Reviews — G. P. Iddings — Problem of Volcanism. 331 



■with some plant-remains. A useful feature of the memoir is the 

 account of the geology of the Strathpeffer district and the relation 

 between the mineral waters and the fetid limestones and bituminous 

 shales of the Old Red Sandstone of that locality. This was pointed 

 out long ago by Hugh Miller, but his interesting speculations on the 

 connexion between mineral waters and fossil fishes are not mentioned 

 in the memoir. 



One of the great structural lines of Scotland, the Great Glen fault, 

 passes along the line of the Caledonian Canal, a little north of 

 Inverness. Dr. Home estimates that it has a downthrow to the 

 south-east amounting to at least 6,000 feet, from its effects on the 

 Middle Old Red Sandstone. Movement along this fault gave rise to 

 the Inverness earthquake of 1901, of which Dr. Davison hasremarked 

 the similarity in character with the Japaneae earthquake of 1891, 

 indicating that mountain-building processes are not yet ended in the 

 Scottish Highlands. 



The glacial geology of the district presents no features of special 

 interest, but the raised beaches of the Moray and Cromarty Firths 

 are well known to geologists and geographers. Many passengers on 

 the Highland Railway are familiar with the raised beaches of Kessock, 

 which are illustrated in the memoir by a photographic plate. 

 Visitors to Inverness must also be familiar with the conical gravel 

 hill, known as Tomnahurich, that stands in the Ness Valley to the 

 west of the town. It rises to a height of 200 feet, and was considered 

 hy Helland to be a moraine, but is regarded as of fluvio-glacial origin 

 by the authors of the memoir. 



T 1 



II. — The Problem of Volcantsm. By G. P. Iddings, Ph.B., Sc.D. 

 pp. 273, with 86 figures, mostly photographic plates, Oro-Bathy- 

 graphical Chart of the World, coloured folding plate showing 

 Recent and Tertiary volcanoes. Yale University Press ; Oxford 

 "University Press ; 1914. Price £l ls.net. 



'HE treatment of the subject is frankly speculative. Once volcanic 

 1 phenomena have been introduced by the citation of familiar 

 •examples, the question of the source of volcanic temperatures is 

 raised. To meet this an account is given of nebular hypotheses, 

 illustrated by fifteen beautiful photographs of nebulse, fourteen of 

 them from the Lick Observatory. The older hypotheses of Buffon, 

 Kant, and Laplace are passed in review, and then a very sympathetic 

 rendering is accorded to the contributions for which we are indebted 

 to Chamberlin working, as that author tells us, in collaboration with 

 Moulton. Chamberlin's contention is that the solar system has 

 evolved from a spiral nebula, which in its turn may have originated 

 in a tidal explosion of the sun during the near approach of some other 

 star. It must be remembered that Laplace was writing in the dark 

 when he pictured his great nebula. Nowadays improved telescopes 

 coupled with photography enable us to discern such objects in ever 

 increasing numbers. Among them spiral nebuloe, emitting a continuous 



