166 THE HOMING FACULTY. 
ception of direction acquired? I think we must say certainly 
not by the higher perfection of any sense which homing 
animals share in common with us. Insects have organs 
whose functions can only be surmised, and it is conceivable 
that they are, by their aid, sensitive to waves of motion to 
which we are insensible; but birds have no such organs, and 
if, as I suppose, they are sensitive to such waves of motion, 
it must be by means of nerves terminating at the surface of 
the body everywhere, in fact the sense of feeling adapted to 
the reception of impressions to which our nerves are insen- 
sible. The conditions require that such waves of motion 
must be continuous, omnipresent, and always flowing in the 
same direction around the globe. As far as our knowledge 
extends, the magnetic earth-current is the only wave-motion 
which fulfils these conditions. I venture therefore to sug- 
gest as a plausible hypothesis of the homing faculty in so 
many of the lower animals, that they are sensitive to the 
ever-present motion of this current. I assume that it is 
barely appreciable unless the attention is alert and directed 
to it, but the observation of their own sensations is easily 
cultivated in animals which have little else to occupy them. 
The amount of calculation concerned in keeping the outward 
reckoning of the course certainly involves greater mental 
powers than some of you will be willing to ascribe to animals; 
but allowing for the facts, first that animal intelligence being 
developed only in a few narrow grooves, may easily transcend 
ours at points, secondly that all possessing the faculty are 
great roamers, and consequently familiar with the country 
over a wide radius round their homes, which leaves room for 
the correction of a considerable margin of error in calcula- 
tion, and thirdly that even Homing Pigeons do not always 
return, and that only the cleverest of them are useful for long 
flights, I do not think that the measure of intelligence de- 
manded is Arima facie fatal to the hypothesis, 
But is the hypothesis susceptible of proof? I think so. In 
fact it is the certainty that it can be proved experimentally 
