The particular kinds of soil upon which the disease is observed are black, loose, warm, humous soils; also those containing lime, marl, and clay, finally peaty, swampy soils resting upon strata which hold the water, or, in other words, are impervious.
"Special Report on Diseases of Cattle"
U.S. Department of Agriculture J.R. Mohler
In not a few cases, the bogs seem to occupy the sites of ancient lakes, shell-marl often occurring at the bottom of these.
"Geology"
James Geikie
What may be inferred from the occurrence of shell-marl underneath peat?
"Geology"
James Geikie