174 J. EL. Hilgard—Magnetic Declination in the United States. 
I personally instructed in the work. In this way observations 
of the magnetic declination were made at about 200 stations, 
distributed over a large area of the interior country, at 150 of 
which stations the dip and horizontal intensity were also 
observed. These observations will be published in detail 
under the auspices of the National Academy of Sciences. 
Subsequently, when on the extension of the scope of the 
Coast Survey so as to embrace the interior country, you pro- 
posed to undertake the requisite magnetic observations, the 
board of direction of the Bache fund deemed it best to close 
the work that I had been carrying on, and to publish the 
results obtained in the most available form, beside printing the 
observations themselves as a matter of record. Such publica- 
tion can best be effected by combining them with all similar 
data available, and giving a graphic representation of the gen- 
eral result. 
In the accompanying map this has been done for the declina- 
tion (or variation of the compass) which is the element of the 
most practical utility. Since the data obtained by the Coast 
Survey form a very large part of the material used, an early 
publication in the Coast Survey Report is thought to be the 
most advantageous mode of giving the results to the country. 
The incessant demands made upon the office of the Coast 
and Geodetic Survey for information relative to the variation 
of the compass in different parts of the United States bear evi- 
dence of the appreciation in which is held the similar map 
given in the Coast Survey Report for 1865 and published in 
1867. The present map cannot fail to meet acceptably the 
constantly-increasing demand, as it is not only brought up to 
amore recent date, but is based upon a very much greater 
number of exact observations in the interior. 
Northern and of the Northwestern Boundaries by the United 
States Engineers, and those made under the direction of the 
General Land Office in tracing some of the principal meridians 
and base-lines for the surveys of the public lands and the 
boundaries of some of the Territories. Moreover, some very 
valuable observations have been furnished by private observe!s, 
which will be specified in another place. : 
I am indebted to Mr. A. Lindenkohl, chief draughtsman 1? 
the Coast and Geodetic Survey Office, for his valuable aid ™ 
the graphic construction of the [sogonic lines. 4 
It was fortunate that, for the construction of this chart, the 
- researches of my colleague, Assistant Charles A. Schott, on the 
