Jan. 30, 1879] 



NATURE 



305 



in a basin of water, and the circuit completed through a galva- 

 nometer. The temperature of the water in the basin might then 

 be altered till the galvanometer gave zero indication." 



Sir Wm. Thomson now adds the recommendation that, in 

 carrying out this method, the two wires, each well covered with 

 gutta-percha, should be twisted together ; that the wires should 

 be stout and as homogeneous as possible throughout, and that a 

 piece of stout copper tube should be attached to the lower junc- 

 tion, this tube being uncovered and in close contact with the 

 earth all round, its purpose being to insure that the junction 

 takes the proper temperature. 



It would probably be desirable, in filling up the bore, to mix 

 clay with the original material to render it watertight, for it 

 would be impossible to render the filling of the bore as compact 

 as the surrounding rock. 



Several pairs of wires would be buried in the same bore, with 

 their lower junctions at different carefully-measured depths. 



The upper junctions would be kept in a room pro%'ided with a 

 steady table for a mirror-galvanometer. 



THE RAINFALL OF THE WORLD"- 



I. T^HE pamphlet referred to below embodies the outline of 

 -■• an attempt to bring into harmony the disconnected, 

 and in some cases apparentiy irreconcilable results that have 

 hitherto attended comparisons of terrestrial rainfall and sun-spot 

 variations. It relates, therefore, to the entire rainfall system of 

 the globe. 



2. The plan by which it is thought this object will be best 

 attained is one which divides the world into a number of rain- 

 fall zones where either d. priori considerations or actual expe- 

 rience would lead us to expect typical changes in the effects of a 

 recurring secular variation in solar radiated heat upon the rain- 

 fall ; it being immaterial as far as regards the practical advan- 

 tages secured by this method of hyeto -graphical subdivision, 

 whether the solar radiation be ultimately foimd to vary directly 

 or inversely with the sun-spots. 



3. The way in which typical changes may arise in different 

 paits of the earth from the effects of an assumed recurring 

 secular change in solar radiated heat, is sho^vn by a reference to 

 the general scheme of atmospheric cu-culation in conjunction 

 with the two leading factors of variability, viz., season and 

 latitude. 



4. A consideration of these points leads the author to divide 

 the world into five zones, which either theoretically might, or are 

 actually known to, involve some typical change in the secular 

 variation of the rainfall either of one season or the whole year. 



5. Partly to illustrate this mode of subdivision by applying a 

 reasonable working hypothesis, and partly in the absence of 

 absolutely conclusive e\'idence in its favour, by exhibiting the 

 harmony of existing facts with the conditions theoretically 

 deduced fi-om it, to promote its ultimate adoption, the theory 

 of the inverse variation of solar radiated heat ^vith the sun-spots 

 is assumed throughout. 



6. It is also shown in the Introduction that we have a good 

 deal of evidence in favour of the same theory, botli <J priori, 

 fi-om a consideration of the principle of conservation of energy 

 as applied to the sun, as well as indirect, from the residts of 

 thermometrical observations. 



7. In applying this hypothesis to determine the rainfall varia- 

 tion, account is mainly taken of the direct relation between wind 

 velocity and temperature, the secular changes in solar radiation 

 being assumed to cause similar effective secular changes in the 

 velocity of the larger atmospheric convection currents. 



8. An induction from Messrs. Blanford and Eliot's theory of 

 cyclone-generation is then made use of, in combination with the 

 preceding hypothesis, from which it appears that while, owing 

 to the diminished solar temperature, evaporation might be 

 lessened in the tropics at the epoch of maximum sun-spot, the 

 diminished carrying power of the wind (by which the prevalence 

 of cyclones at this epoch would be accounted for, according to 

 Blanford and Eliot's theory) might allow of greater precipitation 

 near the place of evaporation, and therefore of a generally heavier 

 rainfall in these regions. At the opposite epoch, on the other 

 hand, the increased velocity of the wind woiUd probably cause a 

 wider distribution of tropical vapour, and therefore in combina- 

 tion with the direct effects of the assumed increase in solar 



* The Rainfall of the World in Connection with the Eleven-Year Period 

 o{ Sun-spots. With an Introduction and Appendix. By E. D. Archibald, 

 Professor of Mathematics in the Patna College. (Calcutta and London: 

 Thacker and Co. 1878.) 



radiation at the same epoch give rise to a deficiency of rain ia 

 parts, more especially those in which the local coniitions 

 normally tend to produce aridity. 



9. These hypothetical results are then shown to approxi- 

 mately agree with the actual results of observations recorded in 

 these regions. 



10. It is next shown that the effects of the assumed secidar 

 change in the velocity of the anti-trade (the prevailing wind of 

 the temperate zone) should differ considerably from those in the 

 case of the monsoons and trades of the tropics, an increased 

 velocity in the case of the anti-trade causing a greater quantity 

 of tropical vapour to be conveyed to the temperate regions, and 

 consequently a greater degree of humidity to ensue there. When, 

 therefore, the direct effects of the assumed increase of solar 

 heat at such an epoch are at a minimum, that is to say, in the 

 'ddnter, the relative humidity, and consequently the rainfall, 

 should be iiureased. It is also evident that such an effect 

 should be most conspicuously felt in those regions where rain 

 falls only in the winter, and is due to the descent of the anti- 

 trade. 



11. The occurrence of this inverse variation in the zone of 

 winter rains, which in the case of the Mediterranean stations 

 (Zeitschrift fiir Altteorologie, Band viii. No. 6), had hitherto been 

 deemed unfavourable to Messrs. Lockyer and Meldrum's gene- 

 ralisation regarding the direct variation of terrestrial rainfall with 

 the sun-spots, is also shown to be visible in the winter rainfall 

 of Northern India, and the rainfalls of Jerusalem and California, 

 thereby affording some preliminary support to the notion that it 

 holds over a still wider extent of the globe where the rain falls 

 mostly during the ^Tinte^. 



12. The attempt is then made to show that while the direct 

 effects of the secular change in the sun's heat over extra-tropical 

 continents may, during the summer, operate so far as to destroy 

 the indirect effects produced by the corresponding variations in 

 the strength of the anti-trade, and as Dr. Hahn has shown in 

 the case of the summer rainfalls of several stations in Central 

 Europe, actually cause a direct variation with the sim-spots, 

 there are, as there should be, in accordance with the hypothesis, 

 some preliminary indications of an inverse variation of that 

 proportion of the total which falls during the winter months 

 alone, even in those places where the rain falls throughout the 

 year. This fact, then, would imply that a change of season 

 causes a change of type in the character of the variation, so 

 that in order to render the variations distinctly apparent we 

 should compare the winter and summer falls separately. It 

 may also be inferred that the quality of the variation in the 

 total annual fall will depend on the preponderance of the simi- 

 mer or winter falls respectively, which fact may help to account 

 for the numerous anomalies noticed by those who have hitherto 

 compared the total annual falls of places in the temperate zone 

 with sun-spots. 



13. It is finally inferred in the appendix, as a direct result of 

 the hypothesis assumed throughout, that the winter gales of the 

 temperate zone and the cyclones of the tropics should bear a 

 complementary relation to each other, the former being most 

 frequent about the time of minimum, and the latter abeut that 

 of maximum, sun-spot. Some evidence in favour of this notion 

 was recently communicated to Nature by Mr. S. A. Hill 

 (vol. xviii. p. 616). 



14. The pamphlet is intended by the author to be considered 

 as merely tentative, and not by any means conclusive. It is the 

 method of division into zones and the separate comparison of 

 seasonal falls, rather than the accordance of data with theo- 

 retical deductions, to which he desires to give prominence, and 

 which he thinks may be of some assistance to other workers 

 in the same field. 



UNIVERSITY AND EDUCATIONAL 

 INTELLIGENCE 

 The Cambridge Mathematical Tripos list was published on 

 the 24th. This year the list contains 91 names. There are 28 

 classed as Wranglers, 33 as Senior Optimes, 29 as Junior Op- 

 times, and I iEgrotat. In 1878 the list contained 94 names, 

 31 being Wranglers, 30 Senior Optimes, 29 Junior Optimes, and 

 4.^grotant. The first three Wranglers are Mr. A, J. Camp- 

 bell Allen, of St. Peter's, Mr. George Walker, of Queen's, and 

 Mr. Carl Pearson, King's. Mr. Campbell Allen, of St. Peter's 

 College, the Senior Wrangler, is a native of Belfast, and was 

 bom in 1856. He received his elementary education at the 



