Burthen

Nor less, I trust, To them I may have owed another gift, Of aspect more sublime; that blessed mood, In which the burthen of the mystery, In which the heavy and the weary weight Of all this unintelligible world, Is lightened:

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It was with a daughter of Mr Shepherd, who had returned, after an unprosperous marriage, to her father's house, with the additional burthen of two children.

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In some cases the conquering state contented itself with imposing a tribute on the vanquished: who, being, in consideration of that burthen, freed from the expense and trouble of their own military and naval protection, might enjoy under it a considerable share of economical prosperity, […]

Source: wiktionary

Bidding them grope their way out and bestir, […] though the worst Burthen of heat was theirs and the dry thirst

Source: wiktionary