Alexander McFarlane (or MacFarlane or MacFarlan) was the youngest son of John McFarlane of Arrochar. His eldest brother, Walter, was a well-known antiquary and traveller, and his brother William was a physician in Edinburgh. Alexander himself matriculated at Glasgow University in 1725 and graduated with his master's degree in 1728. By late 1735 he was in Kingston, Jamaica, having been appointed the island's first Post Master General. (Some sources state that Edward Dismore, appointed in 1754, was the first Postmaster General). McFarlane was apparently a prosperous merchant and owned over 5000 acres of land. He was also an 'assistant judge' and a member of the Assembly. When he died in 1755 his will divided his considerable property among his relatives in Scotland, including his mother, and his brothers, Walter and William.
His house on the Parade in Kingston, which after his death became part of the city's gaol, illustrated a different aspect of his life. He had a reputation as a fine mathematician and had installed an 'observatory' there, mostly on the specially constructed flat roof which is clearly apparent in the picture of the house. The considerable collection of instruments making up the observatory had been purchased from another Scot, born in Jamaica, Colin Campbell, eldest son of John Campbell who was a survivor of the ill-fated Scottish settlement in Darien, and later a merchant in Black River. Campbell had brought the astronomical equipment to Jamaica when he returned home in 1731 from his studies at Glasgow University. In 1743 the younger Campbell decided to leave Jamaica and sold his 'observatory' to McFarlane.
McFarlane did not produce any outstanding astronomical observations. Those he recorded were observations of a lunar eclipse on November 2, and a transit of Mercury November 5, 1743; observations of a comet in January and February 1744; the longitude of Kingston which he computed in 1743 was used as the basis for the trials of John Harrison's chronometer in 1761-2. In 1747 McFarlane was elected a Fellow of the Royal Society, proposed by fellow Scot James Short, a renowned maker of reflecting telescopes. Since McFarlane never travelled back to the United Kingdom he was never actually admitted as a Fellow.
McFarlane's calculations on the longitude of Kingston: