876 The American Naturalist. [October, 
sion of the series has not been generally accepted, Becke thinks the 
harmony between his natural table and the olderscheme of Tschermak 
a reason for retaining the original classification. The practical method 
of utilizing the results in his table, consists in finding contiguous sec- 
tions of quartz and plagioclase which extinguish nearly parallel to 
one another. By means of the quartz wedge it is then determined 
whether the double refraction of these sections is of the same or of 
opposite sense. If the former, they are said to have parallel position 
and will indicate some of the relations of the first column of the table, 
and, if the latter, they have crossed position and their relations will 
correspond to something in the second column of the table. The 
quartz section always yields w and a value varying but little from e. 
This method applies only to holocrystalline rocks which contain 
quartz, but it is a discovery of much importance which will doubtless be 
of much service in the study of the crystalline schists. The author 
has applied the method to the determination of the feldspar in many 
rocks of the Rosenbusch collection of B. Stiirz, and printed his list of 
determinations. An excellent photogram also accompanies the paper. 
Fluid Enclosures in Sicilian Gypsum.—The Cianciana gyp- 
sum contains cavities filled with liquid, some of which are 3 cm. in 
extent. Sjögren” has analyzed the liquid with the following results: 
K,O Na,O CaO MgO Cl SO, Total O deducted for Cl, pen ec 
21 409 41 39 449141 110.0 10.1 
Corresponding to 
K,SO, NASO, CaSO, NaCl MgCl, Total 
3.7 11.4 9.7 66.2 9.0 100.0 
The saline constituents were 4.023 per cent of the solution. This 
fluid is a fossil water of Miocene age, and differs from ocean water 
chiefly by containing a greater percentage of sulphates. It agrees 
fairly well with the water of some sulphur springs. The author thinks 
that the quantity of sulphates present in the water of the enclosure 
shows that the gypsum and sulphnr cannot have been derived from a 
lagoon of sea water in which organic matters have reduced sulphur 
from the contained sulphates. Whether they-are the product of sul- 
phur springs or of emanations of H,S in a lagoon of sea water in 
which sulphur has been deposited and sulphates formed by action of 
.. SO, on marls, the author is unable to determine. 
!5Bull. Geol, Inst. Upsala, I, (1893), No. 2, pp. 1-7. 
