Sorry John, I have to disagree with the big hammer approach on a Gorton.
Been there, done that, bought the bearings.
The B&S taper is self locking and takes a lot of force to pop free. This seems to get worse with the passage of time.
I don't leave collets in my hobby mill because they are a pain to eject after a week or two.
I am guessing this one has been in place a bit longer and the dried oil has turned into Loctite.
Normally, the B&S taper in the Gorton is no big deal, if you have all the parts.
Top end of the spindle should be equipped with left hand threads and a cap that retains the drawbar so you can push or pull with it.
When the spindle is in the machine, you use the break to lock the quill rotation and then turn the drawbar to draw in a collet or eject it.
No hammering.
There have been a few recent posts about Gorton equipment and I have pointed folks to a site with a lot of Gorton literature.
http://gorton-machine.org/forms/form_1320/index.html and
http://gorton-machine.org/forms/form_1410/page08.html have cut-aways showing the basic configuration on a similar mill.
If the cap is missing, make it. Other than the thread, none of the dimensions are super critical, and its big enough you can single point it.
With the spindle out, you have the perfect opportunity to make the missing cap on the lathe because you can check fit the fit of the internal left hand threads without removing the cap from the chuck.
If the drawbar is missing, time to make it as well. It should be a close fit to the ID of the spindle bore. The threads for the B&S collet are called out in the machineries handbook if you don't have a spare collet to measure.
The B&S taper locks in a lot tighter than an R8 and wont just tap free, and the Gorton spindle is not intended to be hammered on.
Ejecting the B&S collet with a mallet like you do an R8 on a Bridgeport is asking to kill your spindle bearings.
Chances are that if the cap is missing, your bearings have seen a lot of hammer loads and are in bad shape.
If the tool has been in place for a long time, plug it, fill the spindle with a thin solvent or penetrating oil and try to jack it out after a few days of soaking.
If that does not work, heat is the next step.
As others have suggested, remove the spindle from quill and bearings and warm it up. As you heat it, push with the draw bar and stuff should pop free.
Your better off pushing hard and using low heat on a tempered part.