Mineralogy and Geology. 261 
them trimetric and the other triclinic. Orthoclase and albite constitute, 
as he observes, another example. Yet it is one which brings dimorphism 
and Scacchi’s polys are into close relation. Professor Seacchi 
_ Sents a large number of facts illustrating his views, and discusses also 
the origin of the phenomena observed. In his ro memoir, Professor 
Scacchi gives an account of some important observations bearing on the 
= of twin crystals. 
emoire sur | Emploi du Microscope polarisant, et sur Pétude des 
letpridtis optiques een propres & déterminer le systeme cristallin 
dans les Cristaux naturels ou artificiels; par M. Ds Cioizzaux. 60 
PP. 8vo, with two plates. 1864. Paris. (Dunod, éditeur; Quai des Augus- 
tins, 49),—No one has labored more effectually in optical mineralogy than 
Mr. Des Gloisennx. The s cience bears” evidence rubengbeit of progress 
me of his mineralogy yep: in 1862) that this memoir should ap- 
ae as an Appendix to the second ; but the uncertainty w with regard to 
_ the eater of the latter has led to his i issuing it RI 
1, Zire —Zirconium has been the subject of researches by Mr. 
Troost, hicks were recently presented to the Academy of erie at 
Paris, si results go to show that zirconium acts the same part in the 
C es of elements that antimony does in the Nitrogen ; Sil that 
this element c — the passage between silicium and aluminium, thus 
ron gpictettars zirconium a and alumini C 
are monoclinic rhombic prisms of 93°, inclined 108 to the basal plane. 
—Les Mondes, July 20. 
II. MINERALOGY AND GEOLOGY. 
aha On the Sand hills of Cape Henry in Virginia; by B. Henry La- 
EB, Esq a rumeies Au. Ph Ph. Society, vol. iv, p. 439, and Price 
MinerslogiZal Journal, No. iv, 1814).'— —From the falls of the great riv- 
ers of Virginia a over the out-runnings of the granite strata, the general 
level of the land gradually approaches the level of the ocean. Ree the 
falls it is elevated from 150 to 200 feet above the tide; on the sea-shore 
at Cape areas the original coast rises not more than 15 “feet at high- 
ge ark, 
2 | nd 
_ which with many hundred more, were dug out of a well at eo 
from the depth 4 71 feet, prove that the deposition of the super-strata — 
Wi ally published fifty years since, because of its 
ERIE ca? 
the A Atlantic coast. We leam fro Mr. J. jE. Hilgard, of peadicinetiard posi 
