288 FRAGMENTS OF SCIENCE 



and ending with 30 Ibs. pressure. The trumpet was 

 pointed to windward, and in the axis of the instrument 

 the sound was about as effective as that of the 8-oz. 

 rocket. But in a direction at right angles to the axis, 

 and still more in the rear of this direction, the syren fell 

 very sensibly behind even the 2-oz. rocket. 



These are the principal comparative trials made between 

 the gun-cotton rocket and other fog-signals; but they are 

 not the only ones. On the 2d of August, 1877, for ex- 

 ample, experiments were made at Lundy Island with the 

 following results. At 2 miles distant from the firing- 

 point, with land intervening, the 18-pounder, firing a 3-lb. 

 charge, was quite unheard. Both the 4-oz. rocket and the 

 8-oz. rocket, however, reached an elevation which com- 

 manded the acoustic shadow, and yielded loud reports. 

 "When both were in view the rockets were still superior 

 to the gun. On the 6th of August, at St. Ann's, the 

 4-oz. and 8-oz. rockets proved superior to the syren. On 

 the Shambles Light-vessel, when a pressure of 13 Ibs. was 

 employed to sound the syren, the rockets proved greatly 

 superior to that instrument. Proceeding along the sea 

 margin at Flamboro' Head, Mr. Edwards states that at a 

 distance of 1J mile, with the 18-pounder previously used 

 as a fog-signal hidden behind the cliffs, its report was 

 quite unheard, while the 4-oz. rocket, rising to an eleva- 

 tion which brought it clearly into view, yielded a powerful 

 sound in the face of an opposing wind. 



On the evening of February 9, 1877, a remarkable series 

 of experiments were made by Mr. Prentice at Stowmarket 

 with the gun-cotton rocket. From the report with which 

 he has kindly furnished me I extract the following partic- 

 ulars. The first column in the annexed statement con- 



