Anxious, however, about his own safety, he was endeavouring to make his way out of the hummock, when he caught sight, in the distance, of several figures moving among the trees, which, though indistinctly seen, he was convinced were those of Indians. (In the Wilds of Florida by W.H.G. Kingston）
動画の後半部分でリスニング用音声が流れます。
英文を前から読んでいくために、語句のかたまりを作ります。こんな具合に課題文をスラッシュ（斜め線）で区切ります（スラッシュリーディング）。語句のかたまりを意識すると、リスニングで英語の意味をつかむのが楽になります。
Anxious, however, about his own safety,／（主語が文頭にないときの主語の前）he was endeavouring to make his way out of the hummock,／（接続詞の前）when he caught sight, in the distance,／（前置詞の前）of several figures／（動詞のing形の前）moving among the trees,／（関係代名詞の前）which, though indistinctly seen, he was convinced were those of Indians.
語句のかたまりを前から訳していきます。
Anxious, however, about his own safety,
しかし、自分の身の安全を心配して
he was endeavouring to make his way out of the hummock,
彼は丘から出ようとしていた
when he caught sight, in the distance,
そのとき、遠くに見えた
of several figures
何人かの姿が
moving among the trees,
木々の間を移動する
which, though indistinctly seen, he was convinced were those of Indians.
はっきりとは見えなかったが、先住民の姿に違いないと彼は思った
Anxious, however, about his own safety, he was endeavouring to make his way out of the hummock, when he caught sight, in the distance, of several figures moving among the trees, which, though indistinctly seen, he was convinced were those of Indians.
Anxious, however, about his own safety→ 文頭に形容詞が置かれていますが、これは being が省略された分詞構文です。
though indistinctly seen→ ここもbeing が省略された分詞構文です。though が前に置かれているので、「〜だが」という意味です。意味上の主語は several figures です。
しかし、彼が自分の身の安全を心配して丘から出ようとしていたとき、木々の間を移動する何人かの姿が遠くに見えた。はっきりとは見えなかったが、先住民の姿に違いないと彼は思った。
several figures moving among the trees, which, though indistinctly seen, he was convinced were those of Indians
関係代名詞 which の前にコンマがある場合、先行詞を後ろから修飾するのではなく、前から後ろへと訳していきます（非制限用法）。
which 以下の訳し方ですが、まず though indistinctly seen は挿入語句なので、いったん外して考えます→ which he was convinced were those of Indians→ whichを本来の位置に戻します→ he was convinced which were those of Indians→ whichの先行詞 several figures を which に代入します→ he was convinced several figures were those of Indians→「何人かの姿は先住民のものに違いないと彼は思った」→ 最後に though indistinctly seen（「はっきりとは見えなかったが」）を加えます。
