Reviews — Dr. A. Brim's Volcanic Researches. 311 



When compared with other species of the genus, so far as its 

 imperfectly preserved condition admits, we notice that the Dumbleton 

 specimen (Fig. 2) has a small additional posterior tooth upon the 

 margin of the carapace near the cervical furrow, and that the cervical 

 furrow is distinctly bifurcated. This is seen to he the case in Eryon 

 Ifoorei, H. Woodw. (QJ.G.S., vol. xxii, p. 499, pi. xxv, fig. 3, 1866), 

 in JS. Brodiei, H. Woodw. (op. cit., p. 498, pi. xxiv, fig. 2) ; probably 

 also in E. crassichelis, H. Woodw. (op. cit., p. 497, pi. xxv, fig. 2), 

 and in the recent Pentaclieles euthrix, W. Suhm, " Challenger" Report 

 (see also Geol. Mag., 1888, p. 439, fig. 2), but not noticeable in the 

 other species of this genus. 



Although the above characters maybe considered minor distinctions, 

 yet, taken along with the fact of the extremely rounded contour of 

 the carapace in the Dumbleton specimen (Fig. 2), a feature observed 

 only in three, or possibly four, other species (for E. crassichelis may 

 perhaps also have had a rather circular carapace), and being probably 

 the first of these circular forms of Eryon observed in our English 

 Lias, I venture to designate it as E. Richardsoni after its discoverer, 

 Mr. Linsdall Richardson, E.R.S.E., E.G.S., the energetic Secretary of 

 the Cotteswold Club, to whom I am indebted for the opportunity' to 

 figure and describe it. 



The specimen is to be placed in the Cheltenham Town Museum, 

 and forms a part of the ' Holland Collection '. 



IRZE^VIIE^VS. 



I. — A New Vur.cANOLOGY. 1 

 [Concluded from the June Number, p. 273.) 



WE now come to the portion of the book which will attract most 

 attention, the portion, that is, which deals directly with the 

 function of water in volcanic phenomena. An account is given of 

 the methods employed in the quantitative determination of water in 

 natural volcanic emanations. Two methods are used in the field — 

 (1) condensation, (2) hygrometry. Specimens are also taken in sealed 

 tubes to the laboratory, and there examined either hygrometrically or 

 by absorption over phosphoric anhydride. 



The wealth of experimental and observational data which follows 

 may be illustrated by a few selected examples. Brun's main thesis is 

 that paroxysmal eruptions are anhydrous, while solfataric eruptions 

 owe their aqueous character solely to the invasion of volcanic foci by 

 superficial waters as soon as the temperature of the latter falls 

 sufficiently. 



A summary of observations made at Vesuvius in April, 1906, may 

 be taken as typical. 



1. Near the crater the ashes fell quite dry. They continually 

 gave rise to avalanches, and once they were mixed with the air in this 

 manner they entrapped myriads of bubbles, forming an emulsion which 



1 Recherches sur V exhalaison volcaniqiie, by Albert Bran, Cbemist, L.Sc.Ph. 

 Sorbonne, D.Sc.Pb. (honoris causa) Geneva. A large quarto volume, 227 pages, 

 16 text-figures, 27 pbotograpbie plates, and 7 panoramas. Price 30 francs. 



