32-i Scientific Intelligence. 



the specific gravity for the regular diamond may be computed. 

 In the case of tetragonal and hexagonal crystals also, either the 

 axis c or a, or the specific gravity, may be computed ; in the 

 remaining crystal systems, only the specific gravity on the one 

 hand, or the crystal volume on the other may be computed. 

 From the crystal volume one geometric constant may be com- 

 puted backwards, only in case the others are already known. 



Tables VII to XIII give the data and calculated values for a 

 series of isomorphous or eutropic substances, as arsenic, anti- 

 mony, bismuth ; also, beryllium, magnesium, zinc, cadmium ; 

 again, aragonite (CaC0 3 ), strontianite (SrCOJ, witherite (BaC0 3 ), 

 cerussite (PbCOJ, etc. The discussion of these tables, though 

 highly interesting, would require more space than is available 

 here. It must suffice to quote the conclusions deduced by the 

 author from them, as follows : 



(1) The actual volumes of the various chemical compounds, if 

 formed into equivalent crystals, stand in a very simple relation to 

 each other. 



(2) The weights of these equivalent volumes stand in the same 

 relations to each other as the molecular weights. 



(3) The volumes in a eutropic series increase with increasing 

 molecular or atomic weights. 



(4) The weights of equivalent volumes always increase with 

 increasing atomic weights. 



(5) Bodies which are isomorphous but not eutropic likewise 

 stand in a very simple relation to each other according to their 

 crystal volume or their actual volume as the case may be. 



(6) Many crystals which have heretofore been considered 

 eutropic or isomorphic are not so, since they probably possess a 

 larger or smaller molecular weight according to the number of 

 atoms. 



7. The Induction Coil in practical work, including Rdntgen 

 Bays ; by Lewis Wright. 172 pp. London, 1897 (Macmillan 

 & Co.). — This little volume, by a well known writer, appears 

 opportunely at a time when the induction coil is being called 

 upon for active use more generally than ever before. Many of 

 the workers experimenting with X-rays have not had the advan- 

 tages of extensive practice in the laboratory, and they especially, 

 as well as others, will be grateful to the author for preparing this 

 excellent summary of the subject. 



II. Miscellaneous Scientific Intelligence. 



1. British Association. — The sixty-seventh annual meeting of 

 the British Association for the Advancement of Science was held 

 at Toronto from August 18 to 25. It was a more than usually 

 notable occasion, rendered so chiefly by the number and charac- 

 ter of the scientific men who came from England to attend it, 

 also by the enthusiastic work of the Canadians at home, and 

 further by the cooperation of members of the American Associa- 



