On the Agency of Water in Volcanic Eruptions. 135 



" 1843. Decrease of water in the wells of Resina ; it was preceded 

 by emission of lava. 



" 1846. Some wells of Resina dried, and emission of lava fol- 

 lowed. 



"1846. Six adventive cones in the crater; water decreases at 

 Resina in wells. 



" 1847. Decrease of water in the wells of Resina ; great lava 

 flowing. 



" 1848. Water decreases in the wells of Resina and Torre del 

 Greco. Earthquakes in the neighbourhood of Vesuvius. Lava 

 flowing. 



" 1849. The same decrease of water — strong explosions, bellowing, 

 and lavas. 



" 1850. January 23rd, at Resina and Torre del Greco decrease of 

 water in wells. Strong explosions. February 5, lava poured 

 out with bellowing. 



" Before the eruption of 1794, there was at Torre del Greco a small 

 torrent, capable, it is said, of moving four mills. After the eruption 

 the torrent got very poor, so that the water scarcely supplied a foun- 

 tain. After the eruption of 1861, there was an increase of water in 

 this fountain, and in some small springs near the shore, and one was 

 noticed in the sea itself, which lasted nearly a month. 



" There is a well on a farm of some relatives of mine, at St. Georgio 

 di Cremano, in right line nearly 4 miles from Vesuvius, 150 feet deep, 

 and plentifully fed by a spring. After the eruption of 1861, the water 

 began to decrease, and a year after it was quite dry. This was followed 

 by so abundant an emission of carbonic acid, that the well had to be 

 stopped up." 



I must observe, however, that the high authority of Professor 

 Palmieri is against this view.* He states that previous to the eruption 

 of Vesuvius in 1871-72, the water in the wells was neither deficient 

 nor scarce, but was very acid afterwards. He elsewhere mentions 

 that he considers these supposed premonitory signs either only to 

 happen occasionally, or to be mere coincidences, such as the coinci- 

 dence of a dry or rainy season. But the weight of evidence is 

 certainly against this opinion, and, as I shall presently explain, there 

 may be tracts that have an independent water-level which escape the 

 surrounding disturbance, and it is not impossible that this very cir- 

 cumstance has led to the selection of such areas for the sites of towns 

 and villages on the slopes of the mountain. 



The more local springs which supply the shallow surface wells may 

 remain undisturbed, while at other points the deeper-seated springs 

 having a wider range may be tapped and drained. Again, the water in 



* " The Eruption of Vesuvius of 1872," translated by E. Mallet, F.E.S., p. 135. 



