310 MEMORIAL OF JOSEPH HENRY. 



During the progress of these useful labors, no less important 

 investigations were commenced, on the most efficient forms of 

 apparatus for acoustic signalling, as the substitutes for light signals 

 during the prevalence of sea-board fogs. "Among the impedi- 

 ments to navigation, none perhaps are more to be dreaded than 

 those which arise from fogs. - - - The only means at present 

 known for obviating the difficulty, is that of employing powerful 

 sounding instruments which may be heard at a sufficient distance 

 through the fog, to give timely warning of impending danger." * 



Gun signals were early abandoned, as inefficient, dangerous, and 

 expensive : inefficient, because of both " the length of the intervals 

 between the successive explosions, and the brief duration of the 

 sound, which renders it difficult to determine with accuracy its 

 direction." Innumerable projects eagerly pressed upon the Board 

 by visionary inventors (some of them being rattles, gongs, or organ 

 pipes operated by manual cranks, many of them being varieties of 

 automatic horn or whistle operated by the winds or the waves) 

 were impartially tested, and uniformly rejected as wholly insuffi- 

 cient: very few of their projectors having the slightest practical 

 idea of the requirements of the service. Experiments on steam- 

 whistles of large size and on horns with vibrating steel tongues or 

 reeds, sounded by steam-power, or by hot-air engines, varied and 

 continued for several years under wide changes of conditions, 

 finally determined their most efficient size and character, f 



In 1867, comparative trials were made at Sandy Hook (on the 

 Jersey shore, at the entrance to Raritan Bay, and to New York 

 Bay,) with three powerful instruments; a large steam- whistle 

 whose cup was 8 inches in diameter, and made adjustable in pitch; 

 a large reed trumpet 17 feet long and 38 inches in diameter at its 

 flaring mouth, whose steel tongue was 10 inches long, 2} inches 



* Report of Light-House Board for 1874, p. 83. 



f An enterprising inventor had secured a patent for a metallic compound or 

 alloy for steam- whistles, especially adapted to increase greatly their power as fog- 

 signals. In vain was he assured that his "improvement" was a fallacy; that the 

 cylindrical cup of the whistle was not a bell, but only a resonant chamber; and 

 that its material was comparatively unimportant. He was only with difficulty 

 convinced, when HENRY had his whistle formally tested, with a stout cord wound 

 tightly around its cylindrical surface: when its tone under steam escape was 

 proved to be as full, as loud, and as penetrating, as with the cord removed. 



