Intelligence and Miscellaneous Articles. 



397 



I 



falls through all the strata of air lying below the clouds which pro- 

 duce it, becomes impregnated with any matters contained therein, 

 was the first thing to which observers directed their attention. 



Bergmann was the first who appeared in this sphere. He disco- 

 vered nitric acid in rain. Then follow Brandes, Zimmermann, Liebig 

 and Jones. 



The most important result of M. Barral's investigations is, that 

 the rain in every month contains so much nitric acid and ammonia 

 that the quantities of both can be determined. The author's remarks 

 upon the quantity of chlorides contained in the atmosphere are not 

 less interesting; but in the determination of these he has had Brandes, 

 Berzelius, Liebig, Chatin, Meyrac and Isidore Pierre, as predecessors. 



Bergmann had stated that traces of nitric acid occurred in the 

 atmosphere. Brandes, who investigated the air at SalzufFeln from 

 month to month in 1825, stated that he found in it chloride of 

 magnesium, chloride of sodium, suljjhate and carbonate of lime, car- 

 bonate of potash, oxides of iron and manganese, and traces of am- 

 monia, sulphuric acid, and animal and vegetable matters. As regards 

 the occurrence of chloride of iron, oxide of manganese, and chloride 

 of potassium, this has already been questioned by Liebig. Liebig, 

 in the investigation of seventy-seven samples of rain-water, found 

 nitric acid in ten samples after stormy rain, and traces in two only 

 of the remaining sixty. 



Bence Jones, in 1851, found nitric acid in the rain of London, Mel- 

 burgh in Dorsetshire, and Clonakelty, by means of iodide of potas- 

 sium paste, but did not determine its quantity. 



In 1851, Barral commenced his investigations upon the rain col- 

 lected partly upon the platform, and partly in the court of the Ob- 

 servatorj- at Paris. 



The Commission has tried M. Barral's process, and found that his 

 mode of determination was to be depended upon. The process itself 

 is not further described. . 



On the other hand, the following tables give the numbers which 

 express the quantity of nitric acid in the rain. According to them, 

 the rain is never equall}' loaded with nitric acid, and the quantities 

 of nitric acid which fall with the rain upon one hectare of land are 

 not in proportion to the quantity of rain. Calculated from the 

 minimum, 31 kilogs. of nitrogen fall during the year upon one hec- 

 tare of land in the neighbourhood of Paris. 



Average contents of Rain-water from monthly determinations in the 

 Udometers of i lie Observatory of Paris during the second half of the 

 year 1851. The numbers refer to one cubic metre of rain-water. 



