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Encyclopaedia Britannica, 11th Edition, Volume 11, Slice 8 "Germany" to "Gibson, William"

90 metres from the bottom it was 114

temperatures of the several

strata. The results of the observations of Bunsen and A. L. O. Descloizeaux in 1847 were as follows (cf. _Pogg. Ann._, vol. 72 and _Comptes rendus_, vol. 19): About three hours after a great eruption on July 6, the temperature 6 metres from the bottom of the shaft was 121.6 deg. C; at 9.50 metres, 121.1 deg.; at 16.50 metres, 109 deg. (?); and at 19.70 metres, 95 deg. (?). About nine hours after a great eruption on July 6, at about 0.3 metres from the bottom, it was 123 deg.; at 4.8 metres it was 122.7 deg.; at 9.6 metres, 113 deg.; at 14.4 metres, 85.8 deg.; at 19.2 metres, 82.6 deg. On the 7th, there having been no eruption since the previous forenoon, the temperature at the bottom was 127.5 deg.; at 5 metres from the bottom, 123 deg.; at 9 metres, 120.4 deg.; at 14.75 metres, 106.4 deg.; and at 19 metres, 55 deg. About three hours after a small eruption, which took place at forty minutes past three o'clock in the afternoon of the 7th, the temperature at the bottom was 126.5 deg.; at 6.85 metres up it was 121.8 deg.; at 14.75 metres, 110 deg.; and at 19 metres, 55 deg. Thus, continues Bunsen, it is evident that the temperature of the column diminishes from the bottom upwards; that, leaving out of view small irregularities, the temperature in all parts of the column is found to be steadily on the increase in proportion to the time that has elapsed since the previous eruption; that even a few minutes before the great eruption the temperature at no point of the water column reached
the boiling point corresponding to the atmospheric pressure at that part; and finally, that the temperature about half-way up the shaft made the nearest approach to the appropriate boiling point, and that this approach was closer in proportion as an eruption was at hand. The Great Geyser has varied very much in the nature and frequency of its eruptions since it began to be observed. In 1809 and 1810, according to Sir W. J. Hooker and Sir George S. Mackenzie, its columns were 100 or 90 ft. high, and rose at intervals of 30 hours, while, according to Henderson, in 1815 the intervals were of 6 hours and the altitude from 80 to 150 ft.

About 100 paces from the Great Geyser is the _Strokkr_ or churn, which was first described by Stanlay in 1789. The shaft in this case is about 44 ft. deep, and, instead of being cylindrical, is funnel-shaped, having a width of about 8 ft. at the mouth, but contracting to about 10 in. near the centre. By casting stones or turf into the shaft so as to stopper the narrow neck, eruptions can be accelerated, and they often exceed in magnitude those of the Great Geyser itself. During quiescence the column of water fills only the lower part of the shaft, its surface usually lying from 9 to 12 ft. below the level of the soil. Unlike that of the Great Geyser, it is always in ebullition, and its temperature is subject to comparatively slight differences. On the 8th of July 1847 Bunsen found the temperature at the bottom 112.9 deg. C; at 3 metres from the bottom, 111.4 deg.; and at 6 metres, 108 deg.; the whole depth of water was on that occasion 10.15 metres. On the 6th, at 2.90 metres from the bottom it was 114.2 deg.; and at 6.20 metres, 109.3 deg. On the 10th, at 0.35 metres from the bottom, the reading gave 113.9 deg.; at 4.65 metres, 113.7 deg.; and at 8.85 metres, 99.9 deg.

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