762 THE POPULAR SCIENCE MONTHLY.
easily be indicated by a bending of the sensory hairs of the eristcB acousticcB as the liquid in the semicircular canals is thrown this way or that by angular deviation of line of motion. Experi- mental test of the theory is impossible, since, after injury of a single semicircular canal, the birds refuse to fly at all. It must rest, therefore, upon facts obtained from observation of habits and methods employed by homing pigeons. If it is true, there should appear some relation between the flight of a bird home and the course by which it has been carried to the place of libera- tion. It should either tend to retrace its course or to follow a straight line home. However, the writer has not been able to record a single fact which points in this direction.
Graver objections must be admitted to obtain against the theory of M. Caustier, tinted as it is by the " electro-magnetic " romancing of the French hypnotists. He tells us of the bird, en- dowed with " une nature eminemment eledrique," of " Velectricite de I'air," of " magnetisme terrestre," of " Vaction physiologique du magnet isme," and the like. This means that pigeons can sense cur- rents of atmospheric electricity or terrestrial magnetism in such a manner as to be guided by them ; and this can hardly stand even as passing theory, while it remains so thoroughly proved by the experiments of Hermann,* and these have been confirmed with powerful dynamos in at least two laboratories in this coun- try, that the magnetic field has not the least physiological influ- ence (" nicht die geringste Wirhung ") upon the action of any tissue or sense organ or upon the animal as a whole.
But what say homing pigeons for themselves ?
Of first importance to the study of a homing instinct is the method which an animal employs to mark or locate its home. On leaving a new camp for a day's hunt in the Bad Lands, a man naturally turns about and makes a mental note of prominent buttes in the vicinity. This butte with three pine trees on top is just to the left of the gulch where the tents are pitched. " I can tell it as far as I can see it," and he strikes out. Why may not other animals adopt a similar method ? Concerning bees, Thomp- son has observed that, " if the position of a hive be changed, the bees for the first day take no distant flights till they have thor- oughly scrutinized every object in its neighborhood." This would seem to indicate a rational method of procedure.
Upon their arrival in Madison, Wis., from Worcester, Mass., the pigeons were kept confined in a large loft which had but one window, and this happened to be upon the side next another barn close by, so that it afforded no view of the surrounding country.
- Hermann. Hat das magnetische Feld direkte physiologiscbe Wirkung ? Pfluger's
Archiv, vol. xliii, p. 217, 1888.