Geology and Mineralogy. 4:55 



to "depend on equation 204 for its action." In Art 517 we read 

 of 'the " tlow ot magnetic flux." In Art. 582, equation 2 is 

 ascribed to Cavendish but in Art. 330 to Coulomb. The numer- 

 ical value of the velocity of light is virtually given in lour 

 different ways, 300*2, 298,300, and 299 million meters per second. 



15. Alternating Currents and Alttrnatii>g Current Machinery ; 

 by DuGALD C. Jackson, C.E., and Johx Peice Jackson, M.E. 

 pp. xviii and 729. Xew York (The Macmillan Co.). — This book 

 forms the second volume of Jackson's Text- Book on Electro-Mag- 

 netism and the Construction of Dynamos. It is a work intended 

 for the use of students of electrical engineering. In so far as 

 we may judge, without having put the book to actual test in the 

 designing room, the authors have well fultilled their aim to 

 develop a clear exposition of the principles governing the design 

 of electro-magnetic machinery, and present the elements of present 

 engineering practice. The style is concise but never scrappy. 

 Whenever theory can serve as a guide in the construction of a 

 machine and mathematics is necessary, it is introduced, the neces- 

 sary formulas being derived from the beginning. Difliculties are 

 not slurred over nor, on the other hand, does the book have the 

 peculiar character of a mathematical treatise. For the more 

 purely empirical parts of the subject numerous tables are intro- 

 duced. A large number of diagrams and line drawings serve to 

 illustrate the text, but mere pictures of commercial machinery 

 have been excluded. Methods ot measuring the various magnetic 

 quantities, and of testing alternators and transformers, are de- 

 scribed at length. 



On casual reading there appear very few things indeed that 

 suggest adver^e criticism. The classification of armatures (p. 15) 

 seems artificial and of little value. The sentence (p. 78) "All 

 insulated conductors have the property of being able to hold 

 electricity in its static form," might lead the reader to infer that 

 electricity existed in different loi-ms, one of which is known as 

 the static. On the whole the book may be said to be an excellent 

 one for the sphere for which it was written. 



II. Geology axd Mixeealogy. 



"^On some Palcp.ozoic fossils from Baffinland ; by E. M. 

 TiXDLE. (Communicated.) — During the past summer the writer 

 obtained, while with the Cornell University Arctic Expedition, 

 two small collections of fossils from Baffinland. The fii'st of 

 these was collected from the mainland north of Hudson Strait, 

 about lat. 62° 45' and long. 70° W., and from Big Island. The 

 other set of specimens was collected by Mr. Peck, a missionary, 

 who obtained them from the shores of Lake Kennedy, which lies 

 northwest of the head of Cumberland Sound. All of the speci- 

 mens from Big Island and Hudson Strait were picked up from 

 the drift. These are embedded in hard, fine-grained, light-gray 

 limestone, which occurs in small fragments very sparingly dis- 



