Mineralogy and Geology. 271 
~The mean temperature of the column of water was obtained by 
ieahipiping half the sum of the indications of two consecutive ther- 
mometers, by the interval which separates them, and dividing the sum of 
all these products by the sum of the intervals, or the length of the line. 
Twelve minutes after the fourth experiment, at 74 40 in the evening, 
the great eruption took place. 
The following “ hy results of the fifth experiment, commenced 
the 7th July, at 9h 45™ in the evening, two hours after the a erup- 
tion; basin half. alled height of the liquid column, 22™°75; length of 
the F ine, 22-50. 
Heights. 
m 
850. 4 22'50 
Thermometer No. 1,D_. i : 103-0 ‘ 13:50 
Cnet sca ware s ; : 1210 9-70 
Thermom We ak 7 ; lost 4°90 
Pie binidtnetes tw. o. oO : ; 12:2°5 0-30 
Bottom 
Mean temperature of the column of igs: 108°-83. 
The three 9 bereding Mabie show, in an evident manner, that the 
mean = dere ure o column o of water hich fills the central well 
imum, imm ediately en which may be estimated a : 
The results given in the follo owing tables, obtained at different periods 
Ween two consecutive eruptions, show that the phenomena always 
pass in the same manner, and with tolerable regularity :— 
| First Experiment. second veer: 
The 6th Raat at Oh. Tage in the morning; |The 6th Kip: at 8h. 20m. in the morning: 
three hours after great eruption, and; nine hours after a a great eruption, and, 
eleven hours be Hi th followin twenty-three hours before the following 
on. a ban iefall height of the auld eruption. Basin filled: height of the col- 
column, 23”-50; length of the line, 22-85. 
Heights. — 
9° 
22-50 
Therm. No, 5,D . . . 950; 19°70 | Therm. No. 6, D 826 tee 
Therm.No.3,D : | | 1090| 1630 |'Therm.No.5,D. . . ie eo 
No result. 12:90 | Therm. No.2,B. . + IE 7 | 4-80 
Therm. No, 2,B . 1211] 950 | Therm. No.3,D. .. - tds 0-30 
Come No. 1, B 1216 | 600 | Therm.No.1,B. . . Bottom. 
eames number of the 
» 1225) Bhd Mean temperature of the column of 
Bs. temperattire of the column of water, 102°°30. 
112°-68. 
Thus, notwithstanding the relative lightness of the most heated water, 
esi tends to rise to the surface, we see that, even after the eruptions, 
