I begin to think that Sheldon's theory of an early and secret marriage will turn up a trump card; but Heaven only knows how slow or how difficult may be the labour of proving such a marriage.

And then, even if we can find documentary evidence of such an event, we shall have but advanced one step in our obscure path, and should have yet to discover the issue of that union, and to trace the footsteps of Matthew's unknown descendants during the period of a century.
I wonder how Sisyphus felt when the stone kept rolling back upon him.
Did he ever look up to the top of the mountain and calculate the distance he must needs traverse before his task should be done?
The next letter in which I find a passage worth transcribing is of much later date, and abounds in initials.

The postmark is illegible; but I can just make out the letters PO and L, the two first close together, the third after an interval; and there is internal evidence to show that the letter was written from some dull country place.

Might not that place have been Spotswold?
the PO and the L of the postmark would fit very well into the name of that village.

Again I leave this question to the astute Sheldon.