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 
