Mar. 19, 1874] 



NA TURE 



387 



A NEIV THERMOMETER 



OUR readers will doubtless recollect a recent discus- 

 sion in our pages relative to the priority of the 

 invention of protected bulbs for deep-sea thermometers. 

 The discussion has done something more than establish 

 priority of invention, it has been the means of producing 

 what, we believe, will prove to be a new and valuable 

 meteorological instrument, for we have before us a paper 

 by Messrs. Negretti and Zambra, communicated to the 

 Royal Society by Dr. Carpenter at their last meeting, 

 describing a new thermometer of such novel construction 

 that it cannot fail to interest all scientific persons, 

 meteorologists especially. We regret our inability, owing 

 to want of space, to reproduce the paper in its entirety. 

 The following are the main points of this communica- 

 tion. 



In Prof. WyviUe Thomson's " Depths of the Sea," 

 p. 299, occurs the following passage : — " I ought to men- 

 tion that in taking the bottom temperature with the Six's 

 thermometer the instrument simply indicates the lowest 

 temperature to which it has been subjected; so that if the 

 bottom water were warmer than any other stratum 

 through which the thermometer had passed, the observa- 

 tions would be erroneous." 



Undoubtedly no other result could be obtained with 

 the thermometers now in use, for unfortunately the 

 only thermometer available for the purpose of registering 

 temperature and bringing those indications to the sur.^ace, 

 is that which is commonly known as the Six's thermo- 

 meter — an instrument acting by means of alcohol and 

 mercury, and having movable indices with delicate springs 

 of human hair tied to them. This form of instrument 

 registers both maximum and minimum temperatures, and 

 as an ordinary out-door thermometer it is very useful ; 

 but it is unsatisfactory for scientific purposes, and for the 

 object for which it is now used (\iz. the determination of 

 deep-sea temperatures) it leaves much to be desired. 

 Thus the alcohol and mercury are liable to get mi.xed in 

 travelling, or even by merely holding the instrument in a 

 horizontal position ; the indices also are liable either to 

 slip if too free, or to stick if too tight. A sudden jerk or 

 concussion will also cause the instrument to give erro- 

 neous readings by lowering the indices if the blow be 

 downwards, or by raising them if the blow be upwards. 

 It was on reading the passage in the book above refened 

 to that it became a matter of serious consideration with 

 Messrs. Negretti and Zambra, whether a thermometer could 

 be constructed which could not possibly be put out of order 

 in travelling, or by incautious handling, and which should 

 be above suspicion and perfectly trustworthy in its indica- 

 tions. This was no very easy task. But the instrument sub- 

 mitted to the Fellows of the Royal Society seems to fulfil 

 the above onerous conditions, being constructed on a plan 

 different from that of any other self-registering thermo- 

 meter ; and containing, as it does, nothing but mercury, 

 neither alcohol, air, nor indices. Its construction is most 

 novel, and may be said to overthrow our previous ideas 

 of handhng delicate instruments, inasmuch as its indica- 

 tions are only given by upsetting the instrument. Having 

 said this much, it will not be very difficult to guess the 

 action of the thermometer ; for it is by upsetting or 

 throwing out the mercury from the indicating column into 

 a reservoir at a particular moment and in a particular 

 spot, that we obtain a correct reading of the temperature 

 at that moment and in that spot. 



The thermometer in shape is like a syphon with 

 parallel legs, all in one piece, and having a continuous 

 communication, as in the annexed figure. The scale 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 that may be desired. In its descent the ther- 

 mometer 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 the thermo- 

 meter to the surface, the instrument 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 

 siphon 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 turned 

 over. The woodcut shows the position of 

 the mercury a/U-r the instrument has been 

 thus turned on its centre. A is the bulb ; 

 B the outer coating or protecting cylinder ; 

 C is the space of rarefied air, which is 

 reduced if the outer casing be com- 

 pressed ; D is a small glass plug on the 

 principle of Negretti and Zambra's Patent 

 Maximum Thermometer, which cuts off, 

 in the moment of turning, the mercury in 

 the column from that of the bulb in the 

 tube, thereby ensuring that none but the 

 mercury in the tube can be transferred 

 into the indicating column ; E is an en- 

 largement made in the bend so as to 

 enable the mercury to piss quickly from 

 one tube to another in revolvmg ; and F 

 is the indicating tube, or thermometer 

 proper. In its action, as soon as the ther- 

 mometer is put in motion, and immediately 

 the tube has acquired a slightly oblique 

 position, the mercury breaks off at the 

 point D, runs into the curved and en- 

 larged portion E, and eventually falls int j 

 the tube F, when this tube resumes its 

 original perpendicular position. 



The contrivance for turning the ther- 

 mometer over may be described as a 

 short length of wood or metal having 

 attached to it a small rudder or fan ; this 

 fan is placed on a pivot in connection 

 with a second ; on the centre of this is 

 fixed the thermometer. The fan or 

 rudder points upwards in its descent 

 through the water, and necessarily re- 

 verses its position m ascending. This 

 simple motion or half turn of the rudder 

 gives a whole turn to the thermometer, 

 and has been found very effective. ^ ' " 



Various other methods may be used 

 for turning the thermometer, such as a '"' 



simple pulley with a weight which might 

 be released on touching the bottom, or a small vertical 

 propeller which would revolve in passing through the 

 water. 



Messrs. Negretti and Zambra' in their paper merely 

 mention the new thermometer as being available for 

 deep-sea temperatures ; but we believe it will prove to 

 be of great value on land ; for with this thermometer 

 we are at once provided with the means of miking 

 observations which will solve some of the most in- 

 teresting questions connected with atmospheric tem- 

 perature. At present wc do not possess a simple in- 

 strument, in fact none at all which will automatically record 

 out of doors the exact temperature at fixed periods ; we read 

 of the temperature being so many degrees of heat or cold 

 yesterday or last night, but we have no means of record- 

 ing how cold it was (say) at midnight, or how warm at 

 midday, except by actually watching the instrument at 

 those iiours. With the new thermometer in connection 

 with an inexpensive time-piece, we can ascertain and re- 



