Popular Science Monthly/Volume 32/January 1888/Climate of the Lake Region
was impossible to keep out men who were farmers only to the extent of a garden or back yard. In those days lawyers, doctors, merchants, discovered in themselves a marvelous interest in agricultural pursuits, and joined the Grange. As a Granger remarked, they were interested in agriculture as the hawk is interested in the sparrow. Two Granges were organized in New York city; one, the “Manhattan,” on Broadway, with a membership of forty-five wholesale dealers, sewing-machine manufacturers, etc., representing a capital of as many millions; the other, the “Knickerbocker,” one of whose first official acts was to present the National Grange with a handsome copy of the Scriptures — a gift causing some embarrassment. A similar one was organized in Boston, which made great trouble before it could be expelled; and one was found in Jersey City, with a general of the army as its master, a stone-mason as secretary, and the owner of a grain-elevator as chaplain. But discordant elements were not all from other professions. Thousands of farmers had been carried in by the enthusiasm of the movement, with no idea of the nature and aims of the order. Some expected to make a political party; others, to smash the railroads; almost all hoped to find in co-operation a panacea for poverty. There was great lack of discipline, but no discipline could have harmonized such a body. The first outbreak was in the direction of democracy. Lay members were eligible to but four of the seven degrees, and this was denounced as aristocratic, opposed to the spirit of democratic institutions. Along with this came the cry that the National Grange was growing too rich. In vain it made liberal donations of seeds and provisions to sufferers by grasshoppers and floods, and spent large sums in distributing crop-reports among the order. The clamor continued till the faint-hearted in the Charleston session in 1875 carried a measure to distribute $55,000 to the subordinate Granges — about $2.50 to each! Prominent Grangers have maintained that the causes of Grange decay are to be found in this and the other measures of the same session curtailing the power of the National Grange. The true cause has been seen to lie deeper, in the failure of business enterprises. These measures had some influence, however. They were the beginnings of endless tinkering with the constitution, and the cause of quarrels innumerable. Among other quarrels was one with the Grange of Canada, over the question of jurisdiction. Soon afterward came the first open break in the ranks. An Illinois Grange voted to disband, alleging pecuniary reasons and the autocratic rule of the National Grange. Many still had dreams that the order was to spread over the world, but the co-operative leaven had begun to work, and there was soon no mistaking the tendency to decay. At the annual meeting in 1876, four thousand Granges were reported delinquent. Salaries were at once reduced — the master's from $2,000 to $1,200, and the secretary's from $2,500 to $2,000. It was vainly attempted to stem the tide by issuing an official organ, the “Grange Record.” In 1879 the master's salary was dropped entirely, and the secretary's reduced to $600. A bill for services from Herr Prenzel, who had been working for the order in Germany since 1875, was dismissed with little ceremony. The National Grange was not poor, having always kept about $50,000 to its credit invested in Government bonds, but it had given up the idea of converting the world. But the low-water mark had been reached. Cash receipts in 1880 increased two hundred per cent over those in 1879. More Granges had been organized than in any year since 1874. The growth was especially marked in New England. The State Grange of Connecticut was revived after a dormancy of six years, and Maine began to claim more Grangers in proportion to population than any other State. At the session of the National Grange for 1885, held in Boston, delegates were present from all the States and Territories but eight. It is not easy to explain this growth, as there seems to be no great principle underlying it. Some New England Patrons are agitating free trade, but that can not be called a Grange issue, as Pennsylvania Patrons want protection extended to farm-products. The harmless practice of holding great fairs is gaining ground. At a recent one in Pennsylvania, lasting a week, the local paper says: “Over fifty thousand people were present on one day, and the sale of machinery direct to the farmers ran up into the hundreds of thousands of dollars. Never were manufacturers and consumers brought into more direct and friendly relations.” This is, perhaps, the latest development of Grange anti-middleman ideas.
The most enthusiastic Grangers at present are the farmers' wives and daughters, who are attracted by the social opportunities. In fact, the order seems to be going back to the educational and social basis of the founders, and its boasts are no longer co-operative ventures so much as Grange buildings and libraries, and the Grange schools that exist in several States. In these directions, and in what it has done to heal sectional differences between North and South, the Grange can boast its best achievements.
CONNECTED with our considerations upon the climate is a subject which has excited great interest since the first settlement of the country, and about which much has been written, for the most part vaguely. I allude to the variations in the levels of the lake-waters. Many causes contribute to create a perpetual fluctuation, or rise and fall, in these inland seas. . A possible lunar tide; but so small and so broken in upon by greater causes as to be of very uncertain value.
2. The winds, which often cause a difference in level of many feet; strong westerly winds causing a rise at one place, and easterly winds at another. These changes are irregular and transient, but often considerable in amount, ranging from two to five feet.
3. Annual variation attendant upon the seasons and confined to the year. This kind of fluctuation is a winter and summer move- ment. The supply from streams and rains being wholly or partially checked in the cold season, the water is gradually drawn away, low- ering the general level, which reaches its lowest ebb about January or February. As spring advances, with melting snows and increased rainfall, the watei's rise gradually, and attain their greatest height in June or July. They then begin to fall again to their winter level. The extreme of this variation is about 2"30 feet, and is about the same in Lake Ei-ie as in Detroit River.
4. A rise and fall of the waters of the lakes and their connecting channels, extending through several years, and amounting to an extreme difference of five feet. Upon this kind of fluctuation Col- onel Charles Whittlesey has bestowed the name of "secular vari- ation."
The causes of this variation were long involved in much mystery. According to the old French tradition, it is independent of the seasons, and follows periodical intervals of seven years. To what extent these intervals of high and low water are regular in their recurrence, and how far they are connected with meteorological or astronomical causes, can be determined only after continuous and exact observations for a long series of years.
It is hardly more than a decade since the United States Signal Serv- ice has given scientific exactness to observations, and not over thirty years since thoroughly reliable statistics have been tabulated. Records of independent observers often differ widely, and though the writer has culled from different sources data suflicient to enable him to construct a diagram for this region, covering the past fifty years, and even more, many of these data are of uncertain value. For a period of thirty-three years, beginning with 1853, a record has been kept by the Detroit Water Board of the daily fluctuations in the level of the river, and partial records exist of other years since 1835.
In a compai'ison between the height of water in the river and the rainfall at Detroit, no conclusions drawn from these data will apply rigidly to the lakes above and below. The river-levels are influenced not alone by the precipitation on its borders, but by the supply from above. Other causes contribute to its irregularities—local rains, con- fined channel, rapid current. While a sudden increase in the precipi- tation Avill affect the broad surfaces of the lakes uniformly, a rise would take place at such times in the confined straits to a disproportionate extent. In discussing this so-called "secular" variation it becomes necessary to procure data from outside sources.
Milwaukee represents well Lake Michigan, and Cleveland Lake Erie. Each is about half-way between the head and foot of the lake upon which it is situated, and where the changes may fairly be con- sidered as means of the whole. From Milwaukee I have a table of the rainfall from 1844 to 1886, and of the "secular" variations of Lake Michigan from 1859 to 1882. From Cleveland, of the rainfall from 1856 to 1886, and of the lake variations since 1859,
At each of these places the standard or plane of reference is the high water of I808. The standard at Detroit is an arbitrary one, namely, the water-table at the Hydraulic Works, The mean of the last fifty years is five feet below that standard, and corresponds, as nearly as I can determine, to one foot below the mecm of 1838, and two feet below the extreme of June of that year.
Of the fluctuations of the water prior to the period mentioned the only data are derived from the recollections of old settlers. These, though often indefinite and sometimes faulty, are yet of great value. -Dr. Houghton, in his report of 1839, gives certain concordant state- ments of old inhabitants, going back as far as 1800. In a paper pub- lished in "Smithsonian Contributions," volume xii. Colonel Charles Whittlesey has collected items from all sources within his reach, go- ing back as far as 1788. Vague as many of these details are, there is so much that is of definite value, that it seems to me possible to con- struct a curve of the levels of Lake Erie for the whole period, which should exhibit, with tolerable accuracy, the highest and lowest extremes at least. As I propose to use these aids in formulating certain con- clusions, I ought here to give the reader o])portunity to form his own judgment as to their value and authority.
To begin, it may be taken as universally admitted that the lakes were at a higher level in 1838 than at any known period before. In confirmation of this is the fact, among others, that forest-trees of a century's growth and more were killed by the high water of that year. Two other eras of very high water are reported by tradition, the one in 1814-'15, the other in 1788. Facts and comparisons reported render it nearly certain that at both these periods the levels attained to some- where near the standard of 1838. At the former date much land and many buildings were submerged on the Detroit and St. Clair Rivers. Many statements also bear upon the fact of high-water periods between the several dates mentioned. Dr. Houghton relates, on the authority of Colonel Henry Whiting: "Old inhabitants agree that the water was very high in the years 1800 to 1802, roads along Detroit River being completely inundated, and even rendered impassable." And further, that in 1821 the river began to rise, "and in 1828 had again attained the elevation of 1815, submerging wharves that had been built in the interval; and it so remained until 1830." As to low extremes, it seems well ascertained that the one of 1819- '20 was the lowest known prior to 1841—the low depression whir^h succeeded the extreme elevation of 1838, Presumably it was the lowest known during the century. Old Frenchmen of Detroit had no tradition of a level below that of 1819. Statements regarding the stage of the water always make reference to the acknowledged high- est and lowest years. Thus we are enabled to fix upon and determine with considerahle exactness the relative values of other low periods. The water in 1796 was reported by lake captains to he universally low, and indicating a level five feet below the high extreme of 1838, From that year, they say, it rose rapidly, and continued to rise until 1800, Colonel Whittlesey says: "It was ascertained generally that the water was low in 1790, 1796, 1802, and 1810, Between February, 1819, and June, 1838, there was a continual rise, amounting to 6 feet 8 inches," Old settlers compare the low stage of 1802 with that of 1797, In 1806 it was reported at Cleveland lower than in 1801-02, and declining regularly to 1809-'10. At this date it was reported nearly as low at Buffalo as in 1819. From 1828 it was reported as falling, and in 1833 was 3 feet 10 inches below June, 1838. From this year on we are able to trace the "secular" periods of lake and river with considerable accuracy; and data also exist in regard to other elements which it is proposed to include in our discussion. I give two diagrams, intended to exhibit graphically what is shown more in detail in the tables.
Diagram' No, I shows the curve of high and low water of Lake Erie from 1788 to 1838, constructed in accordance with the above data. In connection \vith it is given the sun-spot curve, from 1769 to 1838, according to Wolf's tables, reference to which will be made hereafter. The lengths of the periods are also shown, and the lag of the lake periods behind the sun-spot periods.
Diagram No. 2 gives similar data for the term of years from 1834 to 1887, including, in addition to the curves of lake-levels, those of the rainfall and of the temperature (registered at Detroit), and of the sun-spots, according to Wolf's tables.
In these diagrams my endeavor has been to exhibit by curved lines the recurring maximum and minimum periods, eliminating intermedi- ate and irregular fluctuations.
Confining our attention for the present to the curve of rainfall (Diagram No, 2), let us endeavor to ascertain whether among the many and often abrupt fluctuations it is possible to discover any pe- riodicity.
The vertical columns represent years. In the portion devoted to the rainfall variations the horizontal lines represent the number of inches of annual precipitation.
It will be noted that the years 1836 and 1880 were times of excess- ive rainfall. Between these two extremes, and about equidistant. appears another strongly marked period of excess, culminating in 1855, Again, between these three maxima are two lesser extremes, culminating in 1844 and 1868. Thus our curved line marks five periods of maximum rainfall.
Of low extremes we note four, which have their culminations in the years 1839, 1850, 1860, and 1872.
The intervals between extremes vary from eight to fourteen years, the general mean being eleven years.
Let us now compare with these curves those immediately below, and which represent the periodic changes in the levels of Lake Erie during the half-century. Here the horizontal lines represent the number of feet below the plane of 1838.
It requires but a glance at the diagram to show that some relationship exists between the lake and rainfall periods. The first impression conveyed is that the curves are in opposition — that the high in one corresponds with the low in the other, and the reverse. But I think
the true relation will be made to appear when we notice the important fact (which I endeavor to render more apparent by dotted lines), viz., that the water extremes lag behind the rainfall extremes — following them at intervals of from two to four years. Thus the seeming want of coincidence is reduced to harmony. It will also appear that the rainfall extremes are not only followed invariably by corresponding fluctuations in the water-levels, but that these succeed each other in quite as marked and uniform periods.
The rainfall maxima of 1836, '44, '55, '68, and '80 have their corre- sponding extremes in the water maxima of 1838, '47, '58, 'TO, and '82—the intervals or lag varying from two to three years. The rainfall minima of 1839, '50, '60, '72, and '86 have corresponding lake minima in 1841, '53, '65, and '75—the intervals varying from two to five years. The mean lag is 2 '9 years. The true relation—dependence—of the lake periodicities upon those of the rainfall is thus clearly shown.
It will be observed, that I have chosen to consider the Lake Erie levels rather than those of Detroit River. I do so for the reason that the relations of the former to the precipitation are more simple and di- rect, and are not influenced by caus"S already pointed out (page 375), which tend to create irregularities in the river. A marked illustration is shown between the years 1859 and 1870—where dotted lines repre- sent the rainfall at Milwaukee, and the river-levels as compared with those of Lake Erie—of the effect of excess of precipitation on the lakes above, in keeping up the river to a disproportionate extent.
I do not consider it necessary to examine the various theories which have been broached from time to time, in explanation of the lake peri- odical fluctuations. Xor will I undertake to explain all the irregulari- ties of the river and lake, which would demand many factors that are wanting to the present discussion. It will suflice if I have succeeded in making clear the relations which exist between the variations of the water-levels and the rainfall, and in defining their periodicities. Prob- ably few at this day would dispute the fact that the rise and fall, or "secular" variations, in the waters are dependent upon the rainfall. This is the first attempt, to my knowledge, at demonstration of their true relations.
Thus far I have not alluded to the important element of Tempera- ture in its relation to rainfall. That an intimate relation exists is an admitted fact; it shall be my endeavor to show what this rela- tion is.
In the portion of the diagram devoted to the Detroit temperature curve, the horizontal lines represent the degrees of mean annual tem- perature, which varies from 42°, the lowest, to 52'^', the highest ex- treme. Considering temperature as a controlling element, we should expect to find, a close correspondence between its curves and those of the rainfall. And we do so find, as is shown by the diagram. But, while the maxima and minima of the rainfall and the lake are directly as each other, we discover that those of the rainfall and the tempera- ture are inverse to each other. For a full discussion of the relation between these two elements, no doubt we ought to take into account other important factors—barometric changes, Avinds, magnetic and other phenomena. The conclusions of this paper are deduced only from the data presented. Let us now compare the curves.
The maximum temperature periods of 1839, '49, '60, '70, and '82 at Detroit will correspond to the niinimum, rainfall periods of 1839, '50, '60, '72, and '86—if we credit to the latter a lag or interval behind the temperature periods of to 4 years. The minitnuyn temperature peri- ods of 1834, '43, '55, '06, and '75 correspond to the maximum, rainfall years 1836, '44, '55, '68, and '80, with a lag varying from to 5 years; the mean of the lag being 1*8 years.
If this showing reverses the commonly received opinion that high temperature is followed by extreme rainfall, I can only say that the facts, as I find them, do not warrant such conclusion. Let the reader attempt to connect either the maxima or the minima of the curve of temperature with the like periods of the rainfall, and he will find it necessary to admit intervals of from six to nine years, a conclusion which would be inconsistent with any influence whatever.
I now turn to another element, or phenomenon, which will be found to have an intimate bearing upon our investigation.
Recently, much speculation has been elicited by the ascertained periodicity of spots on the sun's disk. It is now an admitted fact that the increase and decrease of the spots affect the magnetic needle, and influence the earth's magnetic and electrical condition. The extent to which these affect the meteorology of our planet is a moot question with the learned on these subjects.
Some noted observers in Europe and India maintain the theory of an influence exerted by the sun-spots upon the rainfall, and this di- rectly as the number of the spots. In this lake region, attempts to establish or define these relations have been few and unsatisfactory. It will be my part to show that the sun-spots do decidedly influence the temperature, and indirectly the rainfall, and that the curves of temperature correspond directly with those of the sun spots. This 'correspondence holds not only as regards the maxima and minima periods, but as to the general features of the two curves.
Wolf's tables of the sun-spots from 1769 to 1882 show ten periods of maxima and as many of minima, the spots ranging from in a minimum year to 150 in a maximum year. Of these periods, one half are embraced within the sixty-six years from 1769 to 1834. For this cycle there are no reliable statistics of temperature and rainfall; so that my data are confined to the sun-spots and the lake periods, of which I present a tabular statement, as supplementary to Diagram No. 1.
Table No. 1 exhibits in groups:
1. The years of maximum and minimum sun-spots from 1769 to 1834, according to Wolf's numbers—the maxima and minima in sepa- rate columns. 2. The years of maximum and minimum levels of Lake Erie, which are given in feet and tenths below the plane of 1838 — the maxima and minima in separate columns,
3. The lag, or interval in time at which the periodic changes in the lake follow inversely those of the sun-spots. One column gives the number of years lag of the lake maxima behind the sun-spot minima; the other of the lake minima behind the sun maxima.
4. The sun and lake periods In one column are given the number of years between each maximum of sun-spots and the next preceding maximum, and alternately, the number of years between each minimum of spots and the preceding minimum. In the other column are given the like data for the lake periods.
TABLE No. I.
Maximum and Minimum Periods of Sun-Spots and Lake Erie, 1769-1834.
|YEARS||sun-spots||lake erie levels||periods|
|+ No||- No||Below 1838, feet
|1779||155||. .||. .||. .||. .||40|
|1784||. .||12||. .||. .||. .||11|
|1788||140||. .||0·5||. .||4||. .||9|
|1796||. .||. .||. .||4·5||. .||8|
|1798||. .||5||. .||. .||. .||14|
|1800||. .||. .||2||. .||2||. .||. .||12|
|1804||85||. .||. .||. .||. .||. .||16|
|1809||. .||. .||. .||5||. .||5||. .||13|
|1810||. .||0||. .||. .||. .||. .||12|
|1814||. .||. .||1||. .||4||. .||. .||14|
|1816||55||. .||. .||. .||. .||. .||12|
|1819||. .||. .||. .||6||. .||3||. .||10|
|1822||. .||0||. .||. .||. .||. .||12|
|1827||. .||. .||2||. .||4||. .||. .||13|
|1830||75||. .||. .||. .||. .||. .||14|
|1833||. .||. .||. .||3·5||. .||2||. .||14|
|Means||. .||. .||1·4||4·7||3·5||4·5||12·3||12·6|
The phenomena which this table makes apparent are: First, that what I have called the sun and lake periods approximate in length, and the means of each are nearly identical — 12·3 and 12·6 years. Second, that the sun and lake periods are not synchronous, but that the changes in the lake follow at considerable distance (lag) behind the sun-spot times. Also that the lake maxima lag behind the sun-spot minima less than do the lake minima behind the sun-spot maxima, the means being, respectively, 3·5 and 4·5 years. That is to say, the waters fall less rapidly than they rise, by the mean of a year. We shall see presently how far these statements tally with the data drawn from fuller sources, for the half-century succeeding.
Let us now turn to Diagram No, 2, which exhibits the sun-spot curves from 1834 to 1884, paralleled with those of the temperature, the rainfall, and the lake.
We see five "periods" of sun-spot maxima, culminating in the years 1838, '48, '60, '70, and '82, the number of spots at each varying from 95 to 150. And five of sun-spot minima—in the years 1834, '44, '56, '67, and '77, the spots in each varying from 5 to 10. The maximum periods recur at intervals of ten to twelve years—and the minimum periods at like intervals—the means being 10'8 years. With the aid of the accompanying Table No. 2, we may proceed to compare results. ^
Table No. 2 aims to give in a succinct form all the data which our discussion requires. These are grouped in columns, as follows;
The first group gives (in three columns) the sun-spot data, in the same manner as in Table No. 1, viz., the years of maxima and minima, the number of spots at each, and the lengths of the periods.
The second or temperature group gives (in two columns) for those years of maxima and minima which conform to the sun-spot maxima and minima, the degrees of temperature (the mean of the year at De- troit), and the lengths of the periods.
The i-ainfall has three groups. The first gives for Detroit (in three columns) the maximum and minimum periods, the precipitation in inches at each, and the lag or interval at which each follows, in- versely, behind those of the temperature. Like data are given for the rainfall at Milwaukee and at Cleveland, so far as I possess data, omit- ting the column of lag.
For the water-levels there are two groups, each showing (in three separate columns) the periodicities, the measurements in feet and tenths below the plane of 1838, and the lag behind the rainfall at Detroit.
Lastly are given (as in Table No. 1) the lag of the lake behind the sun-spot periods—lake maxima behind sun-spot minima, and the reverse.
My aim is to exhibit those fluctuations in the elements under dis- cussion which conform to the sun-spot periodicities, according to the law which seems to govern, viz., temperature directly as the sun-spots; rainfall inversely as the temperature; lake-levels directly as the rain- fall, and the periodical changes in each, following uniformly those of the preceding or influencing element by a lag of short interval; and this increasing in length according to the remoteness from the original source of influence.
When we consider that the sun is itself the ultimate source of all our meteorological phenomena, the fact that the periods of greater and less energy indicated by spots on its disk have a well-marked relationship to the temperature and rainfall is not surprising. While there are many fluctuations for which no solution is attempted, it suffices if we are able to point out well-defined maxima and minima periodical fluctuations which conform to each other within small limitations.
The proof does not rest alone upon the Detroit observations. Though the rainfall at Milwaukee and Cleveland differs, often considerably, in times and amount, from the Detroit record, we find a close conformity in the periods. In fact, there is almost identity in the periodic means of all the elements contained in the table.
TABLE No. II.
Maximum and Minimum Periods of Sun-Spots, Temperature, Rainfall, and Water-Levels, 1834-1887.
Lake Erie behind the sun-spots at each period, furnish a remarkable confirmation of the general conclusions. (.Comparing the two tables, it will be seen that the mean periodicity of the sun-spots is larger for the first half-century than for the last by 1"7 years. Yet the same rela- tion to the lake periods is maintained throughout both cycles. The lag for the maxima and for the minima periods is the same in both tables, the means being 3 "5 years and 4'5 years, respectively. This re- sult is not merely remarkable; it would be incomprehensible on any other theory than that here contended for. Its truth or fallacy the reader has the means of determining if he will closely study the details given in the table and the diagram.
Another feature of too much importance to escape attention is the difference in all the curves between the scales of increase and of de- crease. This is shown by the diagram, and is computable from the tables. Thus, the times of increase in the sun-spot curve, from minima to maxima, are almost uniformly four years; those of decrease, or from maxima to minima, six to eight years. The temperature curve attains its maxima at the same time or a year later than the sun-spots, but its minima are often reached a year earlier than those of the sun. The result is to nearly equalize the times of temperature increase and decrease, the rising scale being accomplished in 5, and the falling in 5 '4 years.
The rainfall curves show a closer correspondence with the sun's times, but in reversed order, the rising scale being accomplished in about 6*5 years, the falling in about 4*5 years.
The lag of the lake curve behind the rainfall at its minima exceeds that of its maxima by nearly one and a half years (3'75 and 2*4). The tendency is to equalize the times of the lake increase and decrease, so that the "secular periods" exhibit nearly equal scales (5"4 and 5"25). During the cycle from 1779 to 1834 the scales differ more—rising 5-75 and falling 6*75 years. These are the closest correspondences I have been able to find to the traditional French period of 7 years.
Thus the cycle of change is "never ending, still beginning." On its restless sea, man is tossed at the caprice of billows, whose wave- lengths are intervals of eleven years. The law of change runs through the scale from cold to warm, and from -warm to cold in nearly equal times, but demands half a year's less time in the descent from wet to dry; while the upward scale, or from dry to w^et, is longer by two years than the downward scale of temperature, and with intervals or lag of one and a half years.
To sum up, it seems to me demonstrated, as regards this region:
1. That the so-called "secular" changes in the levels of the river and lakes are dependent upon the rainfall.
2. That these changes in their maxima and minima fall behind the rainfall extremes in time, varying from two to five years. 3. That the times of maximum and minimum rainfall occur inversely as the temperature, and follow after, with mean intervals of one to four years,
4. That the times of maximum and minimum temperature occur directly as the sun-spots, with small or no intervals.
5. That the times of high and low water of the lakes and river follow behind the sun-spots, inversely, by a double lag—of lake be- hind rainfall and of rainfall behind sim-spots—the mean of both being four years.
6. That the periods of maximum and minimum sun-spots, tempera- ture, and rainfall have an intimate relation to each other, and that this relation appears in the respective periodicities, which differ but little, while the means are nearly identical.
The question naturally arises, How far do the conclusions here recorded afford a foundation for forecasting the meteorology of the future?
If all the wave periods were of equal lengths and time?, with suffi- cient allowance made for other factors not within our present discus- sion, we ought to do so with exactitude. But though our sovereign governor—the sun—exhibits a considerable degree of regularity in the increase and decrease of his spots, he has not as yet admitted us into the secret either of the cause or of the extent and frequency of his variations.
We have also seen that while the curves of temperature and rain- fall are controlled by the sun-spot periods, their times of maxima and minima are not therefore synchronous. This is true to some extent as between the sun and the temperature, while those of the rainfall are not only inverse to, but lag behind, the temperature extremes, with varying times. There follows, therefore, a difference, both in the lengths and the times of the periodicities of each.* Owing to this lag, and its variation in time of one to four years, it follows that when the temperature curve is at its maximum or its minimum, that of the rainfall is not necessarily at its lowest or its highest. In fact, such a conjunction may be brought about in the progress of time, that a wet period may correspond in time to a warm one, or nearly so, and vice versa, and yet the law of opposites continue absolutely persistent.
This observation applies with even greater force to the lake curves, the lag in which is uniformly greater than in those of precipitation. Thus it has happened three times within the last half-century that high water in Lake Erie has corresponded in time with a high sun- spot period.
We observe, also, in noting the curves of temperature, as each ap- proaches its low extreme, a sudden dropping of the temperature from
- While the periodic times in the curve of temperature range from nine to twelve
ears, those of rainfall ranje from eight to fifteen.
- From "Memorials of a Half-Century." New York and London. G. P. Putnam's Sons. 1887.