500 EESEAECHES IN SOUND. 



Cape Ann Light- Station, Massachusetts, August 31, 1873. — This is one of 

 the most important stations on the New England coast. It is furnished 

 with two first-order lights, and a 12-inch steam- whistle, actuated by 60 

 pounds pressure of steam. The present is the foiu?th engine which has 

 been erected at this station, in consequence of the complaints either as 

 to the inefficiency of the sound or its failure to be heard in certain direc- 

 tions. It was at first proposed to sail entirely around the island in order 

 to test the intensity of the sound in different directions, but this was 

 I found impracticable on account of want of depth of water on the inland 

 'side ; the observations were therefore confined to the direction in which 

 complaints had been made as to the deficiency of the signal, namely, in 

 a southerly direction. The result of these observations, the points of 

 which included an arc of 120°, was that the sound was heard with equal 

 intensity except when the direction of the station was to the northward 

 and eastward of the observers ; then, in one instance, the sound became 

 very indistinct, and in another was entirely lost, both at a distance of 

 about two miles. In these cases the line of sight between the observers 

 and the signal was interrupted, in the first by a small building, the gable- 

 end of which was within 10 feet of the whistle, and in the second by the 

 south light-tower, which is within 30 feet of the whistle. In this series 

 of experiments, as with the last, the wind was against the sound; the 

 efiect was noted by passiug over the arc several times at different dis- 

 tances. The wind was from the southward and westward and very 

 light, and the sound was finally lost at about six miles, and in the direc- 

 tion of the obstructions. 



Boston Light- 8tativ7i, Aiigust 31, 1873. — The light-house is situated on 

 a low, rocky island, on the north side of the main outer entrance to Bos- 

 ton Harbor, nine miles from the city. It is furnished with three caloric 

 engines, two of the second class and one of the first. The two second- 

 class engines are so arranged as to act separately or together, and in the 

 latter arrangement serve to duplicate the larger engine. At the time 

 tlie observations were made, the larger engine was about being repaired, 

 and one of the smaller engines with the double air-reservoir was used. 

 The larger engine is used with 12 pounds pressure of air, which falls to 

 S pounds in producing the sound. The smaller engine, with the double 

 reservoir, is started with 1) pounds pressure, which falls to 8 pounds. 

 This difference in the pressure of air in the two engines is caused by the 

 larger ratio of the rese»'voir to the size of the reed. With a greater 

 pressure than 12 pounds to the square inch in the larger engine and 9 

 pounds in the smaller no sound is produced ; the reed is unable to act 

 against the pressure, and, consequently, the orifice remains closed. The 

 trumpet of the larger of the engines is rej^orted to have been heard 

 eighteen miles at sea, which, in consideration of the results obtained at 

 Wliitehead, we thought very probable. The time required, from start- 

 ing fires, to get a good working-pressure, is about half an hour. The 

 amount of coal consumed per hour is 17 i)Ouuds. 



