Final answer:
The underlined portion in the excerpt is an adjectival clause that describes the ditch.
Step-by-step explanation:
The underlined portion in the excerpt from Elie Wiesel's Night is an adjectival clause. An adjectival clause functions as an adjective in a sentence, providing additional information about a noun or a pronoun. In this case, the adjectival clause 'from which an infernal heat is rising' describes the ditch that the speaker is drawing closer to. The adjectival clause modifies the noun 'ditch' and provides more details about it.
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