Is this the rear roll-down window, or the front windshield that's known as V/V? I assume the front is fixed, but how does lowering the rear bring air to the front passengers' feet?

The front windshield is not fixed, it rolls up three inches, therefore, it is called "Vision and Ventilation".

Doggie,
The first 1 1/2 inch that the windshield rolls up directs air toward the dash which has a curved top edge. That directs air past the back side of the dash. Raising the lower edge of the glass above the top of the dash gives direct air flow toward the occupants. The windshield glass is also tilted backwards slightly to reduce reflection and glare. That is the vision part of the V/V.

Chippy Dippy! I know all about that. However, "Proscriptus" was under the impression that the windshield was fixed, so I was just letting him know that the windshield was not fixed and it rolled up three inches. Since you are the TA for 1931 I figured that I would let you give him the skinny on the finer details.

Sorry Dogface,
I originally wrote a reply to you and then decided to change it to add a bit to your post. Forgot to re-address the post to "Proscriptus". Just wondered if he wrote in Latin and translated to Americanese or Amerglish

To add a few words about the design of the 1929 six cylinder engine - engineer Alex Taub drew almost immediate criticism for his 3 main bearing design as well as the "dipper" method of rod bearing lubrication. He replied that this engine is really 2 three cylinder engines, each of which is inherently balanced, thus producing minimal stresses across the center main bearing. The crankshaft is a 3 plane "mirror image" design somewhat like the one first used by Royce as early as 1905. Taub also claimed that in production, there would be fewer problems from metal chips and debris by not drilling the crank for oil passage. And the cast iron pistons were used primarily to reduce to manufacturing cost.