Dear Lee, unfortunately, I have not the full text of this letter, only
a part in the Russian-language monograph by V.P. Kartzev on the
history of development of electromagnetic ideas "Adventures of great
equations" [Znanie, Moscow, 1970, p. 178-179]. Above the cited before,
this book contains Faraday's final words explaining the aim of this
letter. Here I am citing them in reverse translation:

<< Faraday wrote that he had a wish "to secure this discovery for
myself by a definite date and thus to have a right, in case of
experimental corroboration, to claim this date as the date of my
discovery. At present, as far as I can know, no one of scientists
except me has such insight" >>

I can only add, this is a trustworthy author, you can refer to him. I
am pleased if it can be of help. If someone can prompt, where can we
get a full text, I would be grateful. Still I have what I have. ;-)

Sergey