C. GENERAL PHYSICS. ?l 



C. GENERAL PHYSICS. 







ADJUSTMENT OF SHIPS* COMPASSES. 



Professor E. Dubois, of the naval school at Brest, has spent 

 much time in studying the best means of obviating the dan- 

 gers which arise to ships in consequence of the deviations of 

 their compasses. With this view he has constructed a gyro- 

 scopic compass, revolving 8000 times per minute, mounted 

 upon Cardan's triple suspension, and carrying a needle sup- 

 ported above a graduated circle. In accordance with a well- 

 known property of the gyroscope, this circle maintains an in- 

 variable position, and indicates the precise number of degrees 

 through which the vessel may be turned to starboard or port, 

 thus furnishing the means of determining the true direction 

 of her head at any time after it has once been obtained from 

 observations on a headland. This instrument may therefore 

 be used to determine all the deviations on the compass on 

 board ship. Some experiments made with it on the corvette 

 Bougainville in the roadstead of Brest are said to have been 

 extremely satisfactory. 3 j5, i., 1872, 3. 



ELECTRIC APPARATUS FOR DEEP-SEA TEMPERATURES. 



Professor Davidson, of the Coast Survey, has lately devised 

 an apparatus for recording the temperature at different 

 depths by means of an electro-thermal pile. He proposes to 

 register the depth by breaking the circuit of an electric cur- 

 rent passing through two insulated wires in the sounding-line 

 at about every one hundred fathoms by means of the wheel- 

 work of the Massey or similar apparatus. In the changes of 

 temperature, an electro-thermal pile eighteen inches long, in- 

 sulated, and surrounded by a non-conductor except at one 

 end, is used in combination with a Thompson's reflecting gal- 

 vanometer, not liable to derangement on shipboard. At ev- 

 ery one hundred fathoms, when the chromograph registers 

 the depth, the observer notices the readings of the galvanom- 

 eter, which readings are reduced to Fahrenheit degrees. 

 San Francisco Bulletin. 



