230 Dr. Cooper on Volcanoes 
these rocks and the basalt connected with them. Dolomieu 
remarks the same, as to the basalt and greenstone of 
Egypt: some very important observations to the same pur- 
pose have lately been made by Dr. M’Culloch in his paper 
on the granite of Aberdeenshire. The vulcanists say, these 
are not different formations, but one connected and con- 
tinued series of ejections, under different degrees of heat 
operating on them; and they apply this reasoning to the 
slenitic granite of Christiana, observed by Von Buch 
and Haussman: Cellular, or vesicular basalt, often incloses 
in its cells, peridot, carbonat of lime, Zeolytes: of various 
kinds, prehnites, green earth, &c. In the large cells of 
Geodes (as at Oberstein) we find Agate, Chalcedony, 
Quartz. The cells are sometimes round, and sometimes 
elongated in one direction. 
Until lately, on the suggestion of M. Cordier, the pres- 
ence of Augit has not been particularly noticed in basalts ; 
which are sometimes augitic, and sometimes amphibolic ; 
but within my own experience more commonly indetermi- 
nate. Observers with good eyes and a good microscope, 
breaking the basalt into minute fragments, but not into dust, 
may often determine this very important point. 
Analysis of basalt. Bergman. Klapr. Kennedy. 
Silex - - 50 - 44 50 - 46 
Alumina - 15 - 16 75 - 16 
Lime - - 8 - 9 50 - 9 
Magnesia - 2 - 2 25 - 0 
Oxyd of iron - 25 - 20 - 16 
Soda - - 2 60 - 4 
Ox. Manganese - - 12 - 
Mur. acid - - - 5 - 1 
Water - - 2 - 5 
Loss - - 2 23 - 3 
100 100 100 
The varieties thus analyzed appear to be of the Fleetz 
trap formation. 
