i 7 2 THE POPULAR SCIENCE MONTHLY. 



begun. We also know how quickly animals acquire the idea of the 

 time of day. Sparrows know when it is time for the bread to be 

 thrown out for them, and collect around the spot at that hour. Lace- 

 pede tells of a toad which used to come out of its hole at the time 

 it was accustomed to be fed. I had a lizard that would leave its nest 

 and climb up my sleeve at dinner-time. Persons of my age, in Liege, 

 used to be acquainted with a vagabond dog that regularly at the same 

 hour made the round of the cafes for the bones or the lumps of sugar 

 which he was sure to receive from his friends there ; and would as 

 regularly every evening go to his sleeping-place under a particular 

 gateway. This animal evidently perceived the time of day by certain 

 signs that had been taught him by observation ; and M. Dubuc's dog 

 knew when it was Sunday, or hunting-day, by the same means. And 

 if, on some Saturday, the house had been arranged and the household 

 had managed to behave in the manner usual to Sunday, the dog too 

 would have been found all prepared for his anticipated hunting excur- 

 sion, just as if it had not been one day short of his accustomed seven. 



This faculty of attentive observation of dogs may be stretched so 

 far as to deceive an experimenter who is a little prepossessed on the 

 subject. 



In his paper before the British Association at Aberdeen, Sir John 

 Lubbock related how Mr. Huggins, having arranged cards bearing the 

 ten ciphers, gave his dog a problem, such as to give the square root 

 of nine, or of sixteen, or the sum of two numbers. He would then 

 touch each card in succession, and the dog would make a sound to 

 inform his master when he came to the right one. The dog was 

 always right. The secret of the experiment was that Mr. Huggins un- 

 consciously informed the dog by his attitude when he came to the 

 card that gave the answer. Sir John Lubbock tried to train his dog 

 not to take a piece of bread till he had counted seven ; but when 

 he used a metronome the dog showed that he was lost. I made 

 analogous and systematic experiments with my Mouston. They ex- 

 tended to the number four, and I aimed to make the sign of the num- 

 ber more and more indistinct, on each repetition of the experiment. 

 As soon as it was quite effaced, the dog lost his knowledge of it, and 

 his perplexed and inquiring look was amusing. 



Sir John Lubbock mentions that Lichtenberg pretended to have a 

 nightingale that could count three. Every day he gave it three meal- 

 maggots, one at a time, and the bird never came back after it had got 

 the third. This observation is very interesting, but we ought to know 

 whether the nightingale did not perceive by some sign that the meal 

 was over. I have no doubt that, if, in the experiments which I have 

 made on siskins and gold-finches, I had had only three grains of hemp- 

 seed in my mouth, they would not have returned after having taken 

 the third seed, or at least would have been likely not to return ; but in 

 fact I had many grains, and I frightened them away when they had 



