106 SECRETS OF ANIMAL LIFE 



base of the wing. Chirping or trilling is due to some 

 sort of " stridulating " organ, one hard part being 

 scraped against another, as the bow on the fiddle 

 it may be leg against wing, or limb against body. 

 A true voice, due to the vibration of vocal cords 

 as the air from the windpipe passes over them, 

 began in the amphibians, but did not come to its 

 own till birds and mammals appeared on the scene. 



As the inorganic sounds of Temperate zones are, 

 on the whole, less violent than those of the Tropics, 

 so is it also with the sounds made by our animals. 

 They may be included in the reproach implied in 

 Heine's definition of silence as the conversation of 

 an Englishman. How little we have that can be 

 compared with the serenading of the tree-frogs, the 

 orchestra of grasshoppers and Cicadas, the chatter 

 of parrots and monkeys in warmer countries! 

 Except during the time of bird-courtship our coun- 

 try is certainly very quiet. We visited the other 

 day an apiary with about a hundred hives; the 

 air was thick with bees, and their coming and going 

 along the broad glass-covered tunnel of an observa- 

 tion hive was like the Strand at a crowded hour. 

 There were hundreds of thousands of bees, and 

 though the hum was stronger than we ever heard 

 before, even in an avenue of lime-trees in flower, 

 it merely filled the air with a pleasant, tremulous 

 bourdon of sound. 



We went in the August gloaming to a beautiful 

 lake hidden in a forest of Scots pine and spruce. 

 As far as one could see there were only two birds 



