718 



away into small tins shut off by insulating tape, and look them 

 to Groningen for immediate investigation. 



Finally a couple of samples the radio-activity of which was said 

 to have manifested itself by means of radiograms, were added to 

 these; and yet: two other samples 1. dregs of sulphur-bacteria '2. 

 very wet mud from the ditch that skirts the lake. All these samples 

 were investigated by Miss Folmkr, who will describe below more 

 fully her mode of working and the results. 



§ 2. Measurements. 



The researches, the desirability of which was demonstrated by 

 Dr. Blaauw in his Introduction and which in coimection with the 

 experience obtained in the course of the experiment were constantly 

 enlarging, can principally be reduced to the two following parts: 



I. To this belongs the investigation (cf. Introduction) concerning 

 the 12 samples of boring, the 7 samples for comparison, the samples 

 1, II, and III, the Fango of Battaglia, already long known to be 

 radio-active and finally the sample: mould. All these have been 

 investigated according to the "emanation method", of which further 

 details will follow below. 



II. In contradistinction with the preceding the "direct" measuring 

 method defined more closely below, was yet applied to the second 

 series of experiments in which the emanation obtained from the 

 mud was not investigated, but the mud itself with regard to radio- 

 activity. This second series of experiments principally extended over 

 the 48 mud samples (cf. Introduction), all of them taken from the 

 neighbourhood of the Betjenskelder or from the Betjenskelder itself. 



A closer consideration of researches I and II may set forth the 

 motive for these two series of experiments performed at such various 

 times, as well as the different choice of methods of investigation. 



Part I. 



Description of the investigation accordiny to the ''Emanation 

 methocr . 



Here the first part certainly is the laborious dissolving of the 

 various samples for which I used the method as indicated in outline 

 by various investigators. ^) 150 grammes were taken from each 

 sample after having been dried by a slight heat, then sifted minutely 

 and shaken forcibly for five minutes; then 5 grammes of this were 



1) Gf. for this: B. B. Boltwood, Phil. Mag. 1905. J. Joly, Radioactivity and 

 Geology, 1910. E. H. Büchner. Ghem. Weekly 1913. 



