330 



PL A 



TLO 



ihe'n particular nature, divide, sof- 

 ten, enrich, warm, or stiffen the 

 soils with which they are mixed. 

 The quantity of plaster spread 

 upon the land is so trifling, that it 

 can have little effect on the soil. 

 ' I speak from experience. Plas- 

 ter buried in the earth where sain- 

 foin has been sown, has produced 

 no visible alteration ; whilst the 

 same quantity of plaster spread 

 over the same surface of sainfoin, 

 has produced the most beautiful 

 vegetation. 



" From this experience, so uni- 

 form in the application of plaster, 

 I am led to believe, that one must 

 consult as well the nature of the 

 soil, as the kinds of plants to which 

 we apply plair ter. Thus, whatever 

 may be the soil on which clover, 

 lucern, and sainfoin naturally flour- 

 ish vigorously, or with that vigour 

 which encourages us to apply ma- 

 nure, there is no risk in trying 

 ■plaster. 



" It is to be remarked, that plas- 

 ter operates on plants in a direct 

 ratio to the size and number of 

 their leaves. 1 have spread plas- 

 ter on land, where sainfoin was 

 mixed with the common grasses 

 which compose our meadows. 

 The growth of the sainfoin and 

 wild honey-suckle has been, be- 

 yond comparison, greater than that 

 of the common grasses. It is to 

 this cause I attribute the failure of 

 success on grass-ground, chiefly 

 tilled with common grasses. I 

 have a field of lucern separated 

 from a natural meadow only by a 

 brook. I have greatly increased 

 the lucern by the plaster, whilst 

 the effect of a like quantity on the 



adjoining grass-land, was scarcely, 

 if at all, perceptible." 



PLOUGH. It would not be 

 possible to give any accurate idea 

 of modern improvements in the 

 construction of this very useful 

 implement, without long descrip- 

 tions, and expensive drawings, in- 

 compatible with the general design 

 of this work, we can, therefore, 

 only give some general rules for 

 the construction of ploughs, and 

 refer our readers to more volumi- 

 nous and elaborate works for fur- 

 ther and more minute information 

 on this subject. 



" The great points to be attend- 

 ed to in ploughing, are, 1., to open 

 a fair regular furrow ; and 2., to 

 do this with as little resistance as 

 possible. It is believed that these 

 advantages are to be obtained, by 

 the use of a plough, to which the 

 mould-board, invented by Thomas 

 Jefferson, is affixed, and of which 

 the annexed views will give a clear 

 idea. 



" The following account of this 

 mould-board, and of the principles 

 upon which it is constructed, are 

 taken from a communication, ad- 

 dressed to Sir John Sinclair, in 

 1 798, then President of the British 

 Board of Agriculture, and inserted 

 in the 4th volume of the Transac- 

 tions of the American Philosophi- 

 cal Society, vol. IV. p. 314. 



" The mould-board should be a 

 continuation of the wing of the 

 ploughshare, beginning at its hin- 

 der edge, and in the same plane. 

 Its first ofl^ce is to receive the sod 

 horizontally from the wing ; to 

 raise it to a proper height for be- 

 ing turned over; and to make, in 



