700 The American Naturalist. [August, 
pared by mixing solutions of the two simple sulphates in equal molec- 
ular proportions. The study shows that the bivalent metal exerts no 
appreciable effect on the crystals, the predominant effect being due to 
the univalent metal present. The crystals of the potassium, rubidium, 
and cæsium salts have each a peculiar habit, that of the rubidium be- 
ing intermediate between the other two. The axial angle £ increases 
from the cesium, through the rubidium to the potassium salt, its value 
in the rubidium salt being midway between the values in the cæsium 
and potassium salts. This is in close correspondence with the differ- 
ences between the atomic weights of those bases. Tutton says “The 
relative amounts of change brought about in the magnitude of the 
axial angle by replacing the alkali metal potassium by rubidium and 
the rubidium subsequently by cæsium, are approximately in direct 
simple proportion to the relative differences between the atomic 
weights of the metals interchanged.” The other crystal angles of the 
rubidium salts are likewise intermediate in value between those of the 
potassium and cæsium salts, but they do not show the same relation to 
the atomic weights of the alkali bases, the maximum deviation from 
such a relation being found in the prism zone. As these angles are for 
rubidium nearer to those of potassium than to those of cæsium, the 
author thinks that as the atomie weight of the alkali metal introduced 
gets higher, the effect of the metal on certain angles increases beyond 
a mere numerical proportion. Professor Tutton announces that this 
communication will be followed by another, which will discuss the 
changes in the optical constants of the crystals due to the same chemi- 
cal substitutions. 
Spangolite from Cornwall.— Miers' has found in a collection of 
Cornwall minerals presented to the British Museum, small crystals of 
the new mineral spangolite described by Penfield in 1890. The Corn- 
wall crystals show the hexagonal prism, pyramid, and base. Their 
association is remarkably like that of Penfield’s spangolite, as they 
occur with cuprite and its alteration products. From the characters 
of the associated liroconite and clinoclase, Miers thinks that there ean 
be no doubt that the specimen is from St. Day, near Redruth. 
Eudialite from the Kola Peninsula.—The occurrence of eudia- 
lite in the nephelene syenite and pegmatite of the Lujawr-Urt and 
Umptek in Russian Lapland, recently mentioned by Ramsay, has 
now been studied in detail.’ The crystals have developed on them the 
*Neues Jahrbuch, 1893, TI, 174. 
*Neues Jahrbuch, Beil. Bd., VIII, (1893) 722. 
car ee ANS NS oe cent i Tus c E MK coal 
