Sept. 13, 1877] 



NA TURE 



421 



A NEW REGISTERING THERMOMETER-^ 



THE registration of temperature is one of the most 

 difficult of meteorological problems. Among 

 the registering instruments employed the thermometer 

 is cenainly that to which most attention has been 

 devoted, and yet no soluiion has hitherto given re- 

 sults altogether satisfactory. The extreme mobility of 

 the temperature of the air and the small force at our 

 disposal for acting upon the registering apparatus, are 

 special hindrances to the solution of the problem. In 

 England, in the various observatories, the photographic 

 method is used. The reservoir of the thermometer is 

 placed outside under cover, and the tube, entering the 

 wall, is re-curved vertically in the interior ; a photo- 

 graphic apparatus placed opposite this column of mer- 



cury registers the different heights. This process neces- 

 sitates a thermometric reservoir of considerable volume 

 in order that the displacements of the column of mercury 

 may be appreciable for very small variations. These 

 exigencies afifect the sensitiveness of the apparatus ; it is 

 not a less serious inconvenience that the reservoir must be 

 placed near the wall of the shelter where the self-recording 

 photogiaphic apparatus is arranged. In Switzerland the 

 metallic thermometer is employed, and is more easily 

 managed, but here again the metallic spiral must be 

 placed very close to the registering apparatus. 



The new registering thermometer which M. Herv^ 

 Mangon has sought to construct by utilising the differen- 

 tial wheeljvork of M. Redier, seems to us based upon a 

 sound principle. It consists of a mercurial thermometer 

 with weights so arranged that the thermometer may 



M. Herve Mangoa's New R 



ructea by M Red;t 



be placed at such a distance from any dwelling as j 

 rot to be subject to the influence cf surrounding ' 

 objects. Communication between the thermometer and 

 the registeiing apparatus is established by weans of 

 electricity. 



The ins'rument consists of two quite distinct paits : — ' 

 I. The thermometer proper, and the balance which serves 

 to indicate the differences of weight which are the result of , 

 variations of temperature. 2. The registering apparatus. 

 The thermometer, the diameter of the mercuriol column j 

 of whi(.h we have considerably amplified in our illustra- 

 tion, to render it appreciable, is composed of a very fine 

 tube, R ; it presents a large su:face, containing in reality 

 only a very thin column of mercury. This tube R is 



* From an article in La Nature by M. Ga*;ton Tissandier. 



supported by a cast-iron frame-woik, and is connected 

 with a bell-glass v ; its very slender extremity is plunged 

 into a small cup^o-', containing mercury, and placed upon 

 one of the scales of the balance b. 



The balance b is an ordinary balance of precision ; it 

 be?rs above the beam a small metallic disc which deter- 

 mines a contact at C every time the equilibrium is broken 

 in consequence of an increase of temperature. The second 

 scale also bears a cup_j-, containing glycirine. A glass tube 

 T T, connected with the registering apparatus, dips into this 

 cup g^ and communicates at its other extremity with an- 

 other cup, G, which forms avessel communicating v ith the 

 former. The bell-glass v covers the balance, ard permits 

 the exposure, without danger, of that part of the instru- 

 ment to the inclemencies of the air. It will be at once 

 seen bow to arrange things in order to put the in;trument 



