506 



NATURE 



{April %o, 1874 



number of observations which have come down to us, 

 that any variations of importance have escaped notice. 



In the upper part of the diagram, the unbroken line 

 represents Carrington's curve founded on the number of 

 sun-spots. The broken hne is a reduction of a mean 

 curve based on the area of the spots given by De la Rue, 

 Stewart, and Loewy in the Philosophical Transactions for 

 1870 ; and is introduced as showing the solar periods to 

 a later date. 



3. General Ecmarks.— The first four maxima of sun- 

 spots represented in the table being separated by long 

 intervals of years with few spots, and not being very 

 intense, would appear to have been closely followed by 

 L. Erie. More especially 1837, the year of greatest 

 known intensity according to both spot curves (333 new 

 groups of spots according to Schwabe), was marked in its 

 effects on the lakes, giving rise in 1838 to the highest re- 

 corded level of the waters in Erie and Ontario, and pro- 

 bably also in Superior, though here the data are not so 

 certain. The high-water mark of 1838 has since been 

 employed as the datum to which all the measurements of 

 the Lake Survey are reduced. 



The three last periods of maxima of sun-spots are 



extreme, and the intervals characterised by their deficiency 

 so short that the lakes seem to have been unable to follow 

 them as closely as before. One period of high water 

 being to a great extent merged in the next, and resulting 

 in a general high state of the lakes for the last thirty years, 

 which may be connected with the Wolfian Cycle of fifty- 

 six years in the development of sun-spots. The lakes do 

 not seem to have responded to the maximum of 1848, but 

 by a reference to the curve of area of sun-spots, it will be 

 seen that the intensity of this period was not so great as 

 of those on either side of it, and the period of maximum 

 was maintained for a very short time only. The im- 

 portant sun-spot maximum of 1859-60 was evident in its 

 effect on the lakes even at their present general hi^h level. 

 With regard to the Lake of the Woods the data are slight, 

 but it may be mentioned that this lake is known to have 

 been very low in 1S23, and in 1859 to have attained a 

 point which it has never touched since, and which is about 

 3 feet higher than the present level. The lake is also 

 known to have been for a good many years higher than 

 usual, and at least one well-marked high water took place 

 between 1823 and 1859, which may very probably have 

 been synchronous with that of 183S on the great lakes. 



Comparative Dia^r: 



I of the Fluctuations of Lake Erie, and Periods of greater or less olar Activity as indicated by the occ irrence of Sun-spots, i. Solar 

 Spot Curves, a. High Water, June 1838. 3, Lake Erie. 



This lake derives its waterfront the western slope of the 

 same Laurentian range which feeds Lake Superior. 



The correspondence between the periods of maxima and 

 minima in solar-spot cycles and in the fluctuation of the 

 grcrft lakes, though by no means absolute, seems to be suffi- 

 ciently close to open a very interesting field of inquiry, 

 and to show the extension of the meteorological cycle 

 already deduced by Messrs. Meldrum and Lockyer for 

 oceanic areas in the southern hemisphere, to continental 

 ones in the northern. 



The great lakes in their changes of mean yearly level 

 probably show a very correct average of the rainfall over 

 a large area, and thus indicate the relative amount of 

 evaporation taking place in different seasons. It is to be 

 observed, however, that the actual mean annual outflow 

 of the lakes would be a better criterion, and that from the 

 form of the river valleys giving exit to the waters, this 

 must necessarily increase in a much greater ratio than 

 the measured change of level in the lake itself. It is 

 much to be desired that such observations should be sys- 

 tematically made. The occurrence of seasons of great 

 activity of evaporation and precipitation, as indicated 

 by the lakes synchronously with those of maximum in 

 solar-spot production, would tend to confirm the opinions 

 previously formed as to the coincidence of the latter with 

 periods of greater solar activity. Wolf, as quoted by 

 Chambers, states from an examination of the Chronicles 



of Zurich, " that years rich in solar spots are in 

 general drier and more fruitful than those of an opposite 

 character, while the latter are wetter and stormier] than 

 the former." Gautier, from a more extended series of 

 observations, including both Europe and America, has 

 deduced an exactly opposite conclusion, which, from the 

 evidence of the great lakes, would appear to be the 

 correct one. 



It is quite possible, however, that both maybe true (see 

 " Solar Physics," p. 430). The great lakes lying at the 

 base of the Laurentides, where moisture-bearing winds 

 from the southward and westward are interrupted in their 

 course, and meet with cold currents journeying over these 

 hills from the north, are essentially in an [area of precipi- 

 tation, and greater precipitation would hero be the natural 

 result of greater solar energy. In other legions excessive 

 evaporation may result from the same cause, and this 

 may account for the gradual desiccation which on the 

 authority of many observers is going on at present over 

 great areas of the inland plains of the west. 



The observations here given cannot be accepted as 

 conclusive, but derive additional importance from the 

 large area which they represent, and may suggest more 

 systematic investigation of the subject, and the accumu- 

 lation of accurate observations, which in the course of 

 years may lead to results of greater value. 



G. M. D.WVSON 



