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humic acid which Hkewise pass into the subsoil. The lack of calcium makes 

 more difficult the decomposition of the humus substances and the nitrogen 

 enclosed in them remains inaccessible to the plants. At times the bacterial 

 flora is scanty in acid soils. The free sulfurous and sulfuric acids may act 

 injuriously also on animal organisms such as earth worms. Soils in smoky 

 localities will become impoverished or poisoned by all these factors. 



Wieler ascribes the death of plants and especially chronic injuries to 

 the scantier absorption capacity of soil, which has been poisoned and weak- 

 ened by sulfuric acid or also by hydrochloric acid, but certainly goes too 

 far into this, since all experiments show that the direct contact with the 

 smoke forms the chief cause of death' of the aerial organs: also comparative 

 chemical analyses of the foliage and of the soil from which it is produced, 

 do not always indicate an impoverishment of the supply of bases, but at 

 times, in fact, a strong increase of calcium and magnesium^ Yet, neverthe- 

 less, this aspect of the effect of acid smoke remains of the greatest impor- 

 tance and the attention of practical workers should be directed to period- 

 ically repeated application of calcium to the soil. 



We must refer to special works for the influence of currents of air and 

 their constitution, especially their water content, as well as for proving acids 

 in the air and the regulations for overcoming injuries due to smoke. We 

 would like to mention only that Ost' has given a simple method for deter- 

 mining the amount of sulfuric acid in the air. He saturated small pieces 

 of cloth with corrosive barite and dried them. He then hung them in 

 exposed positions in the places where the experiments were being made and 

 after a certain time investigated their sulfuric acid content. By this method 

 even pure mountain air showed a certain amount of sulfuric acid as its 

 normal mixture, which must increase significantly in the neighborhood of 

 \ illages. We have found recently in a lecture by the chief forestry com- 

 missioner, Reuss'% a summary of the requirements of foresters for the pro- 

 tection of the forest against smoke. He indicates the necessity of forming 

 indemnification societies in regions where many factories are placed close 

 together. 



The fact should not be left unconsidered that when damages are 

 demanded the objection is raised not infrequently by the injuring smelters 

 and factories that eating by insects is the chief cause. In this connection, 

 Gerlach* calls attention to the fact that spruce plantations, diseased by 

 smoke, are preferred by the resin weevil. Not only Pissodes Herciniac and 

 P. scahricollis, but also other insects, like Grapholithia pactolana and G. 

 Chermes increase to a devastating degree in forests injured by smoke. 



1 Die landwirtschaftlicliG Versuchsstation in Miinster 1. W. Denkschrift von J. 

 Konig. Miinster 1S96, p. 191 ft. 



~ Ost, H. Die Verbreitung- der Schwefelsaure in der Atmosphare. Die chem. 

 Industrie 1900; cit. Zeitschr. f. Pflanzenkrankh. 1901, p. 248. 



3 Reuss, Karl. Massnahmen gegen die Ausbreitung- von Hiittenrauchschaden 

 im Walde. Internat. Landw. Kongress zu Wein 1907, Section 8, Ref. 5. 



4 Gerlach, Beobachtungen und Erfahrungen tiber charakteristische Beweis- 

 mittel uzw. Merkmale von Rauchschaden. Osterr. Forst- u. Jagdzeitung; cit. Bot, 

 Centralbl. 1907, No. 40, p. 360, 



