Geological Society. 119 



prevented from giving to each experiment the additional time 

 which would be necessary in order to secure a good result. 



The experiments described in the book before us are well arranged, 

 and under each experiment the methods of procedure, the prin- 

 ciples involved, and the nature and methods of correcting the 

 various errors are all clearly set forth. In this respect the book is 

 all that could be desired. The amount of mathematics involved is 

 trifling, and is stated clearly and concisely, so that it could be 

 followed easily by most students. 



Among the experiments described in this first part we notice one 

 or two that are entirely new, and other older experiments have been 

 slightly modified in form. Foremost among the new experiments 

 is a method of determining the specific heat of air at constant 

 volume. A wire heated electrically by a measured current is used 

 to heat the air, and the rise in temperature of the air is calculated 

 from the observed increase of its pressure. We have not yet had 

 an opportunity of trying this experiment, but if it yields a satis- 

 factory result it will certainly form a valuable addition to the 

 existing calorimetric methods. A good modification is also intro- 

 duced into Dulong and Petit's apparatus for determining the 

 absolute coefficient of expansion of mercury. In order to more 

 easily compare the heights of the two columns of mercury they are 

 brought nearer together at the top than is usually the case in the 

 text- books. Several modifications of this kind appear throughout 

 the book, and furnish valuable suggestions for obtaining increased 

 accuracy in the results of experiments. 



The illustrations and diagrams in the book have not been designed 

 with a view to artistic excellence, but they show in most cases all 

 the essential details of the apparatus. There is, however, room 

 for improvement in this respect. In conclusion we believe that 

 this work will be found useful by those teachers who wish to give 

 their students a good training in practical physical measurement, 

 without rushing through the subject at the pace usually required 

 by those who are candidates for examination. 



James L. Howabd. 



X. Proceedings of Learned Societies. 



GEOLOGICAL SOCIETY. 



[Continued from vol. xxix. p. 289.] 



February 26, 1890.— J. W. Hulke, Esq., F.R.S., Vice-President, 

 in the Chair. 



r fTELE following communication was read : — 



J- " On the Relation of the Westleton Beds or ' Pebbly Sands ' of 

 Suffolk to those of Norfolk, and on their extension inland, with some 

 observations on the Period of the final Elevation and Denudation of 



