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giving when dissolved in acids a black colour to so-lution of galls, and a bright blue precipitate to so-lution of prussiate of potassa and iron.

6. The oxide of manganesum is the substancecommonly called manganese, and used in bleach-ing. It appears to be composed of one proportionof manganesum 113, and three of oxygene 45. Itis distinguished from the other substances found insoils, by its property of decomposing muriatic acid,and converting it into chlorine.

. Vegetable and animal matters are known by theirsensible qualities, and by their property of beingdecomposed by heat. Their characters may belearnt from the details in the last Lecture.

8. The saline compounds found in soils, are com-mon salt, sulphate of magnesia, sometimes sulphateof iron, nitrates of lime anu of magnesia, sulphateof potassa, and carbonates of potassa and soda. Todescribe their characters minutely will be unneces-sary ; the tests, for most of them have been noticedp. 114.

The silica in soils is usually combined with alu-mina and oxide of iron, or with alumina, lime, mag-nesia and oxide of iron, forming gravel and sandof different degrees of fineness. The carbonate oflime is usually in an impalpable form: but some-times in the state of calcareous sand. The mag-nesia, if not combined in the gravel and sand ofsoil, is in a fine powder united to carbonic acid.The impalpable part of the soil, which is usually