584 



NATURE 



[April 21, 1892 



The dust observations promise to be of special value 

 in the study of weather types. In some weather types, 

 not only are the dust values very abnormal, but the daily 

 variation is in some instances quite abnormal also, indi- 

 cating that the cloud or dust strata are differently situated 

 from what they are in average weather, and also that 

 their daily rise and fall occur at different times. In 

 March 1890, the dust values show this very well : below 

 are the three-hourly means for each of three different 

 periods : — 



First Period (12 days). 

 Hour I 4 7 10 13 16 19 22 



Number per 

 cubic centi- 

 metre . . 78 61 78 67 113 408 258 102 



Second Period (3 days). 

 2867 1785 917 4733 4213 4295 3417 2533 



Third Period (5 days). 

 65 25 37 19 2 



28 



93 76 



During the third period of five days the weather was 

 very remarkable. A large depression was slowly pro- 

 gressing eastwards to the north of Scotland, and the 

 winds on Ben Nevis were blowing., almost straight out 

 from the centre, while the winds at sea-level were circu- 

 lating in the normal direction. This is the usual type 

 when low dust values are obtained ; but it is difficult to 

 quite account for the daily variation in the dust values 

 being reversed, the higher values occurring at night, and 

 the lower in the middle of the day. This and many other 

 points have not been studied yet. 



Dr. Buchan, in his recently published work on " Atmo- 

 spheric Circulation," hinges his explanations of various 

 atmospheric phenomena on the effect of solar and 

 nocturnal radiation on the dust in the atmosphere, and 

 accounts it one of the most important factors in the study 

 of modern meteorology. The observations made at Ben 

 Nevis Observatory clearly show that for observing the 

 number of dust particles in the air, with a view to the 

 observations being applied to the study of atmospheric 

 phenomena, a true peak is of all places the best, because 

 we can study not only the horizontal distribution of dust 

 as brought by the different winds, but also, to a certain 

 extent, the vertical distribution by the ascending and 

 descending motions of the air past the place of obser- 

 vation. Angus Rankin. 



ABSTRACT OF MR. A. RICCO'S ACCOUNT OF 

 THE SUBMARINE ERUPTION NORTH- 

 WEST OF PANTELLERIA, OCTOBER 1891.1 

 /^F what happens in submarine eruptions we naturally 

 ^-^ know little. Theevidenceof Graham's Island (i 831)- 

 and the eruption off Pantelleria (1891), to the south of 

 Sicily, and of the damaged telegraph cables and various 

 surface phenomena ^ to the north, towards the Lipari Isles, 

 shows us that such eruptions are not rare in the Sicilian 

 district, and any records of these fleeting occurrences that 

 we can get, in the way of observation and specimens, may 

 well prove of increasing interest as others are obtained 

 to compare with them. 



Mr. A. Ricco has recently published ^ a detailed and 

 illustrated account of the facts he was able to gather, con- 

 cerning last October's submarine eruption north-west of 

 Pantelleria, either in person or from local and other ob- 

 servers, he having reached the island during the latter 

 part of the eruption. From this, at the suggestion of 



I Annali dell' Ufficio centrale Meteorologico e Geodinamico, ser. ii., 

 Parte 3, vol. xi. 



'' (a) Lyell's "Principles of Geology"; and {b), for Bibliography, 

 Johnston- La vis's " South Italian Volcanoes," pp. 105-107. 

 ^^ 3 (a) " South Italian Volcanoes," pp. 64 and 65 ; and (b) Giov. Platania, 

 " I Fenomeni Sottomarini durante I'Eruzione di Vulcano (Eolie) nel 1888- 

 1889," Alt. Rend. Ace. Sc. Let. Art. Acireale, n. ser., vol. i., 1889, 

 pp. 16, tables 3. 



Prof. Judd, who has kindly sent me a copy, I extract the 

 following : - 



Pantelleria, an island (13-5 by 8 kilometres), situated 

 between Sicily and Tunis, is entirely of volcanic origin.-^ 

 The volcanic activity would at present appear to be a 

 shade less marked than in the " Phlegrasan Fields," west 

 of Naples. 



In Pantelleria we have exhalations of CO2 ; hot springs 

 (of which those at the lake called " Bagno del Acqua," 

 among other things are, we are told, so rich in alkalies as 

 to lather, and be used for washing clothes !), and fuma- 

 roles, some of which exhale steam harmless to vegetation, 

 and with little if any specific effect on the rocks, while 

 others give out sulphurous vapours at 88^ C. or more, 

 decomposing the rocks about them. 



There is but doubtful record of seismic disturbances in 

 the island prior to the summer of 1890. Then, however, 

 earthquakes occurred, with elevation of part of the north 

 coast, the cracking of cisterns, and an increase in the 

 number and activity of the fumaroles, so that vineyards 

 formed in some of the old craters were damaged. After 

 more than a year's interval, earthquakes again commenced 

 October 14, 1891 (three days before the eruption). These 

 were accompanied by drying up of certain springs, and 

 apparently a further rise on the north coast, with surface 

 cracks in that district. 



As the shocks were most violent and vertical at the 

 little town of Pantelleria itself (at the end of the island 

 nearest the scene of eruption), they caused considerable 

 consternation ; and if one went by the account of the 

 overstrung inhabitants, who felt shocks not recognized 

 by the seismoscopes, one might exaggerate their violence. 

 On the other hand, the wails of the houses, which out- 

 side the town have frequently no upper story, are, on the 

 whole, substantially built, so that the insignificant damage 

 done is perhaps hardly a gauge. Part of the north coast 

 (Pig. i) appears to have been raised, in the two years, 



NO. I I 73, VOL. 45] 



Fig. I. — Map of Pantelleria, showing the position, according to Ricco, of (a) 

 the submarine eruption of October 1891, and (^, ^) of the raised coast. 



some 80 cm., the old sea-level being marked by a line of 

 white incrustations ; and we are told that, according to 

 a recent estimate," the tide in this part of the Mediterra- 

 nean has an amplitude of but some 8 cm. ; besides, there 

 was the evidence of inhabitants who had bathed, boated, 

 and fished along the coast. The submarine eruption 

 (4 kilometres north-west of the island. Fig. i) began on 



' Foerstner, " Nota preliminare suUa Geologia dell' Isola di Pantelleria" 

 (with geological map), Boll. Com. Geol. d'ltal., 1881. 



'■' Prof. G. Grablovitz, "Le isorachie della marea nel Mediterraneo," 

 Rendiconti della R. Accad. del Lincei, 16 Agosto, 1891. 



