MARYLAND GEOLOGICAL SURVEY 401

———— Topographical Sheets. Gunpowder.

13 5/8x17 1/2, 20 ft. contour. Scale 1/62500.

———— Topographical Sheets. Harpers Ferry.

133 5/8x17 1/2, 100 ft. contour. Scale 1/62500,

Topographical Sheets. Laurel.

133 7/8x17 1/2, 20 ft. contour. Scale 1/62500.

Topographical Sheets. Mt. Vernon.

133 7/8x17 1/2, 20 ft. contour. Scale 1/62500.

———— Topographical Sheets. North Point.

133 7/8x17 1/2, 20 ft. contours. Scale 1/62500.

———— Topographical Sheets. Relay.

13 5/8x17 1/2, 20 ft. contour. Scale 1/62500.

———— Topographical Sheets. Sharps Island.

13 7/8x17 1/2 20 ft. contour. Scale 1/62500.

VAN DER HOOGT, C. W. (Sec). Map of Maryland, Delaware and
District of Columbia prepared by the State Bureau, of Immigration.

21x13 1/4, counties colored. Scale about 12 miles to an inch. (J. H. U.)

ADDENDA.

BAIRD, G. W. Experiment to Determine the Economic Vaporiza-
tion of George's Creek Cumberland Coal, Under Conditions of Actual
Practice on board the Dolphin in port.

Jour. Amer. Soc. Naval Eng., vol. vii, 1895, pp. 329-331.

The most careful determinations yet made are here recorded.

HAYDEN, H. H. Geological Sketch of Baltimore. (Baltimore
Medical and Philosophical Journal, vol. I.)

Bruce's Amer. Min. Jour., vol. i, New York, 1814, pp. 243-248.
This is practically a reprint of the earlier publication written as an abstract by the
author.

MITCHILL, SAML. L. A Sketch of the Scenery in the region around
Harper's ferry, where the ridge of Blue Mountains is penetrated by
the joint waters of the Potomac and Shenandoah rivers. In a letter
.... to the Editor; dated Harpers ferry, July 4th, 1812.

Bruce's Amer. Min. Jour., vol. i, New York, 1814, pp, 211-218.

The author discusses the geology and stratigraphy along the Potomac between
Harper's Ferry and Washington and regards the slates as older than the limestones.