174 



Having formed equations exactly as in the process already 

 explained for the dip, the sums of the several columns are 

 found to be : — 



whence. 



The Isodynamic lines, which result from this computation, 

 are drawn on the Map. 



In Table B', the mean values of x and y are employed for 

 calculating the Intensity at each of the 35 Stations; the third 

 column shews the differences between calculation and observa- 

 tion. 



Table B'. 



PLACE OF OBSERVATION. 



Newcastle 



Carlisle 



Penrith 



Croft 



Lazenby 



Whitby 



N. Allerton 



Osmotherley 



Hambleton 



Scarborough 



Thirsk 



Helmsley 



Craike 



Malton 



York 



Flamborough 



