J. J. Griffith 369 



4. Artificial waterways (leats), some of them miles in leiigtb, made 

 to conduct washing water from one mine to another. In many places 

 these leats almost follow the contour lines and thus the motion of the 

 water is very slow so that there is a great tendency for the suspended 

 slime to settle down. The bed of the leat is thus gradually raised and the 

 slimy water overflows and contaminates the land which hes lower down 

 the slope. See photograph of leat (photograph " W") and also analytical 

 results given in Table IV. 



5. Water drawn from polluted rivers and carried along artificial 

 water-courses towards various mills and farms to provide water-power 

 has in many instances poisoned stock and contaminated adjoining fields. 

 A sample of the sediment from a mill pond in the Leri valley was analysed 

 and found to contain 1-74 per cent, of lead. 



6. Water running out of mine levels, both active and disused, is 

 often highly contaminated with lead, zinc and other metallic substances. 

 A special feature of this means of contamination is that the poisonous 

 metals are in solution in the water. Consequently the injurious effects 

 upon land and stock are much more pronounced and immediate. A 

 sample of the water flowing from an old level near Cwmystwyth was 

 found to contain in solution -3 part of lead per 1,000,000. This water 

 was suspected of having poisoned a number of sheep which had been 

 grazing on adjoining land. 



7. In the case of farms situated in the immediate vicinity of mine 

 wastes the animals themselves, especially poultry, pick up and consume 

 the poisonous substances direct from the heaps. In fact, on many farms 

 it is well recognised that poultry cannot be kept in places where they 

 have any access to the mine heaps. 



8. Several cases are on record where farmers having used material 

 obtained from polluted ditches for making composts have lowered 

 the fertility of the land. Also, sand and gravel obtained from the mines 

 and utilised for making building mortar, covering pathways and other 

 purposes, have often led to the poisoning of farm animals. 



9. Elvers in times of floods have been the means of depositing enor- 

 mous quantities of mine refuse upon the land, more especially in the 

 lower river valleys where the conditions are favourable to sedimentation. 

 Undoubtedly this is the manner in which most of the land has been 

 aft'ected. The great majority of the mines are situated on river banks 

 in the upper reaches of the valleys in the eastern portion of the comity 

 (see map "A"). It thus follows that most of the land in the river valleys 

 all the way to the sea is liable to be affected. 



