402 



Presents. 



[Apr. 4 r 



the magnetism of the earth, we may imagine that the increased values 

 not only of the average declination-range but also of the sub-periods 

 of these during times of maximum sun-spots may be due to one of two 

 causes, or to both of these together. Thus we may imagine that the 

 sun has an increased magnetic influence during such periods, or we 

 may imagine that there is an increase in the magnetic susceptibility of 

 the earth ; or, finally, we may imagine that both of these causes operate 

 together. I cannot help thinking that we have some evidence of an 

 increase of the magnetic susceptibility of the earth on such occasions 

 derived from two facts discovered by Mr. Broun, The one is that the 

 magnetic influence of the moon on the earth shows traces of following 

 the solar period, this influence being greater during times of maximum 

 than during times of minimum sun-spots. The other is that at Trevan- 

 drum the lunar magnetic influence, without changing its type, exhibits 

 an increase of value when the sun is above the horizon at that place, as 

 if on such occasions there were an increase of susceptibility to the lunar 

 influence. These, however, are points which can only be determined 

 by a further discussion of observations. 



In conclusion, I beg to record my thanks to Mr. W. Dodgson and to 

 Mr. Morisabro Hiraoka, who have kindly assisted me in the work of 

 this paper. 



Presents, April 4, 1878. 



Transactions. 



Berlin : — Koniglich Preussische Akademie der Wissenschaf ten. Mo- 



natsbericht. December 1877. 8vo. The Academy. 



Brussels : — Societe Malacologique de Belgique. Proces-Verbaux des 



Seances. Annee 1877. Tome VI. 8vo. Brunettes. The Society. 

 Dublin : — Royal Geological Society of Ireland. Journal. Vol. XIV. 



(New Series. Vol. IV). Part 3. 8vo. 1876. The Society. 



Frankfort: — Nene Zoologische Gesellschaft. Der Zoologische Garten: 



Zeitschrift fur Beobachtung, Pflege und Zucht der Thiere. 



Jahrgang XVIII. No. 4-6. 8vo. Frankfurt-a.-M. 1877. 



The Society. 



London : — Iron and Steel Institute. Journal. 1877. No. 2. 8vo. 



The Institute. 



Victoria Institute. Journal of Transactions. Vol. XI. No. 42-44. 



Vol XII. No. 45. 8vo. 1877-78. The Institute. 



Zoological Society. Transactions. Vol. X. Part 3, 4, 5. 4to. 

 1877-78. Proceedings of the Scientific Meetings for the year 

 1877. Part 3, 4. 8vo. 1877-78. The Society. 



Paris : — Societe Francaise de Physique. Seances. Avril-Decembre 

 1877. 8vo. The Society. 



