398 M. Descloizeaux's Physical and Geological Observatioiis 



Depth of the well, including that of the basin : — ^ 



1. In the direction of the first diameter . . . 23*50 



2. In the direction of the second diameter . . 21*50 



Depth of the cup in the centre 1*57 



As we took care, in each experiment, to alter the order of 



our thermometers, that their indications might be checked, I 

 shall indicate by numbers and by the letter B those of M. 

 Bunsen, and by the letter D those which belonged to me. 



It will be conceived that the temperature at the surface of 

 the water which fills the basin must be excessively variable ; 

 for that temperature depends at the same time on the tempe- 

 rature of the sides of the basin, on that of the air, on the force 

 and direction of the wind, and on the hygrometric state of 

 the atmosphere, whicii allows of a more or less speedy evapo- 

 ration. This is the reason why the numbers given by differ- 

 ent travellers, for the temperature of the water on the edge of 

 the basin, agree so little; we ourselves made a series of ob- 

 servations, the terms of which differ considerably among them- 

 selves. They are as follow : — 



„ Temp, at the margin. 



lo4o. h ra o 



3rd July, at 10 30 a.m.; basin filled . 86*0 centigrade. 



3rd July, at 10 58 a.m. ; Id. ... 89-0 



3rd July, at 1 1 30 A.M. ; /r/. . . . 88*0 



3rd .Tuly, at 3 25 p.m.; /rf. . . . 89*7 



■ith July, at 12 35 P.M.; /rf. . . . 76*0 



4-th July, at 117 P.M.; M . . . 85*0 



9th July, at 1 50 p.m.; basin half-full 82*5 in the wind. 



9th July, at 1 50 p.m.; Id. ... 86*0 under the wind. 



We will admit that the mean temperature of the water at 

 the surface and in the centre of the basin is 85° C. 



The following table indicates the temperatures found in 

 different points of the liquid column, immediately before a 

 great eruption : — 



