26 On Magnetic Variations. 



variation became gradually accelerated from 7\' per annum, in 

 1580, to 13i' in 1723, and yet during this period, viz., at 1657, the 

 line of no variation was passed. 



Again, in 1784 the variation at St. Petersburg ceased to move 

 to the west, at Paris the same thing did not take place until 

 1814, and at London until 1819, showing that the progress of 

 the change in the western variation is from east to west, or that 

 the change begins at the eastern station, a fact which so far has 

 been borne out here ; the change at Sydney being eight years in 

 advance of Melbourne, and since this distance 6^0 of longitude 

 took 8 years, it is probable that about Wentwortli the variation 

 has still an easterly increase. 



It thus appears that in the Northern Hemisphere, 35 years 

 elapsed from the time greatest west variation was reached at St. 

 Petersburg till the same thing took place in London, which is 

 30° to the west, and here 50 years passed between the change at 

 London, and (making allowance for the difference of position 

 with regard to the North Pole) Sydney 29° west. The decrease 

 of variation and peculiarity of the Sydney curve from 1813 to 

 1823 was preceded by a similar motion of the magnet at London 

 from 1722 to 1773, so it would appear that great changes in the 

 magnetic variation take place at London from 50 to 70 years in 

 advance of Sydney, although the passing disturbances are simul- 

 taneous. 



"VVe are indebted to the Eev. "W. B. Clarke for making the 

 first list of variations detennined at Sydney and Parramatta, and 

 publishing it in the " Australian Almanac " for 1858. 



The first determination of the variation in Australia which I 

 find recorded, was made by Captain Cook at Botany Bay, on 29th 

 April, 1770. He then made it 11° 3' east. There can be no 

 doubt from subsequent observations that this result is consider- 

 ably in error — probably too large by nearly 3°. In 1788, 

 Lieutenant Shutland, then in command of the Alexander, trans- 

 port, made the variation 8° G' east — a result which is probably too 

 small by about half a degree. In 1793, Brewster made it 8° 46 

 east. In 1803, Flinders made it 8° 51' east ; the longitude, lati- 

 tude, and other results obtained by this observer are so good that 

 I am inclined to place much reliance upon this result (Flinders, 

 vol. 1, p. 239). Brewster again, in 1813, observed at Parramatta, 

 and the result corrected to Sydney by the difference between the 

 two places, is 8° 51' 34", or a change of 34 seconds in a period of 

 ten years. Captain P. P. King, in his voyage to Australia in 

 1817, made the variation at Sydney 8° 42' east. Surveyor- 

 General Oxley, in April, 1818, after determining the position of 

 Macquarie Lighthouse, South Head, states that all the bearings 

 are magnetic, and the variation 9' east. This is probably only an 



