According to John Welch, even though we find the account of the brother of Jared in chapter 3 of the book of Ether, it is unclear whether Ether ever read the account of the brother of Jared. First of all, the brother of Jared was commanded by the Lord to "show it to no man" (Ether 3:21). Second, the language the brother of Jared wrote it in was "confounded" (Ether 3:24). And third, the Lord provided "these (two) stones" as the only apparent means by which men would see the things which the brother of Jared wrote (Ether 3:23-24).
Since the Lord had forbidden the brother of Jared to allow his words to go forth unto the world until after He had come in the flesh (Ether 3:21, 4:1), there is reason why Ether may not have been privy to their content in detail.
Moroni, however, appears to have known from firsthand experience the impact these words had upon a reader because he said "thou hast not made us mighty in writing like unto the brother of Jared, for thou madest him that the things which he wrote were mighty even as thou art, unto the overpowering of man to read them." (Ether 12:24) [John W. Welch, "Preliminary Comments on the Sources behind the Book of Ether," F.A.R.M.S., 1986, p. 5]