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372 Derivatives. Loam, according to Mr. Woodward, confifis of clay, mixed with fine fand, that is, in other words, of clay, with a fuperabundance of fand *; and in effedf, Mr. Bergman, having analyzcd fome found in the neighbourhood of London, and confidered as very excellent, found it to con- fift of 87 per ct. of a reddifh grey fand, as fine as meal, and 13 of argill. Now if we fuppofe clay to confift, as it moft frequentlv does, of 30 peV ct. of argill, and 70 of fine fand, we fhall find that loam of the beft kind contains an excefs of fand amounting to 17 per ct; if the excefs of „fand be greater it will form what is called a fandy loam ; if fmaller clayey loam. Mr. Bergman found nothing calcareous in the loam ; when it contains any, it fo far inclines to the nature of marl, and this marlaceous loam may be either fandy or clayey, according as the pro- portion above indicated is exceeded on either fide; offandy loam, fee a fpecimen in Lefke S. 1061. But loams moft frequently contain alfo a portion of calx of iron, and this calx is more or lefs oxygenated, a circumfiance which produces a confiderable varietyin the colours, and proba- bly alfo in the vegetative powers of this earth ; if its proportion be confiderable, namely, 4 or 5 per ct. they ofte'n contain alfo fome proportion of vitriolic acid; the colour of loam frequently proceedsfrom that of thecalces of iron contained in it, but more frequently from its fandy part. Gravel, is a coarfer fort of fand, either of a calcareous or filiceous nature, is often mixed with loams, and alfo pebbles, from whence new diftindtions arife of importance to agriculture. * Being derived from the German word Leime-, it figni- fied in ancient times a vifcid earth. See Johnfon’s Diflionary. Moulds