534 SEC.. 12. APPLIED MECHANICS. 



2183. Drawing of a Light Vessel with deck plans showing 

 internal arrangements and disposition of Syren Fog Signal 

 machinery. Trinity House, London. 



The hull is designed after that of tlie vessel now at South Sand Head 

 (Goodwin), built last year, of about 212 tons, and fitted with a syren fog- 

 signal, giving one blast every two minutes, by means of compressed air, at a 

 pressure of 30 Ibs. to the square inch, the apparatus being driven by a caloric 

 engine, which also works the windlass. 



The illuminating apparatus represents that in use at the Royal Sovereign 

 Shoal, off the coast of Sussex ; it is catoptric, and is upon the " group-flashing " 

 principle, giving three flashes in quick succession every minute. The crew 

 space is for seven men, including the officer in charge. The hollow iron 

 mast affords access to the lantern, and allows of the lamps being trimmed in 

 all weathers without danger of extinction. 



2184. Two Syrens, each a portion of the present First 

 Class Fog Signal, and a diagram showing the method by which 

 they are put in action. Trinity House, London. 



The disc syren, with the trumpet by which its sound is directed, is shown 

 in the diagram. It is composed of a fixed disc, forming one end of the 

 chamber into which steam or compressed air is forced, and a movable disc 

 rotating rapidly by separate mechanism outside it. Both are perforated by 

 12 radial slits exactly corresponding each to each, and the rotation of the 

 moving disc, close to and upon a common axis with its fixed associate, 

 permits the compressed air or steam to escape when the slits coincide, and 

 shuts it off when they do not. The vibrations thus produced being repeated 

 in the instrument described, at the rate of more than 400 per second, emit a 

 sound of very great intensity, which is directed by the trumpet towards any 

 desired point. 



The cylindrical syren is a later form of the instrument, in which the 

 chamber for compressed air surrounds a fixed cylinder having 24 slits, within 

 which another cylinder coincidently perforated rotates, and the vibrations 

 pass through the open end of the inner cylinder to the trumpet. 



Syrens sounded by steam have for some time been used for fog-sig- 

 nalling on the coasts of America, and have lately been adopted, with the 

 substitution of compressed air for steam, in Great Britain as a result of expe- 

 riments made by the Trinity House with the assistance of Professor Tyndall 

 during the winter of 1873. 



2185. Fog Signal Apparatus. Designed by Dr. G. Amadi, 

 of Trieste. 



The Imperial and Royal Maritime Government at Trieste. 



By this apparatus deep tones, like those of an organ, are produced by 

 metallic tongues, driven by steam, and sent through a trumpet in a given 

 direction. These, from experiments, have extended as far as 16 nautical, or 

 nearly four German miles. 



In working this apparatus, of which already three are in use, at Trieste, 

 Salvore, and Grado, the sounds are made self-producing at certain intervals 

 by means of a steam-engine. 



2185a. Holmes' Shipwreck Distress Signal Flare and 

 Life Buoy Rescue lights. N. J. Holmes. 



These have the remarkable property of bursting into flame when placed in 

 contact with water, and when once ignited are absolutely inextinguishable by 



