66 National Geographic Magazine. 



diegree the spirit of progress that has ever been the active prin- 

 ciple and guide in the conduct of the work, and advanced its 

 methods to a state of perfection that has called forth the admira- 

 tion of the scientific world. 



The determination of the magnetic elements has been a sub- 

 ject of investigation from the early days of the survey ; the 

 knowledge sought was essential to the navigator, and in recent 

 years, especially, has proved to be of the greatest practical value 

 on shore. Limited by small appropriations the research was at 

 first slow. But a trust fund left by Professor Bache, who 

 always evinced the warmest interest in this particular investiga- 

 tion, added largely to the rapidity with which observations could 

 be obtained, until now we have magnetic maps of the United 

 States of such reasonable precision that they are authoritative, 

 and are in almost daily demand. The results are more far reach- 

 ing than their mere tabulation for the current year, as laws have 

 been determined by which the declination in a locality can be 

 ascertained for any year in the past. 



There are but few places where the needle remains stationary, 

 or points in the same direction, for any great length of time ; it 

 even changes daily and during the hours of a day ; but the 

 aggregate for a year will rarely exceed three or four minutes of 

 arc. If we refiect then, upon the great use made of the compass^ 

 in the settlement of the continent, and the proverbial neglect of 

 the country surveyor of those days to record the local variation, 

 or declination, with his work, we may see a little of the utility 

 and practical purposes to which the results are constantly being 

 applied. Property so little thought of a hundred years ago tliat 

 a few acres more or less, lost or acquired, in its transfer defined 

 by compass surveys, may suddenly assume a value in these days 

 of progress that every square foot is worth dollars. When a 

 dispute arises, deeds are examined, lost or obliterated mai'ks are 

 diligently sought for, perhaps one is found, surveyors are em- 

 ployed to run out the lines but only make the confusion worse. 

 Instead of a few rods that were in doubt according to the best 

 information, the surveyor's line makes it acres, and litigation, 

 looms up to eat the profits of the sudden rise, and there seems 

 even then no satisfactory solution of the vexing problem. How 

 valuable then must be the fact, that it is possible to compute the 

 variation for years back, to the time the oi'iginal survey was 

 made, and furnish the deflection that will re-run the lines so 



