280 Canadian Record of Science. 



Even in the matter of secular changes in the variation of 

 the compass we find that the marine charts instruct that 

 an allowance of increased easterly variation of 2min. per 

 annum must be made, and as this has now accumulated 

 since 1850 it involves a very sensible correction to be 

 adopted by a shipmaster in making the land or standing 

 along the coast ; but we find from the recently published 

 work of the Challenger that this tendency to change has 

 for some time back ceased to affect the New Zealand area, 

 and as the deduction appears only to have been founded on 

 a single triplet observation of the dip taken at Wellington 

 and one azimuth observation taken off Cape Palliser, it 

 would be well to have this fact verified. With regard to 

 the local variation in the magnetic currents on land and 

 close in shore, the requirement for exact survey is even 

 more imperative. Captain Creak, in his splendid essay, 

 quotes the observations made by the late Surveyor-General, 

 Mi\ J. T. Thomson, at the Bluff Hill, which indicate that a 

 compass on the north side was deflected more than 9deg to 

 the west, while on the east side of the hill the deflection is 

 46deg. to the east of the average deviation in Poveaux 

 Strait. He adds that if a similar island-like hill happened 

 to occur on the coast, but submerged beneath the sea to a 

 sufficient depth for navigation, serious accidents might take 

 place, and he instances a case near Cossack, on the north 

 coast of Australia, when H.M.S. Medea, sailing on a straight 

 course in eight fathoms of water, experienced a compass 

 deflection of 30deg. for the distance of a mile. A glance at 

 the variation entered on the meridian circuit maps of New 

 Zealand shows that on land we have extraordinary differ- 

 ences between different trig, stations at short distances 

 apart. For instance, in our close vicinity, at Mount Plea- 

 sant, behind Godley Head lighthouse, at the entrance to 

 Lyttelton harbor, the variation is only 9deg. 3min. east, or 

 6deg. less than the normal; while at Eolleston it is 15deg. 

 33min., and at Lake Coleridge 14deg. 2min. In Otago we 

 have still greater differences recorded, for we find on Flag- 

 staff Hill, which is an igneous formation, 14deg. 34min., 



