Transcription:

'Sir, As I cannot swear who it was set fire to your property perhaps I am wrong in pointing your attention to any person in particular but as I have strong reasons for suspecting a party (and having received favours at your hands and those of your family) I will if you wish it give the name (through the medium of the person who delivers you this) of the one I believe to be the offender; but it must be under the promise that my name shall never appear a yes, or no, will be understood. I am Sir respectfully yours'.