Septeuber 21, 1SS3.] 



SCIENCE. 



399 



from the precipitous flanks of Epomeo, have covered 

 a wide extent of chestiiut^groves and vineyard*; and 

 on the soutliern slope are great fissures in tlie earth. 



In summing up my observations of all the locali- 

 ties most devastated by the calamity, I am convinced 

 that the buildings standing upon the trachyte at 

 Lacco Ameno and Monte Zale suffered incalculably 

 less than those built upon the tufa of Epomeo and 

 the argillite resulting from its disintegration. Casa- 

 micciola was almost entirely built upon this argillite; 

 and it can be said without exaggeration, that not one 

 stone rests upon another. Forio was buitt upon tufa; 

 and of this town, also, very little remains standing. 

 At Lacco, the houses and walls erected on the tra- 

 cliyte offered, as was stated above, great resistance to 

 the shock, while those built upon the tufa were 

 destroyed. 



Tills agrees completely with the theory of Mallet. 

 Mallet says, that when a seismic or a terrestrial wave 

 passes rapidly from a soil possessing limited elasti- 

 city, — as would be the case with our tufas and 

 clays, — to another soil of great elasticity, like the 

 trachytic lavas, it changes not only its velocity, but 

 in some degree also its direction; one part being re- 

 flected, the other refracted. The seismic wave, be- 

 ing thus checked, produces a shock in the opposite 

 direction, causing great injury to buildings by the re- 

 coil. At the same time the shocks are diminished in 

 force when they reach the more elastic soil, such as 

 granite or trachyte. 



This would explain very satisfactorily why Ischia, 

 separated from the cleft AB by the great masses of 

 trachytic lava of Rotaro, Montagnone, and Arso, 

 which would absorb much of the energy of the seis- 

 mic wave, felt it in so slight a degree. 



With respect to the causes of these seismic disturb- 

 ances, which still continued after the great earth- 

 quake of the 28lh July, other shocks, accompanied 

 by subterranean rumbling, being felt even when I 

 was on the island and afterwards, it seems to me that 

 they must be attributed to an awakening of the re- 

 sidual volcanic activity of Epomeo. The opinion has 

 been advanced by the illustrious Professor Palmieri, 

 that the violence of the shocks might be especially 

 attributed to the fact of the existence of great sub- 

 terranean caverns directly beneath Casamicciola, and 

 to the giving-way of the supports which upheld these 

 vaults, caused by seismic action, and facilitated by 

 the weakening of these supports by the underground 

 flow of thermal waters. This opinion does not ap- 

 pear to me to be fully demonstrable. There exist, 

 it is true, in the neighborhood of Casamicciola, cav- 

 erns of plastic argillite, formed by the lapse of ages; 

 but certainly it is not of these that the illustrious 

 professor of Naples intends to speak : the cause would 

 assuredly be insufficient to produce effects so im- 

 posing, and such far-reaching seismic disturbances. 

 I could not enter these caves, for want of persons 

 disposed to serve as guides at such a time; but it is 

 certain that they could be only more or less tortuous 

 galleries of small diameter and but a few metres in 

 height, as is generally the case in such formations. 

 I have been assure.1 also, by persons worthy of trust, 



and experienced in these caverns, that this is the 

 case. ISesidcs, neither at Casamicciola nor in the 

 vicinity could I see any lowering whatever of the 

 level of the soil: the roads which lead from Guar- 

 diola or the shore to Casamicciola, fnun Casamicciola 

 to Lacco, from Lacco to Forio, have preserved their 

 level perfectly, and show only the longitudinal or 

 transverse fissures inevitable after such a telluric 

 commotion. The only road coraplelcly destroyed 

 (but not depressed) is that which leads from Forio to 

 Casamicciola, along the side of Monte Epomeo, 

 which, as we have seen, is directly along the cleft 

 A B. 



In any event, when this period of desolation and 

 ruin has passed, when perhaps the time shall have 

 come to decide upon the fittest place to rebuild the 

 shattered dwellings, it would be useful to make a 

 most accurate inspection of all the ancient and mod- 

 ern caverns of the island, and to determine what in- 

 fluence they may have upon the stability of the soil 

 and the superincumbent buildings. 



In conclusion, then, it appears to me, 1°. that no 

 other cause need be sought for the shocks which 

 have desolated the island than the volcanic activity 

 which still remains, and awakes at intervals; 2°. that 

 the residual volcain'c activity of the island is maiu- 

 fested along two principal fissures, one, A B, a curve 

 with its convexity to the north, from the baths of 

 Ischia to Forio, the other, C D, directed approxi- 

 mately north-north-west and south-south-east, be- 

 tween Lacco Ameno and the stufas of Testaccio; 

 3°. that the place where Casamicciola stood is upon 

 the intersection of these two lines, and, therefore, at 

 the very focus of seismic activity, and that it has 

 been, and always will be, the looality most liable to 

 be devastated by earthquakes; 4°, finally, that build- 

 ings erected upon trachytic lava offer a resistance to 

 the shocks, far superior to that of buildings erected 

 upon tufa or clay, and that this circumstance should 

 be borne in mind when it is proposed to restore the 

 ruined villages. 



Korae, Aug. 9, 18S3. 



JULY REPORTS OF STATE WEATHER 

 SERVICES. 



A NUMBER of States have organized weather ser- 

 vices which are of material benefit to the people. A 

 brief summary of the July reports that have been 

 received is here given. 



Georgia. — The July crop report contains meteoro- 

 logical data from fifteen stations. The special feature 

 is the drought, of which it is said. " In northern and 

 middle Georgia, the drought has been almost con- 

 tinuous since April 2:5, — the date of the last general 

 rain in the state, — broken only by light and ineffec- 

 tive showers at considerable intervals. A few 

 p.)ints reported sufficient rain, but the northern 

 half of the state, with these exceptions, has suf- 

 fered a most prolonged drought, which is yet un- 

 relieved." 



Illinoin. — Minimum temperatures of 47° were re- 

 ported, and maximum of 09^. The prevailing wind 



