igoo-i.j Effects of Water on Foliage Leaves. 337 



chloride in solution from the atmosphere, resulting in a decrease in the 

 amount during summer. If it were not for plants, therefore, there 

 would be a greater amount in the atmosphere in the summer than in 

 the winter ; and when vegetation is checked in October and November, 

 and leaves have fallen, one would expect the largest amount when the 

 temperature was still comparatively high and the leaves incapable of 

 absorbing much of the chlorides. This is, however, only a suggestion. 



In Griffon's researches (1899) '^ is shown that leaves of plants in the 

 vicinity of the sea differ in assimilating power from those of the same 

 species inland. He shows that for a given unit of area of leaf surface 

 there is less assimilation in the leaf of a plant grown near the sea than 

 of one inland. Whether this is due to salts in the soil or to salts in the 

 air Griffon does not say. This may in part be due to salt water in the 

 soil, but possibly not wholly so, as the chief differences are to be found 

 in the leaf rather than in other parts of the plant. 



In the work of Smith (1872), there are many and extensive 

 collections of tabulated results of analyses of rain-water in northern 

 Europe. The principal analyses were made of the rain-fall of England 

 and Scotland, and minute details are given. He shows that chlorides 

 and sulphates, as well as many other substances, are found in the air, 

 and states that the amount of chlorides depends upon two things: — (i) 

 the proximity to the sea ; (2) the combustion of fuel in factories. He 

 concludes, however, that the presence of chlorides was not wholly due 

 to spray, for he says : — " The common salt from the sea is not spray, or 

 at least not spray purely ; if it were so there would be the relative 

 amount of sulphates to chlorides which we find in sea-water." It has 

 been observed that salt is often found on windows far from the sea 

 when a violent wind is blowing. Now the question naturally arises, 

 did the salt reach the glass as an aqueous solution (in small drops) or as 

 dry particles ? If it were carried in the form of small drops that would 

 be simply as rain or mist ; but such, however, is not the case as there is 

 neither rain nor mist, but simply a strong wind blowing from the sea. 

 If it were in the form of dry particles one would scarcely expect it to 

 stick to the dry pane of glass. How then was the salt conveyed from 

 the sea? It was this question that the writer attempted to answer by 

 the experiments described at the beginning of this chapter. Though 

 some rather important phenomena were developed in the course of the 

 experiments, yet little light was thrown upon the above mentioned 

 question. That chlorides and sulphates and other inorganic salts are in 

 the air in rather considerable and constant quantities is what mainly 

 concerns us here. 



