Personally I think it was rash of Mr. Strickland, in refuting the account which had gained belief of a certain unpleasantness between his father and mother, to state that Charles Strickland in a letter written from Paris had described her as an excellent woman, since Dr. Weitbrecht-Rotholz was able to print the letter in facsimile, and it appears that the passage referred to ran in fact as follows: God damn my wife. She is an excellent woman. I wish she was in hell. It is not thus that the Church in its great days dealt with evidence that was unwelcome.
关于：since Dr. Weitbrecht-Rotholz was able to...中的since，书上翻译成“而，但，可是”， 表转折。
但翻遍词典，却没找到since有这种解释？ 还有，这里的since是连词还是副词呢？
since为连词，引导缘由状语从句。你理解英语句子要依据英语句子语法结构与所表达的逻辑关系，而不是依据某人的汉语翻译。
句子为：I think it is rash of sb to do sth, since..., 我觉得某人做某事太轻率，由于...