A transpired, for which I thank you, by which B abided, about which D wrote, ...
1. In the model sentence above, what are the italicised words called? I'm guessing prepositional clause? What are some formal terms describing this question?
2. How can I preserve the structure of this sentence with the relative clauses, but writing which only once? This question 2 is what ought to be expressed by this question's title.
[See para 4 for a real example]: the other was a proposition from Mr George Th. Taylor of Prince George expressive of sentiments similar to those which have been declared by other legislatures of the union on our controversy with France, in the place of which was substituted by a majority of twenty nine a counter proposition termed an amendment which was offered by Colo. Nicholas of Albermarle and which seems calculated to evince to France and to the world, that Virginia is very far from harmonizing with the American government or her sister States.