Dec. 16, 1881.] 



♦ KNOWLEDGE • 



129 



AN. U0JiSI«j^ED 



MAGplNEOf^NCE 



MLAM^RBED -EXACTl fesCR IBEDJ 



LONDON: FRIDAY, DECEMBER lo, 16S1. 



CONTENTS. 



PAGS 



Recent Studies of Volcanic Action. 



By G. F. KodvreU 129 



Dreams. — Part IT. B/ Edward 



Clodd 130 ; 



Betting and Mathematics. By the I 



Editor 132 



Our Unliiddrn Guests. Bjr Br. | 



Andrew Wilson. F.R.S.E 133' 



Statistics of Suicide 134 | 



The Destroyed Comet. By the 



Editor (ni'iulrattJ) 135 



To«i in a Hole. Bv Dr. Andrew | 



Wilson, F.K.S.E. '. 136' 



EasT Lessous in Blowpipe Chemistrv. I 



By Lieut.-Col. \V. A. Eoss, K.A. 137 



PAOB 



Hints to Local Meteorological Ob- 

 servers.— I. Hailstorms 137 



Anecdotes of Dors 13S 



CoBBBSPoyuESCB. — Editorial 

 Letter — Jupiter : Denning's 

 Comet — The True Spirit of 



Science: Water Spherules 130 



The Westerm Skies in December— 



(lUntlraltJ) 141 



Queries 1« 



Replies to Queries 145 



Our Mathematical Column — The 



Witch of .^gnesi 14^ 



Our Whist Column 149 



Answers to Correspondents 149 



RECENT STUDIES OF VOLCANIC 

 ACTION. 



By G. F. Rodwell. 



ALTHOUGH, during the last few years, no great 

 eruption of a European volcano, similar to that of 

 Vcsu\nus in 1872, has occurred, and no great earthquake 

 comparable with that which devastated Calabria in 1783, 

 the records of minor volcanic disturbances have been 

 unusually numerous. In 1878 Etna poured out a stream 

 of lava wliieli ran for .six miles ; a few months before, 

 Hekla threw up a new monticule, from which a quantity of 

 lava issued ; Vesuvius more than once since 1872 has 

 furnished enough lava to run into the Atrio del Cavallo ; 

 Santorin was active from 1866 to 1870 ; Stromboli is 

 always more or less energetic ; and Volcano has given 

 evidence that its vitality is by no means dormant Again, 

 within the last year, three disastrous earthquakes have 

 occurred in Europe — at Agram, in Ischia, and in Chios 

 — and many minor shocks have been recorded. In fact, 

 earthquakes arc much more common than we gene- 

 rally realise. A year ago (Nov. 28, 1880) an earth- 

 quake was reported from no less than fifty different 

 stations in Scotland ; some days ago a severe shock was 

 announced from Agi-am ; the previous day from Switzer- 

 land. During a few months of 1879, earthquake shocks 

 were felt in such widely-distant places as Florence, 

 Aachen, North Wales, Carinthia, Agram, Athens, and 

 Swizerlaiul. In 1878 there were more than a hundred 

 earthquakes and twelve volcanic eruptions. 



For another reason it appears to be a not inappropriate 

 time for reviewing recent European Vulcanology. The 

 literature of the subject has lately received some important 

 additions in the form of such books as Dr. Arnold von 

 Lasaulx's " Der jEtna " ; il. Fouque's " Santorin et ses 

 Eruptions" ; the " Studien uber Erdbeben ' of Dr. Julius 

 Schmidt ; the United States" " Report of the Geology of 

 Utah," by Captain Dutton ; the '• Mineralogie Micro- 

 graphique " of MM. Fouque and Michel Lewy ; and the 

 treatise on '■ Volcanoes " of Professor J. W. Judd, which 

 only within the last few months has issued from the 

 ponderous and iron jaws of the pre.ss. The rapid growth of 



the literature of the subject may be fairly judged of from 

 the fact that Von Lasaubc prints sixteen quarto pages 

 of " ^tna-Literatur." 



Vulcanology is a recent science. If any one man can 

 originate a science, Spallanzani must be regarded as the 

 father of vulcanolog)-. There had been many observers 

 before his time, for the great phenomena of nature receive 

 the earnest attention even of unlettered men, but they 

 had observed Vjlindly, and without method. They recorded 

 their observations, but they made no attempt to classify or 

 correlate them, fonued no hypothesis to embrace them, 

 and did not follow up the particular line of thought sug- 

 gested by one or other of them. The value of a good 

 working hypothesis, even in the early stages of a science, 

 cannot be overrated. Moreover, the earlier %'ulcanologists 

 did not go to work in the right way ; they either watched, 

 necessarily at a distance, some grand paroxysmal outburst, 

 or they visited the scene of its action when the main effects 

 had died out Spallanzani did otherwise. He chose as 

 the source of his obsenations an ever-active volcano, which 

 never approaches the paroxysmal violence of Etna, Hekla, 

 and Vesuvius during their gi-eat eruptions, and never sinks 

 to the quasi-dormant condition which a Volcano commonly 

 presents. Stromboli has been active for more than 2,000 

 years, and so moderately active, that the scene of its opera- 

 tions can be closely approached, and from a projection 

 which is situated a little above the crater, the observer 

 may sit for hours when the steam and vapours are blown 

 out to sea, and watch the phenomena which are taking 

 place within the crater. Spallanzani did this ; and for the 

 first time realised and enunciated the important fact, that 

 volcanic phenomena are mainly, if not entirely, due to 

 tlie violent escape of steam and other gases at high 

 pressure from molten matter. 



In 187i, Professor .J. W. .Judd, already an accomplished 

 disciple of Scrope, visited Stromboli, and minutely ex- 

 amined, from the vantage-ground erst occupied by Spal- 

 lanzani, the operations taking place upon the floor of 

 its crater. He divides them into three classes. From 

 certain large apertures in the floor steam escaped in loud, 

 irregular puffs ; within, some lava could be seen, which at 

 intervals rose and swelled out, at the same time emitting 

 large volumes of steam ; while within the depths of other 

 openings, viscous molten matter was seen to be hea^TDg up 

 and down, and violently agitated, like boiling water. Ever 

 and anon, as the agitation increased, a great bubble of lava 

 would swell put, and suddenly burst, emitting steam at 

 high pressure, the force of which hurled the red-hot scum 

 high into the air. Thus, the three essential conditions for 

 the production of \ olcanic phenomena appear to be : — 

 (1) apertures or fissures affording communication with 

 the interior of the earth ; (2) highly-heated matter beneath 

 the surface ; and (-3) subterranean water which, in the 

 form of high-pressure steam, is competent to produce 

 all the crater operations. A mass of lava within a small 

 active crater precisely resembles a boiling fluid. In one 

 of the lateral cones of Vesuvius the writer once saw a 

 veritable geyser of fire, imitating in all respects its great 

 prototype at Haukadalr. The \tscous seething mass of 

 lava within the bocca contains water entangled in its ma.ss, 

 and when this rises to the upper part of the column of 

 lava, it is relieved from pressiire, and flashes explosively 

 into steam. This restores equilibrium for awhile, during 

 which more steam is being generated, and presently another 

 outburst occurs. The pressure of the steam which thus 

 accumulates may be judged of by the fact that, during the 

 eruption of Vesuvius in 1872, masses of vapour (and, it is 

 said, fragments of scoria;), were projected to a height of 

 nearly four miles. The friction of this steam against the 



