■June 1, 1898.] 



KNOWLEDGE, 



12J5 



or less than our share of rain ? " This curve supplies 

 answers for the months of 18'.t7. The first three months 

 were wet. This excess was brought down in the next 

 four ; so that by the end of July we had had nearly our 



■f 3cra 

 +75-0 



+ "200 



+ laa 



■tSo 







-i'o 



^^ 



6 12. J 

 X)c<r »S97 



■J/^ 3o S II 17 23 2o M- 

 3a-n. /6<29 Tib 



FiQ. 1. — Gain and Loss Curve of Daily Terapevaturo at Greenwicli last Winter. 



proper amount. But by the end of the year there 

 was about two and a half inches (as we may say) still 

 due. 



Let us see what kind of curve we get from the daily 

 temperatures (at Greenwich) in the remarkably mild 

 wmter we have lately passed through. (The relation of 

 these to the average is given in the WeekUj TUturn.) The 

 curve is that marked A (Fig. 1). 



In these curves a rise means a plus value, and a fall a 

 minus ; we may speak of the one class as " gains," the 



downward course of the curve continue some time ? It 

 would be difficult to say. 



We may take a wider survey in this matter of tempera- 

 ture. Consider the years as hot or cold. Here is a curve 

 (B, Fig. 2)which shows, 

 in the case of Green- 

 wich, the result of the 

 method as applied to 

 the years since 1841. 

 Up to 1878 there has 

 been a general rise ; 

 since 1878, a general 

 fall. More hot years 

 than cold in the former 

 case (twenty-three to 

 fifteen) , more cold than 

 hot in the latter (twelve 

 to seven). The rise 

 since 1892 may be the 

 beginning of a long 

 general ascent : but it 

 seems not inconsistent 

 with our being still on 

 the " down grade." 

 Can we go further back with confidence? Earlier 

 figures are in some uncertainty. If we take a table of 

 estimated Greenwich temperatures, by Mr. Glaisher, in the 

 Philosopln>-<il Tmnsiictions for 18-30, and extending from 

 1771 to 1849, and apply our method, we get the curve C. 

 An interesting table by Dr. Buchan, for the North-East of 

 Scotland (chiefly Gordon Castle and Culloden), from 1764 

 to 1892, yields the curve D. There is a degree of similarity 

 between these two curves, and they may be taken to afford 

 a general idea of the truth. They dip down to low points 



2? 



-t 



>n«.r 



f^ ?*• 3o 



17^0 &> 72 'S n'SU'go '6 'mz''8 'l/f'TV '6 '32 'S '44 "io '6 '6Z. 'd '7^ '90 '6 '92. '8 



Fig. 2. — Gain and Loss Curves of Annual Temperature, Greenwich, Xorti-East Scotland, and Harvard. 



other as " losses "; and we see that in this curve, from the 

 beginning of December to February 17th, the gains were 

 much more than the losses. Neglecting for the present 

 the individual amounts of gain or loss, we find that the 

 warm days were much more numerous than the cold. 

 After February 17th the balance was the other way. Here 

 are some figures : from December 1st to February 17th we 

 had sixty-one warm days and only eighteen cold ; there- 

 after thirty-two cold days and only ten warm. Will this 



in the second and third decades of this century ; after 

 which comes a long rise to the seventies. The first twenty 

 years of our century evidently included some very intense 

 cold. Perhaps the severest wmter of the century (thus far) 

 is 1813-14, when a fair was held on the Thames, and there 

 was a snowstorm lasting forty-eight hours. 



It is a curious fact that in America the weather is often 

 opposite to ours. Thus, if winter is severe on the continent 

 of Europe it is generally mild in America, and rice nrsd. 



