GO NEGEETTI AND ZA.MBRA, HOI/BORN VIADUCT, B.C., 



NEG-BETTI & ZAMBEA'S 

 RECORDING DEEP SEA THERMOMETERS. 



78. Deep Sea Sounding Thermometers, Self-Registering, the 

 original double tube principle, invented by Negretti and Zambra, specially- 

 constructed for the Board of Trade and Admiralty. Warranted to stand 

 a pressure of 450 atmospheres. Price 2 10 



This manner of protecting the bulb was invented by Messrs. Negretti and Zambra in 

 1857, and is described by the late Admiral R. FitzRoy, in the first number of Meteorological 

 Papers, p. 55, published July 5th. 1857, as follows : 



" Referring to the erroneous readings of all thermometers, consequent on their 

 delicate bulbs being compressed by the great pressure of the ocean, he says : ' With a 

 view to obviate this failing Messrs. Negretti and Zambra undertook to make a case for the 

 weak bulbs, which should transmit temperature, but resist pressure. Accordingly a tube 

 of thick glass is sealed outside the delicate bulb, between which and the casing is a space 

 all round, which is nearly filled with mercury. The small space not so filled is a vacuum, 

 into which the mercury can be expanded, or forced by heat or mechanical compression, 

 without doing injury to or even compressing the inner or much more delicate bulb.'" 



The bulb of the Thermometer thus protected resists the pressure of the ocean, which 

 varies according to its depth that of three thousand fathoms being something like three 

 tons pressure upon the square inch. 



79. Negretti and Zambra's Small Deep Sea Sounding 

 Thermometers, the so-called Dr. Miller's pattern in Copper. Case. 



Price 2 10 330 



R. H. SCOTT, Esq., F.R.S., in a paper published in the Journal of the Meteo- 

 rological Society, January 17th, 1872, speaking of Negretti and Zambra's Deep- 

 Sea Thermometers, described by Admiral FitzRoy in the first number of 

 Meteorological Papers, published July 5th, 1857, says : 



" The number of the thermometers of this particular pattern, which was supplied to the 

 Meteorological Department of the Board of Trade by Messrs. Negretti and Zambra, the 

 makers, was upwards of fifty, and they were supplied to several ships in the Royal Navy, 

 especially those employed on certain well-known deep-sea sounding expeditions. I was not 

 able to find any record of any of these thermometers having been tested in an hydraulic 

 press, and, accordingly, as soon as the Miller pattern thermometer had been definitely 

 adopted by the Hydrographer, it was resolved to subject one of the old thermometers 

 (Negretti and Zambra's) in the Meteorological Office to the same test as that which the new 

 instruments were made to undergo, in order to see whether or not the construction of the 

 original instruments offered sufficient security against alteration of the shape of the bulb, 

 owing to pressure. The experiments were carried out on the 28th of September, 1869, in 



