DR DAVY ON THE RAIN-FALL IN THE LAKE-DISTRICT. 63 



lowing :— When nitrate of silver, in the first instance, produced a distinct effect, 

 then the results were very similar to those last described, showing a predomi- 

 nance of common salt and of magnesian salt. When, on the contrary, nitrate of 

 silver had little or no effect on the unconcentrated water, then the results were 

 marked chiefly either by the entire absence of common salt, or by an only just 

 appreciable presence of it, and by the presence of lime and ammoniacal salts. In 

 most instances the evaporated water showed an acid reaction, and afforded proof 

 of the presence of sulphuric acid ; and in most there was a trace of copper, 

 derived, it must be inferred, from the gauge, and owing probably to the action of 

 the acid existing in the rain. 



What are the inferences that may be drawn from these observations and 

 experiments ? 



1st, Do they not seem to accord in this, that rain-water, such as falls in this 

 part of England, is rarely, if ever, perfectly pure, but contains something almost 

 constantly — indeed, may it not be said constantly — derived either from the sea or 

 land, from town or country ? 



2d, That when the wind is from the sea, and especially when it is strong, 

 the ingredients most predominant in the rain are those which exist in sea-water, 

 the same that washes our shores ?* 



2d, That during a calm state of the atmosphere, or with a gentle wind, and 

 from the N. or N.E,, rain-water is least impregnated with foreign matter — 

 least with those likely to be derived from the sea — more with those likely to be 

 derived from the land, and especially from our great manufacturing towns, such 

 as ammoniacal salts, salts of lime, organised matter, and soot the matter of 

 smoke, itself very compounded ? 



If these inferences are borne out by the results, are they not in accordance 

 with the nature of the atmosphere, considered as the great receptacle of all 

 matters volatile, and of all such as are capable, when in a very finely divided 

 state, of being mechanically diffused by the action of the winds ? 



Facts in proof of such diffusion of matter by the winds are so well known as 

 not to require being insisted on. I shall briefly advert only to a very few. After 

 severe gales, common salt has often been found deposited in a quantity so con- 

 siderable, as to attract the attention of ordinary observers, and this more 

 than fifty miles from the nearest sea, even in parts of our midland counties 

 most remote from our shores.! Volcanic dust, and dust from the deserts of 



* Sea-water which I have examined, taken from the neighbouring sea, I have found to contain, 

 besides the ordinary ingredients of sea- water, lime in a notable quantity, some alumina and sulphuric 

 acid, and traces of ammonia and phosphoric acid. 



■j" I have been informed by a friend residing at Meltham Parsonage, and by another residing at 

 Armitage Bridge, both places in the neighbourhood of Huddersfield, and about eighty miles from 

 Scarborough, and about sixty from Liverpool, the nearest ports of the opposite coasts, that after 

 the great storm of January 1, 1839, salt was observed deposited on the leaves of the trees at both 

 places ; — they were about four miles apart. 



