1870.] of Sewage Irrigation. 21 



hand, where manures are applied as top-dressings in the solid form, 

 it is proved by experience that after heavy showers of rain the solid 

 manure is washed away, bodily as it were, into the ditches and 

 watercourses; so that whilst the outfalls from land top-dressed 

 and undrained are turbid with the matter carried away, and com- 

 plained of as a nuisance, the outfalls from drained land, richly 

 manured with the liquid, discharge pellucid streams." 



Liquid sewage has a special value distinct from the fertilizing 

 matter it contains, and also from the water that transports it ; and 

 this is its temperature. The value of this peculiar property cannot 

 be over-estimated in a country similar to this, in which extreme 

 changes of atmospheric temperature often take place suddenly, and 

 injuriously affect both plants and animals, and this is more particu- 

 larly demonstrated in the depth of winter and during long and con- 

 tinuous frosts. " It is a rather remarkable circumstance," observes 

 Mr. Baldwin Latham, " that when the greatest degree of tempera- 

 ture is required the sewage possesses it, that is, the temperature of 

 sewage has been found by the author to increase with the period 

 of duration of frost. This is probably owing to the stagnation of 

 surface-water, and also to the habits of the people, as much less 

 cold water is used in the depth of winter than at other times. So 

 great is the value of temperature, that a crop under sewage irriga- 

 tion may be seen growing even at the time of a severe frost." 



It does not appear that there exist any soils to which sewage 

 irrigation may not be beneficially applied. That portion of the 

 Craigentinny Meadows at Edinburgh known as Figgate Whinns, 

 consists of absolutely pure sand, whilst the soil of other parts is a 

 good loam passing into a strong clay; the former, which was 

 originally worthless, now produces grass crops which sell at 

 from 20/. to 28/. per acre per annum, thus showing that no land 

 can be too poor for profitable cultivation where liquid sewage is 

 obtainable in sufficient quantity. A larger amount of sewage 

 is required for light than for heavy soils, particularly during the 

 first year of its application ; and clay appears of all others to possess 

 the peculiar property of separating the manurial ingredients more 

 completely, and of retaining them better, than any other soil, and 

 it is consequently found that the crops grown are much heavier, 

 and that altogether clay soils produce a far better result than those 

 of a light, sandy nature. Gravelly soils require a certain time to 

 become thoroughly saturated with the sewage, and absorb it 

 greedily while the operation is in progress. 



The value of a good system of drainage in all agricultural land 

 is sufficiently understood at the present day ; but if it be beneficial 

 under ordinary circumstances, it is absolutely necessary where irri- 

 gation is adopted, especially in heavy soils. " I have no doubt," 

 says Mr. Denton, in the letter above referred to, " that in cases of 



