EXHIBIT 5.1

                      [Letterhead of Emerson Electric Co.]

                                February 18, 1999

         Emerson Electric Co.
         8000 West Florissant Avenue
         St. Louis, MO 63136

         Gentlemen:

                  I am  Assistant  General  Counsel and  Assistant  Secretary of
         Emerson  Electric  Co.  (the  "Company"),  and in  such  capacity  I am
         familiar  with the  Registration  Statement  on Form S-8 to which  this
         opinion is filed as an exhibit  (the  "Registration  Statement")  which
         registers  under the Securities Act of 1933, as amended,  71,106 shares
         of  Common  Stock of the  Company  ("Shares")  which  may be  purchased
         pursuant  to the Astec  (BSR) Plc 1991 Senior  Executive  Share  Option
         Scheme and the Astec (BSR) Plc United  States  Senior  Executive  Share
         Option  Scheme  (collectively,  the "Astec  Plans"),  including  71,106
         Preferred Share Purchase Rights.

                  I have  examined  originals or copies,  certified or otherwise
         identified to my satisfaction,  of such documents,  corporate  records,
         certificates  of public  officials  and other  instruments  as I deemed
         necessary for the purposes of the opinion expressed herein.

                  On the basis of the  foregoing,  I am of the opinion  that the
         Shares  (including the Preferred  Share  Purchase  Rights) to which the
         Registration  Statement  relates,  when  sold in  accordance  with  the
         provisions  of the  Plan,  will  be  legally  issued,  fully  paid  and
         non-assessable.

                  I consent to the  filing of this  opinion as an exhibit to the
         Registration  Statement.  I also consent to your filing  copies of this
         opinion  as an  exhibit  to the  Registration  Statement  and with such
         agencies  of  such  states  as you  deem  necessary  in the  course  of
         complying with the laws of such states  regarding the offering and sale
         of the Shares. In giving this consent,  I do not admit that I am in the
         category of persons  whose  consent is required  under Section 7 of the
         Securities  Act or the  rules and  regulations  of the  Securities  and
         Exchange Commission.

                                             Yours truly,

                                             /s/ HARLEY M. SMITH

                                             Harley M. Smith