45, CORNHILL, E.G., AND 122, EEGENT STREET, W., LONDON. 



173 



MARINE THERMOMETERS. 



403 



404 

 405 



406 



FIG, 407. 



FIG. 408. 



FIG. 404. 



FIG. 406. 



SELF-REGISTERING THERMOMETERS, 

 ADAPTED FOR DEEP SEA SOUNDINGS. 

 Board of Trade Marine Thermometer, the scale divided on its stem, 



Each. 



and mounted on Negretti and Zambra's PATENT PORCELAIN SCALES, s. d. 



in japanned Metal Case 10 6 



ditto in COPPER CASE (fig. 404) 12 6 



1 10 



Board of Trade Marine Thermometer, in round Copper case . . 1 10 

 Johnson's Registering Metallic Marine Thermometer. The indications are 

 obtained by the varying expansion of brass and steel bars acting upon an 

 index on the principle of the Thermostat (fig. 401) . . . 550 

 For description see N. and Z.'s Treatise on Meteorological Instruments. 



407 Deep Sea Sounding Thermometers, Self-Registering, the original double tube 



principle, as invented by Negretti and Zambra, specially constructed for 

 and supplied to the Board of Trade and Admiralty (fig. 407). Warranted 

 to stand a pressure of 450 atmospheres 2 10 



Many have been the contrivances for obtaining correct deep sea indications. Thermometers and 

 machines of various sorts have been suggested, adopted, and eventually abandoned as only approximate 

 instruments. The principal reason for such instruments failing to give correct or reliable indications has 

 been that the weight or pressure at great depths has interfered with the correct reading of the Instrument. 

 Thermometers have been enclosed in strong, water-tight cases to resist the pressure ; but this contrivance 

 has only had the tendency to retard the action, so much as to throw a doubt on the indications obtained 

 by the instrument so constructed. 



408 Negretti and Zambra's Small Deep Sea Sounding Thermometer, Dr. Miller's 



pattern in Copper Case (as fig. 403). Price 2 10s. 3 3e. 



The Deep Sea Sounding Thermometers (Nos. 406, 407 and 408) having all been 

 found defective in their indications, their use is not recommended for reasons 

 stated in pages 60 to 70. 



