xxviii 
APPENDIX. 
the quantity of variation is 18 0 , it decreases with great rapidity, and finally 
to nothing, in going eastwards to India, or south-westward to South Ame- 
rica : and that from the same point, it increases, in going NNJV, towards 
Ireland, or to the opposite quarter, towards the coast of Cqffraria. But the 
change is not in any proportion so rapid in the increase, in going north or 
south, as in the decrease, in going east or west. Such are the outlines of 
this system; by which, if a person was to set out from Cape Verd, or Cape 
Blanco, to traverse Africa from WSW to ENE, to Upper or Lower Egypt, 
he would find at setting out, from 15- to i6\ degrees of westerly variation, 
which would increase to 1 8° about the centre of the continent, and after- 
wards decrease to a less quantity than at his setting out. Mr. Park's tra- 
vels being comprized between Cape Verd and the centre of Africa, will 
therefore be in the quarter that has from 16 to 18 degrees; and the part 
more particularly, where, from the want of observations of latitude, we must 
depend on his compass bearings, nearer 18 0 than 17°.* I shall now proceed 
to the detail of Mr. Park's materials. 
Leaving Pisania, Mr. Park proceeded eastward to Medina,t the capital 
place, and at a given time, is of less importance to the present question, than that of 
the bearing of the lines of equal quantities, at any recent period : and this object is, I 
think, tolerably well obtained, by the materials btfore me. Any change that may have 
taken place since 1793, is in favour of a greater quantity of variation, within the limits 
of Mr. Park's travels. 
In the Atlantic, the increase appears to be about a degree in seven years. In the 
Indian ocean, less : and in the Red sea, there seems to have been little alteration be- 
tween 1762, and 1776. 
The lines, as far as they are founded on authority, are continuous ; but broken in the 
parts assumed. 
* It is in proof of the existence of this quantity of variation, that, on closing Mr. 
Park's route at Woolli, there appeared to be only a small deficiency of distance on the 
Map, when 17° variation were allowed. Had the quantity allowed been less, this ought 
not to have happened, as Jarra is placed according to its latitude. 
f Major Houghton's point of outset in 1791 was Medina. His route falls into that of 
Mr. Park at several points, and finally branches off from it about 30 miles short of the 
Faleme river, which the Major crossed at Calcullo, near 20 miles higher up than Naye, 
where Mr. Park crossed it. 
