50 The American Geologist. January, i895 
color. Tlu'V .-irf liolocn stalliiic witli bipyriimidal ([uartz, microcliiic, 
miiscovite. chlorite, pyrite, and zircon liavinji' plcochroic aurook's. 
(3) Gneiss without amphibole of the Yal Pellino. This is distinctly 
stratified, lias a granular structure, and is compostMl of quartz predom- 
inantly, orthoclase and ))lajiioclase. l)iotite with inclusionsof ma<^netilc, 
and associated chlorite and muscovite, apparently alteration products. 
Zircon occurs as an inclusion in quartz, with a mineral doubtfully rec- 
ognized as cordierite. Andalusite is aKso present. 
(4) Amphibole gneiss stratified with amphibolite. This rock shows 
slightly different phases, but is always schistose. It is made up of 
quartz, orthoclase, plagioclase, and amphibole. The latter is of intense 
green color and characteristic pleochroism. 
(5) Amphibolite. This has a uniform dark green color and is made 
up of a network of acicular crystals of amphibole traversed by rare 
veins of quartz or feldspar, the latter mainly plagioclase. 
(6) Serpentine. This is represented by a considerable mass of dark 
green mineral, traversed by small and more or less sinuous veins. Un- 
der the microscope, the mass is seen to be individualized, the green 
mineral breaking up into small intricate bands. Dispensed granules of 
high relief and without crystalline form are noticed. These granules 
arc surrounded by serpentine. A mineral giving high interference col- 
ors and with fresh aspect is referred to actinolite. Muscovite and chlo- 
rite as alteration products, and granules of magnetite, are noticed. An 
undetermined mineral, undoubtedly represented in the granules of higli 
relief, is present. Since, however, the crystalline form, and for the 
most part even the cleavage lines, are lacking, diagnostic characters 
are not present. This mineral has been considered to be olivine becaus(.' 
of the high colors of polarization; but the author considers this refer- 
ence incorrect. Where the granules are sejaarated by serpentine, a web 
structure is seen, the strings being serpentine, and the intervening 
spaces being filled with the mineral in question. These lines meet at 
an angle of about 1)0.° Such a structure has been described by Hussack 
as "balkenstructur," and is characteristic of pyro.xenite serpentine. 
The mineral here shows kinshij) to both orthorhombic pyroxene (ensta- 
tite?) and to monoclinic (salileV). 
The observations e.xclude the belief that the serpentine is derived di- 
rectly from the amphibole, and confirm rather the opinion of Cossa 
that it comes from pyroxene. n. f. b. 
Thefieoloyicalhidortj of ItorheKtcr, N. ¥.. By H. L. Faihciiild. (Pro(;. 
Rochester Acad. Sci., vol. ii, pp. 215-223, June, 1894.) In this paper 
Prof. Fail-child has given a sketch of that part of geologic history which 
can be read from the rocks at Rochester. The strata below the upper 
part of the Medina are known only from drill records which go down 
over 3,000 feet. The lowest rocks mentioned are a siliceous limestone 
and a ferruginous quartz rock, whose exact age is uncertain; they im- 
mediately underly the Calciferous. A large part of the section is com- 
posed of 054 fetit of Trenton dark limestone and 1,075 feet of Medina red 
