MECHANICS AND USEFUL AKTS. 71 



by advice of the inventor, so that the distance might be marked. It 

 is probable that, under the same circumstances, the tones of a bell 

 could not have been heard more than from one half to three fourths of 

 a mile. The pilot of the steamer Knickerbocker reports that he 

 made the whistle, during a dense fog, thirteen minutes' running-time 

 of the steamer, before coming up with the station where it is located. 

 He therefore must have been some four or five miles distant from it 

 when he heard it. 



This whistle consists of an air-chamber or condenser, of boiler-iron, 

 sufficiently strong to resist almost any pressure, an air-pump, and a 

 whistle similar to the ordinary ones used on locomotives. By means 

 of the air-pump operating into this chamber, a pressure of air is ob- 

 tained in it of any required amount, say one, two, or three hundred 

 pounds to the square inch. When the air is so compressed, it is made 

 to operate the whistle by simply opening a valve, and gives a distinct, 

 clear sound. 



A memorial has been presented to the Treasury Department, signed 

 by most of the commanders and pilots of the steamboats running 

 through Long Island and Fisher's Island Sounds, setting forth the 

 advantages to be derived to navigation from this whistle, and urging 

 that it be introduced into the light vessels, and at all stations where 

 the government intends to afford protection to navigation. 



REPORT ON LIGHT-HOUSES IN THE UNITED STATES. 



MR. PLEASANTOX, the Fifth Auditor of the Treasury, has published 

 a small pamphlet, containing a list of the light-houses, beacons, and 

 floating lights of the United States, with a statement of then- location, 

 heights, distance at which they are visible in clear weather, &c. It 

 is accompanied by three distinct and beautifully engraved lithographic 

 charts. The first exhibits the light-houses and light-vessels on the 

 American coast from Maine to Virginia inclusive. The second pre- 

 sents a similar exhibit of the coast from Virginia, exclusive, to* Texas, 

 inclusive, with the lights, of course, along the coast of Florida, and 

 in the Florida Keys, &c. The third chart exhibits the position of the 

 lighthouses on the Lake coast. They are represented on the maps by 

 red circles diverging into rays. There are 14 on Lake Michigan, 1 

 at the Straits of Michilimackinac, 7 on Lake Huron, 1 on Lake Su- 

 perior, 2 on Lake St. Clair, 20 on Lake Erie, 13 on Lake Ontario 

 and the St. Lawrence, and 3 on Lake Champlain. 



The general list exhibits strong evidence of the energy of the bu- 

 reau of the Fifth Auditor in the extension of the system. Up to the 

 1st of July, 1848, there were 270 light-houses, some of them revolv- 

 ing, varying in the time of their revolution ; but most of them are 

 fixed lights, differing in the height of the lanterns, and in the distance 

 at which they are visible. The longest distance is 30 miles, on the 

 highlands of Neversink, on the coast of New Jersey, there being 

 two lights, one of them revolving. 



The light-houses are so distributed, according to the necessities of 

 the service, that there are 32 light-houses on the coast of Maine, 3 in 



