100 



SIXTH REPORT — 1836. 



tiire; and at which consequently the dip, observed with sufl&cient 

 care and repetition, might be presumed to be due solely to the 

 geographical position of the station. With this view, I have 

 deemed it preferable to take an arbitrary geographical position, 

 nearly central in regard to Scotland and to the body of the ob- 

 servations, and to compute the most probable dip for that po- 

 sition by a combination of the results at all the stations of obser- 

 vation. The central position adopted is lat. 56° 27', long. 4° 25' 

 W. of Greenwich. The coordinates of distance in latitude and 

 longitude of the several stations from the central position, ex- 

 pressed in geographical miles, are inserted in the subjoined 

 table, together with the observed dips at each station, in degrees 

 and decimals of a degree. 



Table 11. 



We have then three unknown quantities to seek; viz. S = the 

 dip at the central position ; n = the angle which the isoclinal 

 line passing through the central position makes with the me- 

 ridian ; and r = the coefficient determining the rate of increase 

 of the dip in the normal direction. 



Putting r cos m = x, and ?• sin it = y, the equations of con- 

 dition to be combined by the method of least squares are of the 

 following form : 



Loch Scavig 

 Loch Slapin 

 Golspie . . . 



73-047 = 8 + 55.07 -47.y, 

 72-995 = 8 + 52.0,- - 47.^, 

 72-885 = 8 - 15..r — 91. y. 



