342 G. Poulett-Scrope— Source of Volcanic Seat. 



II. — The Source of Volcanic Heat. 

 By G. Poulett-Scrope, F.R.S., F.G.S., etc. 

 N his letter to the Editor, inserted in the last Number of this Maga- 

 zine (p. 332), Mr. Mallet says he is "compelled to repeat" the 

 statements he had persistently made, and I had more than once denied, 

 as to my having, " in almost all my writings," upheld "the moribund 

 thin crust and liquid nucleus theory," and " Hopkins's fiery lakes." ^ 

 He defends himself from the charge of having "misapprehended," as 

 was suggested in an Editorial foot-note to his paper, or, as I more truly 

 phrased it, "misrepresented," my views on these subjects, refusing to 

 be bound by what I may have " written in the scattered magazine 

 articles " to which he was referred, on the plea that "an author's notions 

 are usually gathered from his acknowleged systematic works." Now 

 when one public writer imputes to another opinions which the latter 

 denies to have ever been his, candour and courtesy — not to speak of 

 higher considerations — surely require of the former some examina- 

 tion into the fact before he repeats the imputation. What then is 

 the fact ? The only " systematic work " on volcanic geology to 

 which I can plead authorship is the Treatise on Volcanos, etc., 

 pp. 462, Longmans, 1862, re-issued without alteration, 1872, with 

 which Mr. Mallet must be acquainted, since he did me the honour to 

 accept a copy from me in, I think, the year 1865. Had Mr. Mallet, 

 upon my disavowal of the views he imputed to me, before repeating the 

 imputation twice over, only taken the trouble to open the volume and 

 consult the Index, or but cursorily turn it over, he must have seen in 

 its proper place in the work two pages, headed in capitals, " Theory 

 OF A Fluid Nucleus to the Globe, Doubtful." In these two 

 pages and the subsequent four (264-269), I give my reasons in 

 detail for believing that the glohe is at present solid throughout, with 

 the exception of such locally " separate parts or pockets, as it were, 

 of more or less intensely heated and liquefied mineral matter, as may 

 exist at greater or less depths or distances," within or beneath the 

 " foci " of active volcanos (p. 267), To this last extent, and no 

 further, I exj^ressed my concurrence with Mr. Hopkins's theory, 

 while dissenting from his view of " a widely extended belt or con- 

 tinuous shell of molten mineral matter between the nucleus of the 

 globe, solidified by compression, and its outer crust" (p. 268). In 

 fact, I there, as well as in my " scattered writings," expressed 



1 In order that there may be no room for evasion as to the nature of the theory 

 attributed to me from first to last by Mr. Mallet, I quote here one or two passages 

 from his "Eeply" to my Observations on his Theory, etc., Geol. Mag. for March, 

 1874, p. 127:—" The so-called mechanical theory of a liquid nucleus, that is, of a 

 nucleus in liquid fusion beneath an extremely thin solid crust, has already given 

 way, etc." " JJ/r. Scrope's oivn notions, which involve that very thin crust and liquid 

 nucleus, as most recently formulated by him, do not, I believe, materially differ from 

 those formed and enunciated by him some thirty years ago." ..." The progress 

 of science has, however, shown the untenability of the views still espoused by Mr. 

 Scrope, of an immense liquid nucleus, and an excessively thin solid crust, as well as 

 the notion of subterranean fiery lakes, or a continuous liquid shell between the crust 

 and nucleus." . . . " Yet this gigantic incandescent nucleus and parenchymatous 

 surface skin Mr. Scrope, and the school to which he belongs, must have, or their 

 theories are impossible." 



