Kjn the occasion of my exploration of the hot springs in the south-west of 

 Iceland in the summer of 1904, it was shown that the gases from these springs 

 contain radioactive emanations, and at the subsequent investigation in the laboratory, 

 it was again proved by Prof. K. Prytz and myself, that the gases emanating from 

 the springs contain argon and helium. As these investigations seemed to justify 

 the opinion that a more extensive exploration of the radioactivity of the Icelandic 

 springs would, on account ot the isolated position and the volcanic nature of the 

 island, contribute considerably to an elucidation of the question as to what extent 

 radioactive substances are to be found in the earth, as well as their significance 

 with regard to the earth's temperature, I undertook, in the summer of 1906, a new 

 expedition to the hot springs of Iceland. 



I received from the Carlsberg Fund for the expenses of this expedition, 5800 

 Kroner, {Ï 322. 4. 6), — 5000 Kroner for the journey, and 800 Kroner for the examina- 

 tion of the materials collected on the journey. I herewith tender the directors of 

 the Carlsberg Fund my respectful thanks for this support. 



The experimental part of the preparations for the journey, as well as the 

 analytical work necessary to determine the composition of the hot spring gases, by 

 means of the sample gases taken, was carried out, with Prof. K. Prytz's permission, 

 in the "Polytekniske Læreanstalts fysiske Laboratorium" (the physical laboratory of 

 the Polytechnic Academy) in Copenhagen. For this permission, and for his kind 

 advice in regard to the experimental work, 1 offer Prof. K. Prytz my heartfelt thanks. 

 I also thank Mr. S. Jonsson, who accompanied me on my journey in 190Î, for his 

 interest in these investigations, evidenced by his willingness to enter a second time 

 on the hardships of the journey, in order to help me in the scientific work. The 

 results 1 have attained through this expedition, are to a great extent due to his 

 capable assistance. 



The present treatise will deal freely only with the scientific work done on 

 the journey and in the laboratory, together with its results, disregarding for the 

 most part the equipment and the details of the journey. But for the sake of 

 orientation, 1 have included a small map of Iceland (Fig. 1), on which our route 

 and the spring districts visited are marked. 



' K. Prytz og Th. Thorkelsson : Oversigt over det kgl. danske Videnskabernes Selskabs Forhand- 

 linger 1U05, p. 317. 



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