THE RAINFALL ON THE ST. MARY CHURCH ROAD, TORQUAY, DURING THE FIVE YEARS

ENDING DECEMBER 31, 1868.

BY W. PENGELLY, F.R.S., F.G.S.

HAVING carefully measured and registered the rain which fell on the St. Mary Church Road, Torquay, during the five years ending December 31st, 1868, I have from the materials thus collected constructed a series of tables which, with a few explanatory remarks, I now beg to lay before the Association.

It may, perhaps, be well to state that I use one of the fiveinch gauges made by Mr. Cassela, under the auspices of the British Association for the Advancement of Science; that it is placed, with its top nine inches above the ground, in the middle of a small lawn, 200 feet above the sea; that the nearest arm of the sea is Torbay, about one mile to the south; and that the centre of Dartmoor-the great upland of Devonshire-bears W.N.W., and is nineteen miles distant.

TABLE I.

In Table I. the first line shows the annual rainfall during the five years, and also the average fall per year during the same period; from which it appears that 1864 alone was below the annual average, and that of the remaining four years, 1865 was the wettest and 1868 the driest.

In the second line the rainfall is reduced to gallons, and in the third to tons, per acre. The latter is based on the assumption that a cubic foot of water weighs 1000 ounces Avoirdupoisan estimate rather below than above the truth.

The 4th line shows the relative falls; the annual average being put = 1000, and the actual annual falls equated to it. Thus, in 1864 the fall was 359 below the average of the five years, whilst that in 1865 was 190 above it.

The 5th line shows the number of "wet days;" that is, of days on which there fell not less than 01 inch-the least quantity which is measured. It appears that, on the average,

rather more than half the days of each year were wet ones; that 1864 was, in this sense also, the driest year of the five; and that 1866 was the wettest, though it was surpassed in its rainfall by both 1865 and 1867.

The 6th line shows the relative number of wet days, and is calculated by putting the average annual number=100, and equating the actual number in each year to it. From this line it appears that the fluctuation, from year to year, in the number of wet days, was less than that of the rainfall; the former ranging from 9 per cent. below to 18 per cent. above the average, whilst the latter oscillated from 36 per cent. below to 19 above,-a total range of 27 against 55, or as 1 to 2. It is also seen that whilst there was but one year of defective rainfall, there were two in which the number of wet days was below the average.

The "average daily fall," shown in the seventh line, is determined by dividing the rainfall of each year by its number of wet days. It was greatest in 1865, and least in 1864. In other words, the amount of rain in relation to the number of wet days was unusually great in the former; or, what amounts to the same thing, the number of wet days was, as compared with the average, small for the rainfall. Two years only had a mean daily rate below the average for the five years. As might have been anticipated, the days on which the fall was above the average rate were in every year less numerous than those on which it was below. From the eighth and ninth lines it appears that for the entire period these days were very nearly as 1 to 2.

The 10th line shows that the days on which the actual rate was the same as the average were very few, and, for the entire five years, amounted to no more than two per year.

From the 11th line it is seen that the dry 1864 and the wet 1865 were indicated, so to speak, by their greatest falls in 24 hours; that of the former being no more than 1.15 inch, whilst that of the latter amounted to as much as 2.13 inches the former being, as the twelfth line shows, 047, and the latter 046 of the yearly falls respectively. These were the least and the greatest maximum falls in 24 hours during the five years. On the average the maximum fall in 24 hours amounted to 1:53 inch, or about 4. per cent. of the average annual fall.

The 13th line shows that the heaviest fall in 24 hours was not confined to any particular season or part of the year.

The longest periods without rain in the different years had nothing like an approach to uniformity in their duration, as

is shown in the 14th line; amounting to 11 days only in 1866, but to as many as 44 in 1865. It also appears that the duration of the longest rainless period of a year afforded no criterion as to the character of the year as a whole: 1865 surpassed all the other years in the duration of its longest rainless period, and also in its total amount of rain. It, moreover, surpassed two of the years in the number of its wet days.

With the exception of 1868, the longest rainless periods of the several years occurred after Midsummer, but not in the same month in any two years, as is shown in the 15th line. It may be remarked also that 1868 formed an exception as to the date of its heaviest fall in 24 hours. It occurred after Midsummer, whereas in all the other years it was before, as is shown in the 13th line.

The 16th line shows that the number of rainless periods of at least a week's duration each, ranged from 5 to 8 per year, and averaged 7. They were most numerous in the two driest years-1864 and 1868,-but not least numerous in the years of heaviest annual falls. They were somewhat more closely related to the total number of dry days in their respective years.

The 17th line shows that the month of greatest fall in each year was, with the exception of 1866 only, always between Midsummer and Christmas, but never the same as the month in which occurred the greatest fall in 24 hours.

As is seen in the 18th line, the maximum monthly falls varied from 3.79 inches, in November, 1864, to 8.90 inches in December, 1868; or, as it is put in the 19th line, from 153 to 227 of the total rainfalls in their respective years.

The 20th line shows that the three wettest consecutive months have always been the first or the last three of the year; the former having obtained this distinction three times. and the latter twice. Their united rainfalls have varied, as is seen in the 21st line, from 8.33 inches in 1864 to 18.69 inches in 1865, or, as is set forth in the 22nd line, from 336 to 407 of the total fall in their respective years. It may be remarked in passing that the fall in December 1868 alone, exceeded the united falls of the three wettest consecutive months in 1864. October, November, and December in 1865 were the three wettest consecutive months during the five years. The month of greatest fall was not in all cases one of the three wettest consecutive months.

It appears from the 23rd line, that the month of the greatest number of wet days oscillated from September to

March inclusive, omitting both November and January. September alone, during the five years, was twice distinguished for its excessive number of wet days, but on one of these occasions (1864) it was bracketted with March. The month thus prominent was not in all cases one of the three wettest consecutive months.

Lines 24 and 25 point out that the maximum number of wet days per month varied from 21 in 1864, to 30 in 1868, and averaged 26; or from 12.5 to 175 per cent. of the total number of wet days in their respective years. Neither September in 1866, nor December in 1868, had more than one rainless day.

In September, 1865, as the 26th line shows, no rain fell during the entire month. No other instance of a rainless month occurred during the five years, and the instance just mentioned happened in the wettest year of the five. During the remaining four years, June and July equally divided the honour of being the driest months.

The 27th and 28th lines show that the minimum monthly fall ranged from 0 in September 1865, to 0.95 inch in June 1866, and averaged 0.52 inch. The fall during the driest month appears to have had no relation to the rainfall of the year. The least monthly minimum occurred in 1865-the wettest of the five years,—and the greatest in 1866, the rainfall of which exceeded that of two, and was also exceeded by that of two years. The minimum monthly fall never exceeded 023 of the total fall of the year. On the average it amounted to 013 of it.

According to the 29th line, the three driest consecutive months ranged from March to December inclusive, with the omission of September. On comparing the 20th and 29th lines it will be seen that October, November, and December were in one year the three driest, and in two others, the three wettest consecutive months of the year.

We learn from the 30th and 31st lines that the total fall of the three driest consecutive months varied from 2.33 inches in 1868, to 7 inches in 1865, and averaged 4.7 inches; or from 059 to 153 of the annual falls in their respective years, the average being 122.

The month of least number of wet days according to lines 32, 33, and 34 oscillated from June to November, with the omission of August and October. The number of days varied from 0 in September 1865, to 11 in July 1866, and averaged 5; or from 0 to 5 per cent., and averaged 27 per cent.