OF FOREST.TREES. 



pires the rest of the liquid at the summity and tops of the branches into CHAP, 

 the atmosphere, and leaving some of the less-refined matter in a viscid ^""^ 

 honey-dew, or other exsudations, (often perceived on the leaves and 

 blossoms,) anon descending and joining again with what they meet, repeat 

 this course in perpetual circulation. Add to this, that from hence those 

 regions and places, crowded with numerous and thick-standing forest- 

 green provender. The dung of ruminant animals, as cows and sheep, is preferable to that 

 of horses at grass, owing to the quantity of animal juices mixed with their food in chewing. 

 And here I beg leave to remark in general, that the fatter the animal, cceleris paribus, 

 the richer the dung. Human ordure is full of oil and a volatile alkaline salt. By itself, it 

 is too strong a manure for any land ; it should therefore be made into a compost before it 

 is used. The dung of carnivorous animals is plentifully stored with oil. Animals that 

 feed upon seeds and grains come next, and after them follow those which subsist upon 

 grass only. To suit these different manures to their proper soils, requires the greatest 

 judgment of the farmer, as what may be proper for one soil may be highly detrimental to 

 another. 



In order to strengthen my argument in favour of oil being the principal food of plants, 

 I must beg leave to observe, that all vegetables, whose seeds are of an oily nature, are 

 found to be remarkable impoverishers of the soil, as hemp, rape, and flax; for Avhich 

 reason, the best manures for lands worn out by these crops, are such as have a good deal 

 of oil in their composition ; but then they must be laid on with lime, chalk, marl, or soap- 

 ashes, so as to render the oily particles miscible with water. The book of nature may be 

 displayed, to show that oily particles constitute the nourishment of plants in their embryo 

 state ; and, by a fair iftference, we may suppose that something of the same nature is con- 

 tinued to them as they advance in growth. The oily seeds, as rape, hemp, line, and 

 turnip, consist of two lobes, which, when spread upon the surface, form the seminal leaves. 

 In them the whole oil of the seed is contained. The moisture of the atmosphere pene- 

 trates the cuticle of the leaves, and, mixing with the oil, constitutes a kind of milk for the 

 nourishment of the plant. The sweetness of this balmy fluid invites the fly, against which 

 no sufficient remedy has, as yet, been discovered. The oleaginous liquor being consumed, 

 the seminal leaves decay, having performed the office of a mother to her tender infant. 

 To persons unacquainted with the analogy between plants and animals, this reflection will 

 appear strange. Nothing, however, is more demonstrable. Most of the leguminous and 

 farinaceous plants keep their placenta, or seminal leaves, within the earth; in which 

 situation they supply the tender germ with oily nutriment, until its roots are grown suf- 

 ficiently strong to penetrate the soil. 



It is usual to talk of the salts of the earth ; but chymistry has not been able to discover 

 any salts in land which has not been manured, though, it is said, that oil may be obtained 

 from every soil, the very sandy ones excepted. Marl, though a rich manure, has no salts. 

 It is thought to contain a small portion of oleaginous matter, and an absorbent earth, of a 

 nature similar to limestone, with a large quantity of clay intermixed. Lime mixed with 

 clay comes nearest to the nature of marl of any factitious body that we know of, and may 



