On Agricultural Mechanics. 117 



brought into Berwickshire, is very applicahle : — " I believe it is not 

 found universally applicable in grounds containing irregularities of sur- 

 face and numerous stones, both of which are apt to force it, by encoun- 

 tering the wheels, from its proper direction. Besides, I am apt to be- 

 lieve that the chief use of the wheels, in favourable soils, is to relieve 

 the ploughman from attention and labour, by adding considerably to the 

 draught of the horses.'* 



4. The Harrow. 



In describing this implement I shall follow the rule I have 

 already imposed on myself, first considering its object and use, 

 and then pointing out what form best answers the purpose in- 

 tended. 



The barrow is required not merely to break the surface clods 

 of rough ploughed land, nor to gather weeds out of it, but a great 

 part of its value also depends on its power of loosening the sur- 

 face of the soil, and thus allowing the air access to the roots of 

 the plants growing on it, and to the manure lying in it. This is 

 evidently the case from the advantage, frequently most marked, 

 that attends the use of this implement, in spring, over young 

 wheat or corn of any kind. A harrowing in such a case, which 

 would appear most likely to destroy the young plants, is found to 

 cause them to sprout and shoot out with increased vigour. This 

 is especially the case on those soils which are termed sleepy, from 

 their tendency to run together after rain, and thus to form a sur- 

 face almost impervious to air. The harrow is used for three pur- 

 poses, — first, to break the surface- clods, and reduce the surface 

 of ploughed land; secondly, to gather together and shake out the 

 weeds that are in the soil ; thirdly, to cover the seed. 



For the last purpose a lighter implement is used than for the 

 former, and the teeth are nearer together. 



The common form of the harrow, it is evident, is not a good form ; the 

 teeth are closest together in the front part of the implement, and the dis- 

 tance between them widens towards the end of the machine. Now, if 

 it be used to reduce a rough surface — if there is to be any irregularity 

 in the distance of the teeth — they should be nearer towards the back 

 part of the machine ; for the clods of earth will be partially broken by 

 the front teeth, and will thus be more efficiently acted on by those be- 

 hind. It is evidently incorrect to have the teeth closest where the earth 

 is roughest, and farthest apart where it is finest. 



The best form of the harrow is the rhomboidal, with the teeth at equal 

 distance throughout. A pair, when hinged together, gives sufficient 

 work for a pair of horses. It is this form alone which ensures that all 

 the teeth shall work in different paths, and that thus the whole of the 

 ground shall be uniformly stirred and broken: a consideration of the 

 annexed figure will make this appear. 



