DISTRIBUTION OF AMMONIA. 273 



rises exactly "where you might expect more organic matter 

 to exist. The lowest is from Prince's Road, outside the 

 town and almost half a mile from the extreme of the 

 Manchester houses. The next is obtained from an empty 

 yard behind my laboratory; but it is still pure, because 

 there was wind and rain ; and any one who observes how 

 unusually pleasant it is to breathe the air even of a smoky 

 town during rain and wind will not be surprised. I have 

 not yet, however, had the purest air. I shall require to 

 make a campaign on the moors, hills, and seas before I 

 can give numbers for it. I have not even obtained the 

 best on land at a distance from manufactures. All this 

 will be done in time'^. 



In my office the amount is larger than outside. I shall 

 give here a specimen of numbers obtained simply by 

 washing a volume of air and Nesslerizing direct. These 

 numbers do not compare with those, already given. The 

 highest amount was obtained at the front of the Cathedral, 

 about midday on the 8th of February 1878, when the 

 amount was i"25, or I4f times as much as had been found 

 in Prince's Road, showing a considerable range. 



Milligrammes of Ammonia per cubic metre of Air, 



Prince's Eoad "086 



Open yard during rain "i 19 and '102 



Front of laboratory -167 ordinary. 



Office -iGj 



Front and back during fog -476 



Close-sbut-up room '413 



Closet outside '800 to "900 



Densest part of fog vt.^ 



A fuller list may now be added to the above, which has 

 already been published as an abstract. 



* Since the paper was read I examined trees and stones at Skelmorlie and 

 Wemyss Bay, finding very little ammonia. 



SER. III. VOL. VI. T 



