A more consistent form has been given to the error by Grainge, who in
1862 published a memoir of the Life of Sir William Slingsby, Discoverer
of the first Spaw at Harrogate. Grainge, like Hargrove, had only access
to Short's summary, but he sees the difficulty to which I have alluded,
for he writes[14]:--

"From the uncertain expression of the Dr. 'about 50 years ago' the
date of this discovery is generally fixed in the year 1576, though
it is probably twenty years or more too early, as at that time
Slingsby would only be fourteen years of age: and could not have
travelled much in Germany or elsewhere: while the expression 'in
his younger days' would infer that the discovery was not made until
he had attained middle age at least."

Grainge accordingly dates Captain (or Sir) William Slingsby's discovery
to 1596 or later, the origin of the expression "near the close of the
16th Century" of the recognised history.

In the first place Dr. Short is inaccurate in that Deane states it was
discovered "55" years ago, and not "50." In the second place, the only
authority whom Grainge could rely upon was Deane, either directly or
indirectly, and Deane could not have made the discoverer to be a boy of
nine years of age (not fourteen) for he must have known Sir William
Slingsby, a contemporary. Finally, Grainge only consulted the summary of
"Spadacrene Anglica" and not the actual work, and it is to be noted that
Deane in Chapter 6 says the first discoverer "so far forth as I can
learn." These words are not in the summary, but they show that Deane had
given care to his work, and if Sir William Slingsby had been the
discoverer, Deane could have obtained his information at first hand, and
would have given Sir William Slingsby as his authority.