136 
The age of these intrusives is a matter of considerable inter- 
est. That the dikes occurring at Manheim, Syracuse, Dewitt, 
Ludlowville, and Ithaca, all date from the same general disturb- 
ance can scarcely be doubted, when we consider their striking 
similarity as shown by the microscope and otherwise. The Man- 
heim intrusion is known to be newer than the Utica slate; the 
Syracuse dikes penetrate the Upper Group of the Salina shales; 
the Dewitt rock cuts through the gypseous Salina shales, al- 
though the Oriskany and Helderberg formations were also 
thrown out in the excavations as indicated by the fossils; the Lud- 
lowville dikes penetrate the Genesee slate; and the Ithaca dikes, 
the Portage group. Hence they are no doubt later than the Devo- 
nian. | techie Mia 
Smith,* however, has shown that the Manheim dike occurr- 
ing as it does in one of a series of parallel faults which have 
affected the rocks from the Archean gneisses to the Utica slate, 
and which it is generally believed mark the western extension of 
the forces of the Appalachian uplift, no doubt dates from the close 
of the Carboniferous, and suggests this as the date of the others 
also. He adds that “ Diller has also suggested this as the age of 
the Elliot Co., Ky., peridotite, cutting through Carboniferous 
strata, although he considers a later date more probable.” 
THE OIL WELLS OF THE UNITED SY 3 eee 
Mr. Joun T. KILHAmM. 
NOVEMBER 21, 1902. 
I will try and make a sketch in crude oil, which will be only 
an outline, for we lack the time to go into the detail of colorings, 
shades and tints that are required to produce a finished picture in 
oil. 
Oil is a slippery subject, and this is literally true in more. 
ways than one. The study of oil should be classed with the Fine 
Arts, for like art, it has but one end, the beginning. 
*Amer. Jour. Sci., April, 1892, pp. 322-327. 
