DISCOVERY AND INVENTION 



By Alexander 



I AM going to begin tonight by asking 

 you a rather startling question : Did 

 you ever put your head under water 

 and chuck two stones together to see what 

 the sound is like? If you have never 

 done that, try it, and you'll get a new 

 sensation. I did it once, and it sounded 

 as if a man were hammering for all he 

 was worth at my very ear. 



I then took two tiny little pebbles and 

 tapped them together quite lightly under 

 water, and it sounded like a man knock- 

 ing at the door. It was rather startling 

 to hear such a loud, noise from such a 

 slight cause. 



Of course, the question at once arose 

 in the mind : How far off could we hear 

 the sound? So I sent a boy a hundred 

 feet up the beach with a couple of stones, 

 directing him to strike them together 

 under water. I then submerged my head, 

 and I could hear the sound about as read- 

 ily as before. 



Well, I determined to test the maxi- 

 mum possible distance, and sent the boy 

 across the bay in a boat to the other side, 

 to a point at least a mile away from the 

 place where I stood, and I followed him 

 with field glasses to see that he carried 

 out my instructions. I saw him land on 

 the other side, take off his coat, roll up 

 his sleeves, and go down to a little plank 

 wharf on the shore rising only a few 

 inches out of water. He lay down upon 

 the wharf, face downward, and put his 

 hands into the water, and I then knew he 

 was making signals with these stones. 



Now, the question was : Could I hear 

 him ? Quietly and gently I went into the 

 water at my side of the bay, submerged 

 my head, and listened for all I was worth. 

 Well, you know, the signals came per- 

 fectly clear and distinct, through more 

 than a mile of water, to my ear. It was 

 one of the most astonishing revelations of 

 what could be done with water. 



You know if you look away in the 

 distance at a man firing a gun you can 

 see the flash, and after a time you get the 



*An address to the graduating class of the 

 May 22, 1914. 



Graham Bell 



report ; the sound takes time to travel 

 through the air. It goes about 1,100 feet 

 per second ; but in the water it goes five 

 times as fast as that — over 5,000 feet per 

 second. Water is a much better conductor 

 of sound than air. 



DO FISH SIGNAL TO ONE) ANOTHER BY 

 SOUNDS ? 



Reflecting upon these various experi- 

 ments, the thought occurred: If two little 

 stones tapped together can be heard under 

 water, why, every tiny lobster that snaps 

 his claws must make an audible click. I 

 wonder if there are creatures in the water 

 that signal to one another by sound. 



Well, I had occasion to try it once. 

 Bathing in the Grand River in Ontario a 

 great many years ago, I put my head very 

 gently under water and listened, and, sure 

 enough, "tick, tick," came a sound like a 

 grasshopper's chirrup, and a little while 

 after that a chirrup on the other side. 

 There were creatures under the water 

 that were calling to one another. 



I don't know whether all fish make 

 sounds or not, but there are some fish that 

 certainly do. The drumfish on our coast 

 drums away in the water so loudly that 

 you can hear him while you are walking 

 on the shore. 



It is also a significant fact that all fish 

 have ears. Why should they have ears 

 if there is nothing for them to hear? 



Of this we may be certain — that there 

 is a whole world of sound beneath the 

 waves waiting to be explored, perhaps by 

 some of you. 



I have wanted you to see how one obser- 

 vation leads to another. Starting with a 

 very small thing — the chucking together 

 of two pebbles under water, and follow- 

 ing this up by other observations — we 

 broaden our field of knowledge and reach 

 generalizations of considerable magni- 

 tude as the resultant of numerous small 

 thoughts brought together in the mind 

 and carefully considered. 



Friends' School, Washington, D. C, delivered 



649 



