On the Theory and Practice of Water- Meadows. 465 



found that round rods of transparent glass suspended over grass 

 acted as well as opaque bodies in promoting its growth. Is it not 

 possible that the rippling water may act like these rods of glass ? 

 It is true that water, after passing over a portion of water-meadow, 

 is found to have lost much of its power when turned over another 

 portion. This we should expect, because in travelling over and 

 through the ground it has parted with its native heat, and will 

 produce a diminished effect. I believe that it produces still some 

 effect, otherwise the conjecture must, of course, fall to the ground 

 — the point need, however, not be pursued further. 



But, it may be asked, if streams act by their warmth when 

 turned over meadows, why do not all streams of the same tem- 

 perature act equally well ? Why are some streams better than 

 others ? Why do some not act at all ? The answer, I believe, 

 is this. Several foreign substances, present sometimes in streams, 

 are found by experience to be noxious to vegetation. Thus it 

 was mentioned above that water for irrigation should feel, in a 

 practised hand, oily as well as warm. This oiliness, T suppose, 

 is the same with what is commonly called softness, the opposite 

 of hardness, which is caused by the presence of carbonic acid, 

 of which latter quality the laundress also complains when the 

 soap will not dissolve in her washing-tub without the aid of 

 wood ashes or of soda. A spring which contains carbonic acid 

 largely is a petrifying one. We have some streamlets in this 

 neighbourhood which, for the first mile or two of their course, en- 

 crust their sides and bottoms with lime. Such are declared to 

 be unfit for irrigation, why I know not, but so experience teaches. 

 It is observed that the two favourable and the two unfavourable 

 qualities are generally found together in springs ; softness with 

 warmth, and cold with hardness. Ochrey springs, having on their 

 surface a film, which presents the colours of the rainbow, and 

 containing iron, are said also to be injurious ; though in one district 

 this iridescence was mentioned to me as even a favourable sign for 

 irrigation. There is another substance most certainly mischievous 

 to vegetation — the matter suspended in bog-water. Such water 

 is destructive to the growth of meadow-grass. Marsh peat is 

 itself so highly injurious, that when marsh peat has been put 

 by a mistake into flower-beds for the growth of rhododendrons, 

 it destroyed the garden turf for some breadth on each border. 

 But this is not a hopeless obstacle, though found in a stream. 

 I have seen water which a year or two before dribbling from 

 a bog had been worse than useless, now issuing from the drain- 

 pipes of that bog, itself cultivated, and after resting in a reser- 

 voir, spreading verdure over a field lower down the hill-side. 

 This vegetable extract, however, sometimes infects rivers them- 

 selves, as in the romantic scenery of West Somerset round Dul- 



