Semicolon followed by an em-dash

Solution 1:

Good catch - it shows careful reading. But consider that the story was published in 1846 (and probably written the year before). Today we might use either the semicolon or the em-dash (but not both). Typically, the part after a semicolon is a complete sentence - one that is closely related to the first part (also usually a complete sentence).

(I'm glad to hear you read it for pleasure - rather than as punishment.)

Solution 2:

I'd say that there are differences in length-of-pause indication signalled by different choices of punctuation. From quick run-on to full pause for thought, I'd suggest:

In this respect I did not differ from him materially, as I was skilful in the Italian vintages myself, and bought largely whenever I could.

In this respect I did not differ from him materially: I was skilful in the Italian vintages myself, and bought largely whenever I could.

In this respect I did not differ from him materially; I was skilful in the Italian vintages myself, and bought largely whenever I could.

In this respect I did not differ from him materially - I was skilful in the Italian vintages myself, and bought largely whenever I could.

In this respect I did not differ from him materially. I was skilful in the Italian vintages myself, and bought largely whenever I could.