112 DR MILLER ON THE METEOROLOGY OF 



impounded on the mountain passes, and in the hollows and basin-shaped cavities 

 on the mountains, than on their summits. In passing over the tops, the vesicles 

 are cooled and rendered heavier, and volumes of vapour flow down into the hol- 

 lows and gorges, where they are hemmed in as in a cul de sac, and are converted 

 into water. As decomposition proceeds, fresh masses of mist roll down the slopes, 

 which in their turn are condensed and precipitated by the surrounding cold high 

 land, and, as in the former case, the fall is both copious and uninterrupted, while 

 the vapour in its swift transit over the adjacent peaks is but partially meta- 

 morphosed into drops of rain. 



I also find that a gauge moderately sheltered receives more rain than one near 

 it fully exposed to the weather. At Seathwaite, there are two rain gauges within a 

 very short distance of each other, — the one at 10 inches, the other at 22 inches 

 above the surface. The former is placed in a small garden surrounded by low walls ; 

 the latter is planted in an adjoining large field. On an average of 6 years, the 

 garden gauge received 3 CI inches annually more rain than the field gauge. 

 That the difference in the receipts of the two instruments is entirely due to the 

 degree of exposure, and not to the difference in the heights of the receiving 

 surfaces above the soil, is clearly shewn by the fact — that when both the gauges 

 were located in the garden side by side, (as they were from June to December 

 1846) the higher impounded rather more rain than the lower. 



In a former paper, I alluded to the rapid increment in the fall of rain in ap- 

 proaching the head or terminal point of a valley, and it was shewn numerically, 

 that the effect of such approach was appreciable at intervals of one or two 

 hundred yards. The difference in the quantity of water deposited at places 

 closely contiguous to each other on the mountains is also sometimes surprisingly 

 great. In the four years 1846-49, Seatollar Common, at 1338 feet, received 10 per 

 cent, less rain annually than the valley at Seathwaite. In August 1849, the first 

 mentioned gauge was removed 90 yards to the south-westward of its then posi- 

 tion, and about five feet lower down the mountain. In the four following years, 

 1850-53, the excess was in favour of the "Common" to the extent of 0-5 per cent. 

 The only circumstance attending the change which can be supposed materially to 

 have affected the rain fall, is that of the new locality being somewhat more 

 sheltered than the old one. 



In a previous paper, published in the Philosophical Transactions, (Part i. for 

 1849) I have endeavoured to account for the great difference in the percentage of 

 rain between the summer and winter half-year on the mountains, (particularly 

 on Sea Fell and Gabel) which I attribute conjointly to the loss sustained by the 

 gauge when the precipitation is in the form of snow, and to the lower altitude of 

 the principal plane of condensation in the colder months. 



copious supply of vapour poured into this narrow valley from the " Stye" pass — which trends nearly 

 in the direction of the prevailing aerial current — that Seathwaite is chiefly indebted for the great 

 excess of its rain-fall over every other locality in the Lake District. 



