creating my own library

[eluser]Clooner[/eluser]
What are you trying to accomplish here? Is the mongo_db already loaded using the autoload functionality? Loading a library works different than a class try it like so

Code:

$this->load->library('mongo_db', 'mongolib')

this will make the library availabre under $CI->mongolib

Then you would be able to make it available under $this->mongo as such

Code:

$this->mongo =& $CI->mongolib

Please see the userguide about this topic
http://ellislab.com/codeigniter/user-gui...aries.html