1911.] STEVENSON— FORMATION OF COAL BEDS. 577 



But in peat from another locality, the process of change was 

 dififerent : 



Muck-carbon, etc 80.0 



Apocrenic acids 17.0 



Crenic acids i .0 



Ash 2.0 



Julien notes the difference in ash between peat and the plants 

 whence it is derived. Sphagnum has from 3 to 4 per cent, and the 

 peat varies from i to 25 per cent. Vohl found only 1.25 per cent, 

 of ash in a Hochmoor or Sphagmon peat. In the ash of living 

 plants he found 20 per cent, of alkalies and 42 per cent, of silica, but 

 only 3 to 4 per cent, of each in the peat or in the soil. On the other 

 hand, there was concentration of alumina, ferric oxide and calcium 

 carbonate as well as of phosphoric and sulphuric acids. Pyrite occa- 

 sionally abounds in peat and its decomposition gives a basic ferric 

 sulphate to the bog iron ores. 



Nitrogen is always present in peat, sometimes as much as 3 per 

 cent. ]\Iany suggestions have been made to explain its occurrence ; 

 but Julien thinks that most probably it has been derived from animals 

 living in the peat or in the soil. The vast number of insect cases 

 found in peat bogs is well known and Scudder has proved that 

 insects were very abundant in the coal period. The nitrogen content 

 is due very largely to the exuviae of insects, and its frequent concen- 

 tration in the lower layers of bogs may be due to the survival of 

 those exuviae as chitin. 



In the humus one finds as inert substances, nitrolin (rotten wood) 

 and humin. which is black and forms the chief constituent of humus ; 

 but it is so mingled with nitrolin that its exact composition cannot 

 be determined. Mulder studied humus and humic acid from the 

 black peat of the Haarlem sea ; he obtained ulmic acid from rotten 

 wood as well as from the light brown Frisian peat. The formulas 

 of the several acids obtained seemed to be 



Humic acid C^oHnOe 



Geic acid C20H12O7 



Ulmic acid CmHuOo 



Stern, however, thought humic and ulmic acids isomeric, with the 



175 



