ADDITIONAL NOTES. 585

probably contributes moft to the growth of vegetables, and next to

that the calcareous part; there is reafon to conclude, that if a few: pounds of different foils are dried by the fame degree of heat, and

then weighed, and afterwards expofed to a red heat in an open fire;

that the foil, which lofes moft weight, 1s probably the moît fertile;

becaufe the carbonic matter will almoft all efcape in flame, and almoft

half the weight of the calcareous earth in carbonic acid.:

Another method of giving fome conjecture concerning the fertility of a foil may be by examining its fpecific gravity; as the fpecific gra- vity of garden-mould is faid by Mufchenbroek to be 1,030, compar- ed to 1,000 of water. And Fabroni found the fpecific gravity of barren fandy land to be 2,210 to 1,000 of water. This experiment would not be difficult to try with fufficient accuracy by drying two different foils at an equal diftance from a fire, or in the fame oven, and then weïghing a pound of each in a thin bladder with apertures near its top or neck; and then letting the bladder fink fo low into water, as to admit the water through the apertures amongft the foil; and laftly, obferving the difference between their refpective weights in air, and in water,

Neverthelefs the method moft in ufe by the purchafers of land to judge of its value is by attending to the growth and colour of the ve- getables, which cover it; which requires an experienced eye, and can- not be eafly defcribed in words. Add to this that vegetables, which grow wild on foils, will in fome meafure indicate the nature of them. As the digitalis, and arenarea, are found generally on fandy foils, the veronica becabunga, and crefles of fome kinds, belong to moift fitua- tions, and others to mountainous ones. À particular catalogue of fuch plants, as fpontaneoufly grew in different fituations, might affift in dif- covering the degree of fertility, and the nature of the foil; as other flowers by the time of their opening in each climate, which is term- ed the Calendar of Flora, may teach the temperature of the feafon.

In fome parts of the country the fpontaneous production of many 4 FE docks,