PHYSICAL GEOLOaT. 169 



sedimentary rocks to check the escape of internal heat ; and hence the 

 cooling of the moon has gone on very rapidly. A. H. G. 



ScBOPE, G. P. The Mechanism of Stromboli. Geol. Mag. dec. 2, 

 vol. i. pp. 529-542, 3 woodcuts. A criticism on Mr. R. Mallet's 

 paper on this subject (see p. 166). 



Shows that Mr. Mallet's measurements of the height of various 

 points of the mountain above the sca-le vol,- which were made with an 

 aneroid, are different from those of the best authorities. Maintains 

 that a fortuitous concurrence of water, steam, and lava, such as Mr. 

 Mallet's explanation requires, is a complicated and wholly imaginarj^ 

 supposition, without example and unsupported by any facts or reason- 

 ing of the slightest value, the grounds on which this judgment is based 

 being fully given. A. H. G. 



SiLVESTKi, Prof. Okazio. Fenomeni erruttivi dell' Etna nell' interno 



del cratere centrale. [Eruptive phenomena in the interior of 



the crater of Etna, July, 1874.] Boll. 11. Com. geol. Ital. 



pp. 244-247. 



Finding the volcano increasing in premonitory symptoms, the author 



predicted an eruption (which ensued the month after). On looking 



into the crater, flashes of light were seen every two or three minutes, 



soon succeeded by reports as of artillery. Calculating from the rate of 



transmission of sound, the ignited matter must have been at a depth of 



600 metres. The mountain has had five years of unusual repose. 



See also his letter on the same subject in Zeitsch. deutsch. geol. Gesel. 



Bd. xxvi. Heft 4, pp. 928-930. E. B. T. 



. Notizie sulla eruzione doll' Etna del 29 Agosto 1874. 



[Notice of the eruption of Etna, August 29, 1874.] Boll. R. Com. 



geol. Ital. pp. 312-322. Reprinted from the Catania Gazette. 



See also ' Nature,' vol. x. p. 522. 

 The eruption began with two shocks and the emission of a huge mass 

 of black smoke ; it lasted only seven hours, and then began to diminish. 

 At the height of 2450 metres an enormous crack was produced, running 

 N. 8° E., with a width of 60 metres at the widest, and with a total 

 length of 3 kilometres. Along this chasm are numerous little craters, 

 1 to 3 metres, from which a few ashes and scoriae were vomited. The 

 reason of the eruption ceasing before it had scarcely developed itself the 

 author considers to be the diversion of the lava into some subterranean 

 channels possibly existing below. E. B. T. 



Skey, W. On the Evolution of Heat during the Hydration of Clay- 

 slate, Clay, and Coal. Chem. News, vol. xxx. no. 787, pp. 290, 

 291. 

 On mixing ground clay-slate with water heat was evolved, this heat 

 being attributed by the author to the chemical hydration of the rock. 

 Some other rocks and minerals behaved in a similar way. The author 

 concludes that heat is generally evolved during the disintegration of 

 rocks, and that the differences in temperature sometimes observed 



