The label next to "concierge" reads "descenseur". It's a reference to the French word for a lift, "ascenseur", from "ascension", "to go upwards". A descenseur would then be the exact opposite of a lift - an apparatus to go downwards. :)
The sense of perspective in these is mind-bending. Look at the lady passenger, and imagine her taking a couple of steps 'away' from the viewer, to approach the green walkway.
By then she has to be short enough to fit under the wing, and after walking over the gangway, she has to be small enough to get in the Alice-in-Wonderland door, under the wing with no headroom, into a box so small the coachman-pilot would barely squash into it.
The walkway is on top of a building high enough to have an elevator, but the handrail varies Escher style from shin-height to shoulder-height along it's ~two meter length. (And if it is shin height like the steps side suggests, then it's of no use, and if it's shoulder height like the door side suggests then she would fall between the railings, and the gap to the door is a circus acrobat's leap!).
Then the wings, which are about the height of the pilot, but also about thrice the height of the door - not to mention it's a winged vehicle which hovers.
"In the year 2000" the unshielded outside light bulb would be a health and safety violation, let alone all the other aerial acrobatic bits!
It reminds me a little of ukiyo-e, where even beautiful and finely detailed images would have basic errors of perspective.
(For example, in http://loc.gov/pictures/resource/cph.3g08423/ , the way the boat meets the water is baffling. As far as I can tell, this is an error, not a knowing artistic cheat.)
I assume that the drafting skill of even low-quality drawing went up quickly as photographs became ubiquitous, but I don’t have the art history background to support the notion.
My theory is that this isn't a pun, but rather a term that's no longer in use.
I seem to remember that some early elevator systems had two connected shafts and two cars, instead of one car and a counterweight like modern elevators. In this arrangement, cars go in a loop around a pulley at the top and bottom, always in the same direction. Thus, one shaft is the "up" shaft and one is the "down" shaft.
This image depicts the top floor, so elevators only go down from there. It may have been common practice at the time in France to call the elevator shaft that carries you down to be the descenseur and the one that carries you up to be the ascenseur. Nowadays, ascenseur is used all the time because an elevator car goes both ways.
This is amazing. I didn't know this system at all. a-priori's comment is probably in the right then!
(And "descenseur" seems to be an actual French word according to http://fr.wiktionary.org/wiki/descenseur, so much for showing off and knowing my native tongue.)
Well, this is the pun; although I guess a better description would be "a made-up word with a meaning that might not be instantly clear to non-French speakers" rather than a "pun".
The label next to "concierge" reads "descenseur". It's a reference to the French word for a lift, "ascenseur", from "ascension", "to go upwards". A descenseur would then be the exact opposite of a lift - an apparatus to go downwards. :)