276 Tne American Geologist. April, 1897 
still an attempt is commendable. Having given some attention to the 
subject we venture the following criticisms. In general the "hard rock'" 
which he has thought to be the Sioux quartzite is probably not that, 
whei'e remote from exposures of that formation, as at Wolsey, AV)erdeen 
and Plankinton. At the last locality, according to the testimony of the 
well-borer employed at both, it was the same as found at Scotland, 
which was a sandstone cemented with lime instead of silica. Numerous 
hard layers occur in the Dakota sandstone, and it is not unlikely that 
some older rocks intervene between that formation and the crystalline 
rocks in the lower portions of the basin. Moreover, the samples of sup- 
posed ""Archean rock" preserved in the high school collection at Aber- 
deen are a fine gravel, not crystalline at all. 
Some rather striking irregularities represented in this floor are possi- 
bly traceable to misconceptions of topography. In fact one deficiency 
in the reports of the wells is the omission of the altitude of the mouth. 
This criticism probably applies to the bay-like depressions in northern 
Minnehaha and Yankton counties. That in Douglas county seems to 
rest on the somewhat doubtful evidence of one well. 
To explain the irregularities of pressure, besides that of leakage along 
the eastern margin, our author recognizes local leakage, asatChamber- 
lin; the closing of certain water strata toward the east while others are 
open: and the varying coarseness of the water-bearing deposit and con- 
sequent variation in the velocity of subterranean currents eastward. He 
also suggests the imperfect construction of wells and the consequent 
subterranean leakage of some wells. 
If more weight had been given to this factor his map of pressure and 
of the limits of the basin would be saved some complexities. Another 
cause of discrepancies may be hasty or mistaken reading of pressures. 
Still anoth£r, doubtless, is the derivation of waters from different strata. 
This may perhaps most plausibly explain the lower pressure at James- 
town and Pierre. 
The paper is not only of scientific value, but is of such economic util- 
ity that we hope it may be issued separately for wider distribution. 
J. E. T. 
3Ilu4ralogie dc la France et de ses colonies, tome ii, Ire partie. A. 
Lacroix. Paris, Beaudry et Cie, 189(5. 355 pp., numerous illustraticms: 
15 francs. This work continues the physical and chemical description 
of the minerals of France, and embraces a study of the geological con- 
ditions of their natural occurrences. With this part the work is not 
concluded, but another part will contain the metals, arsenides, antimo- 
nides, the sulphides and sulphates of the different metals. The present 
fascicle is devoted almost entirely to the feldspars and zeolites. These 
difficult minerals are defined and distinguished by the new and refined 
optical methods of the French petrographers as well as by the usual 
chemical and more obvious physical characters. The work marks a 
distinct advance in descriptive mineralogy and in petrographical classi- 
fication. N. H. w. 
