JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



produce so marked an effect upon the living protoplasma, makes 

 the latter itself a reagent with which chemical tests cannot com- 

 pete." 



The questions which have occupied my attention, and which 

 are discussed here, are the precise nature of the injuries to plants 

 caused by fog, and the participation in these results of the 

 various conditions unfavourable to vegetation which are incident 

 to fog. 



It is advisable to include here a few analyses of the deposits 

 left by fogs as giving an indication of the impurities with which 

 we have to deal. 



And first I will give the analyses of the deposits left on the 

 glass roofs of plant-houses at Chelsea and Kew during the severe 

 fogs in February?1891 : — 



Chelsea. 



Carbon 39 per cent 



Hydrocarbons 



Organic bases 



Sulphuric acid 



Hydrochloric acid 



Ammonia ... ... ... 



Metallic iron and magnetic oxide... 

 Other mineral matter, chiefly silica and 

 ferric oxide 



12-3 

 2-0 

 4-33 

 1-43 



1- 37 



2- 63 



31-24 



Water not determined. 



Kew. 

 42-5 per cent. 



4'78 



0-83 

 M4 



41-15 



Detailed analyses of soot, taken from London and Glasgow, 

 were published * more than twenty years ago. These I append 

 for comparison with the deposits. They are the only analyses 

 of the kind which I have been able to discover : — 



London. 



Glasgow 



Carbon 



53-18 



35-7 



Tar and oil 



18-00 



15-0 



Ammonia 



1-75 



2-8 



Potash 



•20 



0-3 



Soda 



•34 



03 



Lime 



1-00 



0-8 



Magnesia 



0-30 



Trace 



Phosphate of lime and alumina 



2-08 



3-2 



Iron 



0-40 



0-7 



Sulphuric acid ... 



4-00 



7-9 



Chlorine ... 



Trace 



0-4 



Sulphocyanogen... 



0-25 



None 



Carbonic acid 



0-70 



Trace 



Band 



14-40 



25-7 



Water 



2-80 



72 





100-00 



100-0 



* W. R. Hutton, Chemical News, vol. 



xx. p. 307. 





