1850.] MURCHISON— VENTS OF HOT VAPOUR IN TUSCANY. 379 



the ridges above described as penetrated by serpentine, gabbro, and 

 other eruptive rocks, I was struck with the fact, that the most pow- 

 erful vibratory disturbance occurred in the low hills and hillocks of 

 incoherent materials along this very line. The shocks from north 

 to south being most powerful in this parallel of longitude, it was na- 

 tural that they should produce the most disastrous effect in that 

 portion of the tract where edifices were placed on slightly coherent 

 marl that rises into hillocks void of lateral support. The buildings 

 which rested on the adjacent harder rocks of alberese, gabbro, ser- 

 pentine, and greenstone were comparatively unafPected, whilst those 

 which stood on marl had fallen or were much shattered. It is fur- 

 ther worthy of notice, that in the deepest denudations amongst the 

 hillocks of marl, particularly near Lorenzana, where the earth opened 

 into chasms, subterraneous waters which had been hitherto impri- 

 soned rose suddenly to the surface ; just as if artesian wells had 

 been sunk, and that the overlying crust of a basin had been broken 

 through. Spouting forth sand and mud, these jets of water so threw 

 out solid contents, that when dried up they resembled so many 

 molehills with radii ; the centre or box of each wheel-shaped body 

 being composed of concentrically laminated sands, marking the point 

 at which the water issued. These appearances not only served to 

 explain the origin of the larger muddy bosses of similar form, 

 common in the incoherent subsoils of Calabria, which have been so 

 frequently subject to great earthquakes, but may also be viewed as 

 another link which connects the present small disturbances of the 

 surface, with the former powerful subterranean energy proceeding 

 from igneous and gaseous development we have been considering. 



Thus, in reference to my preceding memoirs and in reasoning by 

 analogy, we are led to infer, that the great evolution of molten mat- 

 ter in former or plutonic times, accompanied by so much heat and 

 its gaseous attendants as to metamorphose whole mountain chains, 

 was succeeded, as the bottoms of the sea rose, by a considerable dif- 

 fusion of volcanic materials, chiefly of subaqueous origin, but in part 

 subaerial ; and that, finally, the lands assuming their present rela- 

 tions to the sea, the extension of molten matter has been confined 

 to a very limited number of fissures or vents of eruption, many of 

 which have become extinct with the lapse of time. A portion, how- 

 ever, of these eruptions in Europe is still in continuous activity, 

 whether emitting solid matter, as at Stromboli, or hot springs and 

 vapours, as in the Tuscan Soffioni ; whilst another portion is inter- 

 mittent, as viewed in the paroxysmal outpourings of Etna and Vesu- 

 vius, the occasional formation of small new cones and craters under 

 the waters of the Mediterranean, and the fitful lines of earthquake 

 shocks with their accompanying outbursts of water. 



In viewing the intimate connexion between all these phsenomena, 

 and in looking to the powers of the Soffioni of Tuscany, we might 

 perhaps infer, that if these gusts of heat were entirely repressed by 

 closing up the orifices through which they now esca{)e, earthquakes 

 to some slight extent might be expected still more to prevail in the 

 neighbourhood, until the expansive forces were liberated ; just as the 



VOL. VI. — PART I. 2 E 



