Nov. 2 2, 1877] 



NATURE 



59 



notably on the Severn, wbicb, according to Mr. Alfred Tyler, 

 F.G. S., is seen to best advantage with a rising sun from Stone- 

 bench Inn, about three miles below Gloucester. 



From the above table it appears that the highest tides of the 

 year will occur on March 20-21 and September 28. The heights 

 will be found probably to exceed those of the Admiralty Tables, 

 as I have employed larger factors in the necessary corrections to 

 the semi-menstrual inequality. 



As a London tide table appears to be a desideratum, I have 

 been induced to publish one for next year, in which the "dan- 

 ger " tides will be distinguished in a new, bold, and unmistak- 

 able manner. Edward Roberts 



3, Verulam Buildings, Gray's Inn, November 17 



Rainfall in the Temperate Zone in Connection with 

 the Sun-spot Cycle 



This month's number of the Nineteenth Century contains an 

 article on the connection of rainfall with the eleven years' cycle 

 of sun-spots. It takes a carefully-selected area in which such a 

 coincidence, if it existed, would be well marked. The great 

 tract of water spreading southwards from Asia to the southern 

 pole affords an arena for the undisturbed play of solar activity. 

 It may readily be understood that any excess of solar energy has 

 a more direct and uniform influence upon the rainfall gathered 

 from this vast aqueous expanse, than it would have upon smaller 

 areas of water interminjiled with tracts of land, and cut off from 

 each other by ranges of mountains, as in the European and 

 American continents. Other reasons exist which would render 

 solar influence a more directly potent factor in the rainfall 

 gathered from the Indian Ocean than in that of the temperate 

 zone. Without doing more than alluding to the fact that sun- 

 spot activity is confined to a belt of considerable thickness on 

 either side of the sun's equator, there are several well-ascertained 

 causes which would render an excess of solar activity more 

 directly felt in the equatorial regions of our earth than in those 

 nearer the poles. While, therefore, I believe that the coinci- 

 dence of a rain cycle and of a cycle of wind disturbances with 

 the eleven years' cycle of sun-spots, has now been established as 



regards the Indian Ocean and the Madras rainfall, I am anxious 

 to guard against the conclusion beinij pushed too far. The 

 article in the Nineteenth Century proves much, but it would be 

 a misfortune at this still early stage of the inquiry, if wider 

 inductions were drawn from it than are justified by the evidence 

 which it brings forward. 



. It seems right, therefore, to state that so far as my investiga- 

 tion of the rain returns of the temperate zone yet enables me to 

 form an opinion, the cyclic coincidence of the rainfall with the 

 eleven years' cycle of sun-spots, seems to shade off in extra- 

 tropical regions until it ceases to exist at all. This opinion is 

 ^ased upon an examination of the returns of between one and two 

 hundred stations in different parts of the world, but only with 

 regard to one-third of them is the evidence sufficiently complete as 

 to raise more than a presumption either for or against the exist- 

 ence of a cycle. Further, I have not yet been able, except in 

 comparatively small groups of stations, to examine the monthly 

 returns or to separate the winter from the summer rainfall. This 

 separation forms one of the first essentials to arriving a' a final 

 opinion on the question. Subject to these remarks, I beg to 

 state the facts with regard to the rainfall of the northern extra- 

 tropical zone in India, Europe, and America. It is chiefly with 

 the first and last-named countries that the present contribution 

 will deal. 



In my " Cycle of Drought and Famine," printed in India on the 

 commencement of the late dearth, I mentioned that the rainfall 

 which, in periods of minimum sun-spots, passes uncondensed over 

 the Southern Presidency, might possibly "fill in the temperate 

 zone. The excessive rain, if it takes place anywhere, will probably 

 be found in India between the 22nd and 32nd degree of north lati- 

 tude, to the south of the great Himalayan partition wall." Tne 

 conjecture was based upon the configuration of the Indian con- 

 tinent, which, in its lower and middle regions, receives the rainfall 

 gathered from a vast ocean, and is provided with a barrier at 

 the upper end to arrest the rain-clouds on their further progress 

 northward. Prof. Archibald's examination of the rainfall in 

 Northern India now throws a clear light on this side of the 

 question. He has published in the leading Calcutta paper, the 

 Englishmaft, a series of carefully-compiled returns from stations 

 within the ten degrees of latitude above mentioned. He shows 

 that the rainfall of the sub-tropical region, from 22° to, say, 30°, 

 is in some respects (but only in some respects) complementary 

 to the rainfall of Southern India, and in a recent letter to me he 

 thus summarises his conclusions : — First, the winter-rainfall of 

 Northern India varies inversely with the sun-spots in a well- 

 marked manner at all the stations. Second, the summer rain- 

 fall varies directly with the sun-spots, in a manner well marked 

 in the north-western provinces, by no means marked in the 

 lower provinces of Bengal, but sufficiently well marked when 

 the returns of the several stations are combined. 



Let us examine the meaning of these facts. The returns from 

 Madras and Bombay (lately published in Nature and elsewhere) 

 prove that when the summer monsoon strikes Southern India, 

 its aqueous burden varies directly with the sun-spots. Prof. 

 Archibald's returns now show that the ramfall brought by the 

 summer monsoon to Northern India also varies directly with the 

 sun-spots. But they prove more than this. They show that 

 the rain-clouds which, in years of minimum sun-spots pass over 

 India without dropping their watery burden, are found, on their 

 being stopped by the Himalayan partition wall, to be charged 

 with a more than average surplus (so to speak) of moisture. In 

 Northern India, therefore, the summer monsoon, on its passage 

 up, brings, as in Southern India, a rainfall varying directly with 

 sun-spot activity ; but the winter rainfall, i.e., the immediate 

 rebound of the rain-clouds from the Himalayan barrier, varies 

 inversely with sun-spot activity. I say the immediate rebound, 

 for it must not be forgotten that the north-eastern monsoon 

 (October to December), when it strikes Madras in its full develop- 

 ment, after collecting its aqueous freight from the Bay of Bengal, 

 follows the same law as the summer monsoon (May to Sep- 

 tember), and varies directly with the sun-spots. 



Passing from the sub-tropical region of Northern India (22° to 

 32° lat.) to the temperate zone, we find the evidence of a cycle 

 either very faint or altogether wanting. With regard to Europe, 

 I am not yet prepared to offer any new facts. The existing 

 evidence only amounts to this : (i) Mr. Baxendell, from observa- 

 tions for a comparatively short period but very carefully recorded 

 and scrutinised, came to the conclusion that even at an English 

 station, notwithstanding the manifold disturbing influences 

 incident to our insular meteorology, changes take place in the 

 rainfall as well as in the temperature and barometric pressure, 



