September 18, 1885.] 



SCIENCE. 



255 



should not see the use of such experiments is quite 

 natural. To one who does understand their impor- 

 tance, the wonder is that such an opinion should 

 have any weight in such a matter. The standard in 

 the early days of Bache is still the standard of the 

 coast-survey work of to-day. Let us hope that no 

 ignorant criticism will have power to lower or im- 

 pair the efficiency of a department of whose scientific 

 record the country may well be proud. 



While criticising the article of the Evening post, 

 so far as it relates to the coast-survey, let me express 

 my complete agreement with its condemnation of the 

 'political scientist.' It is time that the system thus 

 attacked should be abandoned, and that indiscrimi- 

 nate scientific assistance, given by the heads of bu- 

 reaus to institutions and individuals, and never 

 contemplated or sanctioned by congress, should be 

 discontinued. It has brought nothing but discredit 

 upon the official science of the country. Let the 

 most liberal appropriations be made for the work of 

 our scientific bureaus, but let the requisitions be so 

 complete and detailed as to invite a fair and open 

 criticism. 



Alexander Agassiz, 



Cambridge, Mass., Sept. 9. 



THE THEORY OF VOLCANOES. 



This work is a brief statement of the most 

 general facts relating to volcanoes, with the 

 citation of many examples of volcanoes of vari- 

 ous classes, and their subordinate phenomena, 

 by way of illustration . It is evidently intended 

 for the most intelligent class of general readers, 

 though valuable also to the specialist. 



In the first chapter, Mr. Velain describes the 

 phenomena attending a volcanic eruption of 

 the normal type, and with great propriety 

 treats such an occurrence as a manifestation 

 of the energy of the elastic vapors contained 

 in the erupting materials, — a fundamental fact 

 which should always be impressed as forcibly 

 as possible upon the general reader. He also 

 describes the various forms given to the lavas, 

 the modes of accumulation of volcanic piles, 

 the formation of cinder-cones, and the many 

 forms of craters. He gives descriptions of 

 some of the more remarkable eruptions of which 

 records have been preserved, and these are 

 chosen so as to illustrate the typical cases of 

 the several classes of volcanoes. In this chap- 

 ter may be found much information about vol- 

 canoes not described in English treatises on 

 this subject, such as those of Reunion and 

 the Island of St. Paul. 



The second chapter, on the gaseous emana- 

 tions, is, to the American student, probably the 



Les volcans, ce gu'ils sont et ce quHls nous appreiinenf. 

 Par M. Ch. Velain, docteur des sciences, maitre de conferences 

 ii la Sorbonne. Paris, Gauthier- Villars, 1884. 8°. 



most instructive one in the book. The inves- 

 tigations of Charles Saint-Claire Deville, of 

 Scacchi, of Fouque and Levy, are set forth in 

 considerable detail, and well summarized. 

 These are of great importance, and have, no 

 doubt, received less attention from writers in 

 the English language than they are entitled 

 to. It may be remarked, however, that much 

 more extended observations upon this class of 

 phenomena are needed than those upon which 

 the conclusions of Deville and Fouque are 

 founded. The pre-eminence of those investi- 

 gators is a high warrant for the validity of their 

 conclusions ; but the experienced vulcanolo- 

 gist will perhaps feel that they are even more 

 systematic and beautiful than he is accustomed 

 to find volcanic phenomena to be, and he would 

 like to see them tested by the widest possible 

 verification. The whole chapter is admirable 

 reading, and excellentl}^ arranged by Mr. 

 Velain. 



The third chapter describes the lavas them- 

 selves, their methods of flow, and the forms 

 they assume at solidification. Ver}^ little eflfort 

 is made to describe the micro-characters of the 

 lava, and this was probably judicious on the 

 author's part ; for these characters cannot be 

 briefly summarized, and any attempt to do so 

 would have exceeded the scope of his work. 



The fourth chapter treats of the geographic 

 distribution of volcanoes. The main fact he 

 seeks to establish is, that volcanoes are, with 

 the rarest exceptions, situated near the sea, or 

 within it. At considerable length, and with 

 reference to this generalization, he passes in 

 review all the lines of active vents in the world. 

 As a mere statement of facts, apart from any 

 conclusions, his summar}', though not fi'ee from 

 errors, is' a valuable one on mau}^ accounts : con- 

 sidered with reference to his generalizations, 

 his treatment of the subject is open to grave 

 criticism. One of the most important and 

 comprehensive propositions he insists upon, is 

 the linear arrangement of volcanoes. This 

 idea has certainly a large amount of truth in 

 it, but it has been enormousl}' overloaded and 

 overworked bj^ writers of general treatises. 

 The occurrence of half a dozen to a dozen small 

 cones upon a single line of fracture twenty-five 

 to a hundred kilometers in length, is very fre- 

 quent in districts where the volcanic action has 

 been diff'use. But a linear arrangement on a 

 grand scale is another matter. The strongest 

 case of it which can be cited is in South Amer- 

 ica, where many volcanoes are scattered in a 

 most irregular arra}^ along the Andes ; but no 

 evidence has 3^et been brought to light, that awx 

 six, or even any three, of them have been built 



