98 NATURE-STUDY REVIEW [7 14— Apr., 1911 



duce another echo, and if we listen we might possible hear the 

 third, produced from the first. There are places in the great 

 hills and mountains where the echo is repeated until it seems to 

 have wandered away over to the country miles away. In such 

 places music or song of short duration produces the best results. 



It may pay us to listen to the whistle of the locomotive as 

 the train speeds along through the country. It very often pro- 

 duces a very pleasing echo. Such is often heard by passengers 

 on the rear end of the train to which the locomotive is attached. 

 There is an instance recorded where the echo of a locomotive 

 whistle was so distinct from the opposite direction from the 

 actual sound that a gentleman was misled by the sound and was 

 run down and killed by the train. 



It is interesting to watch cattle or dogs bawling or barking 

 in answer to another supposed animal, when it is nothing but 

 an echo. 



Those who cannot go to the country may study the echo if 

 they will but watch and listen. The shape and size of city build- 

 ings, and the width and angle of streets and alleys will very 

 often produce some interesting echoes which are easily studied. 

 A very good way to do in the city is to move about quietly, or 

 remain at the open window, and listen for the echo from some 

 sound produced by some one else. There will be plenty of 

 sounds. The peculiar whir of an electric car as it approaches 

 the corner is often reproduced on some building, making it seem 

 as if the car was approaching from some other direction. The 

 puffing of a locomotive as it moves through the railroad yards, or 

 out along the track, often makes a very interesting echo, as it 

 sounds as if there were several locomotives. The writer once 

 knew a lad who called from his window to produce an echo, and 

 in doing so he caused a neighbor boy to think he was making 

 sport of him, and it resulted in a quarrel ; and another who, 

 calling his sister who was on the street, heard an echo, and 

 thought it was some one mocking him, and he was ready for a 

 fight. 



In some localities the heavy rain clouds that sometimes pass 

 over, leaving a calm, cool atmosphere, will send back an echo. 

 This is caused by the weight and density of the rain cloud. Much 

 of the rumbling of the thunder we hear during a storm is the 

 echo of the first report produced by the great sound waves strik- 

 ing both the hills and heavy clouds. In many deep canons in the 

 rugged mountains, and in some caves, the echo is something 



