868 WRITINGS OF JOSEPH HENRY. [1873 



our coast. At first these signals were principally confined to 

 bells, weighing in some cases from 2,000 to 2,500 pounds. 

 These were rung by winding up a weight which in its des- 

 cent gave motion to a hammer striking the bell. In regard 

 to this signal, an improvement has been introduced, by which 

 an expenditure of about one-tenth of the power produces an 

 equal effect. Bells are still used in cases where the signal 

 is required to be heard only at a comparatively small dis- 

 tance, but in most cases much more powerful instruments 

 are required, such as are founded on what is called resonance, 

 in which the air itself is the resounding body as well as the 

 conductor of sound. These instruments are of three kinds: 

 first, the ordinary locomotive whistle, much enlarged in size 

 and somewhat modified in form, and blown by steam from 

 a high -pressure tubular boiler; second, the reed-trumpet actu- 

 ated by air condensed in a reservoir b}; the power of a caloric 

 engine; third, the syren-trumpet, operated by steam from a 

 boiler sustaining a pressure of from 50 to 70 pounds per square 

 inch. The sound from these instruments is many times 

 more powerful than that from the largest bells. - - - - 



The Light-House Board, during the past year, desirous of 

 acquainting itself minutely with any improvements which 

 of late years may have been introduced into the light-house 

 service in Europe, obtained the sanction of the honorable 

 the Secretary of the Treasury to commission Major George 

 H. Elliot, of the Corps of Engineers of the Army and engi- 

 neer-secretary of the Board, to visit Europe and report upon 

 everything which he might observe relative to light-house 

 apparatus and the management of light-house systems. He 

 has lately returned, after having gathered information which 

 will prove of importance in its application in our country, as 

 is evident from his preliminary report. 



Major Elliot was everywhere received with marked cor- 

 diality, and every facility w^as given him to inspect the 

 various coasts and systems of administration, of which full 

 information was furnished him, together with the drawings 

 and models necessary for a perfect acquaintance with the 

 latest improvements which have been adopted in Great Bri- 



