By keeping the slide permanently depressed, it is possible to play third position in the key of E b minor in a similar manner to the keys of A minor or D minor. You can test this by pressing in the slide and playing any melody you already know in D minor (e.g., St James Infirmary or Minor Swing). To play the E Blues scale, you only need to release the slide for one note (A natural - the flattened fifth degree). The following example demonstrates two octaves of the Eb Blues scale.
Here is a Blues solo derived from the E b Blues scale. Notice the use of octaves here.