324 
Mr . Christie’s theory of the 
likewise, if the sides of the plate were reversed, that is the 
marked face placed east instead of west, the corresponding 
deviations should be all westerly ; and on examining the 
observations which I made with the marked face so placed, 
the compass being in the same horizontal plane as the centre 
of the plate, and opposite to the line of junction of the copper 
and bismuth, I find them to have been ; with the needle to the 
north of the centre of the plate, 8° W., when it was 1*3 inch 
to the east of it, and 5 0 45' W., when 1-3 inch to the west ; 
also 12 0 W., when it was 1-3 inch to the east, and i4°45' W., 
when i*3 inch to the west, and on the south side of the 
centre. The other observations agreed with those in the 
preceding table. 
In the observations which I made with the plane of the 
plate horizontal, and which in every other respect were 
similar to the preceding, the marked face, or that which in the 
other observations had been towards the west or the north, 
was upwards. The compass was placed north, south, east, 
and west of the centre of the plate, and, as before, its centre 
i*3 inch from the surface, and vertically above and below the 
outer edge of the copper ring. It was likewise placed in 
corresponding positions vertically over the line of junction of 
the copper and bismuth ; but the corresponding observations 
could not be made below the plate, as the extremity of the 
needle was in general hid by it. The plate was, as before, 
turned in its own plane, and the deviations of the needle 
noted when the place of heat had different positions with 
respect to the compass. The observations are contained in 
the following table, where the angular distance of the place 
of heat is measured from the needle in the direction of the 
sun’s daily motion round the whole circle. 
