RV: Old English

Hi folks! I got this from a reader of 'How to create a language':

>You write (in your excellent site on language construction):
>"A spontaneous sound change transformed the Old English skaedu into shadow,
>as well as every word beginning with sk- into a new one beginning with sh-
>(most modern English words in sk- are Scandinavian borrowings, in case you
>were wondering)."
>
>I believe the word is spelt "scaedu", as K was rarely or never used in Old
>English. Another point (too pedantic to bother incorporating your text) is
>that sc- was already pronounced /S/ by the time most OE texts were written.

The "skaedu" spelling and the whole example was shamelessly
taken from an issue of Model Languages (thanks Jeffrey!).
I have no elements to doubt this guy is right, but I'd like
to know for sure, on both issues (whether 'sc' was used or
not exclusively, or alternatively with 'sk', and when the
change /sk/ > /S/ took place (was it really Old English,
or somewhat earlier?). Any help would be appreciated.


--Pablo Flores
  http://www.geocities.com/pablo-david/index.html
  ... I cannot combine any characters that the divine Library
  has not foreseen, which in some of its secret tongues do not
  bear some terrible meaning. No-one can articulate a syllable
  not filled of caresses and fears; which is not, in some one
  of those languages, the powerful name of a god...
                   Jorge Luis Borges, _The Library of Babel_