456 WRITINGS OP JOSEPH HENRY. [1875 



trumpet, which itself weighed eight hundred pounds, and 

 also a union of the parts of sufficient strength to resist the 

 pressure of the steam at fifty pounds to the square inch. 



August 7, 1875. — Wind from the S. S. W.: fog continued. 

 The workmen had not as yet completed the attachment. 



August 9, 1875. — Barometer 30*30 inches at 12 m. Dry- 

 bulb thermometer 74° F.; wet bulb 71°-5. Wind S. S. W. 

 Fog dense along the south coast, but light over all the 

 northern portion of the island. The echo was heard all day, 

 not very loud, but distinct. Siren still horizontal, the arrange- 

 ment for elevating it not having been — at 10 a. m., com- 

 pleted. Experiments were made on the reciprocal sounds of 

 the whistles from two steamers, the results to be given here- 

 after. At 5 p. M. the adjustment of the flexible tube to the 

 smaller end of the trumpet was finished, which giving an 

 additional length to the instrument of about 5 feet, threw it 

 out of unison with the siren proper. To restore this unison 

 the speed of revolution of the perforated plate was diminished, 

 and after this the trumpet, still being horizontal, was sounded. 

 An echo — similar in character to those which had been ob- 

 served on the preceding day, and the earlier part of the same 

 day, was produced. 



August 10, 1875.— Barometer 301 inches. Dry bulb 74° ; 

 wet bulb 69° F. Wind W. S. W. ; atmosphere hazy. Obser- 

 vations first made with the trumpet horizontal. Echo as that 

 of preceding days, distinct but not very loud, and coming 

 principally from the portion of the horizon in the direction 

 of the axis of the trumpet. The position of the trumpet was 

 then changed, its axis being turned to the zenith in order to 

 make what was thought might be a crucial experiment. 

 When the trumpet was now sounded a much louder echo 

 was produced than that which was heard with the axis of 

 the trumpet horizontal, and it appeared to encircle the whole 

 horizon; but though special attention was directed to the 

 point by all the party present, no reverberation was heard 

 from the zenith. The echo appeared however to be more 

 regular and prolonged from the ocean portion of the horizon 

 than from that of the land. 



In this experiment, while there was no reflection from the 



