DR DAVY ON THE RAIN-FALL IN THE LAKE-DISTRICT. 61 



3. In the seventy instances of the slight, and very slight effect, the wind was 

 nearly as often from the south as from the north, and from the S.W. as from the 

 N.W., and in point of strength was more frequently gentle than strong, or even 

 moderate. The portions of water evaporated afforded a stain somewhat more 

 strongly marked than the preceding, and, on the whole, more frequently and dis- 

 tinctly crystalline. 



4. In the fifty-seven instances of moderate effects, the prevailing winds were 

 S.W. and S., and most commonly gentle ; a few times the atmosphere was calm 

 and misty. The water evaporated left a stronger stain than the preceding, and 

 with more variety of crystalline forms, of which the cube, like that of common 

 salt, was mostly one, and often a crystallization resembling that of muriate of 

 ammonia. 



5. In the forty-three instances in which the effect was considerable, the wind 

 was almost invariably from the W. and S.W., and either strong, or blowing in 

 gusts, in squalls, and was accompanied by all degrees of rain. The water evapo- 

 rated yielded a still stronger stain or residue than the last, but of nearly similar 

 composition, judging from the crystalline forms. 



6. In the smallest number of instances, the last class, in which the effect was 

 most strongly marked, the wind was chiefly from the W. and S.W., seldom from 

 the N. or N.E., and was almost constantly very strong. The residue obtained by 

 the evaporation of a portion of the rain-water was most considerable of all in 

 quantity, and in variety and distinctness of the crystallization. 



I may remark, generally, that in all the instances in which the residue was 

 well marked, there was a partial deliquescence of the crystals when exposed over 

 night to a damp air, those remaining being commonly minute prisms or plates ; 

 moreover, that when a drop of muriatic acid was added, the appearance of the 

 crystallization indicative of muriate of ammonia was increased ; and further, that 

 when the slide of glass holding the residue was exposed to a charring heat, there 

 was almost constantly a darkening effect, demonstrative of the presence of organ- 

 ised matter. I may add, that there was no well-marked difference in the results, 

 so far as I could judge, when hail or snow were thawed and subjected to the 

 same trials, the effects of the nitrate of silver seeming to be influenced more by 

 the direction of the wind, and its strength, than by any other appreciable circum- 

 stance. As regards the seasons of the year, the effects appeared to be generally 

 most distinct during the winter months, when gales were most prevalent, and 

 the wind accompanying the rain was chiefly from the W. and S.W. 



I have next to state the results which were obtained by evaporating and test- 

 ing, when reduced to a small volume, comparatively large portions of rain-water, 

 each the amount of rain-fall collected in the gauge during twenty-four hours. 



The first portion that was examined was the greater part of that which was 

 found in the gauge in the morning of the 26th November, and which had fallen 



VOL. XXIII. PART I. R 



