British Rainfall 1867, p.18
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British Rainfall 1867 page 18
is at the head of Langdale, nearly in the bottom of the valley; No.23 at the foot of Loughrigg, near Elterwater; and No.24 on the top of Loughrigg, three-quarters of a mile E.N.E. of No.23. Lastly, there are, and have been, at intervals, a large number of gauges at the principal residences in the district. Except, therefore, that there are still some blank spaces too large for so important a locality, we may congratulate ourselves on having infinitely better data than has ever been the case before. Thanks to the liberal help of Mr. Fletcher, and one or two other friends, I hope to keep these new gauges at work for a few years more; but, in the interim, it is of high interest to see the results already ascertained - and which I would dedicate to one (need I say it was not Mr. Fletcher?) who told me that he and Dr. Miller had found out all there was to find. Indeed! I wish he would tell me (before reading the rest of this article) the mean fall on Matterdale Common, at the head of Hawsewater, or in Sleddale, within 20 inches of the truth. APPROXIMATE DETERMINATION OF THE MEAN ANNUAL FALL AT VARIOUS STATIONS IN THE LAKE DISTRICT. As years roll on, and the laws and distribution of rain are gradually developed, the fallacy of practices of the wisest of our precursors is rendered evident to all. Without quoting such preposterous cases as that of tabulating the fall in one year as the mean rainfall of the place of observation, in which case an error of 50 per cent. may occur,* many have thought that five or six years would give a pretty fair mean, especially if two or three stations were taken together. The following table shows that the six years, 1853 to 1858, were more than 20 per cent. below the average of 22 years, and that the five years, 1859-1863, were nearly 20 per cent. above it. Thus we have two periods of six, and five years respectively, in one of which the fall is half as large again as in the other. Thus it becomes obvious that the mean fall can be ascertained only by two methods: either by long-continued observation at the place, or by reference to some proximate long-established gauge. This is the only method by which the observations made in the Lake district can be reduced to their true values. Most fortunately, the registers at The Howe, Troutbeck, at Seathwaite, and at Keswick, extend from the first year of Dr. Miller's work to the present time; they have therefore been employed as standards of reference for all the gauges, Dr. Miller's, Mr. Fletcher's, and my own:- * For example, the fall at Troutbeck, in 1861, was 116 in., and in 1885 it was 47 1/2 in.; in either case it would have been more than 30 in. in error. |
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