"slippery slope"

[Geoffrey Nunberg]

For an article, I'm trying to track the origin of the phrase
"slippery slope" in its figurative sense -- what the OED defines as
"a course leading to disaster or destruction." The OED itself gives
1951 for the first occurrence, but that's easy to antedate. The
earliest cite for a figurative use that I've located, via HTI, is
from The Princeton Review, 1880, in a discussion of a noted
theologian:

For a while he held as a positive tenet that religious
truth could not rest on scientific proof, inasmuch as the latter
requires probable evidence alone, while religion demands
intuitive certainty. For a while he arrested his sliding steps
on the slippery slope down which they were gliding, by finding
in faith a positive insight, or a special religious faculty...

I found a somewhat less laboriously metaphorical use, via JSTOR, in
an article in the American Political Science Review, Nov. 1909,
quoting another publication from the same year:

A writer in the Quarterly Review is not exaggerating the importance
of this legislation in viewing it as "the first step down that
slippery slope at the bottom of which lies a parliamentary government
in India."

I'd be grateful if anyone could point me to earlier examples of this
use of the expression.

Geoff Nunberg