328 The American Geologist. May, \mi 
upper horizons of the eruptive there would be an increase in acidity 
towards the center; the middle horizons would show little differentia- 
tion, while the lower horizons would show an increase in basicity to- 
wards the center. These relations are illustrated graphically by a dia- 
gram. It is not considered that this is ever a sole cause of differentia- 
tion. The ability of gravitation to produce concentration in solutions is 
denied by some physicists, but is upheld by those who have investigated 
it most carefully. m- l. f. 
On the Associated Minerals of Rhodolite. By W. E. Hidden and 
J. H. Pratt. Am. J. Sci., 156, 463-468. 
The more common associated minerals of this new variety of gar- 
net are quartz, corundum, pleonaste, gahnite, chromite, iolite, stauro- 
lite, monazite, zircon, gold and sperrylite. The occurence of each is 
described and analyses by Chas. Baskerville are given for gahnite 
and iolite. m- l. f. 
The Alkaline Reactioti of Same Natural Silicates. By F. W. 
Clarke. J. Am. Chem. Soc., 20, 739-742. 
On adding distilled water containing a very little alcoholic phenolph- 
thalein to samples of certain finely pulverized silicates, including micas, 
feldspars, zeolites, etc., alkaline reactions were immediately obtained. 
As would be expected, the colors were most intense in the case of those 
minerals which in nature are most subject to alteration.. Similar results 
were also obtained from tests upon the common igneous rocks. The 
rapidity of the action is a striking feature. .\i. l. f. 
Petroleutn Inclusions in Quartz Crystals. By Chas. L. Reese. J. 
Am. Chem. Soc, 20, 795-797- 
Crystals of quartz with petroleum inclusions from Marshall Co., Ala., 
are described and illustrated. The petroleum was recognized by its 
fluorescence, odor and combustibility. M. l. f. 
Mineral Resources of Cuba. By Raimunbq Cabrera, translated by 
L. E. Levy. J. Franklin Inst., 146,26-41. 
Descriptions and analvses are given of the more important ores and 
economic deposits including asphaltum, phosphate rock, and the ores of 
gold, silver, lead, copper, iron and manganese. m. l. f. 
The Slate Regions of Pen?tsylvania. By Mansfield Merriman. 
Stone, 17, 77-90. 
A description is givenof each of the principal slate- producing regions, 
accompanied by tables of statistics relating to the output and properties 
of the slates. The probable resistance to corosion by smoke, sulphurous 
vapors, etc., was tested by treatment for 63 hours in a 2 per cent, solu- 
tion of HCl -\- H2SO4. The results are given in a tabulated form. 
M. L. F. 
Iron Making in Alaba?na. By William Battle PhilijIPS. Sec- 
ond Edition. Alabama Geological Survey, Eugene Allen Smith, Direc- 
tor; Montgomery, Ala., 1898. Pages viii, 380. 
The first edition of this report, issued in 1896, is now succeeded by an 
