Ross. — On the Declination of the Magnetic Needle. 7 



of 1857, to the Commissionei's of tlie Waste Land Board, by Mr. J. T. ThomsoB, 

 Chief Surveyor of Otago, and is as follows : — " In a district like this, situated 

 on one of the great volcanic zones, where terrestrial galvanic currents may be 

 supposed to prevail, it will be correctly surmised that the surface sometimes 

 indicates forcibly the presence of magnetic disturbance. This disturbance was 

 more or less sensibly indicated in our observations, but the most remarkable is 

 on the Bluff Peninsula, as will be seen by the following : — 



" On the summit of Bluff - - variation 6° 54' E. 



" Thirty feet north of the same - „ 9° 36' W. 



" Thirty feet west of the same - „ 5° 04' E. 



" Thirty feet east of the same * „ 46° 44' E." 



To this report is appended the following note : — " The bearing of the Siagnet 

 is affected in all parts of the Province where hard compact traps crop out. 

 These are found principally on the higher parts of ridges and mountains." 



Proceeding northward, we find at Kuriwao Hill the declination to be 

 13° 53' 27" E. ; at Toetoes, 14^ 19' 32"; and at Chimney Hill, 14° 56' 50". 

 From this to Port Chalmers no remarkable variation in declination has been 

 recorded. I may observe, however, that at all stations on land near the sea- 

 board the declination is less than it is shown to be at sea on the Admii-alty 

 charts, the mean difference, after the declination has been corrected for 

 difference of dates of observations, amounting to nearly 2 degrees. At Port 

 Chalmers the declination observed by Mr. Kettle, in 1846, was 16° 10' E. ; 

 by Captain Stokes, in 1850, 15° 40' E. ; in 1864, by Mr. McKerrow, it was 

 15° 40' 08" E., so that in the four years, 1846 to 1850, a decrease of 30' is 

 shown ; while in the fourteen years, 1850 to 1864, no change whatever has 

 been observed, the results given by Mr. McKerrow being virtually the same 

 as those given by Captain Stokes. 



North of Port Chalmers the disturbing force at many of the stations is 

 very considerable. In the immediate vicinity of the port at Mihiwaka the 

 declination is shown to be 19° 20' 48" E.; at Flagstaff it is 14° 14' E. ; in 

 Nenthorn District, at Mount Stoker, it is 35° 21' 44" E. In recording this 

 observation in his field book, Mr. McKerrow made the following entry ; — 

 " Hard bluestone boulders on Mount Stoker." At Highlay Hill the decli- 

 nation is 2° 24' 32" E. ; in Hawksbury District, at Mount Watkins, it is 

 3° W. ; and at Taieri Peak, a few miles to the north, it is 104° 47' E. In 

 Moeraki District, at Trig. Station O, it is 26° 10' E. ; and at Trig. Station P 

 it is only 50' E, In Kauroo District, at Mount Difficulty, the declination is 

 1° 02' W. ; at Trig. Station L, 13° 30' E. ; at Trig. S, 22° E. ; at Black Cap, 

 8° 54' W. These four stations are included within a radius of about two and 

 a-quarter miles ; and, lastly, the declination at Kauroo Hill, about five miles 

 N.E. of Black Cap, is 41° 03' 35" E. 



