126 Prof. O. Silvestri on the Eruption of Etna 



of February, 1874), and further, when editing the First Fart for 

 publication in the Journal of the Society, I was unacquainted 

 with the fact that a most complete history of duplex telegraphy 

 had been published by Dr. Karl Eduard Zetzsche* (Leipzig, 

 1865). According to Professor Zetzsche t? the bridge method of 

 duplex telegraphy was already invented in 1863 by Maron, a 

 Prussian telegraph-inspector; and Dr. Zetzsche very truly 

 remarks that the bridge method would seem to be that least 

 affected by variations in the resistance of the line. To this, from 

 an historical point of view, most valuable book I refer the reader. 

 It is to be hoped that an English translation of it may soon be 

 published. 



[To be continued.] 



XVI. The Eruption of Etna on the 29th of August, 1874. 

 By Professor Oeazio Silvestri, of Catania%. 



IN a short account published by me on the 1st of July, 1874 

 (see No. 56 of the Gazzetta del Circolo dei Citiadini, Catania, 

 July 12, 1874; also Bullettino del Vulcanismo Italiano, fascicolo 

 6, 7, Rome, July and August 1874; also Bollettino del R. Comi- 

 tate Geologico d' Italia), of the eruptive phenomena which have 

 been observed since last May in the interior of the great central 

 crater of Etna, I expressed an opinion which attracted such ge- 

 neral attention as to be quoted in the principal Italian and foreign 

 journals, to the effect that an early outbreak on the Mongibello 

 side, and a great eruption immediately after, were to be expected. 

 This opinion has been fulfilled in less than two months, but for- 

 tunately (as I am about to relate) under such conditions as not 

 to produce serious damage, except the consequences of the fear 

 and terror which are generally excited by the more formidable 

 phenomena of this mighty volcano. 



After an uninterrupted succession of eruptive phenomena in 

 the central crater, which has in consequence undergone remark- 

 able modifications, at 4 o'clock on the morning of Saturday, 

 August 29, the rural population scattered round the base or on 

 the slope of the mountain on its northern side, even beyond the 

 villages as far as the cultivated belt reaches, in a semicircle of 

 about 80 kilometres, were awakened by subterranean noises, which 

 were speedily followed by two shocks of earthquake, threatening 



* Die Copiertelegraphen, die TypendrucJctelegraphen, und die Doppel- 

 Telegraphie, ein Beitrag zur Geschichte der electrischen Telegraphie, von 

 Dr. Karl Eduard Zetzsche : Leipzig, 1865. 



f Page 125 in the work quoted. 



% Translated from a pamphlet published by Lorenzo Rizzo, Largo Spirito 

 Santo, Catania (1874). Communicated by Professor H. E. Roscoe, F.R.S. 



