1874] WRITINGS OF JOSEPH HENRY. 429 



axis of the trumpet on the east side, the sound grew slightly 

 less loud until the prolongation of the side of the trumpet 

 was reached, when it became comparatively faint and con- 

 tinued so until the line between the whistle and observer 

 was entirely unobstructed by the side of the trumpet, when 

 the sound was apparently as loud as in the prolongation of 

 the axis itself. On the west side of the axis of the trumpet, 

 the sound in a like manner diminished from the axis until 

 the prolongation of the side of the trumpet was reached, 

 when it became feeble, again slightly increased, and then 

 gradually diminished until the line of direction made an 

 angle of about 80° with the axis of the trumpet, when it 

 ceased to be heard at a distance of about one and a half 

 miles. It should be observed however that at this point the 

 line of sight of the observers was obstructed by the side of 

 the trumpet and the smoke-stack of the boiler. The wind 

 was light, at south-southwest, approximately in opposition 

 to the direction of the sound when it ceased to be heard. 



We are informed that complaints had previously been 

 made by officers of steamers passing near this point that 

 the sound was here inaudible previous to the introduction 

 of this trumpet; it would therefore follow that it is of no 

 use to increase the effect on the western side of the axis, 

 and is of injurv to the sound on the lines of prolongation 

 of its sides. If the sound should cease to be heard at the 

 point mentioned when the trumpet is removed, the only 

 apparent cause of the phenomenon will be the prevailing 

 direction of the wind, which coming from the south-west 

 will be in opposition to the sound of the whistle; but in the 

 case of the present investigation the force of the wind was 

 so small that it scarcely appeared adequate to produce the 

 effect, and this question therefore must be left for further 

 investigation. It may be important to state that in the case 

 where the sound ceased to be heard, it was regained by sail- 

 ing directly toward the station about one mile, or at half a 

 mile from the station. 



After making the foregoing observations as to the in- 

 tensity of sound in different directions from the station, 



