1892.] Geology and Paleontology. 695 
The kind and condition of a mineral constituent may be a means 
of distinguishing the metamorphosed eruptive from the metamorphosed 
sedimentary. 
After discussing the subject in his usual comprehensive manner, 
Prof. Derby concludes that there is a reasonable probability that zir- 
con, and to a less degree monazite, may prove to be guide minerals by 
which eruptives and their derivations can be certainly identified, no 
matter what degree of alteration they may have suffered. This prob- 
ability gives additional interest to the study of the heavy residues of 
rocks which, it is hoped, will lead geologists to thoroughly test this 
hypothesis in other parts of the world. (Proceeds. Rochester Acad. 
Sci., Vol. i, pp. 198-206.) 
A Section of the Strata at Rochester, New York.—A 
boring made by the firm of Otis & Gosline in a search for gas in the 
vicinity of Rochester, N. Y., has made known some interesting facts 
concerning the thickness of the rock strata of that region. The drill 
was sent to a depth in the rock of 3,078 feet, where the exceeding 
hardness of the rock made further progress very difficult. Small 
quantities of gas were found at various depths. A little brine was 
encountered at a depth of 1,330 feet. 
From a carefully kept well record Prof. H. L. Fairchild has pre- , 
pared the following condensed section of the Rochestet well. 
Altitude 484 feet above tide. 
Horizon. THICKNESS. Kinp or Rock. Dept. 
> Niagara limestone, es ra 
Niagara 156 ft. f ak ale C Clicked Kina ee 156 ft. 
22 ft. Clinton upper green em ‘le 
Clinton 15 ft. Clinton (Pentham) limestone 
35 ft. Clinton lower green shale 228 ft. 
Red Medina 1075 ft. Red sandstones and shales 1308 ft. 
25 ft. Blue shaly sandstone 
aman 45 ft. Hard gray sandstone 
ego) 13 ft. (Dark gray shaly sandstone 1386 ft. 
Hudson and Utica 598 ft. Dark shales 1984 
Trento 954 ft. Dark limestone 2938 ft. 
10 ft. Gray pene 
30 ft. Drab limes 
Calciferous ? 50 ft. 4 Dark gray lin ai with shale 
44 ft. Black magie limestone 
3 ft. Dark calcareous — 3075 ft. 
Algonkian ? 2ft. f White quartz sandsto 
or Archean ? 1 ft. f Powdered anois just: 3078 ft. 
