NOME IV. TUFO. 417 



large conical masses of ejected matter, one of 

 them having two summits. The shocks con- 

 tinued to be felt in the succeeding months, but 

 the eastern skirts toward Aci were the most agi- 

 tated ; and in some parts it appeared as if the 

 subterranean winds and vapours would have 

 opened new apertures, struggling as it were to 

 get loose ; while on the same spots long fissures 

 appeared, occasioned by the sinking of the 

 ground. But the circle of these great agents of 

 nature seems to have been confined by the 

 mountain ; for, in the following months, the 

 shocks arrived at Catania with an undulation 

 which was evidently occasioned by a shock 

 from the north to the south : and afterwards, 

 while Etna remained perfectly quiet, these un- 

 dulations violently and repeatedly shook many 

 places of the southern part of Sicily, called Val- 

 dinoto - y and have continued, with still more 

 force and frequency, in the present year 1810." 



To return to a more immediate consideration 

 of tufo, as connected with the present design, 

 this important substance may be arranged under 

 the following divisions : 



VOL. II. 2 E 



