45, COBNHILL, B.C., AND 122, EEGENT STREET, W., LONDON. 61 



the presence of Capt. Toynbee and Mr. Strachan, and the results of the testing have been 

 published in the report of the Meteorological Committee of the Royal Society for 1869. 

 The concluding sentence of this report was as follows (page 32) : 



"'The foregoing experiments are sufficient to show that the original thermometers 

 described by Admiral FitzRoy were good and trustworthy instruments, in so far as regards 

 their capability of resisting pressure.' " 



NEGRETTI AND ZAMBRA'S 

 NEW RECORDING DEEP-SEA THERMOMETERS. 



80. These Instruments differ from all other Recording Thermometers in the 

 following important particulars : I. The Thermometer contains pure mercury 

 only, without any 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 be put out of order except by breakage. 

 And chiefly, it will indicate and record the exact temperature at any depth of 

 the sea, irrespective of either warm or cold currents or stratum through which 

 the Thermometer may have passed in its descent or ascent. This last very 

 special quality renders N. and Z.'s Thermometers superior for Deep Sea tempera- 

 ture to any others ; for those used in the Challenger expedition are liable to 

 give erroneous indications, owing to their indices slipping, and otherwise getting 

 defective (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 these old Thermometers to obtain true temperatures at certain 

 depths which might be required. 



The construction of Negretti and Zambra's original Deep Sea Thermometer 

 is as follows : 



In shape it is like a syphon with parallel legs, having a continuous 

 communication, as seen in the annexed figure, 69. The mounting of the 

 Thermometer is pivoted on a centre, and being attached in a perpendicular 

 position to a simple apparatus (which will be presently described), is lowered 

 to any depth in the water that may be desired. In its descent the Thermometer 

 acts as an ordinary instrument, the mercury rising or falling according to the 

 temperature of the stratum through which it passes ; but so soon as the 

 descent ceases, and a reverse motion is given to the line, so as to pull up 

 the apparatus towards the surface, the Thermometer turns once on its 

 centre, first bulb uppermost, and afterwards bulb downwards. This causes the 

 mercury, which was in the left-hand column, first to pass into the dilated syphon 

 bend at the top, and thence into the right hand tube, where it remains, 

 indicating on a graduated scale the exact temperature at the time it was 



