MARYLAND GEOLOGICAL SURVEY 487

information is contained in Table XIV. The total number of observa-
tions utilized is as follows:

		Maryland
		Geological	Coast and Geodetic
		Survey.	Survey and others.
	Maryland ..............................	...... 38	28
	District of Columbia ....................		4
	Delaware ..............................		9
	Pennsylvania, near the Md. Boundary		23
	Virginia, " " "		9
	W. Virginia, " " "		10
	Total...................	...... 38	83=121

Taking the total number of observations in Maryland, 56, the sta-
tions averaged one to every 218 square miles (564 square kilometers)
of the total area (land and water 12,210 square miles); or, for every
area 15 miles square there was, on the average, one station.

The preliminary reductions of my observations to the mean of day
(24 hours), and the corrections on account of magnetic disturbances,
were made as fully explained elsewhere. The reasons have also
been given for referring the chart to the year 1900. The corrections
necessary to reduce the 1896 observations to January 1st, 1900, were
made assuming for the present that the secular change is at the rate
of 3' per annum over the entire state. From the auxiliary table
X!A we find that the average annual change between 1895 and 1900
is as follows:

		/		/
	I.	3.8	V.	2.8
	IL	3.6	VI.	3.4
	III.	2.6	VII.	2.8
	IV.	3.2	VIII.	3.4
		3.0		3.1

The geographical positions which I assign to my stations are for
the time being taken from the following sources:

Stations 1, 1A, 2, 3, 4, 5, 6, 19, 20, 20A, 26, 28, 31, 34, 32A,
40, 41, 42, from the topographic sheets, of the U. S. Geological
Survey.

Stations 7, 8, 9, 10, 11, 13, 14, 15, 16, 17, 17A, 18, 21, 22, 24,
27, 29, 33, 35, 36, 37, 38, 43, from Martenet's map (3 1/2 miles to the
inch) for 1886.