ock， and it would be enough to watch the extremity of the shadow， so as to ascertain the instant when， alter having successively diminished， it began to lengthen. by inclining his stick to the side opposite to the sun， cyrus harding made the shadow longer， and consequently its modifications would be more easily ascertained. in fact， the longer the needle of a dial is， the more easily can the movement of its point be followed. the shadow of the stick was nothing but the needle of a dial.
一般的情况下，金属埋藏在地里的时候，质地并不纯粹。它们通常和氧或硫化合在一起。赛勒斯?哈顿上次带回来的两种标本就是这样，一种是没有碳化的磁铁矿，另一种是黄铁矿，也叫做硫化铁。因此，他们必须先用炭使氧化铁还原，也就是除去氧，然后才能得到纯粹的铁。这个还原过程是用炭把矿石烧到温度很高的时候进行的，可以用迅速而简便的土法（它的
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