1875] 



WRITINGS OP JOSEPH HENRY. 



479 



These experiments were also made with two vessels. The 

 distances and directions are giveu in Fig. 9. With the ex- 

 ception of the fourth course of the Cactus the other courses 

 would form nearly a symmetrical curve, but in this case the 

 sound of the whistle of the Cactus was lost at the point a at a 

 distance of one mile, and was afterward regained at the point 

 b, and continued audible until the steamer reached the 

 point c. 



Cncius 

 4*f*'Cotwse. -; 



"^^^ 





Fig. 9. 



This presents one of the abnormal phenomena of sound 

 which might in part be accounted for by the existence of a 

 flocculent cloud between a and 6, but whj'' the sound could 

 be heard so much farther in this direction than in the others 

 is not easy to explain on that hypothesis. 



The line h c was described after all the lines of Fig. 9 had 

 been completed, and therefore the curve given in the figure 

 correctly represents the boundary of the area of audition 

 while these courses were being run, the point a being the 

 termination, under that condition of the fourth course of 



