I've rethought this one. I think he's trying to use
Although...yet as a correlative subordinator (ie one with two parts) which is possible, though fairly rare:
Although this was the first time, yet we may flatter ourselves...etc
That works. The real problem, then, is the confusion caused by piling up all those subordinate clauses and prepositional phrases, which make the sentence so difficult to follow. but I take back what I said - he did say what he intended to. It's just that by the time you get to the main clause you've lost track of the sentence structure because of it's complexity. Were he one of my students I'd make him rewrite the whole thing
