June 3, 190,^.] 



SCIENCE. 



855 



The weak part of the treatise, then, con- 

 sists in the undue magnification of the impor- 

 tance of the analogy between gases and solu- 

 tions and the unsuccessful attempt to make 

 the ionic conception the basis of explaining 

 chemical reactions. To eradicate these unde- 

 sirable features will necessarily cause a some- 

 what profound change in the character of the 

 book. The author has everywhere deliberately 

 chosen to entirely omit ' in the interests of 

 the student ' a consideration of opinions which 

 conflict with his own. This course can hardly 

 be justified by the additional care which, it is 

 stated in the preface, was exercised in the 

 choice and exposition of the ideas presented, 

 and will only make it all the more difficult to 

 introduce the changes which sooner or later 

 must be made in future editions of the book 

 if it is to continue to be of real value. 



Louis Kahlenbeeg. 



SOOIETIES AlfD ACADEMIES. 



THE SAN FRANCISCO SECTION OF THE AMERICAN 

 MATHEMATICAL SOCIETY. 



The fifth regular meeting of the San Fran- 

 cisco Section of the American Mathematical 

 Society was held at Stanford University on 

 April 30, 1904. Twelve members of the so- 

 ciety were present. A morning and an after- 

 noon session were held. Both these sessions 

 were attended by a number of local teachers 

 of mathematics who are not members of the 

 society. The following papers were read: 



Pkofessok M. W. Haskell : ' The construction 

 of conies satisfying given conditions.' 



Peofessok H. C. Moreno : ' On a class of ruled 

 loci.' 



Dr. D. N. Lehmbe : ' On a cylinder the inter- 

 section of which with a sphere will develop into 

 an ellipse.' 



Mr. a. W. Whitnet : ' The application of actu- 

 arial methods to fire insurance.' 



Professor E. E. Allardice: 'On the envelope 

 of the directrices of a system of similar conies 

 tlirough three points.' 



Professor Irving Stringham : ' Analytical 

 treatment of certain metrical relations in the non- 

 euclidean plane.' 



Professor G. A. Miller: 'Addition to a 

 theorem due to Frobeuius.' 



Professor H. F. Blichfeldt : ' A theorem con- 

 cerning the invariants of linear homogeneous 

 groups with some application to substitution 

 groups.' 



PitOFESSOR H. F. BLiCHFELftT : ' The linear homo- 

 geneous groups in four variables.' 



Professor M. W. Haskell: 'Triangles in per- 

 spective and the collineations derived therefrom.' 



Professor M. W. Haskell : ' The construction 

 of a twisted cubic from six points.' 



In the absence of Mr. Whitney his paper 

 was read by Professor Stringham. The nest 

 meeting of the section will be held at Cali- 

 fornia University on October 1, 1904. 



G. A. Miller, 



Secretary. 



MINNESOTA ACADEMY OF SCIENCES. 



The meeting of the academy was held in the 

 geological lecture room of the University of 

 Minnesota, on April 11, when the following 

 paper was presented : ' The Gypsum Deposits 

 of New York State,' by Mr. A. L. Parsons, 

 instructor in geology in the University of 

 Minnesota, illustrated by lantern slides. 



Through the courtesy of Dr. Frederick J. 

 H. Merrill, director of the New York State 

 Museum, Mr. Parsons was enabled to present 

 the results of his studies on the geology and 

 economic importance of the gypsum deposits 

 of New York before their publication as a state 

 report. These deposits, which were among 

 the first to be discovered and developed in this 

 country, are in the rocks of the Salina age 

 and are closely related to the salt deposits of 

 the state. All the mines of importance are 

 located in a shallow valley extending from 

 Eome to Buffalo, and east of Rome the de- 

 posits, though of no commercial importance, 

 are found on the south side of the Mohawk 

 Valley as far east as Schoharie. 



The formation of this valley occurred prior 

 to the glacial epoch, and in the region between 

 Syracuse and Eome it has been filled with sev- 

 eral hundred feet of glacial and alluvial debris. 

 The presence of this valley is explained by 

 the wearing away of the soft Salina shales 

 and soluble beds of salt and gypsum which 

 lie between the harder limestones of the 

 Niagara and Helderberg periods. With the 

 development of the cement wall plaster and 



