352 Mr. Robertson’s Observations on the Permanency 
needle from the true meridian, without knowing the quantity 
thereof. 
From this period down to the year 1700, when Dr. Halley 
published his “ Theory of the Variation of the Compass,” no 
observations, ascertaining the quantity of variation, in the 
West Indies, were, I believe, published. He was the first 
that made any in South America, and these were chiefly ap- 
plicable to the coast of Brasil. With his theory was published 
“ A new and correct Chart of the whole Worid, shewing the 
“ Variations of the Compass, &c. as they were found in 1700, 
“ by Direction of Capt. Edm. Halley.” By this chart the 
variation, at Jamaica, appears to have been the same as it is 
at present. His theory could have been known but to few ; 
nor do any observations, in the West Indies, appear to have 
been made for many years after its publication. Indeed I 
know of none till very lately, and these only in a few charts. 
But, however extensive its publicity might have been, it could 
have had no influence in directing the surveys, in Jamaica, 
that preceded it by 30 or 40 years. 
The ascertaining of the true meridian, and, consequently, 
of the magnetical variation from it, requires more scientifical, 
as well as practical, knowledge, than is often to be met wish 
even at this time ; but, 130 or 140 years back, it was entirely 
confined to a very few individuals. The magneticrl needle 
was then the only guide and rule to go by, both at sea and 
at land, and, generally, without any reference being had to 
the true meridian. 
Had the first surveyors ascertamed the quantity of varia- 
tion, and allowed for it, in delineating their diagrams that 
were annexed to the earliest patents in Jamaica, they would 
