[ 161 ] 
III. Account of Magnetic Observations made in the years 1858-61 inclusive , in British 
Columbia , Washington Territory , and Vancouver Island. By Captain R. W. Haig, 
JR.A. Communicated by General Sabine, P.B.S. 
Received November 4, — Read November 26 , 1863. 
In 1858 a Commission was appointed for the purpose of determining and marking the 
forty-ninth parallel of north latitude from the Pacific to the Rocky Mountains. At the 
suggestion of General Sabine, this Commission was provided with a set of portable 
magnetic instruments adapted for the determination of the three magnetic elements, 
Dip, Declination, and Total Force. These instruments were similar in kind to those 
which had been used on the Magnetic Survey of the United Kingdom. Before delivery 
to the Boundary Commission they were examined at the Kew Observatory, and several 
constants and tables for facilitating the computations were determined and prepared 
there. 
The method of transporting the instruments from place to place, and indeed every- 
thing appertaining to the Boundary Commission, was by means of packet mules. Two 
boxes (a very light load for one mule) contained all the magnetic instruments, which 
throughout four years of such rough usage retained their original efficiency. Some of 
the needles became somewhat rusted ; but I can suggest no alteration in the construction 
of such instruments, such as would increase their portability. The declinometer was, I 
think, unsatisfactory as regarded its capability of determining azimuths of the sun : 
when at an astronomical station, I necessarily had a meridian mark for the transit 
instrument, and I referred the direction of the magnet to such meridian . 
In assembling the results and deducing from them the directions and positions of the 
lines of equal dip, force, and declination, no notice has been taken of secular change. 
The only station at which we have data for judging of the extent of secular change is 
Fort Vancouver on the Columbia River. As regards dip, we find there 
1830. Dip 69 39-7 Douglas. 
1839. Dip 69 22-2 Sir E. Belcher. 
1860. Dip 69 17*4 Present observations. 
These figures show an annual diminution of dip of less than 1' per annum. The mean 
results of the present observations may he assumed to belong to the year 1860. The 
method of assembling the results and determining from them the position and direction 
of the lines of equal dip, force, and declination, is the same as that adopted in the 
Survey of the United Kingdom. 
