146 Professor Silliman's Geological Notes. 



eruption of vast volumes of aqueous vapour with the lapilli, 

 scoria, and fine ashes from Vesuvius, which, condensing into 

 rain, produced a deluge of hot mud, filling the most intricate 

 recesses of the Pompeian houses, and producing the appear- 

 ance of an aqueous deposit in the ash hills of the flanks of 

 Vesuvius. In Herculaneum we see the same phenomena in 

 a more remarkable manner. Here, owing to a much longer 

 accumulation of material — ^to subsequent overflows of lava, 

 and the superincumbent weight thus produced, with the aid 

 of water, the ashes were consolidated into so compact a mass 

 that some writers have even doubted whether Herculaneum 

 had not been destroyed by an overflow of lava in the first in- 

 stance. That such was not the fact is well known, and the 

 condition of the antiquities imbedded there quite forbid the 

 idea, were no other evidence attainable. 



4. Meteorological Observatory of Mount Vesuvius. 



The Meteorological Observatory recently erected at Mount 

 Vesuvius, was projected by Professor Melloni, so well known 

 to all the world by his memorable researches on heat, and 

 the most distinguished of all the Italian physicists. The 

 King of Naples gave the enterprise his sanction, and furnished 

 the means to construct the building. The house is of ample 

 dimensions, standing on an artificial terrace at the summit 

 of the hill of ashes, which forms the limit of the arable region 

 of Vesuvius, and at an elevation of about 2000 feet. The 

 centre has three floors above the basement, and the two wrings, 

 each one floor above the basement ; in the rear, and joining 

 the main building, is a round tower, and the roofs are conve- 

 niently arranged for meteorological purposes. All the plans 

 were furnished by Professor Melloni, who also superintended 

 its erection, which, by an inscription on the exterior, appears 

 to have been begun in 1841. 



Unfortunately for science, the revolution of 1848 entirely 

 arrested the farther progress of the undertaking ; the house 

 stands vacant, no instruments are provided, and, worst of all, 

 Professor Melloni has been removed, not only from his direc- 

 tion in the Observatory, but also from his Professorship in tho 

 University, under the caprice of a despot who knows no law 



