74 



Air Pollution by Coal Smoke. 



[APRIL, 



finished product, nor of ammonium compounds — the inter- 

 mediate product, but of undecomposed organic matter — the 

 raw product. This is noticeable in the soil of one area in Leeds 

 where, owing to the abnormal pollution of the atmosphere, 

 even the ammonia-producing organisms are killed off. It can 

 also be seen in the accumulation of matted roots in many old 

 pastures, particularly in smoke-infected areas. 



Effect of Acid Conditions on Grass Land. 



In some fields at Garforth, beneath the actual turf lies a 

 mat, 4 to 6 in. deep, of undecayed vegetable matter, because 

 the soil is so acid that even the vigorous putrefactive organisms 

 are unable to continue working. 



Grass land, possessing such a layer of undecomposed peat 

 above the soil, will sufTer severely in times of drought, burning 

 up and turning brown quickly. The. peaty mat will absorb 

 any rain which falls, to such an extent that heavy and prolonged 

 rain is required to wet the soil below. In 191 7 the country 

 suffered a period of practical drought from the middle of April 

 until the end oi July. August, on the other hand, was a month 

 of heavy and continuous rain ; yet at the end of the month, 

 although rain had fallen 28 days out of the 31 and the total 

 rainfall for the month had been more than 6 \ in., the soil 

 below the peaty mat was quite dry and powdery. Many of 

 the soils on the coal measures in the West Riding of Yorkshire 

 are naturally deficient in lime, and, where this deficiency is 

 accentuated by smoke pollution, they may require as much as 

 2 or even 3 tons of quicklime per acre to neutralise the 

 acidity. Once this acidity is neutralised by the application 

 of chalk or lime the putrefactive organisms can work, and the 

 mat disappears. In November, 1911, estimates were made of 

 the water-contents of the soil taken from two adjacent plots 

 at Garforth. The soil from one plot, which had received a 

 dressing of 6 tons of quicklime per acre in December, 1890, 

 contained 22 per cent, of moisture ; whereas the soil from the 

 second plot, which had received no dressing of lime and which 

 had a thick mat below the turf, only contained 8 per cent, of 

 moisture. 



Deficiency of Lime due to Acidity in Soil. 



It has already been pointed out that the acid rains tend to 

 neutralise the free lime present in the soil, the calcium sul- 

 phate thus produced being washed out and finding its way into 

 the drains. This action naturally tends to leave the soils poor 

 in " available lime." Practically none of the soils on the farm 



