the slightest hesitation, toward the end of the boat nearest home. To make doubly sure that vision was impossible, Tom was wrapped up and gently held flat in the bottom of the boat. This made no difference. Whether the boat was turned by a single stroke, as on a pivot, or rowed slowly around in a circle, the result was always the same. Tom went, without hesitation, invariably to the end or side of the boat nearest home.
Members of the party were blindfolded and required to guess whether the boat was turned or allowed to stand still, or was rowed in a straight line or in a circle; and it was an even chance whether they guessed right or wrong. Tom had a far better head for direction than any of us.
It was suggested that possibly a gentle current of air might be serving Tom as a direction-constant. This, however, could hardly have penetrated the shawl, and certainly not when in the bottom of the boat. Still, might not such a current be conveying odors imperceptible to man, but not to a cat? None of our number could feel the slightest breath of air on our faces, and even with the moistened finger held above the head, it was impossible to detect any flow of air. Might not then a wake of odor hanging in the air over our course serve as the needed direction-constant? This could hardly be, since we had rowed about so much that anything of the sort must have become thoroughly diffused.
Sight, smell, and touch would thus seem to be inadequate to explain the feat. Hearing still remains. But not a sound from any shore broke the silence. No town or city was near to furnish a roar, hum, or series of sounds of any sort. We could hear no bands of music, nor even the occasional bark of a dog. For minutes at a time we could hear absolutely no sound. And yet, may it not be that Tom heard every note some Tabby was making on the shore a mile away? If we were dealing with a sense as delicate as this, further experiment was useless. We had no means of stopping Tom's ears, and no microphone with which to explore the darkness for sounds inaudible to our ears.
The above explanation is open to serious objections. The chief of these, aside from such acuteness of hearing, is the fact that at no moment during the hour or more we were experimenting with him did Tom show the least doubt as to his direction. The auditory constant, therefore, must have been uninterrupted, and supposing it to have been the mewing of some cat, or cats, we all know what the possibilities are. At the time, the writer was quite convinced to the contrary, but several years afterward an incident occurred which threw the balance of probability strongly toward the side of the auditory explanation.
While hunting deer in Montana, I once lay on the top of a hill watching a doe as she kept guard while her two fawns were feed-