Sept. 14, 1882] 



NATURE 



489 



Now there is I think preliminary evidence to show that both kinds 

 of weather are due very greatly, if not altogether, to changes in 

 the sun, a large declination-range, and a large temperature- 

 range denoting an increase of solar power. There is also 

 evidence that temperature-range weather once produced travels 

 from west to east, taking probably on an average eight or nine 

 clays to cross the Atlantic. 



There is also, I think, preliminary evidence that declination- 

 range weather travels likewise from west to east, but quicker 

 than temperature range weather, taking about two days to cross 

 the Atlantic. 



Now if this be true it might be expected that the declination- 

 range weather of to-day should be found similar to the 

 temperature-range weather six or seven days afterward-, >o that 

 by a study of the declination-range weather of to-day, we should 

 be able with a certain measure of success to predict the 

 temperature-range weather six or seven days afterwards. 



I have here given the train of thought which led to this 

 investigation, but, I ought to say that the results obtained do not 

 depend upon the exact truth of every step of this train of 

 reasoning. 



This is in reality a matter of fact investigation undertaken 

 with the view of ascertaining whether or not there is any re- 

 cognisable connexion between these two weathers in Great 

 Britain. The result obtained I may add was reported to the 

 .Solar Physics Committee, and by them communicated to the 

 Royal Society. 



In order to avoid as much as possible the influence of 1 icalily, 

 I obtained through the kindness of the Meteorological Council 

 the diurnal temperature ranges at Stonyhurst, Kew, and Falmouth 

 for the years 1871 and 1872. I obtained likewise through the 

 kindness of the Kew Committee, the diurnal ranges of magnetic 

 declination at the Kew Observatory for the same two years, 

 excluding disturbed observations. The temperature ranges dis- 

 cussed aie therefore the means of those at the three observatories 

 above mentioned, and still further to tone down or equalize 

 individual fluctuations, the daily numbers exhibited are each the 

 sum of four daily ranges the two before and the two after. 

 Finally the object being to represent fluctuations of range rather 

 than their absolute values, a daily series representing the mean 

 of twenty-five daily numbers has been obtained. Each daily 

 number is thus compared with the mean of twenty-five daily 

 numbers both columns being symmetrically placed with regard to 

 lime and the differences whether positive or negative between the 

 two columns is taken to represent temperature range fluctuations. 



A precisely similar course has been taken irith respect to the 

 Kew declination ranges. 



By this means two years of daily numbers, sometimes positive 

 and sometimes negative, representing temperature range weather, 

 and two years of daily numbers sometimes positive and some- 

 times negative representing declination range weather, have 

 been obtained. The next object is to compare the two series 

 with one another. 



Now when two series of waves representing elevations and 

 depressions come together it is well known that we shall have 

 the greatest result when the crests of the one series coincide with 

 the crests of the other, and the smallest result, perhaps even 

 none at all, when the crests of the one series coincide with the 

 hollows of the other. This indeed is the well known explanation 

 of musical beats. 



Now if there be any marked likeness between the two weathers 

 and if it be true that declination-range weather precedes tern) era- 

 ture weather by six or seven days, the algebraic sum of the two 

 sets of fluctuations representing these weathers will be greatest 

 when the declination is pushed forward in point of time so that 

 the declination fluctuations of to-day shall be summed up with 

 the temperature fluctuation six or seven days after. 



For suppose that the declination fluctuation of to-day is repre- 

 sented by a very large positive number ; if the above theory be 

 true, the temperature fluctuation six or seven days afterwards will 

 be represented by a large positive number also, so that we shall 

 have the addition of two large positive numbers, whereas, if we 

 add the declination weather of to-day to the temperature weather 

 of to-day it may chance that we are really adding a large positive 

 to a large negative quantity in which case the result will be very 

 small. It may also happen that this amount of precedence of 

 declination-weather is greater at one season of the year than at 

 another. 



We have therefore to pursue a plan somew hat of the following 

 nature. Take a month's temperature-weather say for the month 



of August and add to it a month's declination-weather, extending 

 say from July 21st to August 21st, let the sum be 262. Here 

 the declination month has been pushed forward 1 1 days. Next 

 push it forward 12 days and let the sum be 273, then 13 days 

 and let the sum be 276, next 14 days and let the sum be 270. 

 It thus appears that the greatest sum is got by pushing the decli- 

 nation forward 13 days, and we may therefore presume that at 

 this season of the year 13 days denotes the precedence of the 

 declination weather. 



On this principle the following table has been constructed. 

 Table showing by how many days the declination-range fluc- 

 tuation precedes the corresponding temperature-range fluctuation. 

 Corresponding to middle Precedence of Declination. 



of month. First year. Second year. Mean. 



January ... ... — ... S ... 8 



February ... 6 ... 4 ... 5 



March 6 ... 5 ... 5'5 



April 5 ... S ... 5 



May 9 ... 9 ... 9 



June 9 ... 9 ••• 9 



lulv 12 ... II ... 11*5 



August 13 ... 13 ... 13 



September ... 9 ... 10 ... 9'5 



October ... 7 ... 5 ... 6 



November ... 10 ... 7 ... 8' 5 



December ... 12 ... — ... 12 



It thus appears from each year that the precedence of declina- 

 tion is smallest about the equinoxes, and greatest about the 

 solstices, and it seems probable that were a considerable number 

 of years so treated, more exact values would be obtained. 

 Having thus determined the amount of precedence of the declina- 

 tion from month to month, the next point is to ascertain to what 

 extent the two fluctuations when brought together in a maimer 

 regulated by this precedence show any distinct resemblance to 

 each other. This has been done in a graphical representation 

 which accompanies the report above-mentioned and I think I 

 may say that there is a considerable likeness between the two 

 curves, the one exhibiting temperature-range weather and the 

 other declination-range weather so pushed forward. 



It would thus seem as if a comparison of magnetical and 

 meteorological weather might be made a promising subject of 

 inquiry besides being one which may perhaps lead to results of 

 practical importance. 



On a Supposed Connection between the Heights of Rivers and the 

 number 0} Sunspots on the Sun, by Prof. Balfour Stewart, 

 M.A., LL.D., F.R.S. — While a connection between the state 

 of the sun's surface as regards spots, and the magnetic state 

 of the earth, may be considered as well established, the fact 

 of a connection between sunspots and terrestrial meteorology 

 is still sui judice, and without attempting to assert the truth of 

 such a connection, the following may perhaps be regarded as a 

 slight contribution tending to throw light upon the subject. 

 The heights of the rivers Elbe and Seine have already been 

 examined by Fritz, who reported in favour of such a connection 

 as would make a great height correspond to a large number of 

 sunspots, and all that I have done has been to treat the evidence 

 in a somewhat different manner. I divide each sun period with- 

 out regard to its exact length into twelve portions, and put 

 together the recorded river heights, corresponding in time to 

 similar portions of con-ecutive sun-periods. I find by this 

 means residual differences from the average, representing the 

 same law whether we take the whole, or either half of all the 

 recorded observations, and whether we lake the Elbe or the 

 Seine. This law is that there is a maximum of river height 

 about the time of maximum sun-pots, and another subsidiary 

 maximum about the time of minimum sunspots. It is of interest 

 to know whether the same behaviour is followed by the River 

 Nile. Through the kindness of General Stone Pacha, and 

 through the Science and Art Department, South Kensington, 

 information has been obtained about this river. This informa- 

 niation shows us that the Nile agrees with the European rivers 

 in exhibiting a maximum about the times of maximum sunspots 

 and a subsidiary maximum about the time of minimum sunspots, 

 only the subsidiary maximum is greater than for the European 

 rivers already named. It also appears that the date of maximum 

 height of the Nile is latest on these years for which the yearly 

 height is greatest. Now the present year is, perhaps, cot very 

 far removed from a solar maximum, and I am thus induced to 

 think that the Nile may this year be somewhat late in attaining 

 its maximum rise. 



