GR translation: bone-deep laborings up impossible grades

[Mike Jing]

P260.25-40   A week later he’s in Zürich, after a long passage by train.
While the metal creatures in their solitude, days of snug and stable fog,
pass the hours at mime, at playing molecules, imitating industrial
synthesis as they are broken up, put together, coupled and recoupled, he
dozes in and out of a hallucination of Alps, fogs, abysses, tunnels,
bone-deep la-borings up impossible grades, cowbells in the darkness, in the
morning green banks, smells of wet pasture, always out the windows an
unshaven work crew on the way to repair some stretch of track, long waits
in marshaling-yards whose rails run like layers of an onion cut end to end,
gray and desolate places, nights of whistles, coupling, crashes, sidings,
staring cows on the evening hillsides, army convoys waiting at the
crossings as the train puffs by, never a clear sense of nationality
anywhere, nor even of belligerent sides, only the War, a single damaged
landscape, in which “neutral Switzerland” is a rather stuffy convention,
observed but with as much sarcasm as “liberated France” or “totalitarian
Germany,” “Fascist Spain,” and others. . . .

What is "bone-deep" trying to invoke here?
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://waste.org/pipermail/pynchon-l/attachments/20130307/614372ce/attachment.html>