194 Scientific Intelligence. 



13. A Laboratory Manual of Alternating Currents / by John 

 H. Morecroft. Pp. viii, 247, 184 figures, 27 plates. New York, 

 1912 (Longmans, Green and Co.). — The thirty-nine experiments 

 described are designed for the use of senior students of electrical 

 engineering, and hence a thorough knowledge of the laws of 

 alternating currents is assumed. In the opinion of the author 

 most laboratory texts are conducive to mere perfunctory manipu- 

 lation on the part of the student and hence he has laid special 

 stress on the careful analysis of the test to be performed, of the 

 different variables involved and their relations to one another, of 

 the errors likely to be introduced, etc. Also, as far as reasonable, 

 the student is expected to work out for himself the scheme of 

 connections, to select the most suitable meters, and to prepare his 

 record sheets in advance. In order that the student may thor- 

 oughly appreciate the principles involved in the construction of 

 his measuring apparatus and that he shall know the limitations of 

 the instruments, a more detailed analysis of the action of alter- 

 nating current meters is given than may be found elsewhere. 

 Another new feature of the text consists in a mathematical dis- 

 cussion of armature reaction in single and polyphase machines. 

 The appendix includes the plates, which are reproductions of 

 ondograph and oscillograph records. These curves have been 

 carefully selected for the purpose of clearing up certain involved 

 points indicated at different parts of the text. " It is the writer's 

 opinion that much more of this type of work should be incorpo- 

 rated in our laboratory courses." The paper used is very good, 

 the type and diagrams are above reproach, and no effort seems to 

 have been spared to make the volume as useful and attractive as 

 possible. h. s. u. 



II. Geology and Natural History. 



1. Cambrian Brachiopoda ; by Charles D. Walcott. 

 Monograph 51, XL S. Geol. Surv. ; parts 1 and 2, 1912, pp. 872, 

 pis. 104. — The monograph on the Cambrian Brachiopoda by 

 Charles D. Walcott has been going through the press for so 

 long a time and the date of its publication so nearly coincides 

 with the calendar year that an exact statement concerning its 

 publication and first distribution may be of value to bibliog- 

 raphers. Part II (plates) was received by the IT. S. Geological 

 Survey from the Government Printing Office during the fall of 

 1912, the exact date being of no consequence because no copies 

 were sent out at that time. Part I (text) was received from the 

 Government Printing Office on December 24, 1912, and copies of 

 both parts were sent out on December 28 to the following : 

 Messrs. Charles Barrois, W. C. Brogger, J. M. Clarke, W. H. 

 Dall, Karl A. Gronwall, G. F. Matthew, J. C. Moberg, A. G. 

 Nathorst, D. P. Oehlert, J. F. Pompeckj, Charles Schuchert, 



