Alexander Henderson, father of William, sheriff substitute of Caithness

Interested in the family of John Henderson author of "Caithness Family History", his father was William in Scotscalder.
In the "Old Latheron" section of Graven Images, there is a reference, (#167) to a "stone placed here by William Henderson, sheriff substitute of
Caithness, in memory of his father Alexander Henderson, tacksman of Dalacher, died July 15th 1801 age 72".
From the "Biographical Sketch" of the book, I have noticed that John's father and uncles, are not listed in any parish record baptisms in the
range of the ages and dates given, to an Alexander. Curiously the family of John "McEan" Henderson and Janet Sinclair in Brims have close
matches, except their William is 6 years too early.
If the inscription is correct, the place name "Dalacher" could be Dalnacher, which I understand is in the immediate Tacher area.

Any thoughts would be appreciated,
Tom.