mg cen- 



Fig. 1. Thinning out of the foliage of a fir (Abies) growing near a nianufa 

 tcr due to an excess of sulphur dioxide in the air. 



Fig. 2. Destruction of the grass at the corner of a building due to dust emitted with 

 the smoke from a brass mill. In this case the dust accumulated on the roof was washed 

 by rains over this part of the lawn. 



Fig. .■'>. Destruction of the grass at the base of a tree in Naugatuck Valley due to dust 

 emitted with the smoke from a brass mill. In this case the dust which accumulated on the 

 tree crown was washed by rains down the trunk. 



Fig. 4. Characteristic mosaic appearance of the foliage of broad-leaved species due to 

 pn excess of sulphur dioxide in the air. Photograph taken nenr a manufacturing center. 

 (a) Kim. (b) Asli. 



