472 TRANSACTIONS OF ROYAL SCOTTISH ARBORICULTURAL SOCIETY. 



course were in shade, to be so pale in colour as to be nearly 

 white. 



The effect on the timber is probably to make it more brittle, 

 because when an affected tree falls, the branches and even the 

 small twigs on the upper side of the prostrate trunk are 

 frequently all broken by the fall instead of springing back into 

 their original position, as one would expect if the tree were 

 sound. 



Another effect, probably caused by the sulphuric acid, is that 

 the leaves fall rather earlier in autumn than they do in neigh- 

 bouring districts which are not affected by shale-works. And this 

 is true of districts where the harvest is generally a fortnight 

 earlier than in the shale district. Such are the effects of the 

 shale industry upon trees. The smoke and vapours to which 

 they are exposed are of a mixed character, and the trees which 

 seem to stand it best are sycamores, limes, and black Italian 

 poplars. 



