536 Scientific Intelligence. 



Annalen and are hence not inaccessible, at the same time the 

 subject is one of snch unique interest that their republication in 

 a single volume is a service on the part of the publishers for 

 which all physicists will be grateful. Moreover, this has given 

 the author an opportunity to present a general summary of the 

 subject from the present standpoint with the correction of some 

 errors, and this gives unity and completeness to the whole 

 subject. 



8. Yorlesungen ilber MaxieelVs Theorie der Elektricitat and 

 des Lichtes von Dr. Lttdwig Boltzmann. I Theil, Ableitung der 

 Grundgleichungen fur ruhende, homogene, isotrope Korper. 139 

 pp. 8vo. Leipzig, 1891. — This volume is a highly valuable contri- 

 bution to the subject of Maxwell's theory. Starting from Helm- 

 holtz's theory of cyclical movements, the author has developed the 

 theory of electrical oscillations in circuits with condensers ; then 

 the general equations of electrical movement in stationary homo- 

 geneous and isotropic conductors and semiconductors, with applica- 

 tions to the fundamental problems of electrodynamics, induction, 

 electrostatics and the theory of light. The author intends to fol- 

 low this contribution by other parts in which he will give the 

 application to anistropic bodies and those in motion, the theory 

 of dispersion, double refraction, the rotation of the plane of polari- 

 zation and finally the oscillations discovered by Hertz. 



II. Geology and Natural History. 



1. A Summary Description of the Geology of Pennsylvania y , 

 in three volumes, with a new Geological Map of the State, a 

 map and list of Bituminous Mines and other illustrations; by J. 

 P. Leslet, State Geologist. Vol. I, 719 pp. 8vo. Harrisburg, 

 Pa. — The long series of Annual Reports of the Second Geolog- 

 ical Survey of Pennsylvania, under Prof. Lesley as Director, 

 yield in value to none from the other State surveys. They do 

 not comprise a full account of the animal paleontology of the 

 State and some points are left doubtful on this account. But in 

 other respects the geology has been well studied and described 

 by an able corps of geologists ; and, in view of the position of 

 the ai - ea with reference to the Appalachians, and its comprising 

 the whole Paleozoic series, the final Summary Report should be a 

 work of great interest. The first of the three volumes of the 

 final Report, has been recently issued. It treats of the Lauren- 

 tian, Huronian, Cambrian and Lower Silurian formations. It 

 opens with extended remarks on the nature and uncertainties of 

 geological knowledge and reasoning. The discussion of the 

 various views of the investigators of the Archaean and Cambrian 

 formations occupy the next 120 pages. In the remaining part of 

 the volume, treating of the overlying formations, and their strati- 

 graphical relations, many sections and maps illustrate finely the 

 flexures and positions of the rocks, and several pages of plates, 

 made up of figures of fossils from various sources, are intro- 



