As I could not give in this paper anything like a full account of my observations and the results of my studies concerning this question made during an expedition through Iceland in the summer of 1908, I must refer the reader to my special papers on this subject. Everyone will find there the reasons which have induced me first to suppose the independence of the so-called ‘Schild’ volcanoes in Iceland of pre-existing fissures. This idea is confirmed by collecting proof after proof on the subject in the field during my researches. Naturally I could not give all the details in a first short preliminary communication, a fact which, I am sorry to say, has caused Professor Schwarz to doubt the correctness of part of my observations and conclusions. I may therefore be allowed to discuss shortly the two main objections of Professor Schwarz to my theory.