modal + perfect tense

“To speak truth, sir, I don’t understand you at all; I cannot keep up the conversation, because it has got out of my depth. Only one thing, I know: you said you were not as good as you should like to be, and that you regretted your own imperfection; one thing I can comprehend: you intimated that to have a sullied memory was a perpetual bane. It seems to me, that if you tried hard, you would in time find it possible to become what you yourself would approve; and that if from this day you began with resolution to correct your thoughts and actions, you would in a few years have laid up a new and stainless store of recollections, to which you might revert with pleasure.” (Jane Eyre)

Does the modal+perfect tense mean the future perfect, or the previous past of ‘to which you might revert with pleasure’, or both?

Answer

if you tried ... you would ... find ...

if ... you began ... you would ... have laid up ...

Both of these woulds represent future constructions cast into past form to agree with the 'hypothetical' past form in their respective if clauses. They might with perfect propriety be expressed using present forms:

if you try ... you will ... find ...
if ... you begin ... you will ... have laid up ...

To which you might revert is a present form with future reference, again cast into the past form to express hypotheticality. Its Event time is its main clause’s Reference time, in a few years. Once more, all of these could be expressed with present forms:

if from [NOW] you begin ... to correct your thoughts and actions, you will in a few years have laid up a new and stainless store of recollections, to which you may [AT THAT FUTURE TIME] revert with pleasure.

Jane, however, is careful to keep her moralising in the hypothetical mode, whether because she is reluctant to instruct too directly an older and far more sophisticated man, who is moreover her employer and social superior, or because she is “sensible that the character of my interlocutor was beyond my penetration; at least, beyond its present reach; and feeling the uncertainty, the vague sense of insecurity, which accompanies a conviction of ignorance.”