§55 
of the Variation of the Compass at 'Jamaica. 
When Sir Henry Moore, (who was considered a great 
surveyor,) was governor of Jamaica, about the year 1760, 
maps of that island were constructed, under his immediate 
direction, by Mr. Craskell, the island engineer, and Mr. 
Simpson, both eminent surveyors. But, in these maps, the 
magnetical meridian only is represented. Neither the mag-* 
netical variation nor the true meridian is mentioned: the 
island's place on the globe, as to latitude and longitude, 
is not given. In short, the true meridian has never been 
noticed, nor the quantity of variation ascertained, nor the 
variation even mentioned, nor the latitude and longitude, ob« 
served by any surveyor or engineer in Jamaica, but myself. 
Although the discovery of the variation's not varying, in 
Jamaica, is established on the clearest evidence without the 
aid of other data, yet it is highly gratifying to find Dr. Hal- 
ley, as it were, confirming it to the minutest accuracy, as will 
appear from the recital of the following observations of Mr. 
Long, in his History of Jamaica. 
“ The variations of the magnetical needle were observed 
“ by Dr. Halley to be very small, near the equator. I have 
“ seen no account of them for this island, that can be relied 
“ upon ; but, if observations should be faithfully made here, 
4 ‘ they would probably confirm his opinion. According to 
“ Mountain's chart, constructed in the year 1700, from Dr. 
“ Halley's tables, the variation at Port Royal then was about 
“ degrees east. But, as in most parts of the world it is 
“ found to be continually either increasing or decreasing, so 
“ we may reasonably conclude, that it may have altered in 
“ both respects very much during this long interval that has 
“ passed since the constructing of the chart." 
