What is the meaning of following sentence?
Is "if they could" a conditional ?
It was about this time that Professor William Crookes conducted his inquiries into the medium's powers, and issued that whole-hearted report which is dealt with later when Crookes's early connexion with Spiritualism comes to be discussed. These careful observations show that the rappings constituted only a small part of Kate Fox's psychic powers, and that if they could be adequately explained by normal means they would still leave us amid mysteries. Thus Crookes recounts how, when the only people present besides himself and Miss Fox were his wife and a lady relative "I was holding the medium's two hands in one of mine, while her feet were resting on my feet. Paper was on the table before us, and my disengaged hand was holding a pencil.