THE TILT BOX. 167 



much on fclieir ears, and as nature has taught them, 

 during thousands, or perhaps millions, of generations, 

 to give heed to a language among themselves, they have 

 a natural aptitude for learning the meaning of sound 

 signals. After they have been taught, they will heed a 

 bell hung at a great distance from their apartment, or, 



D 



FIG. 72. TILT BOX REVERSE OF FIG. 76. 



as we have said, the slightest noise made by the friction 

 or jarring of the feed-dropping apparatus, or its connect- 

 ing parts, will render a bell unnecessary. 



In Fig. 71, the axle, 14, is represented as fitted with 

 a ratchet, 17, and pawl, 18 ; but these are unnecessary, 

 the friction of 14 against its wooden supports being suf- 

 ficient to hold it in the position it is left by the operator, 

 unless the axle supports quite a long row of cylinders. 



