Qualities of Expression: Ease using "and which"

"And which" used as conjunction + interrogative pronoun rather than conjunction + beginning of relative clause.
        (Source:  Michael Maslin, New Yorker Magazine)

From Beginnings of Rhetoric and Composition, by Adams Hill:

EASE AS AFFECTED BY WORD CHOICE

"And which"

Among the constructions that jar on a reader's sense of harmony is the use of "and" before a relative clause which it does not connect with another relative clause. 

In some cases, as has already been noted, this construction is objectionable from a grammatical point of view; but in one form or another it occurs so often, even in the works of good authors, that it cannot be absolutely condemned. It should, however, be avoided by a writer who studies the comfort of his readers.

A: The principal excellence of Virgil—one which, in my opinion, he possesses beyond all other poets—is tenderness.
B: The principal excellence of Virgil and which in my opinion he possesses beyond all poets is tenderness.
A: The order signed by Mr. Frick, to the effect that men who returned to work would be insured against removal,—an order which was given in the dispatches of last night,—is the final peace offering of the firm to the strikers.
B: The order signed by Mr. Frick to the effect that men returning to work would be insured against removal, and which was given in the dispatches of last night, is the final peace-offering of the firm to the strikers.

In each of the B sentences, "and" tries to connect "which" with its antecedent; but it really separates the two. In the last two examples, clearness is promoted by the repetition of the antecedents in a condensed form.

A:
(a) The Cotes family is an old and good one, which has long been established in Shropshire, and which has for years been returned to Parliament in the person of one of its members.
(b) The Cotes family is an old and good one, long established in Shropshire, and has for years been returned to Parliament in the person of one of its members.
(c) The Cotes family is an old and good one, long established in Shropshire, — a family which has for years been returned to Parliament in the person of one of its members.
(d) The Cotes family, long established in Shropshire, is an old and good one, which has for years been returned to Parliament in the person of one of its members.

B: The Cotes family is an old and good one, long established in Shropshire, and which has for years been returned to Parliament in the person of one of its members.

In Sentence B, "and" tries to connect a relative clause with a participial phrase. We may remove the difficulty in one of four ways: we may (a) turn the participial phrase into a relative clause, — a change that makes the sentence long and heavy, — or (b) omit "which" and thus enable "and" to connect "is an old and good one" with "has for years been returned," or (c) substitute "a family" for "and," or (d) by changing the order and omitting "and," make "one" the direct antecedent of "which," as in (a). These changes do not affect the meaning of the sentence as a whole; but they do affect the relative importance of the several facts mentioned.