首页
登录
职称英语
The city water pipes in Rome were usually of baked clay or lead; copper was
The city water pipes in Rome were usually of baked clay or lead; copper was
游客
2025-01-16
34
管理
问题
The city water pipes in Rome were usually of baked clay or lead; copper was sometimes used and also hollowed stone. For the large supply conduits leading to the city the Romans used covered channels with free water surfaces, rather than pipes. Perhaps this choice was a matter of economics, for apparently they could make lead pipes up to 15 inches in diameter. While pipes can follow the profile of undulating ground, with the pressure increasing in the lower areas, channels cannot. They must slope continuously downwards, because water in channels does not normally flow uphill; and the grade must be flat, from 1 in 60 in small channels to perhaps 1 in 3,000 in large ones, to keep the water speed down to a few feet per second. Thus the main supply channels or aqueducts had long lengths of flat grade and where they crossed depressions or valleys they were carried on elevated stone bridges in the form of tiered arches. At the beginning of the Christian era there were over 30 miles of these raised aqueducts in the 250 miles of channels and tunnels bringing water to Rome. The channels were up to 6 feet wide and 5 to 8 feet high. Sometimes channels were later added on the tops of existing ones. The remains of some of these aqueducts still grace the skyline on the outskirts of Rome and elsewhere in Europe similar ruins are found.
Brick and stone drains were constructed in various parts of Rome. The oldest existing one is the Cloaca Maxima which follows the course of an old stream. It dates back at least to the third century B.C. Later the drains were used for sewage, flushed by water from the public baths and fountains, as well as street storm run-off.
The truly surprising aspect of the achievements of all the ancient hydraulic artisans is the lack of theoretical knowledge behind their designs. Apart from the hydrostatics of Archimedes, there was no sound understanding of the most elementary principles of fluid behaviour. Sextus Frontinus, Rome’s water commissioner around A.D. 100, did not fully realize that in order to calculate the volume rate of flow in a channel it is necessary to allow for the speed of the flow as well as the area of cross-section. The Romans’ flow standard was the rate at which water would flow through a bronze pipe roughly 4/3 inch in diameter and 9 inches long. When this pipe was connected to the side of a water-supply pipe or channel as a delivery outlet, it was assumed that the outflow was at the standard rate. In fact, the amount of water delivered depended not only on the cross-sectional area of the outlet pipe but also on the speed of water flowing through it and this speed depended on the pressure in the supply pipe. [br] Covered channels were used instead of pipes to supply large quantities of water probably because ______
选项
A、the Romans could build them more cheaply
B、these channels could follow uneven ground more easily
C、the Romans could not build large pipes
D、these channels avoided rapid changes of pressure
答案
A
解析
从文章的第一段第二句可以看出答案是A。“For the large supply conduits leading to the city the Romans used covered channels with free water surfaces,rather than pipes.Perhaps this choice was a matter of economics,for apparently they could make lead pipes up to 15 inches in diameter.”(也许这种选择是出于经济考虑,因为很显然他们用铅来做可以把直径做到15英寸那么宽。)为了更经济,也就是更便宜。故选A。
转载请注明原文地址:https://tihaiku.com/zcyy/3915375.html
相关试题推荐
Sympathyoftenengenderslove,whichisusuallyunreliable.A、negatesB、controls
Agoodhandatmanagementusuallyhassecond________toone’sbow,abestcardto
Thepessimistsusuallyratedthemselvestoolow.Thenegativeexpectationofthe
Suchgamesareusuallyplayedbehindcloseddoorsorinsecludedplacesduetot
ThecitywaterpipesinRomewereusuallyofbakedclayorlead;copperwas
ThecitywaterpipesinRomewereusuallyofbakedclayorlead;copperwas
ThecitywaterpipesinRomewereusuallyofbakedclayorlead;copperwas
ThecitywaterpipesinRomewereusuallyofbakedclayorlead;copperwas
Middlebornchildrenwilltellyouthattheyusuallydidn’tfeelallthatsp
Doesusingawordprocessoraffectawriter’sstyle?Themediumusuallydoes
随机试题
FuneralSermonforMammyCarolineBarrW.FaulknerCarolinehasknownm
Scientistsknowthattherearetwobasicapproachestoprolongingforlife.
商标无效宣告复审案件的申请人,应为()。A.利益关系人 B.在先权利人
下列玻璃顶棚构造的说法,哪条正确?( )A.其顶棚面层的玻璃宜选用钢化玻璃
反滤料填筑的工序包括()。A.取样检查 B.卸料 C.铺料 D.界面处理
下列关于开停车安全管理的做法中,错误的是( )。A.停车过程中的设备、管线低点的
患儿,女,11岁。发热20余天,体温37.5~38.2℃,双手指指关节和掌指关节
( )是可转换公司债券最主要的金融特征。A:风险收益的限定性 B:套期保值
某生产经营企业在进行设备安装过程中,发生一起事故,造成2人当场死亡,4人重伤。该
DNA上某段碱基顺序为5'-ATCGGC-3',其互补链的碱基顺序是A.5'-A
最新回复
(
0
)