May 29, 1896.] 



SCIENCE. 



817 



through aluminum of one-tenth of a millimeter 

 and one millimeter respectively, as unity : 



Aluminum 1. 1. 



Glass 1.016 1.180 



Green tourmaline 1 .016 1. 180 



Herapathite 1.036 1.435 



Platinum 0.000696 



Finally, it is shown that the actinic eflFect of 

 the Rontgen rays varies inversely as the square 

 of the distance of the sensitive plate from the 

 radiant source. 



George I. Adams gives an extended memoir 

 on the 'Extinct Felidse of North America.' 

 In this the literature of the subject is summar- 

 ized; new points are added in regard to the 

 family in general, with the description of cer- 

 tain typical species, particularly of Hoploplio- 

 neus primxvus, and finally the paper closes with 

 a new classification intended to avoid the diffi- 

 culties involved in those given hitherto. The 

 paper is accompanied by three plates. 



Arnold Hague discusses the age of the Igne- 

 ous rocks of the Yellowstone National Park, 

 the study by Knowlton of the flora found in a 

 number of localities having made it possible to 

 arrive at definite conclusions. The author re- 

 marks that ' ' the facts brought together here 

 clearly demonstrate that the pouring out of ig- 

 neous rocks began with the post-Laramie uplift 

 or closely followed, and from the time of the 

 first appearance of these rocks volcanic erup- 

 tions continued with greater or less energy 

 throughout Tertiary time. It is evident that 

 from the time of the post-Laramie uplift there 

 was, as shown in the geological history of the 

 region, a succession of events of great impor- 

 tance in the development of the Rocky Moun- 

 tains, and that each period of this history was 

 characterized by distinct phases of volcanic 

 phenomena." 



The occurrence of several rare species of min- 

 erals, namely, pollucite, mangano-columbite 

 and microlite, of Rumford, Maine, is described 

 by H. "W. Foote, with analyses and crystallo- 

 graphic details. A. J. Moses describes a sim- 

 ple method of plotting the axial cross for the 

 crystals of any species. A. W. Pierce discusses 

 the gravimetric determination of selenium by 

 the use of potassium iodide. 



AMERICAN CHEMICAL JOURNAL, MAY. 



Transformations of Parasulphamine-benzoic Acid 

 under the influence of heat: By Iea Remsen 

 and A. M. Muchenfuss. When parasulpham- 

 ine-benzoic acid is heated to 285° a remarkable 

 change takes place, consisting of the inter- 

 charge of the amide and hydroxyl groups : 



p „ ^ COOH 



-s r TT .^ CONH, 



At lower temperatures other products are 

 formed, among them being a diamide and a 

 parasulphamine-benzoic acid different from the 

 ordinary variety. The method of preparation 

 and properties of these substances have been 

 studied; but their structures are as yet un- 

 known. 



The heat of Electrolytic Dissociation of some acids,- 

 By F. L. KoETEiGHT ; The author has studied 

 the effect of difference of constitution on the 

 heat of electrolytic dissociation and finds 

 that certain groups produce definite thermal 

 changes, which are however dependents on the 

 relative position of the groups in the molecule. 



On the existence of Pentaethyl Nitrogen: By 

 A. Lachman. Although a number of meth- 

 ods were tried which it was expected would 

 produce this substance, no evidence of its for- 

 mation could be obtained. 



The Conductivity of Solutions of Acetylene in 

 water: By H. C. Jones and C. R. Allen. 

 The authors show that some dissociation takes 

 place in solutions of acetylene in water, as 

 would be expected from its weak acid nature. 



The use of Phenolphthalein in illustrating the 

 Dissociation of Water : By H. C. Jones and 

 C. R. Allen. A solution of ammonia in alco- 

 hol produces no color with phenolphthalein, as 

 the ammonia is not dissociated by alcohol. 

 When, however, water is added to this solution 

 the color appears, its intensity being propor- 

 tional to the amount of water added and, there- 

 fore, to the amount of dissociation caused by 

 the water. Sodium and potassium hydroxides, 

 however, are dissociated in alcohol and there- 

 fore produce the color in this solvent. 



The action of Acid Chlorides on the Silver Salts 

 of the Anilides : By N. L. Wheeler and B. B. 

 BoLTWOOD. When silver formanilide is treated 

 with benzoylchloride a diacidanilide is obtained 



