NEGRETTI & ZAMBRA’S
PATENT RECORDING AND DEEP-SEA THERMOMETER.[20]
This Thermometer differs from all other Registering or Recording Thermometers in the following important particulars:—
I. The Thermometer contains only Mercury without any admixture of Alcohol or other fluid.
II. It has no indices or springs, and its indications are by the column of Mercury only.
III. It can be carried in any position, and cannot possibly be put out of order except by actual breakage of the instrument.
And lastly, it will indicate and record the exact temperature at any hour of the day or night, or the exact temperature at any depth of the sea, irrespective of either warm or cold currents, or stratum through which the Thermometer may have to pass in its descent or ascent, this last very special quality renders this Thermometer superior for deep-sea temperatures to any others; for those now being used in the “Challenger” sounding expedition are liable to give erroneous indications owing to their indices slipping, and otherwise getting deranged—(This was proved by Messrs. Negretti and Zambra at a Meeting of the British Meteorological Society,) and under certain conditions of temperature it is not possible by the old Thermometers to obtain true temperatures at certain depths which might be required. Annexed is a copy of a report to the Admiralty from Captain G. S. Nares, of H.M.S. “Challenger,” dated Melbourne, March 25th, 1874, which we have taken from Nature, July 30th, 1874, proving the assertion.
“In the report to the Admiralty of Capt. G. S. Nares, of H.M.S. Challenger dated Melbourne, March 25, 1874, Capt. Nares, speaking of the temperature of the ocean, especially near the pack edge of the ice, says:—‘At a short distance from the pack, the surface water rose to 32°, but at a depth of 40 fathoms we always found the temperature to be 29°; this continued to 300 fathoms, the depth in which most of the icebergs float, after which there is a stratum of slightly warmer water of 33° or 34°. As the thermometers had to pass through these two belts of water before reaching the bottom, the indices registered those temperatures, and it was impossible to obtain the exact temperature of the bottom whilst near the ice, but the observations made in lower latitudes show that it is about 31°. More exact results could not have been obtained even had Mr. Siemens’s apparatus been on board.’ It seems to us that the difficulty mentioned is one which would certainly have been surmounted by Messrs. Negretti and Zambra’s new Recording Thermometers, a description of which appeared in Nature, vol. ix. p. 387; this being exactly one of the cases to which this instrument is peculiarly adapted. We believe the inventors and makers have greatly improved their Thermometer since our description appeared, and no doubt means will be taken by the Admiralty to transmit one to the Challenger.”
Fig. 1.