DRIVING A NAIL UNDER WATER. 



679 



be seen, alter this darkness. The distrust of his sight grows 

 stronger in the diver with his experience. The eye is accus- 

 tomed to judge of form, proportion and distance, in a thinner 

 medium, and is continually deceived in a denser one, until ex- 

 perience has taught the diver how to estimate rightly the differeni 

 impressions. Perhaps the most striking illustration of this 

 difference, the diver finds in trying to drive a nail under 

 water. If depending on sight, untaught by experience, he is 

 sure to fail. lie will instinctively strike just where the naii 

 is not. For this reason, even the electric light below the 

 water, does not furnish all that is wanting : the familiar medium 

 of the upper world is wanting, and this the electric light does 

 not supply. By practice, therefore, the diver learns to depend 

 entirely upon the sense of touch, and with experience, becomes 

 able to engage in works under the sea which require labor and 

 skill, with the easy assurance of a blind man who finds his 

 way with confidence along a crowded thoroughfare. 



The conveyance of sound through water is so difficult, that 

 under the sea has been called the world of silence. But this 

 is not strictly correct. Some fish have the power of making 

 sounds, and they all have simple and imperfect auditory organs* 

 To the diver, however, save for the cascade of air through his 

 air-pipe, the sea is silent. No shout, or word from above, 

 reaches him. A cannon shot is dull, and muffled, and if dis- 

 tant, he does not hear it. A sharp, quick sound, especially if 

 produced by striking something on the water, can be heard. 

 The sound of driving a nail on the ship above, or a sharp 

 tap on the diving-bell below, can be heard. Conversation 

 between two divers, below the water, is, by the ordinary 

 methods, impossible, but by touching their helmets together, 

 they can converse, the vibrations being transmitted through 

 the metallic substance, and to the air inside. 



The diver has also a new revelation of the character and 

 beauty of fish and other inhabitants of the sea when he thus 



