Geology and Mineralogy. 67 
rior, and Chapter XII the causes of volcanic action, stating at 
len neth the several theories advanced by different authorities on 
nucleus within the earth, and would attribute the volcanic action 
in general to high temperature joined ne ich i of vapors 
and gases beneath the volcanic vent; but no new theory is offered 
to account for the occurrence of these boudisions within the crust 
The book is illustrated with numerous diagrams and wood cuts 
and will well repay the general reader, as ie as those who are 
more especially interested in Vuleano ology. s a fair presentation, 
so far as its limits allow, of the present state of Knowledge oe es 
ion in that department ‘of science. 
Princeton, Nov. 26, 1881. 
planes were J and 2-i=(#P, 2P 2 Hardness of the crystals 
about 6; color, white, reddish and red. The ey dissolved in no 
acid except hydrofluoric acid, but were easily decom osed by 
fusion with the carbonates of sodium and potassiu Ithoug 
the greatest care was taken to get the crystals fox the analysis 
in a pure state, a magnifying lens still shows a few very small 
particles of the ore oe with them, so that in the analysis 
elow the amount of Fe, ould be somewhat diminished. It 
is evident that an analysis ‘of the poriaeily. white crystals would 
not afford any iron. The reddish and red crystals contain— 
SiO, Al,O; Fes0; CaO MgO K,O Na H,0 
63712 17546 1°644 0714 0°172 13°807 0-233 0-612 0°606= 99-046 
The P.O, in another sample amounted to 0°685 Pe cent. 
(2.)° On regular ae whet ged fat in sane tite. Some time 
dently effected their aca Not the smallest particle of 
this mineral, however, could be met with either in these cavities 
or in any other part of the ore. 
Cleveland, Ohio, N ovember, 1881. 
