66 Mr. Beke's Additional Remarks on the former extent of 



16. I am disposed to think that the correction for tempera- 

 ture is always open to a certain degree of doubt. Perhaps 

 the condition of magnetism in the needle is not necessarily that 

 due to the temperature it possesses at the moment, but rather 

 to a temperature it had formerly. I think I have in some 

 cases perceived indications of this. The needle No. 1, which 

 is more slender than the " flat," seemed to be more steady in 

 its indications than the other, and as I have always placed 

 more reliance upon its indications, so the effect of temperature 

 was determined with most care. 



17. IV. Variations in the Earth's Magnetic Intensity. — 

 These variations must affect observations of the relative inten- 

 sity at two places, if the observations be not simultaneous. 

 These variations are either (1.) secular, showing a progressive 

 change from year to year ; (2.) periodical, that is, subject to 

 short periods of variation and regular, as at different seasons 

 of the year, and at different hours of the day; or, (3.) acci- 

 dental, arising from the aurora borealis, or from unknown 

 causes*. The numerical laws of these three may be said to 

 be almost equally unknown ; the variations of the second class 

 have indeed been studied by Hansteen, Christie, Dove, and 

 others, but the results are not sufficiently accordant to permit 

 me to apply any of them to my observations. As, however, 

 the epochs are always recorded, this correction may be ap- 

 plied at a future time, and in a more advanced state of science. 



[To be continued.] 



XIII. Additional Remarks on the former Extent of the Persian 

 Gulf and on the Distinction between Babel and Babylon, 

 By Charles T. Bekf, Esq., F.S.A. 

 To the Editors of the Philosophical Magazine and Journal. 

 Gentlemen, 



"CMiOM the length of time which has elapsed since the 

 A insertion of m} T last communicationf, I am led to conclude 

 that the controversy which during the last three years has oc- 

 cupied so many pages of your valuable journal is now at an end. 

 Before, however, allowing the subject to be entirely dismissed, 



* My friend Professor Necker of Geneva has pointed out to me one of 

 the first recorded observations o( the influence of the aurora upon the mag- 

 netic needle, the more interesting because the coincidence was unnoticed 

 (apparently) by the observer himself. In Saussure's Voyages dans les Jlpes, 

 vol. iv. p. 300, that enterprising traveller notices an auroral appearance, ob- 

 served from the Col du Geant on the 12th of July 1/88, and in another 

 part of the same volume (p. 308), records, amongst his magnetical observa- 

 tions, the unsettled state of the needle during the whole of that evening. 



f See Lund, and Edinb. Phil. Mag. for July 1836, vol. ix. p. 34, ei seq. 



