55 233 



channels and great heat energy supplied by hot water and steam, and hot springs 

 with wider channels and less heat energy. The former are constantly boiling 

 because the hot water cannot settle in the narrow channels on account of the hot 

 vapours and water which pass through them with great force. The latter are 

 periodic geysers. The wide and, (as at "Störi Geysir"), perpendicular channels are 

 filled with water which is almost stagnant. The temperature of the water at the 

 surface is kept a little below boiling point, but the temperature increases in pro- 

 portion to the depth of the water. The temperature is, however, always a little 

 below the boiling point of water at the same pressure. 



Immediately after an eruption, this difference is rather great, but it gradually 

 lessens, until, just before the next eruption, according to measurements of the 

 temperature made in the geyser channel itself, the difference is so small that a 

 slight rising of the water column is sufficient to cause the water to boil. 



The rising of the water is, according to Bunsen, explained by the fact that 

 many great basins with hot water, at "Störi Geysir" as well as at Reykjafoss, do 

 not give off air bubbles steadily, but periodically. Taking for granted that the 

 same thing happens at the bottom of the geyser channel, it will then cause a 

 periodic rising of the water, and thereby possibly an eruption. 



As before stated, there are many objections to this theory. Lang', for instance, 

 regards the Bunsen theory as unsatisfactory, and as conflicting with other geological 

 theories, because it does not take into account the circulation of the water in the 

 geyser channel caused by the hotter water lower down in the channel having less 

 density than the colder water higher up. Neither does the Bunsen theory, in his 

 opinion, explain the intensity and periodicity of the eruptions. In this last point 

 I agree with Lang, though I have arrived at this conclusion on considerations 

 somewhat different to his. 



In accordance with Bunsen's curves of the temperature in the geyser channel, 

 a rising of the water column immediately before an eruption would only result in 

 the temperature of the water in a small part of the channel becoming higher than 

 the boiling point at the same pressure. Then, of course, the water in this part of 

 the channel boils. But in ordinary circumstances this would by no means cause 

 an eruption. If the Bunsen theory be correct there must be some particular causes 

 at work in the geyser channel, but evidence on this point is entirely wanting. 



Again, it is questionable whether Bunsen's method of dealing with the tempera- 

 ture measurements in the geyser channel, made by him and Desclgizeaux, is ab- 

 solutely correct. Of the five series of measurements they have made-, Bunsen 

 only uses the 2nd., 3rd. and 4th., without giving any reason for omitting the first 

 and the last series of observations. But these very observations omitted are of 

 primary importance, in that they are the first measurements made after eruptions. 

 Indeed, it seems as if the observers themselves do not have very much confidence 



' loc. cit. 



- Compt. Rend. 23, 934. 1847. 



