Professor J. Johj — Salt ami Geological Time, 345 



and the consideration of some other points raised in the discussion, 

 are more in place in a geological than in a chemical journal. 

 I would therefore seek for space in the Geological Magazine 

 wherein to repeat in part what I have said in the Chemical News, 

 adding some matters more especially suited to geological readers. 



If all the chlorine in rivers were combined with sodium present 

 in the river- water, much the larger part of the sodium would remain 

 over. The quantity of sodium in river-water which finds its 

 equivalent of chlorine in the water requires special consideration. 

 It obviously may in part be derived from the ocean by the agencj' 

 of winds and rains. That this part only can be considered as 

 derived from such a source a simple proof is given later on. The 

 question then arises as to what amount of sodium chloride is 

 observed to fall in rain, or what amount of chlorine falls with rain ; 

 the assumption being made, not quite accurately, that the sodium 

 cai'ried by rain is measured by the chlorine present. 



Verj^ full information relating to the chlorine content of rain- 

 water falling in various parts of England and Scotland, and some 

 other coastal parts of the world, is on record. What is wanted is 

 fuller knowledge of the chemical character of rains falling in inland 

 areas, more especially as to their content of sodium. The broad 

 fact at our disposal is, that as we proceed inland a rapid diminution 

 of the percentage of chlorine appears. In inhabited parts of 

 Europe but 200 miles from the sea, the proportion observed appears 

 to be one-twelfth, normally, of what is observed 30 or 40 miles 

 from the sea. In India, about 300 miles from the sea it was found 

 to be 0-04 per 100,000. 



In a country like ours where no point is more than a few score 

 miles from the sea, coastal conditions prevail over its entire area. 

 Even within the small British area, however, there appears to be 

 a rapid diminution in the proportion of chlorine carried by the 

 wind to more inland parts. This is observed even in the more 

 inhabited parts, notwithstanding the fact pointed out by Dr. Angus 

 Smith that where coal is being consumed on a considerable scale 

 this proportion must be expected to rise. Although this is so, I do 

 not think it can be doubted that a large part of the chlorine of 

 British rivers, and of well waters also, must be sea-derived. 

 A simple comparison of the chlorine content of British surface 

 waters and of rain, bearing in mind the inevitable concentration of 

 the latter by evaporation, sufficiently demonstrates this fact. 

 This is pointed out in my paper " An Estimate of the Geological 

 Age of the Earth" (p. 35). 



In inland countries on the other hand it is extremely doubtful, 

 according to our present knowledge, if any of the chlorine observed 

 in rain is derived from the sea, for the circulation of salt from the 

 earth to the air or from inland salt deposits, along with other mineral 

 dust, may be accepted as inevitable. Raised with every wind, again 

 washed down with rains, evaporated to dryness, and again raised 

 mingled with the light dust of soils, an amount of saline matter 

 comparable with so minute a quantity of chlorine as was observed 



