions burst out suddenly, 

 discharging clouds of vapour, with dust lapilli, and more or 

 fewer bombs and fragments of compact lava, and such an 

 explosion was then followed at short intervals by feebler ones, 

 which merely discharged the smaller materials, or vapours 

 only. 



{d) The more violent explosions were generally separated by 

 longish intervals, either of absolute repose, or with insignificant 

 explosions ; and, on the other hand, when eruptions took place 

 every few minutes, they were generally feeble. 



(e) (p. 113, 70) Observations of atmospheric pressure extend- 

 ing over a day, or short period of time, show no relation to the 

 frequency or degree of violence of the explosions. But viewing 

 the 20 months of the eruption as a whole, it is found that 

 Vulcano enjoyed comparative repose during periods of high 

 atmospheric pressure, or of small change, and was most active 

 during periods of change from fair to stormy weather, with 

 marked fall of barometer. 



(/) Though during the 20 months of the eruption there were 

 altogether a good many earthquakes recorded either by the 

 seismoscope, or by some of the inhabitants (pp. 134-37), still 

 these were but slight, and, as stated, formed no feature of the 

 eruption, being very rare compared with the explosions. 



It was found (pp. 125-28) that for making observations of the 

 shocks or tremors accompanying theexplosiveeruptions,even close 

 to the foot of Vulcano, seismoscopes were as a rule not sensitive 

 enough. On the other hand, owing to the frequency of the 

 explosions, a tromometer was never quiet. The simplest method 

 is often the best, and recourse was had to pools of mercury (at 

 once sensitive and stable). With the aid of a reflector it was 

 then easy to keep an eye at once on the reflection of some object 

 in the mercury, and on the lip of the crater, and so observe the 

 time relation between the tremors and the explosive outbursts. 



Observations made near the base of Vulcano showed that each 

 eruption was preceded by a short tremor (apparently the result 

 of a deep-seated explosion), followed after a short interval of 

 calm, of from a few seconds to three-quarters of a minute, by 

 another, the result, apparently, of the superficial explosion that 

 made a vent for the vaporous and solid ejecta. The interval 

 was shorter in the case of the more violent explosions. 



(g) In the first three days of the eruption (pp. 54 and 152- 

 58), August 3-5, 1888, the ejecta consisted mainly of a variety 

 of old materials blocking the neck of the volcano. These, much 

 of which was more or less altered by solfataric action, were dis- 

 charged in pieces of all sizes from fine dust to large masses.^ 



(k) After an interval of thirteen days, the second main period 

 of the eruption set in. The older materials soon became almost 

 entirely replaced by newly elaborated matter in the form of 

 dust, lapilli, lighter or heavier "bread-crust" bombs,'^ and masses 

 of compacter lava. These, as opposed to the matter discharged 

 during the first three days, were all, except for inclusions of 

 older rocks, of essentially similar mineralogical and chemical 

 constitution (of andesitic type (p. 165), with 62-67 per 

 cent, of silica, the percentage of which might be greater 

 in the centre than in the crust of the same bomb). The larger 

 masses on leaving the crater had a high initial temperature, 

 and were plastic, taking rounded, elongated, or flattened forms, 

 and on reaching the ground melted various metallic wires — 

 silver (1000° C), and copper (perhaps 1200°, but, as we are 

 cautioneil, the copper might oxidize and then fuse lower). 



From the preceding, Silvestri draws the following con- 

 clusions : — 



(Excluding the ejecta of the first three days) The high 

 temperature and plasticity, with the presence of inclusions of 

 older rocks, and the uniform composition of the ejecta, point 

 to their being derived from a molten magma of recent elabo- 



I The Report describes these as not so hot as the later ejecta. However, 

 from Mr. Narlian's graphic account {7ymes, September 13, 1888, and Brit. 

 Assoc. Report, 1888, p. 665) it would seem that, at the first outburst, some 

 of the ejecta fell red-hot, so as to set hedges, &c., on fire. 



'■' Dr. Lavis, in Nature, vol. xxxix. p. ito. 



