368 SCIENCE OF AGRICULTURE. Part II. 



part of their heat in passing over a surface so much lower in temperature. The vari- 

 able nature of our climate is chiefly owing to the unequal breadths of watery surface 

 which surround us ; on one side, a channel of a few leagues in breadth ; on the other, 

 the Atlantic Ocean. The temperature of the British seas rarely descends below 53 

 or 54^. 



24S8. The British climate varies materially within itself: some districts are dry, as the 

 east ; others moist, as the west coast ; in the northern extremity, dry, cold, and windy ; 

 in the south, warm and moist. Even in moist districts some spots are excessively dry, 

 as part of Wigtonshire, from the influence of the Isle of Man in warding off the 

 watery clouds of the Atlantic ; and, in dry districts, some spots are moist, from the 

 influence of high mountains in attracting and condensing clouds charged with watery 

 vapour. The mean temperature of London equals 50 36 ; that of Edinburgh equals 

 47* 84' ; and the probable mean temperature of all Britain will equal 48. The usual 

 range of the barometer is within three inches. The mean annual rain is probably about 

 32 inches. The climate is variable, and subject to sudden alternations of heat and cold, 

 which are supposed to render pulmonary complaints common with us : but on the whole 

 it is healthy, and the moisture of our clouded atmosphere clothes our fields with a lasting 

 verdure unknown to the more favoured regions of Southern Europe. (T.) 



2439. The deterioration of the Bntish cliyyiate is an idea entertained by some ; but 

 whether in regard to general regularity, temperature, moisture, or wind, the alleged 

 changes are unsupported by satisfactory proofs. It is not improbable but the humiSty 

 of our climate, as Williams alleges {Climate of Britain, &c. 1816), has of late years 

 been increased by the increase of evaporating surface, produced by the multiplicity of 

 hedges and plantations ; a surface covered with leaves being found to evaporate con- 

 siderably more than a naked surface. If the humidity of the climate were greater 

 before the drainage of morasses and the eradication of forests for agricultural purposes, a 

 comparative return to the same state, by artificial planting and irrigation, must have a 

 tendency to produce the same results. However, it will be long before the irrigation of 

 lands is carried to such a degree as to produce the insalubrious effects of undrained 

 morasses ; and as to our woods and hedges, we must console ourselves with the beauty 

 and the shelter which they produce, for the increase of vapour supposed to proceed from 

 them. 



BOOK IV. 



OF THE MECHANICAL AGENTS EMPLOYED IN AGRICULTURE. 



2440. Having taken a view of the vegetable and animal kingdoms, as supplying the 

 subjects of agricultural improvement, and of the mineral kingdom, manures, and the 

 weather, as the natural agents of their growth and culture ; our next course is to examine 

 the mechanical agents, or implements, machines, and buildings employed in agricultural 

 operations. In a rude state of husbandry few implements are required besides the plough 

 and the cart, and few buildings besides the stable and the barn. The ground is ploughed 

 and the seed thrown in and covered with a bush ; at harvest it is cut down and carted to 

 the barn ; and the three grand operations of the farmer are sowing, reaping, and thresh- 

 ing : but in our improved state of society, where all the science of mechanics as well as 

 of chemistry is made to bear on agriculture, the implements, machines, and buildings 

 become numerous, and equally so the operations. So numerous are the former, indeed, 

 that the theoretical enquirer is often puzzled in making a selection. The whole of the 

 most improved agriculture, however, may be, and in fact is, carried on with a very 

 limited variety both of implements and buildings. Intricate and complicated machines 

 are not adapted for a rustic art like agriculture, and a great variety are not required for 

 one, the operations of which are so simple as almost to be universally understood and 

 practised. In our enumeration we shall include a number that we do not consider of 

 much consequence ; but we shall always distinguish between the essential, and such as 

 are comparatively objects of superfluous ingenuity and expense. We shall adopt the 

 order of Implements of Manual Labour, Implements or Machines impelled by Quadrupeds 

 or other Powers, Structures, and Buildings. We shall give a considerable variety, net 

 altogether on account of their individual excellence, but to assist the mechanical reader 

 in inventing for himself. 



