Unloading cement in the 1940's?

[Chris333]

I have my eye on scratch building this nice little bulk cement silo:
https://www.flickr.com/photos/kossconstruction/6277840878/
https://www.flickr.com/photos/kossconstruction/6277191274/
2 others for reference
https://www.flickr.com/photos/kossconstruction/6277191706/
https://www.flickr.com/photos/kossconstruction/6277317021/

Question is how was the cement removed from the hoppers? Was is dropped out of the bottom into a pit or sucked out of the top? As you see some of the top hatches are open in the photos. I know in modern times it was dropped with a "car shaker" attached to the hopper bays, but i'm looking to find exactly what is going on in the photos.

And as extra credit.  Does anyone have a link to a similar 1940's era storage silo?

[C855B]

Pit. That tall, square protrusion on the track side of the silo covers a bucket conveyor lift. Hatches are open to break any vacuum and/or facilitate jumping up there with a rod to break-up clumps.