RECURRING PERIODS. 29 ANALYSIS OF THE EPITOME OF THE YEAR 1814; OR THE RECURRING PERIODIC CRITICAL DAYS, AS INDICATED BY THE BAROMETER AND THERMOMETER. 30 SYMBOLS AND FORMULA. To the Epitome I have prefixed the two last months of 1813, in order to show their natural connection with the winter season, of which they formed a part. The table presents an array of figures which seem to import little, and to be a barren, dry, uninstructive abstract. But although such may be the first impression, a little consideration will induce a more favourable opinion of their value and utility. They are the recognised and usual meteorological results, and may be consulted as faithful records of the past, and as the guides to future experience. They are the four cardinal points, and embody the specific characters of the months. Each term of the barometer, or thermometer, may be regarded as the "symbol," or sign, of an element, or state of an element; and all the four terms become the formula," which would represent the constitution of the month in abbreviated characters. 66 I shall refrain from any further remarks upon the epitome until I have given an analysis, or rather an accordance of the dates affixed to the table, shewing, although time is an element, but that order is heaven's first law, and which presides over time and space alike. If meteorologists could be induced to adopt some uniform mode of recording their observations, and a system of well-arranged symbols and formula expressive of facts, and especially of a method of delineation, instead of so many figures, much benefit and advantage would result. The leading facts would be much more obvious, and address themselves to the senses, and admit of com RECURRING PERIODS-CRITICAL DAYS. 31 parison and analysis. But at present there is such an heterogeneous mass of figures, that confound and repel most students. The Analysis displays a different arrangement of the days of the month, and conveys the idea of a tendency to a recurrence, more or less frequent, of certain obvious and marked states of the atmosphere, as pourtrayed or indicated by the barometer and thermometer. The extreme points are taken in the same manner as that of high and low water of the tides. They are the most proper, the most correct, and most suitable for purpose, and the ones usually adopted and recog the nised. We cannot fail to perceive the broad and general fact that the same day occurs sometimes in succession for two or three months. Or that the following, or approximate days, of two or three months are the same, showing that there is a tendency to a periodic action in the atmosphere; and the little sections of the Analysis are the groups of approximate days of the respective months. These days of highest and lowest barometer and thermometer I propose to regard as critical days; and their recurrence about the same day, as the periodic critical days, or recurrent monthly periods of the average of thirty days, extending, in their extreme range, from twenty-eight to thirty-two days-altogether five days. But I am more generally disposed to limit it to a day before and a day after, contracting the extreme range to the limit of three days. 32 THE CRITICAL DAYS. But when we consider the small amount of 1° of temperature of Fahrenheit's thermometer, it is very remarkable that the critical days should occur so accurately within such a narrow compass, for 1° of temperature can only be regarded as a point. And this extreme precision gives a value and importance to the fact of recurring, or periodical, critical days. The days on which the highest and lowest barometer and thermometer occur, are called the critical days of the month; there are, of course, two critical days pertaining to every month, both of the thermometer and of the barometer. And these two instruments rarely accord. The barometric critical days differ from the critical days of temperature, and each must be distinguished and separated accordingly; although occasionally there is an accordance between the two. The critical days indicate a change, and may in time lead us to judge of the coming states of the weather. They form an important feature in meteorology, and open inquiry. a wide and extended field of useful The records of the past may become the heralds of the future, and the vestibule leading to the knowledge of the laws which regulate and pervade the atmosphere. We cannot reject the testimony of the Analysis of the year 1814, as we perceive the day of highest barometer of one month is answered by the same or following day of next month being the lowest barometer ; or two or three months in succession present us on THE CONSECUTIVE SERIES. 33 the same days, or approximate days, with a repetition of the same state of barometer or thermometer, as respects their highest or lowest indication. Thus 24th June, day of highest barometer, is succeeded by 23rd July, day of highest barometer. 24th August, day of lowest barometer. 24th September, day of lowest barometer. Now these cannot be casual coincidences, especially as we observe a repetition, on a smaller scale, on many occasions. THE THE CONSECUTIVE SERIES, OR STATE OF INSTRUMENTS WAS AS FOLLOWS, FROM NOVEMBER 1813 TO FEBRUARY 1814. |