•J:'.!' Stevens — Sympathetic Vibrations of Small Amplitude. 



ported bj a brick pier 15 feet from the ground. When the 

 fork which was in unison with the mirror-fork was excited and 

 touched to the bottom of the pier, corresponding vibrations 

 were detected. If, however, the pitch of the fork was changed 

 by three or four vibrations per second, no motion of the fringes 

 could be observed. The passing of an electric car 300 feet 

 distant caused a motion of the fringes; and work was practi- 

 cally impossible, except in the evening, when the building was 

 unoccupied. 



University of Maine, 

 Orono, Alaine. 



SCIENTIFIC INTELLIGENCE. 

 I. Geology. 



1. Die Kristallinen Schiefer des Laacher Seegebietes und Hire 

 Umbildung zu Sanidinit • von R. Brauns. 4°, pp. 61, 18 tables ; 



in case. Stuttgart, 1911. — The well-known ejected bombs of 

 sanidinite, so called, which are found in the volcanic products of 

 the Eifel, and especially at Lake Laach, like those from Vesuvius 

 and other places, have had various origins ascribed to them. They 

 have been chiefly regarded, either as agglomerations of early 

 formed minerals, in a molten magma, or as fragments of some 

 related igneous rock torn off and brought up by the magma. Pro- 

 fessor Brauns, as the result of his studies, brings forward the idea 

 that in reality they are fragments of the sedimentary gneisses, 

 schists, etc., on which the lower Devonian of the area rests, changed 

 by contact metamorphism. He adduces arguments in favor of 

 this view, and shows by chemical equations how, for example, a 

 biotite- muscovite-quartz schist, by a simple exchange of mole- 

 cules, yields a rock consisting of sankline, hypersthene, corundum, 

 and cordierite. Thus by simple melting and recrystallization many 

 cases could be explained ; and to this origin, aided by the compo- 

 nents of the alkalic magmas and their contained volatile constitu- 

 ents he is inclined to ascribe the other ejected masses with their 

 varied minerals. The work is illustrated by many handsome 

 half-tone plates of microphotographs explanatory of the text. 



l. v. p. 



2. British and Foreign Building Stones ; by John Watson. 

 12°, pp. 483. Camb. Press, 1911. — One-half of this book, as 

 indicated in the sub -title, is a descriptive catalogue of the rock 

 specimens in the Sedgwick Museum at Cambridge. The first 

 part of the work is, however, of a descriptive nature. The writer 

 first considers the plutonic igneous rocks, giving a general 

 account of British granites and their occurrences, and from this 



