Physics and Chemistry. 389 



following table, together with the corresponding angles taken 

 from Kokscharow. 



e * e 



122 



/S 



122 



44° 



19£' 



z *z 



112 



A 



112 



53 



37 





112 



A 



112 



53 



42 





112 



A 



112 



44 



30 



X^X 



124 



A 



124 



28 



39 





12-1 



A 



124 



28 



41 



e^z 



122 



A 



112 



17 



H 



m ~m 



110 



a 



110 



80 



6 





110 



/s 



110 



99 



5l£ 



a s*m 



100 



A 



110 



40 



4 



m ~ z 



110 



A 



112 



53 



40 





110 



A 



112 



53 



40 



m *t 



110 



/v 



021 



55 



18 





110 



A 



021 



55 



191 



KOKSCHAEOW. 



44° 



23' 



53 



48 



53 



48 



44 



46 



28 



28 



28 



28 



17 



6 



80 



10 



99 



50 



40 



5 



53 



45 



53 



45 



55 



19 



55 



19 



It will be noticed that the angles agree closely with those 

 given by Kokscharow, and a consideration of those angles cal- 

 culated to determine the monoclinic symmetry of the crystal, 

 i. e., ?n / \z and m^t give us no sufficient ground for assuming 

 that the crystallization is other than orthorhombic. The reflec- 

 tions from the faces of these crystals are usually not very 

 sharp ; those from the one shown in fig. 4 are, however, an 

 exception. In this crystal vicinal faces lay in the prismatic 

 zone making an angle of 0° 39' with m, and with the front 

 edge of the vicinal prism measuring 81° 22'. There is also a 

 vicinal pyramid inclined 0° 21' to 2, and in the zone 2, e, the 

 vicinal faces being nearest to e and showing faint though 

 distinct reflections. 



The gravity of this crystal taken very carefully is 4*084. 



Mineralogical Laboratory, Sheffield Scientific School, March 20, 1886. 



SCIENTIFIC INTELLIGENCE. 



I. Physics and Chemistey. 



1. On the Critical Temperatures and Pressures of certain 

 Gases. — Vincent and Chappuis have determined the critical 

 temperatures and pressures for two series of compound gases, the 

 members of each series differing from one another by CH 2 . In 

 the first series were ammonia and the three methylamines ; in the 

 second, hydrogen chloride and the chloi'ides of methyl and ethyl. 

 The experiments were made in the Cailletet apparatus, the tubes 

 being filled with ammonia or hydrogen chloride by simple dis- 

 placement. The other gases were previously liquefied, and were 

 contained in vessels connected with the laboratory tube by means 

 of a three-way cock, leading to a mercury pump. The tube was 

 carefully exhausted and then the gas was allowed to enter. About 



