432 FIRST REPORT UPON MAGNETIC WORK

miles of land area—such a variety of geological formations as Mary-
land. To quote from the report of the State Geologist: " The most
ancient rocks which make up the earth's crust as well as those still in
the process of deposition are here found, while between these wide
limits there is hardly an important geological epoch which is not
represented. " The investigation of the local disturbances, which are
quite marked in certain regions, and their correlation with geological
structure will, therefore, be of peculiar interest and value in this state.

GENERAL ACCOUNT OF THE MAGNETIC SURVEY OF

MARYLAND.

INTRODUCTORY REMARKS.

In the summer of 1896, while spending a vacation at a little village,
Linden, nine miles north of Washington City, I made some magnetic
observations which clearly showed that the distribution of the earth's
magnetism is quite irregular in the vicinity of Washington—a fact
already noticed to some extent by the observers of the Coast and
Geodetic Survey. It seemed to me most desirable to extend the in-
vestigations over a larger area, if possible, and, accordingly, I laid my
plans for a detailed magnetic survey of Maryland before Professor
William Bullock Clark, in charge of the recently organized Geological
Survey of Maryland. Professor Clark heartily endorsed the idea of
a detailed magnetic survey and authorized me in a letter dated July
25, 1896, to proceed as soon as possible with the survey, putting a
sum of money at my disposal which, with careful management, it
was hoped would suffice to make magnetic observations at one or two
stations in each of the twenty-three counties comprising the state.
With the aid of additional funds, obtained as already stated in the
Introduction, the number of stations at which observations were
made during 1896 could finally be increased to 46, thus averaging