334 TEE POPULAR SCIENCE MONTHLY 



of urban smoke is one of gases as well as solids, of poisonous fumes as 

 well as inconvenient soot. 



Turning now from cities, in which the growth of plants is purely for 

 pleasure, and by no means natural or commercially profitable, we may 

 ask what are the effects of smelting and other works from which poison- 

 ous fumes may be discharged ? 



Manufactories of certain chemicals, or of materials in the prepara- 

 tion of which poisonous substances may be volatilized, and establish- 

 ments in which sulphurous ores are roasted either for the extraction 

 of the metal or in order to obtain sulphur for the preparation of sul- 

 phuric acid, will affect surrounding vegetation more or less seriously. 

 Even locomotive smoke injures the plants along the railroads, as any- 

 one may observe. The herbaceous plants along the track, but quite 

 beyond the reach of steam, often show burned spots on their leaves and 

 stems. These are acid burns due to the fumes, of sulphur principally, 

 discharged from the smoke-stacks of passing engines. One seldom 

 travels over an old railway through woods or forests in which there are 

 not many trees close to the line with branches or tops dead. Often the 

 immediate cause of death is insects or fungi or possibly bacteria; just 

 as tuberculosis may be the immediate cause of death in factory workers 

 debilitated by long hours of labor under conditions unfavorable to 

 robust health. But in many cases, locomotive smoke can be shown to 

 be the immediate as well as the mediate cause of damage or death to 

 trees along a railroad. 



Such cases as these are, however, as unimportant, except as showing 

 a principle, as they are at present unavoidable. On the other hand, 

 where the prosecution of one industry results in the injury of many 

 others, in the destruction of property, public as well as private, and in 

 such changes in the run-off that the flow of water in streams perhaps 

 hundreds of miles away is affected, the question becomes one of great 

 importance. An illustration of this is found in the southeast corner of 

 Tennessee, where, for many years, a low-grade copper ore, rich in 

 sulphur, has been smelted. There are now two smelters in that region. 

 The country is mountainous, the slopes naturally covered with the large- 

 leaved mixed forest of the southern Appalachians, well watered by the 

 frequent summer rains. The virgin forest was long ago cut for mine- 

 timbers and for fuel in that extensive district known as Ducktown, but 

 the second growth is also gone and, up to three years ago, nothing of 

 any value could be cultivated within a distance of miles from these 

 smelters. In the suit won by the state of Georgia before the Supreme 

 Court of 'the United States, it was shown that the poisonous effects of 

 the fumes were visible in Georgia at a distance of forty miles from these 

 Tennessee smelters. Three and a half years ago, so hopeless was the 

 condition of the people attempting to farm there, that they declared 



