1874] WRITINGS OF JOSEPH HENRY. 407 



On the other hand, as it is the most powerful signal, there are certain 

 stations where it should have the preference ; as for example Sandy Hook, 

 which from its importance demands the best signal that can be procured, 

 regardless of cost. Such stations should be provided with duplicate appa- 

 ratus, well supplied with spare parts, to guard against any possibility of 

 accident. 



There should be a keeper whose sole business must be to attend the signal, 

 and who should have sufficient mechanical skill to make the ordinary re- 

 pairs. He should moreover be a licensed engineer. 



There will also be required an assistant, who may be one of the light- 

 keepers, to relieve him during the continuance of foggy weather. 



The steam-whistle is the simplest in construction, most easily managed 

 and kept in repair, and requires the least attention of all the fog-signals. It 

 is sufficiently powerful for most localities, while its consumption of fuel and 

 water is moderate. 



It has been found on this coast that a sufficient quantity of rain-water can 

 be collected to supply the I'i-in. whistle at nearly every station. This has 

 been the case for the last two years at Martinicus. 



The Daboll trumpet, operated by a caloric engine, should only be employed 

 in exceptional cases, such as at stations where no water can be procured, and 

 where — from the proximity of other signals, it may be necessary to vary the 

 nature of the sound. 



The trumpet however may undoubtedly be very much improved by em- 

 ploying steam power for condensing the air. The amount of work required, 

 which is that of compressing 70 cubic feet of air to an average pressure of 8 

 pounds per inch, would be less than two-horse power. For this purpose the 

 expenditure of fuel and water would be moderate ; indeed, the exhaust steam 

 could be condensed and returned to the cistern, should the supply of water 

 be limited. 



The siren also is susceptible of improvement, especially as regards simpli- 

 fication. 



Ill the foregoing remarks I think the General has ex- 

 pressed a somewhat undue partiality for the whistle, and 

 somewhat over-estimated the defects of the other instruments. 

 The trumpets with Ericsson engine have not been aban- 

 doned, except partially in the two districts under the direc- 

 tion of General Duane, to which he probably intended to 

 confine his statement. They are still in use in the third 

 district, where they are preferred by General Woodruff, who 

 finds no difficulty in keeping them in repair, having em- 

 ployed a skilled machinist who has made these instruments 

 his special study, and who — visiting them from time to time, 

 makes repairs and supplies new parts. 



The intermittent action of fog-signals makes it necessary to employ a pecu- 

 liar form of boiler. The steam used is at a high pressure, and drawn oft' at 

 intervals ; consequently there is a tendency to foam and throw out water 

 with the steam. To obviate this difficulty the form of boiler found by ex- 

 perience to be best adapted to this service is a horizontal tubular boiler (loco- 

 motive), with rather more than one-half of the interior space allowed for 

 steam-room. The steam-dome is very large, and is surmounted by a steam 

 pipe 12 ins. in diameter. Both the dome and pipe were formerly made much 



