152 Seventific Intelligence. 
requires a large number of cocks; the Tépler is very fragile on 
account of the convolutions of its parts; and the Sprengel is 
suited only to certain kinds of work. Messrs. Greiner and Fried- 
richs describe a new pump which has a wide range of usefulness, 
with the possibility of obtaining a good vacuum. The chief 
peculiarity of the pump resides in a three-way cock, which is fully 
described in the author’s paper. The use of but one cock gives 
the pump a great practical advantage.-—Ann. der Physik und 
Chemie, No. 12, 1886, p. 672. Teele 
8. Relation of the Electrostatic and Electromagnetic Units.— 
The earlier determinations of this ratio by different investigators 
differ by as mucb as four per cent, and the later determinations of 
Exner (v=29,20.10°), Klemencic (v=30,18.10°) and J. J. Thom- 
son (v=29,63.10°), leave much to be desired. H. Hinstedt has 
made a new determination, and obtains the result »= 30,07.10%. 
The method employed by Hinstedt required only the determin- 
ation of the capacity of a condenser, Q, and a resistance, W, 
together with a ratio of resistances. The observations were 
independent of the electromotive force of the battery employed.— 
Ann. der Physik und Chemie, No. 12, 1886, pp. 560-579. 5. 7. 
II. GkEotocy AND MINERALOGY. 
be 
1. Motes on the Geology of Northern California; by J. S. 
Ditter. (Abstract of paper, from the Proceedings of the Phil. 
Soc. of Washington, Jan. 16, 1886.)—Under the direction of 
Captain Dutton I have spent the last three summers studying the 
geology of northern California and the adjacent portion of Ore- 
gon. The conclusions of a general nature referring to that region 
may be briefly summarized as follows : 
In the northern end of the Sierra Nevada and the central por- 
tion of the Coast range, among the highly plicated, more or less 
metamorphosed strata which are older than those of the Chico 
group, there appears to be but one horizon of limestone, and that 
is of Carboniferous age. 
The northern end of the Sierra Nevada is made up of three 
tilted orographic blocks which are separated from each other by 
great faults. The westernmost of these blocks, stretching far to 
the southeast, appears to form the greater portion of the range. 
As in the Great Basin region, the depressed side of each block 
was occupied by a body of water of considerable size. The de- 
posits formed in these lakes gave rise to the fertile soils of Ameri- 
ean and Indian valleys. 
The plication of the strata in the Sierra Nevada range took 
place, at least in great part, about the close of the Jurassic or be- 
ginning of the Cretaceous period; but the faulting which really 
gave birth to the Sierra as a separate and distinct range by differ- 
entiating it from the great platform stretching eastward into the 
Great Basin region, did not take place until toward the close of 
the Tertiary or the beginning of the Quaternary. Although the 
