55.The air is heated by the flame，expands，and thus becomes less dense. Denser air flows in from below and the result is that irregular layers of air of different densities are formed above the flame.
空气受火焰加热而膨胀，于是变得比较稀薄。较密的空气从底下流人，其结果是，火焰上 方形成了密度不同的不规则的空气层。 （flow in， “流人”。from below， “自下”， “从下面”。 above the flame作地点状语。）
56.Weather is a product of many pLysical factors operating in and on the troposphere with the principal ones being the unequal heating of the earth's surface by the sun and the rather rapid rota tion of the planet on its axis.
天气是许多自然因素在对流层中起作用并对其施加影响的结果，其中太阳对地球表面加热不均等和地球自转比较快则是主要的因素。（with引导的复合结构作定语，用来修饰factors，ones代替factors.）
57.It is the village which suffers most，for it is not easy to break the traditional bonds uniting agriculturist families to families of craftsmen，nor to dispel the idea that some one who follows the traditional calling of this caste is acting in a more“suitable” way than some one who takes up a different occupation.
乡村受害最大，因为从事农业家庭与从事手工业家庭的传统结合是很难分割的。此外，一些人认为一个人遵照等级制度的传统职业来办事要比从事不同的职业更为“合适”，这种想法也很难去掉。 （his.……which为强调句型，强调主语the village.原句是简单句，The village suffers most.for是连词，“因为”。uniting.……to，“把……与……连接”，是分词短语作定语修饰bonds.nor连词，连接两个并列成分，把to break.……和to dispel.……两个不定式短语连接起来。that.……occupation为同位语从句，用来揭示idea的概念内涵。calling意为“职业”，与occupation相呼应。 ina.……way，“以……方式”。）
58.Forging and press-production methods of shaping metal are of tremendous importance in machine-building in general，and in automobile and tractor industry in particular.
金属成形的锻压加工方法，一般在机器制造业、特别是在汽车和拖拉机工业中具有重大意义。（be of……“具有”。in general，“通常”；in particular，“特别”，这两个短语介词在句中作插入语用。）
59.In fact， in the nineteeth century people used to make gardens in the shape of aclock face，with different flowers opening at different times.
在19世纪，人们常常把花园做成钟盘形，不同的花在不同的时间开放。 （with引导的复合结构有定语的意味，用来对the shape of a clock进行修饰。）
60.The modern scientific method Was born with Galileo in the 17th century；however，the development of the natural sciences began to gain speed only in the latter part of the 18th and the early part of the 19th centuries.
现代科学方法产生于17世纪的伽利略时代；然而，只是在18世纪后期和19世纪初期，自然科学才开始迅速发展。（with Galileo.……century有表示时间与空间范围之意，这里是表示时间即伽利略时代。）
