40 LESSONS IN CHEMISTRY. 



temperature of the soil in a field which has been thorough 

 drained and one which is lying neglected beside it. The 

 undrained soil, therefore, is correctly regarded as cold by the 

 farmer, and an extensive system of drainage is among the 

 most important means to be adopted for improving the pro- 

 ductive powers of our fields, and for enabling them to enjoy 

 some of the advantages which other countries derive from a 

 warmer sun. The undrained bogs and sheets of water 

 which, like Loughs Neagh, Corrib, and Allen, cover so much 

 of the country, must exercise a most injurious inflaence upon 

 its general temperature ; thus, it is found that the mean tem- 

 perature of the island is about 49-|- degrees of the thermo- 

 meter, which is only 4^ degrees above the temperature at 

 which many seeds placed in the ground refuse to vegetate. We 

 need not, therefore, be surprised that, in many undrained dis- 

 tricts, especially in our northern counties, but a small return 

 should be given by the soil, and that the harvest should 

 be delayed far beyond the safe and proper season. An 

 excess of moisture in our soils is, in fact, their chief agricul- 

 tural defect, and fortunately it is in the power of our farmers 

 to correct this evil. The thorough drain will remove the 

 water which consumes the heat of the sun, and allow the air 

 to pass into the interior of the soil, warming it and giving it 

 that temperature which will cause the dormant seed to vege- 

 tate, and at the same time supply to the young plant the 

 gases requu'ed to promote its growth.* Nor will the advan- 

 tages to be derived from the drainage of the country be con- 

 fined to the farmer; all classes will be benefited in the 

 increased salubrity of the clunate, and the removal of many 

 causes of disease. 



39. Water, therefore, we have seen, not only, like the air, 

 supplies plants with gases essential to their growth, but also 



* I am informed by Doctor Orr that forty years ago, in a townland 

 about two miles east from the Castlereagh hills in Down, the harvests 

 were twelve or fourteen days on an average earlier than in Castlereagh, 

 where the farms are more elevated and exposed ; but that now, by supe- 

 rior cultivation, draining, manuring, &c. the case is altered, and the 

 crops an-ive at maturity from six to eight days earlier than in the 

 former locality. 



It is stated that in Aberdeenshire, in consequence of extensive 

 drainage during the last twenty years, the crops ripen ten or fourteen 

 days sooner than they formerly did. — Mr. Gray in Prize Essays of 

 the Highland Society. 



