All 3 Uses

speculate
in
The War of the Worlds
(Edited)

He was full of speculation that night about the condition of Mars, and scoffed at the vulgar idea of its having inhabitants who were signalling us.
Chpt 1.1 *

speculation = theories
After working an hour I began to speculate on the distance one had to go before the cloaca was reached, the chances we had of missing it altogether.
Chpt 2.7

speculate = think
But such unproven speculations will scarcely be of interest to the general reader, to whom this story is addressed.
Chpt 2.10

speculations = theories

Definitions:

(1) (speculate as in: don't know, but I'll speculate)
to think about, wonder, guess or theorize with much uncertainty
(2) (speculate as in: speculate in the stock market)
to take a risk for profit--typically a risky investment
(3) (meaning too rare to warrant focus)
Much more rarely, speculation can refer to a gambling card game that was popular in the past.