What is the difference between a newline and a semi-colon?

[Bruce Korb]

    $ . xx ; cat xx ; proj ; pwd ; pwd -P
    alias proj="cd ~/'google drive'/web"
    bash: proj: command not found
    /home/sciadmin/tmp
    /home/sciadmin/tmp
    $ . xx
    $ cat xx ; proj ; pwd ; pwd -P
    alias proj="cd ~/'google drive'/web"
    /home/sciadmin/google drive/web
    /home/sciadmin/foo bar/web

Clearly, there is a behavioral difference.  Is this a bug or feature?

    $ echo $BASH_VERSION ; cat /etc/redhat-release
    4.1.2(1)-release
    CentOS release 6.5 (Final)