Final answer:
The gray fiberglass-like material over the top of the 3rd rail is an insulating cover made of frothy gray glass fibers. It is made of a frothy gray glass composed of sub parallel glass fibers with squashed air bubbles, creating a unique texture and appearance.
Step-by-step explanation:
The gray fiberglass-like material over the top of the 3rd rail in the context of your question is likely an insulating cover. This cover is designed to provide protection and prevent accidental contact with the electrified rail. It is made of a frothy gray glass composed of sub parallel glass fibers with squashed air bubbles, creating a unique texture and appearance.
gray fiberglass-like material over the top of the 3rd rail in the context of your question is likely an insulating cover. This cover is designed to provide protection and prevent accidental contact with the electrified rail. It is made of a frothy gray glass composed of sub parallel glass fibers with squashed air bubbles, creating a unique texture and appearance.