84 Recent Literature. [j^'q 



Further proof against the ability of the birds' sight being sensitive to 

 objects far distant is given in the mathematical fact that the curvature of 

 the earth would necessitate a bird ascending nearly a mile in the air to 

 reach rays from a lighthouse 150 feet high and 100 miles distant, granting 

 the absence of haze which is almost always present. 



It has moreover, been proven that vision in the chick is much less 

 acute than in man and Dr. Watson shows that neither the chick nor the 

 pigeon are sensitive to infra-luminous rays. 



In the terns he also proves that there is no special tactual or olfactory 

 mechanism in the nasal cavity which could aid homing. The facts pre- 

 sented are admittedly negative but Dr. Watson says, " the task of explain- 

 ing distant orientation is an experimental one, which must yield positive 

 results as soon as proper methods are at hand." While the difficulty of 

 explaining it by current theories is admittedly great he does not suggest 

 " the assumption of some new and mysterious sense." 



He suggests work on the sensory equipment of homing pigeons saying 

 that "it is just possible that these animals possess on certain parts of the 

 body (eyelids, ear covering, oral cavity, etc.), sensitive tactual and thermal 

 mechanisms which may assist them in reacting to slight differences in 

 pressure, temperatm-e, and humidity of air columns." 



This contribution contains also a review of the various theories that have 

 been advanced to explain homing, as well as a wealth of detailed investiga- 

 tion that cannot be dealt with here. Much reliable information with 

 regard to homing pigeons and their flights gathered from practical fliers is 

 likewise presented — data which have been in much demand. Ornitho- 

 logists would do well to read the paper in its entirety as it is a good ex- 

 ample of the methods of the student of behavior in eliminating complicating 

 factors and avoiding the unwarranted conclusions into which the untrained 

 investigator rushes blindly. While the ' mystery of mysteries ' still re- 

 mains unsolved, Dr. Watson has made great advances in showing us what 

 factors are not involved in its explanation, and in disposing of a host of 

 theories which tended only to obscm-e the problem, thus leaving it clearly 

 defined for future investigators. — W. S. 



Thorburn's ' British Birds.' ^ — It might be supposed that there was 

 not room for another work on a subject that has received as much attention 

 as the birds of Great Britain; but anyone who examines Mr. Thorbm-n's 

 work, even casually, will we think concede that he has proved the error of 

 this assumption. 



With the wealth of data which is available any competent writer may 



1 British Birds | written and illustrated by | A. Thorburn, P. Z. S. | with eighty 

 plates in colour, showing over 1 four hundred species | In foiu" volumes | Vol. 1 | 

 Longmans, Green and Co. | 39 Paternoster Row, London | P'ourth Avenue & 

 30th Street, New York i Bombay, Calcutta, and Madras | 1915. Large 4°. pp. 

 i-viii + 1-143, pis. 1-20. $40 for the set of four volumes, or payable on delivery 

 at $10 each. No volumes sold separately. 



