Rise Of The Machines

Similar to the concept of the "house divided," Lincoln uses the term "machinery" a few times to illustrate the forces at work beyond the control of him and his audience. We're not sure what it was about Abe's motif-crafting mind—maybe the fact that he was such a kick-butt handyman that he built two boats?—but he definitely had construction on the mind when he wrote this speech.

Let anyone who doubts carefully contemplate that now almost complete legal combination—piece of machinery, so to speak—compounded of the Nebraska doctrine and the Dred Scott decision. Let him consider, not only what work the machinery is adapted to do, and how well adapted, but also let him study the history of its construction and trace, if he can, or rather fail, if he can, to trace the evidences of design and concert of action among its chief architects, from the beginning. (12-13)

As we learned (and also sometimes questioned) in the Terminator series, machines aren't human. They'll also keep going no matter what, unless someone stops them.

He uses the image later as well:

The several points of the Dred Scott decision, in connection with Senator Douglas' "care not" policy, constitute the piece of machinery in its present state of advancement. This was the third point gained. The working points of that machinery are… (46-48)

The notion of an impersonal robot being constructed to enact the recent policies on slavery is kind of scary. Who's driving that thing? Does our side have any control over what it does?

It doesn't sound like it.