66.You should also learn as much about chemistry as possible from your own experience in the laboramry and from your observations of chemical substances and chemical reactions in everyday life．
你们也应该从你们我们的实验室经验中，从你们平时对化学物质和化学反应的察看中学习更多的化学方面的常识
67．You will notice that specific gravity is always the ratio of two weights，and so it is a pure number，such as 3 or 5．25，with out any unit associated with it．
你们将注意到，比重一直两个重量之比，因而它是一个纯数，譬如3或5．25，不需要给它。
概念任何单位。
68．With the increased productionmade possible by the as百度竞价推广bly line，automobiles became much cheaper，and more and more people were able to offord them．
因为装配线所带来的增产，汽车价格实惠多了，买得起汽车的人愈加多。
69．Today physicists1 find that light has the characteristics of both waves and particles with one aspect sometimes predominating and sometimes the other．
物理学家目前发现，光具备波粒二重性，有时波动性起主要用途，有时粒子性起主要用途。
70．It is amatter of common observation that a body A cannot exert force on a second body B without B at the same time exerting force on A．
这是大家一般都能察看到的状况：假如物体B没同时对物体A施加用途力，那样物体A也不可以对B施加用途力。
71．Without the sun's light warming the earth's surface，it would be so terribly cold that lifecould not exist．
假如没阳光来加热地球的表面，地球就会变得很寒冷，使得生命没办法存活。
72．Just as the length and cross-section of the pipe affect the flow of water so it is with conductors of electric current．
正如管道的长度和截面会干扰水流一样，导体对电流的影响也是这样。
73．Water vapor2 may vary from almost nothing to as much as 4％ and is not usually includedwith the other constituents3 which，in terms of global averages，do not vary significantly．
水蒸气的含量是变化的，从近乎为零到多达4％，一般不与其他成分一块计算，依据总平均值来看，其他成分的含量变化不大。
74．This atom，with 92 electrons spinning about the closely packed and complex nucleus，is the element uranium，which seems to be the most complicated of the natural atoms．
这一有着92个电子围着又密集又复杂的原子核旋转的原子，就是元素铀。它好像是天然原子中最复杂的原子了。