bini, two at a time, and oculi, eyes) was originally an adjective used to describe things adapted for the simultaneous use of both eyes, as in "binocular vision," "a binocular telescope or microscope"; now "a binocular" is used as a noun, meaning a binocular microscope, a field-glass, &c.
Meanwhile the staff officer standing in front pointed out something to the general, who looked through his field glass.
"Yes, so it is, so it is," said the general angrily, lowering the field glass and shrugging his shoulders, "so it is!
Prince Andrew, who was a little behind looking at them, turned to an adjutant to ask him for a field glass.
He was looking through a field glass down the highroad before him.