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



when reduced to a drop or two, has been poured on a glass- slide, and reduced to 

 dryness in the same manner as the first mentioned. 



Secondly^ Of the Chemical. — The rain used in these trials has always been 

 collected in the rain-gauge. The ordinary test employed has been a solution of 

 nitrate of silver, the extreme delicacy of which is so well known. And, besides 

 its great delicacy, it has the advantage of taking effect immediately. It has com- 

 monly been used without any concentration of the rain-water by evaporation. 

 Occasionally the whole, or the greater portion of the rain collected in the gauge 

 during the twenty-four hours, has been reduced by evaporation to a small volume, 

 and in this state has been made the subject of experiment. 



The rain-gauge, it may be mentioned, is of copper, both the funnel and the 

 vessel the recipient. It stands about 2\ feet from the ground on a grass-plat in 

 the garden adjoining my house, which is about a quarter of a mile in a northerly 

 direction from the village of Ambleside, and is about 140 feet above the sea-level, 

 and about 30 feet above Windermere. 



Having premised thus much, I shall now give some of the results, and in the 

 order just sketched out. 



^st, Of the Rain-drops. — I shall describe from my notes, taken at the instant 

 the observations were made, a certain number of these results, specifying the 

 kind of weather which prevailed at the time. They are at least recommended 

 by their simplicity, and from being free as much as possible from any source of 

 error. I shall begin with one which was obtained before I entered regularly on 

 the inquiry. 



1. June 2, 1858. — The sky, at 1 p.jl, after a fine early morning, became 

 unusually overcast with dark clouds, producing an obscurity exceeding that 

 occasioned by the then last eclipse, that of July 1851. Some rain fell in large 

 scattered drops. A few were collected on a glass-slide. They left, when evapo- 

 rated, a circular stain, distinguishable by its greyish hue, most strongly marked 

 in its marginal outline. Under the microscope it was seen to consist of dark 

 particles chiefly ; they were of irregular forms, like soot particles, and intermixed 

 with them there were some minute crystalline groups. 



2. On the 30th August 1 860, after a fall of 'OO inch of rain during the preced- 

 ing twent3''-four hours, the wind westerly and strong, there were occasional 

 showers in large drops. A few of these drops, evaporated on a slide, exhibited 

 under the microscope a delicate crystallization. Drops from another shower 

 during the day showed the like crystallization, with which was one crystal, a 

 cube, like that of common salt, and about s J oth of an inch in diameter. 



3. September the 1st. — Showery; the wind from the same quarter; the rain- 

 drops smaller than those of yesterday. Some of them leave no stain on glass ; 

 some only a just perceptible stain. 



4. September the 6th. — During the night a slight shower ('Ol inch). Rain- 



