ANALOGY OF GLACIERS TO LAVA STREAMS. 
155 
mieu, that this same stream moved during part of its course at the rate of 1500 feet 
an hour, and in others took several days to cover a few yards*. 
The lava of 1753 (Vesuvius), starting with a velocity of 2500 feet per hour, soon 
diminished to sixty feet-f-, as did that of 1754 to the same| ; and of 1766 to thirty 
feet per hour§. The lava of 1831 (Vesuvius) moved over 3600 feet in twenty-six 
hours, and finally advanced steadily at the rate of ten feet an hour ||. The lava of 
Etna of November 1843, is said to have moved over three paces per second at the 
distance of a mile from the crater. 
The stream of 1761 (Vesuvius), before it stopped flowing, advanced but three yards 
a day^[ ; and that of 1 766, which continued moving for about nine months, moved 
over but a small space in that time. Had the attention of authors been equally 
directed to the slow as to the rapid advancement of lava, there is no doubt that we 
should find many instances besides these recorded by Dolomieu and Scrope, of con- 
tinuous movements of three feet, and even one foot a day, or less. 
* Dolomieu Isles Ponces, p. 286. Note. f Della Torre, Histoire, &c., p. 196. 
1 Ibid. p. 130. § Hamilton, Campi Phlegrsei, i. 19. 
|| Auldjo, Sketches of Vesuvius, p. 79, with a sketch of the front of the stream whilst advancing at this rate. 
Della Torre, p. 182. 
