lO 



NA rURE 



[May 



past, or on the point of coming to a conclusion, and in 

 all cases tne general tendency of the long period curve 

 is now to rise again. This indication of the increase 

 of the rainfall is represented in the figure b)' the dotted 

 continuation of the secular variation curves ior each 

 station, and should the apparent law hold good, there 

 seems sufficient evidence to mark that this rise will 

 ■continue to take place until about the year 1913, 

 which year will suggest the middle of the next wet 

 epoch. 



It may be mentioned, however, that owing to the 

 great oscillatory nature of the rainfall from year to year, 

 this rise only represents the mean rise when several 

 years are coupled together ; there may be comparatively 

 dry 3-ears even when the secular variation curve is at 

 a maximum, but on the average they will probably 

 be wet. 



What causes this long period of weather variation is 

 not yet definitely known, but it is of the highest im- 

 portance to meteorological science that the matter 

 should be cleared up as soon as possible, for not only 

 is our rainfall involved, but all other meteorological 

 elements show similar fluctuations. 



Bruckner attempted to account for this long period 

 weather cycle by attributing its origin to a change in 

 the activity of the sun, and he investigated the sun- 

 spot data then available for evidence of a periodicity 

 of about thirty-five years. He was not, however, suc- 

 cessful in his research, but he concluded that, although 

 this variation must really exist in the sun, yet it might 

 not necessarily be indicated by sunspots. More recently 

 a minute examination of the sunspot observations made 

 since the year 1832, when a systematic method of ob- 

 servation had been initiated, has led to the discovery 

 •of such a period, a detailed account of which appeared 

 in a previous number of this Journal (Nature, vol. Ixlv. 

 p. 196). _ It was there shown that each sunspot period 

 {reckoning from minimum to minimum) differed in 

 many respects from the one immediately preceding or 

 following It. Some periods, for instance, were not onlv 

 more " spotted " than others, that is, the summation o'f 

 the whole spotted area from one minimum to the next 

 varied regularly, but these particular periods were 

 •closely associated with comparatively rapid rises from 

 minlmumto maximum in those periods. These changes 

 further seemed to be undergoing a regular variation, 

 the cycle of which was determined to be about thirty- 

 five years. 



The connection between Bruckner's cycle and this 

 long period solar change of thirty-five years was there 

 briefly stated, and it was , shown that at those two 

 epochs 'of sunspot minima, namely, 1843 and 1878, 

 which follow the cycles of greatest spotted arpa, the 

 Bruckner rainfall cycle was at a maximum. 



The close correspondence of the epochs of these two 

 cycles suggested at once a probable cause and effect, a 

 cause which Bruckner himself had suggested and 

 looked for, but, unfortunately did not find. 



In the accompanying figure the uppermost curve 

 represents the sunspot curve from the year 1832, and 

 the minima just referred to are indicated by the vertical 

 dotted lines, which are continued through all the curves. 

 The periods of greatest spotted area just precede these 

 epochs, and the times of maxima are shown by the 

 vertical continuous lines drawn in a similar manner. 

 To show the probable times of the recurrence of these 

 epochs during a portion of the next great period of 

 thirty-five years two vertical lines have been inserted at 

 the years 1905, which is the probable epoch of the next 

 great maximum, and 19 13, the following minimum, 

 •so that their relation to the probable variation of rain- 

 fall, as indicated by the dotted portions of the curves, 

 can be seen at a glance. 



NO 1749. VOL. 68] 



In conclusion, attention may be drawn to the fact 

 that during the last few years a far more close con- 

 nection between solar and meteorological phenomena 

 has been made out than was the case some years ago, 

 and since this long period rainfall cycle synchronises so 

 well with the solar changes, the latter may render valu- 

 able assistance in determining the epochs of these dry 

 and wet cycles. William J. S. Lockyer. 



ETIOLATION.' 



•T^HIS monograph is published by the aid of the 

 J- Daly Lydig fund bequeathed by Charles P. Daly, 

 and embodies the results of the author's investigations 

 extending from 1895 to 1902, and one of the first ques- 

 tions it arouses is, to what extent is this sustained 

 experimental work stimulated by the certainty oi ade- 

 quate publication owing to the generosity of patriotic 

 endowment, and to what extent does such work 

 react on the pockets of friendly millionaires and 

 induce the endowments for further work? In any 

 case, Americans are fortunate in their circumstances in 

 these respects. 



The book, which comprises more than 309 pages of 

 text and 176 figures, all admirably done, is divided into 

 three principal sections. There is, first, a summary of 

 the history of the subject, beginning with Ray (1686) 

 and Hales (1727), and occupying 34 pages of more or 

 less critical notes. It is, of course, impossible for us to 

 verify the enormous number of the references to this 

 part of the subject, but if the author has made many 

 such blunders' as those on pp. 27 and 29, where on two 

 separate occasions he cites volumes and pages as 

 from Proc. Roy. Soc. when he should have written 

 Philosophical Transactions, the value of his biblio- 

 graphy rnust suffer. If a leading American plant 

 physiologist does not know the difference between the 

 two publications referred to. It Is time he did; if he 

 does, the Inference that he has not consulted the original 

 memoirs is as inevitable as it is. dispiriting. 



The second chief division of the work occupies the 

 bulk of the book, pp. 35-200, and reflects credit on the 

 author and his pupils for their industry and clearness 

 of description, as well as for the interesting choice of 

 plants selected for experiment. These Include not only 

 ordinary flowering plants, but also more out of the 

 way forms of monocotyledons and dicotyledons, as well 

 as ferns, Equlsetum, &c. The one note of disappoint- 

 ment in this portion of the book will be struck, 

 by the want of plan. Numbers of most interesting 

 observations on the behaviour of particular species in 

 the dark, and Illustrations of their' facies, their 

 anatomy compared with that of normal plants, their 

 curves of growth and so forth will make the book 

 useful to all investigators ; but the plants are arranged 

 in alphabetical order, and when the reader turns to a 

 particular species he has no guide as to how it will 

 be treated. Thus, taking at random Salvia, Sanse- 

 vierla, Sarracenia, Saururus, and Sparaxis, which 

 follow in the order given on pp. 171-180. The first 

 merely heads a . small paragraph stating that the 

 corolla is atrophied in darkness. Under Sansevleria 

 the etiolation of the shoot is described only in so far 

 as external changes are concerned. In Sarracenia 

 tlje effects of etiolation on the histology of the epidermis 

 lining the " pitchers " are well illustrated. In 

 Saururus figures of the anatomy of etiolated and 

 normal stems, and measurements of height and thick- 



1 "The Influence of Li?ht and Darkness upon Growth and Develop- 

 ment." By D T. Macdougal, Ph.D., Mem. New York Bot. Garden. 

 Vol. ii. Pp. xiii + 319. (1903.) 



