734 



with ever increasing organic remains. We )iow see that the i-ad in- 

 activity increases chieflv from the top to the bottom, i.e. with the 

 increase of slime of the river and with the decrease of organic 

 material ; boring 2 with 0.43, boring 4 with 0,54 boring 6 with 

 0.55, boring 8 with 0.61, boring 9 with 0.79, boring 12 with 

 2.16x10-12'. But why that slight fall in borings 10 and 11? It 

 is exactly in these two samples that there is a larger quantity of 

 sand. Sample 9 still consists of very black, fat clay with much 

 fine mineral dust, the feio grains of sand being 100 — 150 ix long 

 at most. Sample 10: watery mud of very fine mineral dust (slime), 

 mixed with more grains of sand, somewhat coarser, at most 350 ^i 

 long; Sample 11: Bluish dark-grey, because the slime is mixed with 

 a few more grains of sand, very much pai-ticularly fine mineral 

 dust, grains of sand at most 300ft long; small remains oï peat and 

 wood. (Treatise p. 38). While in going from 9 —12 one might expect 

 a further rise of radio-activity, this rise is temporarily suppressed, 

 because layers 10 and 11 again contain more and larger grains of 

 sand, especially 11 a few more remains of peat. Only when this has 

 entirely passed in 12, there appears a rather high number. But in 

 sample 13 the activity falls again to the value of 10 and 11 and 

 concerning this was noted down at the time: fat, black clay, many 

 remains of peat, very much fine mineral dust mixed with somewhat 

 larger grains of sand at most 200 -400 (it long (Treatise p. 39). 

 Then again a fall, if mixed with more organic substance and larger 

 grains of sand. So in its details it also tallies entirely with the 

 conclusion drawn higher up, but at the same time it appears from 

 this of how much geological value accurate sensitive determinations 

 of radio-activity can be. 



Finally we may yet draw the attention to the numbers occurring 

 in table 2 as collected by Miss Folmer. There the radio-activity is 

 the stronger as the given number of seconds is smaller. We refer 

 to the table and to Fig. 1. Where 4 or 5 samples were taken from 

 one spot, one higher than the other, it is again striking that the 

 smallest action is always found in the highest layers that were 

 bored; that first the activity increases in the downward direction, 

 is strongest at 150 cm., depth generally and often decreases again 

 at 180 cm. The same may apply here as to the great boring, that 

 the upper layers contain a larger quantity of organic material. The 

 layer of clay goes down to the depth of 13 m. on the spot of 

 boring, on the spots of these shallow gaugings to 5 m. at most, 

 generally far less deep, so that for the rest one can hardly compare 

 the same depths. Moreover, it will be a good thing to pay attention 



