All 3 Uses

tranquil
in
The Mill on the Floss
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On this sin, that a man inordinately loveth himself, almost all dependeth, whatsoever is thoroughly to be overcome; which evil being once overcome and subdued, there will presently ensue great peace and tranquillity....It is but little thou sufferest in comparison of them that have suffered so much, were so strongly tempted, so grievously afflicted, so many ways tried and exercised.†
Chpt 4.3 *

tranquillity = peace and quiet; or calmness

unconventional spelling: This is a British spelling. Americans use tranquility.
Not when that girl is as tranquil-hearted as Lucy, thoroughly possessed with a belief that she knows the state of her companions' affections, and not prone to the feelings which shake such a belief in the absence of positive evidence against it.†
Chpt 6.6
Her tranquil, tender affection for Philip, with its root deep down in her childhood, and its memories of long quiet talk confirming by distinct successive impressions the first instinctive bias,—the fact that in him the appeal was more strongly to her pity and womanly devotedness than to her vanity or other egoistic excitability of her nature,—seemed now to make a sort of sacred place, a sanctuary where she could find refuge from an alluring influence which the best part of herself must resist; which must bring horrible tumult within, wretchedness without.†
Chpt 6.7

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