times moderately coherent; rarely of a stonyhardness, and hence called stone-marl. Some-times of a compact, sometimes of a lamellartexture; often so thin as to be called paper-marl. It often abounds with shells, and thenis called shell-marl; which is looked upon asthe best sort. When in powder, it feels drybetween the fingers; put in water, it quicklyfalls to pieces or powder, and does not form aviscid mass. It chips and moulders by expo-sure to the air and moisture, sooner or later,according to its hardness and the proportion ofits ingredients: if heated, it will not form abrick, but rather lime. It effervesces with allacids. It consists of from 33 to 80 per cent, ofmild calx, and from 66 to 20 per cent, of clay.

To find its composition, pour a few ouncesof weak, but pure spirit of nitre, or commonsalt, into a Florence flask; place them in a scale,and let them be balanced; then reduce a fewounces of dry marl into powder, and let thispowder be carefully and gradually thrown intothe flask, until after repeated agitation no ef-fervescence is any longer perceived; let the re-mainder of the powdered marl be then weighed.