MECHANICS AND USEFUL ARTS. 51 



more or fewer divisions of the scale, that is, to ascertain the depth 

 in metres or fathoms. The little wings are protected by a pierced 

 dome, immediately above which is a ring for the reception of the 

 sounding-line. To the bottom of the cone is attached a cylinder of 

 lead, of sufficient weight to carry it through the water. This lead is 

 concave at the base, and is filled with grease, in order that the nature 

 of the bottom may be ascertained from the portions which adhere to it. 

 When the apparatus is cast into the sea, the resistance offered by the 

 water from below upwards causes the little wings to open, and, from, 

 their vertical position, to revolve. The screw, of course, obeys the 

 movement, and the index quits the zero point, and travels down the 

 scale. As soon as the lead touches the bottom, all motion ceases, the 

 instrument is drawn on board, and its result read off. M. le Coentre's 

 apparatus has been tried upon known soundings, and its results found 

 to be accurate. It is considered by French naval men as being espe- 

 cially valuable, since it enables soundings to be taken either from 

 steamers or sailing-vessels without decreasing the speed of the ship, 

 as on the old plan, and, in fact, while going at the rate of eight or 

 nine knots an hour, and in any weather, even sub-marine currents not 

 operating prejudicially to its effective working. English paper. 



ALTITUDE INSTRUMENT. 



MR. A. GIRARD, of Mobile, Ala., has invented a new instrument for 

 taking the altitude of the sun, at any hour of the day, on sea or land, 

 by its shadow, without an horizon. By adding to the angle given by 

 the instrument the semi-diameter of the sun and its refraction, we ob- 

 tain its true altitude, and by adding the declination at noon, the true 

 altitude of the place where the instrument stands is arrived at, that is, 

 if the latitude and declination are both north ; if, however, one is 

 north and the other south, the declination must be subtracted. 

 Scientific American, July 27. 



THE ATMOPYRE. 



MR. D. O. EDWARDS has devised a plan for substituting coal-gas 

 and other combustible elastic fluids for coal-fires. It is well known 

 that flame is a hollow cone, its exterior being formed by the evanes- 

 cent particles of carbon, which, being for the moment precipitated in 

 a solid form, after the combustion of the hydrogen, and raised to a 

 white heat, give out light in virtue of that transient solidity. This 

 occurs the instant before the union of the carbon with the oxygen of 

 the atmosphere, and their conversion into carbonic acid, which forms 

 an invisible pellicle round the flame. The temperature to which this 

 carbonaceous shell is raised is very great, but as soon as it is engen- 

 dered, it is carried away by currents of the surrounding atmosphere. 

 It is the object of this invention, which was suggested by the Davy 

 safety-lamp, to arrest and detain this heat. This lamp is a chamber, 

 whose walls are perforated with minute holes, through which air and 

 gas freely pass, while they are impermeable to flame. The incandes- 



