IRRIGATION AND DRAINING. 71 



given a good dressing to 100,000 acres of land, Such wa- 

 ters as have flowed out of the sewers of cities or past slaugh- 

 ter-houses and certain manufactories, and received the rich, 

 vegetable food thereby afforded, are the most beneficial when 

 applied to vegetation. Meadows thus irrigated in the neigh, 

 borhood of Edinburgh, have rented by the acre, at the large 

 Mini of $250 per annum. But when none of these can be 

 procured, pure spring water apparently destitute of any solu- 

 ble matters, may be advantageously used. 



Besides its drainage of different matters from remote dis. 

 tances, water freely obsorbes the gases (carbonic acid, oxy- 

 gen and nitrogen, &c.,) in proportions altogether difierent 

 from those existing in the air, and brings them to the roots 

 by which they are greedily appropriated, and in its onward, 

 agitated progress over the field, it again absorbs them from 

 the air, again to be given up when demanded by the roots. 

 When the water is permitted to remain stagnant on the sur- 

 face, this good effect ceases ; and so far from its promoting 

 the growth of the useful and cultivated grasses, they speedily 

 perish and a race of sour and worthless aquatic plants spring 

 up to supply their place. 



Another and important office that water fulfils in ministe- 

 ring to the growth of vegetation, is in disposing the soil to 

 those changes which are essential to its full maturity. 

 Gypsum requires 460, and lime 778 times its bulk of water 

 at 60 to dissolve them. Others among the mineral consti- 

 tuents of plants, also require the presence of large quantities 

 of water to fit them for vegetable assimilation. 



TIME FOR APPLYING WATER TO MEADOWS. In those 

 regions where the winters are not severe, water may be kept 

 in the fields during the entire season of frosts. This prevents 

 its access to the ground, and on the approach of warm wea- 

 ther the grasses at once start into life, and give an early and 

 abundant. But in general, this system cannot be success- 

 fully practiced. The water is admitted at proper intervals, 

 freely during the spring and early part of the summer when 

 vegetation is either just commencing or going forward 

 rapidly. It is sufficient to flood the surface thoroughly, and 

 then shut oft' the water for a time. In very dry weather this 

 may be done with advantage every night. Continued water- 

 ing under a brjght sun, is an unnatural condition with up- 

 land grasses, and could never be long continued without 

 proving fatal to them. Neither should the water be applied 

 after the grasses have commenced ripening. Nature is the 



