1845.] MR. AULDJO AND CAPTAIN HALL QUOTED. 83 



have come under my notice expressive of the analogy just men- 

 tioned.* 



Mr. Auldjo, an intrepid alpine traveller, writing about 

 Vesuvius in 1832, says, " The field of lava in the interior of 

 the crater, inclosed within a lofty and irregular bank, might be 

 likened to a lake whose agitated waves had been suddenly 

 petrified ; and in many respects resembles the Mers de Glace, or 

 level glaciers of Switzerland, although in its origin and materials 

 so very different." f And the view in the same work of "streams 

 of lava on the south-east of the cone" presents a perfect ana- 

 logy to a glacier, bearing on its surface three medial and two 

 lateral moraines. 



Captain Basil Hall, writing of Vesuvius at a later period, 

 uses these remarkable expressions whilst describing an eruption 

 of lava : " The colour of this stream was a brilliant pink, much 

 brighter at the sides than in the middle, where, either from the 

 cooling of the surface, or the accumulation of cinders and broken 

 pieces of stone, a sort of dark ridge or backbone was visible 

 from end to end, not unlike the moraine on the top of a glacier. 

 This reminds me of a curious analogy which often struck me, 

 between two objects so dissimilar as a glacier and a lava stream. 

 They are both, more or less, frozen rivers ; they both obey the 

 law of gravitation with great reluctance, being essentially so 

 sluggish, that although they both move along the bottoms of 

 valleys with a force well nigh irresistible, their motion is some- 

 times scarcely perceptible." J This remarkable passage, worded 

 with the usual scrupulous care of the author, combined with his 

 account of the mechanism of a glacier in the description of the 

 glacier of Miage in the same work, show that he had arrived at 

 more correct notions on the subject than any of his contempo- 

 raries ; notions which chiefly required careful observation to 

 give them the force of demonstration. The allusion to moraines 



* [A quotation from Starke's Italy, previously given in the Sixth Letter, p. 50. 

 of this volume, is here omitted, but the words of Mr. Auldjo and Captain Hall, not 

 before quoted, are retained.] 



f Auldjo's Sketches of Vesuvius, p. 10, published 1833. 



J Patchwork, by Captain Hall, vol. iii. p. 118, published. 1841. 



