408 WRITINGS OF JOSEPH HENRY. [187* 



smaller, but were gradually enlarged as long as any difficulty with regard 

 to foaming was noticed. The steam is drawn off at a point 10 ins. above the 

 water-level in the boiler. The main points to be observed are to have plenty 

 of steam-room, and to draw the steam from a point high above the water- 

 level. It will be readily perceived that a vertical tubular boiler is entirely 

 unsuited to this work. 



It is essential, both as regards economy of fuel and the efficient working 

 of the signal, that the boiler (including the dome and stand-pipe) should be 

 well covered with some good non-conductor of heat. A material (called 

 salamander felting) manufactured in Troy, N. Y., was used on the fog-whistle 

 boiler at House Island during the winter of 1870. There resulted a saving 

 of more than 20 per cent, of fuel over that consumed in the same boiler when 

 uncovered. Where this material cannot be procured, a thick layer of hair 

 felting, covered with canvas, will be found to answer a good purpose. 



Various expedients have been proposed with the view of keeping the water 

 in the boilers hot when the signals are not in operation, that the signal may 

 always be ready to sound at a very short notice, and that the water in the 

 boiler and pipes may be prevented from freezing in extremely cold weather. 

 One of these contrivances is "Sutton's circulating water heater." It consists 

 essentially of a small, vertical, tubular boiler, entirely filled with water, and 

 connected with the boiler or tank which contains the water to be heated, by 

 two pipes on different levels. As soon as the water in the heater is warmed^ 

 a circulation commences, the hot water flowing through the upper pipe into 

 the boiler, and the cold through the lower pipe from the boiler to the heater. 

 As the furnace in the heater is very small but little fuel is consumed, and 

 nearly the entire heat produced by the combustion is utilized. 



The apparatus has been extensively employed in heating the water in 

 tanks designed for filling the steam fire-engine boilers, when the alarm of 

 fire is first given, and appears admirably adapted to this purpose If used 

 in connection with a steam boiler, it should be disconnected before steam is 

 raised in the latter, as from its construction it is not calculated to withstand 

 any considerable pressure. 



An arrangement (similar in principle) has been used in the first light-house 

 district, consisting of a small cylinder coal-stove, of the ordinary pattern, 

 around the interior of which, and above the grate, is introduced a single coil 

 of ^ in. pipe. This coil is connected with the boiler by two pipes, one enter- 

 ing near the bottom, the other about 2 feet higher. It has been found that 

 in consequence of the rapid circulation of the water through this coil, and 

 the great capacity of water for heat, nearly all the heat from the fire 

 in the stove is transferred to the water in the boiler. This arrangement 

 possesses the advantage of the f in. pipe, being strong enough to stand any 

 pressure that can be used in the boiler, thus rendering it unnecessary to dis- 

 connect it at any time. 



Experience has however proved that none of these contrivances are essen- 

 tial. It is seldom that an attentive keeper cannot foresee the approach of fog 

 or snow in time to have the apparatus in operation as soon as required, even 

 when obliged to start his fire with cold water in the boiler. 



Keepers should be directed to watch the state of the weather carefully, and 

 to light their fires at the first indication of fog or snow-storm. As soon as 

 the water in the boiler is near the boiling point, should the necessity for 

 sounding the signal have not yet arisen, the fire may be banked, and in this 

 state the water may be kept hot for any length of time at a moderate expen- 

 diture of fuel. With proper care, no more fuel is required to keep the water 

 at the requisite temperature by means of a banked fire than by any other 

 method, and it is a matter of great importance to avoid complicating fog- 

 signal apparatus by unnecessary appendages. 



The same plan should be adopted in extremely cold weather to prevent 

 the water in the boiler from freezing. There should be a small air-cock in 

 the draught-pipe near its junction with the feed-pump, and in cold weather 



