Let us consider next an observation which shows a very high degree of perceptual intelligence on the part of the dog. Several observers have described dogs, which had occasion to swim across a stream, entering the water at such a point as to allow for the force of the current. And both Dr. Rae and Mr. Fothergill communicated to Mr. Romanes instances[GW] of the dog's observing whether the tide was ebbing or flowing, and acting accordingly. Now, I believe that the dog performs this action through intelligence, and that man explains it by reason. The dog has presumably had frequent experience of the effect of the stream in carrying him with it. He has been carried beyond the landing-place, and had bother with the mud; but when he has entered the stream higher up, he has nearly, if not quite, reached the landing-stage. His keen perceptions come to his aid, and he adjusts his action nicely to effect his purpose. On the bank sits a young student watching him. He sees in the dog's action a problem, which he runs over rapidly in his mind. Velocity of stream, two miles an hour. Width, one-eighth of a mile. Dog takes ten minutes to swim one-eighth of a mile. Distance flowed by the stream in ten minutes, one-third of a mile. Clever dog that! He allows just about the right distance. A little short, though! Has rather a struggle at the end. The dog intelligently performs the feat; the lad reasons it out. I do not know whether I am making my point sufficiently clear. A wanton boy is constantly throwing stones at birds and all sorts of objects. He does not know much about the force of gravitation or the nature of the curve his stone marks out; but he allows pretty accurately for the fall of the stone during its passage through the air. He acquires a catapult; and, being an intelligent lad, he perceives that he must aim a little above the object he wishes to hit. This is a perceptual inference. Reason may subsequently step in and explain the matter, or very possibly, being human, sparks of reason fly around his intelligent action. Am I using the word "reason" in an unnatural and forced sense? I think not. My use is in accord with the normal use of the word by educated people. Two men are working in the employ of a mechanical engineer. Listen to their employer as he describes them. "A most intelligent fellow is A; he does everything by rule of thumb; but he's wonderfully quick at perceiving the bearing of a new bit of work; he sees the right thing to do, though he cannot tell you why it should be done. Now, B is a very different man; he is slow, but he reasons everything out. A knows the right thing to do; and B can tell you why it must be done. A has the keenest intelligence, but B the clearest reasoning faculty. If I have occasion to question them about any mechanical contrivance, A says, 'Let me see it work;' but B says, 'Let me think it out.'"