Some students have leaned strongly toward the possible existence of a "magnetic sense" as being the important factor in the power of geographical orientation. The theory that migratory birds might be responsive to the magnetic field of the earth was conceived as early as 1855, when some experimental work was done in Russia, and nearly 60 years later in France. Recently investigations in this field have been conducted by Yeagley (1947) and by Gordon (1948) with diametrically opposite results. The idea carries with it the implication that contained in the bird's body is an organ that is sensitive to the effect of its motion through the vertical component of the magnetic field and to other related factors. In the tests by Dr. Yeagley, 20 young homing pigeons were given training flights to their home loft from distances up to 100 miles. Permanent magnets were then affixed to the under side of the manus part of the wings of half of the birds while copper plates of equivalent weight were attached to the wings of the other half. All birds were released singly at an air-line distance of about 65 miles from the loft. The results were most suggestive, as only two of the birds carrying magnets returned to the loft, whereas eight of the controls returned. With certain minor modifications, this experiment was repeated by Gordon. In this case 60 pigeons were used and releases were made from points up to 58 miles, where the direction of flight was such that the birds had to navigate across the gradient of the magnetic field. Every bird returned to its loft on the day of release regardless of whether it carried magnets or unmagnetized bars of the same weight. Attempts to demonstrate the effect of radio waves on the navigational ability of birds also have produced contradictory results. In some of these tests, homing pigeons released near broadcasting stations have appeared to be hopelessly confused, whereas in others, apparently conducted in the same manner, no effects could be discerned. It is obvious that before the electromagnetic theory can be accepted or rejected, much additional experimental work is necessary.