大部分通往伦敦的火车只到外伦敦的边界，因为在市区内修建铁路会损害许多古建筑。用马拉的车、有轨电车、出租车和四轮马车被用来将人们送往市中心及其周围一带。不幸的是，马路上车的数量造成了令人难以置信的交通堵塞，道路交通变得如此拥挤以至于无人能够通行。这一交通问题导致了地铁系统的研发。

　　In 1854, the British government gave approval to⑮ the construction by the Metropolitan⑯ Railway Company of an underground railway in the centre of London, between Paddington and Farringdon, via⑰ King's Cross, St Pancras and Euston. However, new trains had to be developed and the plan required raising a large amount of⑱ money⑲， so the digging was postponed⑳ until 1860. The initial tunnels\s\up1(21(21) were opened in 1863 and were just beneath the surface of the ground. Passengers were transported in carriages without windows, which were pulled through the narrow tunnels by steam engines\s\up1(22(22). In 1868, the next section\s\up1(23(23) of the underground system was opened in the south of London by another company called the Metropolitan District Railway. Sixteen years later, in 1884, the Metropolitan Railway Company and the Metropolitan District Railway linked up\s\up1(24(24) and provided underground service in the middle of the city. This later became the Circle Line. Because of the smoke from the steam engines, early underground lines needed large holes leading to the surface at regular intervals\s\up1(25(25)， so that people could get fresh air and would not choke\s\up1(26(26).

　　As better ways for digging tunnels were developed\s\up1(27(27)， the first railway tunnel under the River Thames was dug in 1884. These new ways of digging accelerated the pace of\s\up1(28(28) the London Underground's development. The City and South London Railway opened the first electric underground railway in 1890. Over the next twenty­five years\s\up1(29(29)， six independent\s\up1(30(30) deep underground lines were constructed. Travelling on these lines was not convenient\s\up1(31(31)， though\s\up1(32(32)， as each line was possessed by a different company\s\up1(33(33)， and many were very far from\s\up1(34(34) each other.

⑮give approval to 正式批准

⑯metropolitan/ˌmetrə'pɒlItən/adj.大城市的，大都会的

⑰via/'vaIə/prep.经由，经过(某一地方)；通过，凭借

⑱a large amount of 大量，修饰不可数名词。

large amounts of 大量(修饰不可数名词)

a great deal of 大量(修饰不可数名词)

⑲raise money 集资，筹钱

⑳postpone/pə'spəʊn/vt.延迟，延期

postpone doing sth.推迟做某事

\s\up1(21(21)tunnel/'tʌnl/n.地下通道，隧道

\s\up1(22(22)which were pulled through ... 是which 引导的非限制性定语从句，修饰先行词 carriages。

\s\up1(23(23)section/'sekʃn/n.部分；部件；部门

\s\up1(24(24)link up 联合，连接

\s\up1(25(25)interval/'Intəvl/n.间隔，间隙

at (...) intervals 每隔......距离或时间

\s\up1(26(26)choke/tʃəʊk/vi.& vt.(使)窒息；(使)哽咽；塞满，堵塞 n．哽咽声，呛住的声音

\s\up1(27(27)as引导时间状语从句，意为"随着"。

\s\up1(28(28)accelerate the pace of 加快......的步伐

\s\up1(29(29)over the next twenty­five years 在接下来的25年里，over 表示"在......期间"。

\s\up1(30(30)independent adj.独立的

\s\up1(31(31)convenient adj.方便的，便利的

\s\up1(32(32)though 在句中为副词，意为"不过，可是，然而"。

\s\up1(33(33)as引导原因状语从句。

\s\up1(34(34)far from 远离，远非