Symbol's value as variable is void: Info-directory-list

M-x eshell

--------------------------------------------------------------------------
Welcome to the Emacs shell

$ cd ~
~ $ wget http://www.rubyist.net/~rubikitch/archive/emacs-elisp-info-ja.tgz
~ $ tar xzvf emacs-elisp-info-ja.tgz
--------------------------------------------------------------------------

C-x C-f /usr/share/info/dir

--------------------------------------------------------------------------
 *** /usr/share/info/dir.orig    date.old
 --- /usr/share/info/dir    date.new
 ***************
 *** 213,215 ****
 --- 213,219 ----
 
   GNU Emacs Lisp
   * SKK: (skk).           Simple Kana to Kanji conversion program.
 +
 + * Elisp-ja: (elisp-ja).    Emacs Lisp Reference Manual(Japanease)
 + * Emacs-ja: (emacs-ja).    The extensible self-documenting text editor(Japanease)
 +
--------------------------------------------------------------------------

C-x C-f ~/.emacs.d/init.el

(add-to-list 'Info-directory-list "~/info")

としたら

--------------------------------------------------------------------------
Warning (initialization): An error occurred while loading `/home/user/.emacs.d/init.el':

Symbol's value as variable is void: Info-directory-list
--------------------------------------------------------------------------

といわれ

(require 'info)
(add-to-list 'Info-directory-list "~/info")

としたら、

---------------------------------------------------
Info-insert-dir: Can't find the Info directory node
---------------------------------------------------

といわれる。以下にしたら正常に動作したけど、よくわからない。

;; ------------------------------------------------------------------------
;; @ 日本語 info をいれる
(require 'info)
(add-to-list 'Info-additional-directory-list "/usr/share/info")
(add-to-list 'Info-directory-list "~/info")