degree the spirit of progress that has ever been the active principle and guide in the conduct of the work, and advanced its methods to a state of perfection that has called forth the admiration of the scientific world.
The determination of the magnetic elements has been a subject 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 investigation, 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 reaching 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 reflect 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 that 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 marks are diligently sought for, perhaps one is found, surveyors are employed 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 original survey was made, and furnish the deflection that will re-run the lines so
