t HAP. xin. ON WARPING. 887 



uniformity of conditions in the water-meadows than can possibly exist 

 in ordinary non-irrigated meadows. Particularly is this so with regard 

 to moisture. Year after year are the meads subjected periodically to 

 the beneficent influence of running water, so that even in seasons of 

 the severest drought the removal of the hay-crop brings to view a 

 sward which is bright, fresh, and verdant. This was specially 

 noticeable in the hot droughty summer of 1887, for whilst, at the end 

 of July, the ordinary meadows of the district were bare and scorched, 

 the water-meadows carried a luscious green aftermath, and afforded 

 good grazing for milch cows. Thus, whether the season be wet, or 

 dry, or of average rainfall, it is much the same to the water-meadows, 

 inasmuch as the system of irrigation renders them largely independent 

 of the rainfall. On the other hand, variations in temperature and in 

 the duration of sunshine are probably as operative on the water- 

 meadows as on other grass lands, and it is in this direction that seasonal 

 differences are most likely to prove effective. Assuming, moreover, 

 in accordance with the researches of Boussingault, Gilbert, Risler, and 

 Herve-Mangon, that it requires a certain total amount of heat above 

 an ascertainable minimum temperature to ripen the seed of any given 

 plant, this amount will be the earlier acquired the hotter the season. 

 More seed of certain species of plants will consequently ripen and fall 

 to the ground, and, so far as these species are concerned, they may 

 gain an advantage in the struggle the full effects of which will not 

 make themselves apparent till the following season. 



CHAPTER XIII. 

 ON WAEPING. 



practice of warping is extensively pursued in certain districts. 1 

 JL It consists in directing upon the land the tidal overflow of large 

 rivers, suffering it to deposit the sediment or warp which it contains, 

 and then letting the water run off again as the tide ebbs. The water 

 is admitted by sluices into a still pond, or over a convenient area of 

 country. An embankment preserves it in a great measure from the 

 agitation of the waves, and the earthy matter which the water contains 

 is thus deposited. On the banks of the Humber this operation has 

 long been practised on a most extensive scale. The water is there 

 more than usually turbid, on account of the meeting of the tide and 

 the fresh water. The tide runs for a considerable way inland, and in 



1 Mr. Ralph Creyke, of Rawcliffe, near Goole, appears to have been the pioneer of 

 artificial warping. He obtained a private Act of Parliament in 1821, and led the warp 

 quite three miles by "canal." ' 



