If you use emacs on lxplus, the mousewheel isn't enabled. To add this functionality, open your ~/.emacs file and write in the following lines:

(defun up-slightly () (interactive) (scroll-up 5))
(defun down-slightly () (interactive) (scroll-down 5))

(defun up-one () (interactive) (scroll-up 1))
(defun down-one () (interactive) (scroll-down 1))

(defun up-a-lot () (interactive) (scroll-up))
(defun down-a-lot () (interactive) (scroll-down))

(defun scroll-up-half ()
"Scroll up half a page."
(interactive)
(scroll-up (/ (window-height) 2))
)
(defun scroll-down-half ()
"Scroll down half a page."
(interactive)
(scroll-down (/ (window-height) 2))
)

(global-set-key [(mouse-5)] 'up-slightly)
(global-set-key [(mouse-4)] 'down-slightly)
(global-set-key [S-mouse-4] 'down-one)
(global-set-key [S-mouse-5] 'up-one)
(global-set-key [C-mouse-4] 'down-a-lot)
(global-set-key [C-mouse-5] 'up-a-lot)