392 



not at its upper extremities exceed 4000 feet above the ground ; and 

 is led to the general conclusion, that the aurora borealis is situated 

 in the region immediately above the clouds, and therefore varies much 

 in height according to the different states of the atmosphere. He 

 believes it to be an effect of the developement of electricity from the 

 condensation of vapour. The position of the fringes, which are con- 

 stantly at right angles to the magnetic meridian, their progressive 

 movements from the north magnetic pole, and their influence on the 

 needle whenever they come into the plane of the dip, are all of them 

 circumstances which establish the relation of this phenomenon to 

 magnetism ; while they at the same time illustrate the intimate con- 

 nexion subsisting between magnetism and electricity. 



Remarks on several Icebergs which have been met with in unusually low 

 Latitudes in the Southern Hemisphere. By Captain James Hors- 

 burgh, Hydrographer to the East India Company, F.R.S. Read 

 February 4, 1830. [Phil Trans. 1830, ji. 117.] 



The journals of the ships belonging to the East India Company, 

 the author observes, during the whole of the last century, contain no 

 accounts of icebergs having been seen in the course of their navi- 

 gation in the southern hemisphere, although several of these ships 

 proceeded into the parallels of latitude 40, 41, and 42 south ; but 

 during the last two years, it appears that icebergs have occasionally 

 been met with by several ships in their passage, very near the Cape 

 of Good Hope, between the latitudes of 36 and 39. The particu- 

 lars relating to these observations are detailed in the paper. The 

 most remarkable occurred in the voyage of the brig Eliza, from Ant- 

 werp, bound to Batavia, which on the 28th of April, 1828, fell in 

 with five icebergs in latitude 37 31' south, longitude 18 17' east of 

 Greenwich. They had the appearance of church steeples, of a height 

 from 250 to 300 feet ; and the sea broke so violently against these 

 enormous masses, that it was at first suspected they might be fixed 

 upon some unknown shoal, until, on sounding, no bottom could be 

 discovered. 



It is remarkable that in general, icebergs appear to be met with in 

 low latitudes, nearly at the same period of the year, namely, in April 

 or May, in both the northern and southern hemispheres, although the 

 seasons are reversed in these two divisions of the globe. In order 

 to account for the origin and accretion of the southern icebergs, the 

 author thinks it probable that there exists a large tract of land near 

 the antarctic circle, somewhere between the meridian of London and 

 the twentieth degree of east longitude ; whence these icebergs have 

 been carried in a north and north-north-easterly direction, by the 

 united forces of current, winds, and waves, prevailing from south- 

 south-west and south-west. Bouvet's and Thompson's Islands are not 

 of sufficient magnitude, and Sandwich Land and Kerguelen's Island 

 are too remote to be the source of the icebergs lately observed in the 

 vicinity of the Cape. From their unprecedented descent during the 



