1874] WRITINGS OF JOSEPH HENRY. 375 



trol of keepers. A signal which is liable to be interrupted 

 in its warnings is worse than no signal, since its absence may 

 give confidence of safety in the midst of danger, and thus 

 prevent the necessary caution which would otherwise be 

 employed. 



Guns have been employed on the United States coast, first 

 under the direction of General Bates, engineer of the twelfth 

 district, at Point Bonita, San Francisco Bay, California. The 

 gun at this station consisted of a 24-pounder, furnished by 

 the War Department. The necessary arrangements being 

 made, by the construction of a powder-house, and laying of 

 a platform, and employment of a gunner,— notice to mariners 

 was given that after the 8th of August, 1856, a signal-gun 

 would be fired every hour and half-hour, night and day, 

 during foggy or thick weather. The first year, with the 

 exception of eighty-eight foggy days, omitted for want of 

 powder, 1390 rounds were fired. These consumed 5560 

 pounds of powder, at a cost of $1,487, pay of gunner and 

 incidentals excluded. The following year the discharges 

 were 1582, or about one-eleventh of the number of hours and 

 half-hours of the whole time. The fog-gun was found to 

 answer a useful purpose; vessels by the help of it alone hav- 

 ing come into the harbor during a fog at night, as well as in 

 the day, that otherwise could not possibly have entered. 

 This signal was continued until it was superseded by a bell- 

 boat. A gun was also used at West Quoddy Head, near the 

 extreme eastern part of Maine. It consisted of a short piece 

 or carronade, 5 feet long, with a bore of 5^ inches, charged 

 with four pounds of blasting powder. The powder was made 

 up in cartridges and kept in chests in the work-house. The 

 gun was only fired on foggy days, when the steamboat run- 

 ning between Boston and Saint John, New Brunswick, was 

 approaching the light-house from the former place. In 

 going in the other direction the signal was not so much re- 

 quired, because in the former case (of approach) the vessel 

 had been for some time out of sight of land, and consequently 

 its position could not be so well known. The firing was 

 commenced with the hearing of the steamer's whistle as she 



