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column or cone (see my elegant drawing) of lava [Fig. 4]. I do Letter 486 

 not doubt that the dikes are thus indirectly connected with 

 eruptive vents. E. de B. seems to have observed many of his 

 T ; now without he supposes the whole line of fissure or dike 

 to have poured out lava (which implies, as above remarked, 

 craters of an elliptic or almost linear shape) on both sides, 



Fig. 2. 



how extraordinarily improbable it is, that there should have 

 been in a single line of section so many intersections of 

 points of eruption ; he must, I think, make his orifices of 

 eruption almost linear or, if not so, astonishingly numerous. 



Fig. 3- 



One must refer to what one has seen oneself : do pray, when 

 you go home, look at the section of a minute cone of 

 eruption at the Galapagos, p. IO9, 1 which is the most perfect 

 natural dissection of a crater which I have ever heard of, and 

 the drawing of which you may, I assure you, trust ; here 

 the arching over of the streams as they were poured out over 

 the lip of the crater was evident, and are now thus seen 

 united to the central irregular column. Again, at St. Jago 

 I saw some horizontal sections of the bases of small craters, 

 and the sources or feeders were circular. I really cannot 



Geological Observations on Volcanic Islands. London, 1890, p. 238. 

 VOL. II. 9 



