67 245 



dense again at a considerable depth, for otherwise the spring water would hardly 

 be able to convey such large quantities of dissolved substances as it actually does. 



The surface temperature of the spring water is dependent on several different 

 factors. Some of these are of a more individual character, in that they are con- 

 trolled by the form and nature of the spring. The loss of heat to the surroundings, 

 — whether it is produced by heat conduction from the spring channel or by 

 evaporation from the surface of the water, can be considered among these. The 

 differences in the temperature of springs situated in the same group are chiefly 

 due to these circumstances. There are two other factors likely to be of importance 

 with regard to the temperature of the spring water, which may be supposed to be 

 almost identical in springs belonging to the same group. These factors are the 

 heat supply from below and the loss of heat caused by boiling. 



At Reykir in Skagafjöröur the first of these is the most important factor. The 

 intensity of the heat supply is evidently much less there than at the other places 

 explored. As the highest temperature measured at Reykir was only 68° C, the 

 water in the depth of the earth cannot possibly have as high a temperature as 

 at the other places. 



At the other places investigated, the temperature down in the earth is un- 

 doubtedly considerably higher than 100° C. We know that the temperature in the 

 depth of the earth must be over 100^ C, otherwise the steam in these springs would 

 not possess sufficient power to consummate an eruption. The highest temperature 

 measured by Bunsen and Descloizeaux at the bottom of a geyser channel was 

 127° C. 



When the temperature of the spring water is nearly at boiling point, which 

 is the case at most of the places we explored, the surface temperature is very little 

 influenced by variations in the supply of heat energy. In such cases, the circum- 

 stances of cooling, and, foremost among these, the ebullition, are of the greatest 

 importance with regard to the temperature of the spring. 



The ebullition of the springs is dependent on the standing of the barometer, 

 on the amount of substances dissolved in the spring water and on the volume of 

 the spring gases. The dissolved substances raise the boiling point of the water. It 

 cannot yet be decided how much this amounts to in the case of spring water, as 

 no measurements to this end are available, but probably it only amounts to a 

 small fraction of a degree. Setting this aside, we calculate, in the fourth column 

 of Table I , the boiling point of distilled water, corresponding to the respective 

 height of the barometer. It appears from this table that the boiling point thus 

 calculated is higher throughout than the temperature of the spring. 



The bubbles rising up through the water are not filled only with vapour, as 

 by ordinary boiling, but with a mixture of vapour and spring gas, and it is the 

 combined pressure of the vapour and the spring gases that withstands the atmos- 

 pheric pressure. Assuming that the bubbles are saturated with vapour having the 

 same temperature as the spring, the relation between the spring gases and the 



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