and especially in Scotland. 305 



Signor Capocci, Directeur de I'observatoire de Naples, in a 

 letter to Eliede Beaumont published in theComptes Rendues,* 

 says, " Apres 1' eruption du Janvier dernier, la declinaison de 

 I'aiguille a brusquement diminu^ d*un demi degreaumoins." 



In the Annalen der Physiken,f a Mr Gay is r^erred to as 

 having observed in Chili, for a long period, and with great care, 

 the daily variations of the needle. It is stated on his autho- 

 rity, that, during the earthquake in that country, of 20th Feb- 

 ruary 1835, a great distui-bance was produced in the daily va- 

 riation of the dipping needle, but not in that of the horizontal 

 needle. 



On this point it also deserves to be noticed, that the mean 

 daily changes in the variation of the needle, amount, during 

 the six months of summer, on an average of the last observa- 

 tions in this country, to 10' 48", and in the six winter months 

 to 6' 31", — ^the maximum and minimum being also in Decem- 

 ber and June respectively. t It will be remembered, that, in 

 both these respects, viz., the time of the year and the parti- 

 cular months when the maxima and minima of diurnal vari- 

 ation occur, the register of earthquake-shocks presents a re- 

 markable coincidence or analogy. 



A similar coincidence is discoverable in the magnetic inten- 

 sity^^ which reaches a maximum in December, and a minimum 

 in June : — so that it is, on the whole, difficult to resist the 

 conclusion, that the causes of earthquake-shocks, whatever 

 they are, are, in some way or other, connected with terres- 

 trial magnetism. 



In reviewing the summary which has now been given of the 

 phenomena attending the earthquake-shocks felt in this coun- 

 try, it will be observed that the order proposed has been, as 

 far as possible, preserved, of noticing, firsts the phenomena 

 which explain the nature or character of the shocks; and, 

 next^ the phenomena which seem to throw light upon the 

 causes of them. 



Without venturing to say what these causes are, until, at all 

 events, the observations made during the shocks of 1839, 1840, 

 and 1841, in this country have been detailed, it may be ad- 



* Tomo ix. p. 374. t Vol. xxxvii. p. 480. 



J See article Ma^etism, ia Napier's Encyclopajdift Britannica, p. 730. 

 § Ibid. p. 740. ^ ' * ' ^ 



