B. TERRESTRIAL PHYSICS AND METEOROLOGY. 103 



THE NEW DEEP-SEA THERMOMETER. 



The thermometer recently invented by Messrs. Negretti 

 & Zarnbra, for the self-registration of the temperatures of 

 the water at the bottom of the ocean, is one of such novel 

 construction, and withal of such universal applicability, that 

 it merits a special notice. Hitherto, the registration of deep- 

 sea temperatures has principally been made by means of Six's 

 minimum thermometer, or else by means of metallic thermom- 

 eters, both of which instruments are liable to serious derange- 

 ment ; and, worse than this, although these thermometers 

 register a minimum temperature, yet there is always a grave 

 uncertainty as to the depth of the stratum of water at which 

 that temperature is obtained. The new instrument would be 

 described in a general way as consisting of an ordinary ther- 

 mometer having a very long tube, the upper half of which 

 has been bent over, producing the shape of a siphon, or an in- 

 verted U- The frame to which the thermometer tube is at- 

 tached is pivoted in the centre, and attached to a short length 

 of wood or metal provided with a rudder or fan, and the 

 whole apparatus suspended vertically on the deep-sea line. 

 This fan or rudder, pointing upward as the thermometer is 

 carried down through the water, preserves the instrument in 

 its original or normal position ; but the moment the line is 

 drawn up and the instrument commences to ascend, the rud- 

 der reverses its position, turning the thermometer over into 

 the inverted position, U, and then quickly completes the turn, 

 and resumes its normal state as f\. When the thermometer 

 is thus turning, the mercury in one leg of the f\ separates at 

 a point determined by a glass plug, and the upper portion 

 flowing into the other leg remains detached until the instru- 

 ment is brought to the surface, where its length can be meas- 

 ured, indicating the precise temperature of the stratum of the 

 sea in which the upset took place. The new instrument is 

 guarded from the influences of deep-sea pressures by an outer 

 case of glass, as was done by this eminent firm of instrument- 

 makers many years ago with other apparatus for the Mete- 

 orological Department of the Board of Trade. 



The wood-cut shows the position of the mercury after the 

 instrument has been turned on its centre. A is the bulb ; B 

 is a small glass plug within the tube, and which, in the mo- 



