191 



inoculation material was taken by means of a sterile spatula. The 

 lumps of clay and peat suited onr purpose well, since in the splitting 

 the fracture was not contaminated by crumbling- particles of the 

 edges, which was owing to the solid structure of the samples 

 resulting frotn their humidity. 



The time in which the formation of hydrogen sulphid in the 

 culture-bottles connnenced was very different for the same inoculation- 

 substance and especially for the sulphate reduction it largely depends 

 on the number of viable germs present at the outset of the experiment. 



The clay-, and the peat-samples dredged up with the "puis", 

 were derived fi-om the clay-, and the peat-banks underlying the 

 dunes. They were all compact masses, in which the original stratified 

 structure, arising from sedimentation, had been preserved. These 

 clay-, and peat-layers being all but impermeable to water, their 

 inside represents the original bacteriological conditioji of the stratum, 

 from which the sample has been taken. 



The clay- and peat-lumps were on the outside wet and on the 

 inside, judging superficially at least, moderately humid. The water- 

 content of the clay amounted to about 26%; in the clay-samples 

 which contained peat in the stratified structure, the content of 

 moisture was considerably higher, viz. about OOV^. The peat-samples 

 exhibited the largest amoiinl of water, viz. rather more than 777„. 



The clay- and the peat-lumps varied from very large ones to 

 those of the size of a fist and appeared to meet the bacteriological 

 requirements in every respect. 



§ 4. Summary of re.'iults and observations on the inquiry about 



sulphate- reduction. 



The number of soil-samples of the 9 wells which were examined 

 for sulphate-reduction, have beeit summarized in the subjoined table. 



The quantum of infection-material used for every sulphalereduction- 

 tesl amounted to from 5 to 10 grs. of the soil-sample. After an 

 interval of from 3 (o 20 days sulphate-reduction revealed itself at 

 25° C, which period rose to 5 weeks in the case of the peat- 

 sample B 31 . 



In every well, even the deepest of 34.50 m. below A. P., we 

 chiefly found sand over the whole depth, in which irregularly spread 

 lens-shaped clay-, and peat-layers occurred alternately. 



With a"' few exceptions all the sand- and clay-samples indicated 

 in the subjoined table, yielded on examination for sul[)hate-reduction a 

 conclusive positive result. Oonsequentiy the dull-grey or grey colour 



