PHILOSOPHICAL SOCIETY OF WASHINGTON. 145 



connect a rubber tube with the mouth of the test-tube, placing the 

 other end of the pipe to the ear. Then focus the intermittent beam 

 upon the substance in the tube. I have tried a large number of 

 substances in this way with great success, although it is extremely 

 difficult to get a glimpse of the sun here, and when it does shine 

 the intensity of the light is not to be compared with that to be 

 obtained in Washington. I got splendid effects from crystals of 

 bichromate of potash, crystals of sulphate of copper, and from 

 tobacco smoke. A whole cigar placed in the test-tube produced a 

 very loud sound. I could not hear anything from plain water, but 

 when the water was discolored with ink a feeble sound was heard. 

 I would suggest that you might repeat these experiments and extend 

 the results," &c, &c. 



Upon my return to Washington in the early part of January.* 

 Mr. Tainter communicated to me the results of the experiments he 

 had made in my laboratory during my absence in Europe. 



He had commenced by examining the sonorous properties of a 

 vast number of substances enclosed in test-tubes in a simple em- 

 pirical search for loud effects. He was thus led gradually to the 

 discovery that cotton-wool, worsted, silk, and fibrous materials 

 generally, produced much louder sounds than hard rigid bodies 

 like crystals, or diaphragms such as we had hitherto used. 



In order to study the effects under better circumstances he en- 

 closed his materials in a conical cavity in a piece of brass, closed 

 by a flat plate of glass. A brass tube leading into the cavity 

 served for connection with the hearing-tube. When this conical 

 cavity was stuffed with worsted or other fibrous materials the 

 sounds produced were much louder than when a test-tube was em- 

 ployed. This form of receiver is shown in Figure I. 



Mr. Tainter next collected silks and worsteds of different colors, 

 and speedily found that the darkest shades produced the best effects. 

 Black worsted especially gave an extremely loud sound. 



As white cotton wool had proved itself equal, if not superior, to 

 any other white fibrous material before tried, he was anxious to 

 obtain colored specimens for comparison. Not having any at hand, 

 however, he tried the effect of darkening some cotton-wool with 

 lamp-black. Such a marked reinforcement of the sound resulted 

 that he was induced to try lamp-black alone. 



About a teaspoonful of lamp-black was placed in a test-tube and 



* On the 7th of January. 



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