If we take an of an order of magnitude which we should expect in the case of extreme mass phenomena, then, in the neighbourhood of its characteristic value, ∆p is so highly insensitive to changes of that ∆p hardly changes at all even if the order of The remarks that follow in this paragraph (and some of the discussions later in this section) are, I now believe, clarified and superseded by the considerations in appendix ix; see especially points ff of my Third Note.