DEPARTMENT OF THE INTERIOR

UNITED STATES GEOLOGICAL SURVEY

WASHINGTON D. C.

July 29, 1985

My Dear Sir:-

I have great pleasure in fulfilling my promise of
some weeks ago, by mailing to your address herewith a copy of
one of a few advance copies of our general geologic map of the
United States just received from the printer.

Believe me to remain,

With great respect,

DEPARTMENT OF THE INTERIOR

WASHINGTON D. C.

Oct. 20, 1885.

Dear Sir:

On looking over matters in the drafting room, I find that
your large map has not yet been completed - my draftsman having
found certain discrepancies between our base and your map, in
regard to which he required specific instructions from me.
These instructions have just been given; and the map will be
completed about the end of this week or early next, and will be
shipped to you immediately. The advices which you mention to
me must have related to the advance copy of our general map
which I had communicated to your address some months ago.

I enclose with pleasure the amount which you handed me
in New York.

DEPARTMENT OF THE INTERIOR

WASHINGTON D. C.

Dec. 21, 1885.

Dear Sir:

I have just received the parcel containing a vertebra
from Walker river, and a bone from Putnam's ranch. I am now sat-
isfied that the greater part of the collection made by me in the
Walker river canon has never reached your hands, but has been
lost, I fear irretrievably, either at Salt Lake City, in this Of-
fice, or in the National Museum. I regret the necessity for
troubling you so greatly in my unsuccessful search for the col-
lection.

Believe me to remain,

Very truly yours,

Prof.O.C.Marsh,
Paleontologist, U.S.G.S.,
New Haven, Conn.

DEPARTMENT OF THE INTERIOR

WASHINGTON D. C., Sep. 30, 1887.

My dear Sir:

Owing to absence from the city your favor of the 21st inst., in which you announce that you will send an experienced collector to examine the Potomac Formation for vertebrate fossils, about October 1st, did not reach me until today.

There is no map in existence representing the geographic distribution of the Potomac Formation, and it will be impossible to prepare one in time for transmission to you before the first proximo. I will, however, enclose a list of localities in which the formation occurs north of Washington, which will be of use to Mr. Hatcher in case he decides to collect between New Haven and this point. The most promising localities are in the immediate vicinity of this city; and it will in my judgment be best for Mr. Hatcher to report here to me, when I will direct him to points at which vertebrate remains have been found, and will then prepare a MS map locating other outcrops of the formation, or will give him

O.C.M. #2.

Oral information concerning these exposures, as he may deem best.

Until recently we have not expected Major Powell to return to Washington before say the middle of November; but since we just learned that Mrs. Powell will reach the city about the 21st proximo, we infer that the Major will hasten his return.

Immediately on my return from New York I had your large map boxed, and on leaving for the west a day or two later, left instructions that it should be forwarded to you. Through some oversight this was not done; but I have arranged today for its shipment.

I remain with great respect,

Prof. O. C. Marsh,

U.S.Geological Survey,

New Haven, Conn.

# Exposures of the Potomac Formation.

The northernmost exposure of rocks believed to represent this formation is in the "Sand Hills" surrounding a prominent trap dyke on the "Straight Pike" half way between New Brunswick and Princeton, N.J. The deposit here is a friable ferruginous sandstone, with no traces of organic remains, so far as observed, except bits of lignite and occasional woody impressions.

The next formation is "Yellow Rocks" near the Insane Asylum two or three miles northwest of Trenton. The deposit here is a felspathic sandstone containing sparsely disseminated pebbles of quartz and quartzite, interstratified with pebble beds; the whole occasionally undurated. No organic traces were here observed.

The next considerable masses of the formation occur just behind (i.e., northwest of) Edge Hill and Chestnut Hill, Pennsylvania. The deposits here consist of felspathic sands and quartzitic gravel beds, never well exposed, without traces of organic remains so far as observed.