练习材料：
[Day 1775 2019-08-06]
Lesson 30-1 Exploring the sea-floor
Our knowledge of the oceans a hundred years ago was confined to the two-dimensional shape of the sea surface and the hazards of navigation presented by the
irregularities in depth of the shallow water close to the land. The open sea was deep and
mysterious, and anyone who gave more than a passing thought to the bottom confines
of the oceans probably assumed that the sea bed was flat. Sir James Clark Ross had
obtained a sounding of over 2,400 fathoms in 1839, but it was not until 1869, when H.M.S. Porcupine was put at the disposal of the Royal Society for several cruises, that a series of deep
soundings was obtained in the Atlantic and the first samples were collected by dredging
the bottom. Shortly after this the famous H. M. S. Challenger expedition established
the study of the sea-floor as a subject worthy of the most qualified physicists and
geologists.
任务配置：L0+L1+L4
知识笔记：
hazards n. 危险; 危害; v. 冒失地提出; 冒险猜测; 冒…的风险; 使处于危险;
irregularities n. 不合乎常规的行为; 不正常的做法; 不规则(或无规律)的事物; 不整齐的事物; 不平整的事物;
a passing thought 过眼烟云
sounding n. 意见调查; 征询意见; 水深测量;
v. 听起来好像; 让人听着好像; 听起来…的; (使) 发出声音，响;
fathoms v. 理解; 彻底了解; 弄清真相; n. 英寻(测量水深单位，合6英尺或1.8米);
H.M.S. His/Her Majesty's Ship,一般是上世纪其他国家对英国海军的称呼,意为她/他(国王或者女王陛下的战舰)
Porcupine n. 豪猪; 箭猪;
at the disposal of 网络 任凭……使用;
the Royal Society 网络 英国皇家学会; 皇家学会;
dredging v. 疏浚; 清淤; 挖掘; 打捞; 采捞; 捞取; (用面粉、糖等) 撒，涂;
Shortly after [词典] …之后立即;
expedition n. 远征; 探险; 考察; 远征队; 探险队; 考察队; (短途的) 旅行，出行;
练习感悟：
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