Geology and Natural History. 481 



film varies from 10 X 10~ 6 to 80xl0 _6cm according to the sub- 

 stances used and the conditions of temperature and pressure, and 

 for the water film on glass in saturated vapor at 15 c the thickness 

 is about 13 X 10- 6cm . The author quotes Professor B. J. Thomson's 

 results for the mean radius of drops formed by condensation in 

 electrified gas, namely 89 X 10~ 6cm for negatively electrified oxygen 

 and 68XlO _6cm for positively electrified oxygen.— Phil. Mag., 

 May, 1903, pp. 517-523. j. t. 



13. Speaking Flames. — In a preliminary notice V. Gabrit- 

 schewski and A. Batschinski describe a method of obtaining 

 speech from flames. The poles of an induction coil were con- 

 nected by wires to Bunsen burners or other flames. The primary 

 circuit of the coil included a battery giving about four amperes 

 and a microphone. The distance of the microphone was about 

 30 m . The flames repeated various sounds and speech. It is essen- 

 tial that a sufficient difference of potential should arise at the 

 flame electrodes. — Ann. der Physik., p. 223. j. t. 



1 4. Vorlesung iXber Experimental Physik • von August Kundt. 

 Edited by Karl Scheel. Pp. xxiv, 852, with a half-tone of 

 Kundt, 534 figures and a colored spectrum plate. (Braunschweig : 

 Friedrich Vieweg u. Sohn.) — This volume, prefaced by a resume" 

 of Kundt's life and labors, is the result of an earnest desire on 

 the part of his former students to have, in accessible form, the 

 lectures of this gifted investigator and teacher. It has been pre- 

 pared from Kundt's notes of the lectures he delivered in Berlin 

 ('88-'89) which bear traces of his own editing for publication. 

 There are a total of 150 lectures covering the subjects of 

 Mechanics, including Liquids and Gases, Sound, Heat, Electricity 

 and Magnetism, and Optics — which are models of clearness and 

 thoroughness of presentation. 



The editor has preserved, so far as type permits, those charac- 

 teristics of Kundt which gave him his hold upon the student. 

 Every principle is developed in the simplest and most compre- 

 hensible manner from a consideration of the phenomena them- 

 selves, which he freely reproduced before his classes. This 

 method is adopted in preference to a mathematical development, 

 though the discussions always lead to the fundamental formulae. 



These lectures will undoubtedly prove of great interest and 

 value to all teachers and students of the subject. d. a. k. 



II. Geology and Natukal Histoey. 



1. New York State Museum: Frederick J. H. Merrill, 

 Director. — The following bulletins have recently been received : 



No. 44 (vol. viii) Lime and Cement Industries of New York ; 

 by HeinrichRies and Edwin C. Eckel. Pp. 639-968. 102 pis. 

 The origin, composition, geologic occurrence and commercial 

 uses of the New York limestones have been studied with great 

 care and described in such a manner as to be of most use to 

 quarry owners and limestone users. The chapters on the Port- 

 land Cement Industry, pp. 849-898, were written by Mr. Eckel. 



