ABT OF EOONOMIO DEFELOPMENT 48 forward the hypothesis ? that the irregular periodic fluctuations of harvests which average about 8} years in duration are caused by like fluctuations weather and in the radiation of solar energy. in the It would seem that ?arious economic factors controlling the trade cycle receive their impulse from the harvests*. The curious coincidence of the average period of recurrence of commercial crises with the average period of sunspot ma?ma was noted long ago by my father s. For our present purpose however, it will be sufficient to note what were the years of maxima after which a sudden rapid fall of prices commenced. Going backward along the .curve of prices we find the? were as stated in the left hand column below, the interval being given in the right hand c?lumn :-- Date o! ]?x|mum Years intm'val Yetm interval 1907 7 1847 8 1900 1889 10 14 1890 18?5 lO 7 1880 7 1818 9 1875 9 1809 9 1864 7 1800 4 1857 10 1796 18 1847 1788 ? There is no index number of prices for the century preceding 1782; but the course of prices can be inferred fairly accurately from the total value of foreign trade, as may be seen by comparing prices and trade in the nineteenth century; and fortunately we have official ? $#,; Heat and Traae Act;vitlt. London. P.8. King & Co. 1909. C!mlm. VI ?nd VH. ! W. 8. Jevons, laeest?gat?on? in C#rr?e?,/ a?d l?q?a?u?, ed. 1884, pp. 194 seq., bein? reprint of paper read at British Assoeiation in 1875. 4 The index numbers for 1789 and 1783 are eqmd, but the phenomms of the Etter yemr were skin to those of other yesrs of maximum immedistely lweeeding s
