Not P but Moby-Dick (52)

[Mike Jing]

>From Chapter 68:

True, from the unmarred dead body of the whale, you may scrape off with
your hand an infinitely thin, transparent substance, somewhat resembling
the thinnest shreds of isinglass, only it is almost as flexible and soft as
satin; that is, previous to being dried, when it not only contracts and
thickens, but becomes rather hard and brittle.

What does "isinglass" refer to here?

1. A firm whitish semitransparent substance (being a comparatively pure
form of gelatin) obtained from the sounds or air-bladders of some
freshwater fishes, esp. the sturgeon; used in cookery for making jellies,
etc., also for clarifying liquors, in the manufacture of glue, and for
other purposes. Also extended to similar substances made from hides, hoofs,
etc.

2. A name given to mica, from its resembling in appearance some kinds of
isinglass.