61.All of the atoms of an element contain the same number of protons in their muclei，　and the atoms of one element differ from those of all other elements in the number of protons so contained.

　　同一种元素的所有原子的原子核中含有的质子数都是相同的，而一种元素的原子与其他一切元素的原子的不同点，就在于它们含有的质子数不同。（AdiffersfromBinC.A与B在C方面是不同的。句中in the number.……是differ要求的。）

　　62.The kinds of evidence for the roundness of the world that led finally to its general accep　tance included such data as the shape of the shadow of the earth on the moon during an eclipse of the　moon，the fact that as one sails from port on a ship the building of the port gradually seem to sink　below the surface of the water，and，most convincing，the fact that it is possible to sail all around　the world and return to the starting point of the voyage.

　　最终为人们普遍接受的有关地球是圆形的种种论据，包括：月蚀时地球投在月球表面的阴影形状；当人们乘船离开港口时，港口的建筑物似乎逐渐沉入水下；而最令人信服的是，人们环绕地球航行时，有可能又回到原来的起航点。（The kinds为主句中的主语，谓语是included.

　　介词as引导三个并列同位语：shape，the fact，the fact，说明data.在两个fact后的that都引出同位语从句。）

　　63.The technological breakthrough and the lndustrial Revolution brought with them a mastery of food production and control of infectious disease that reduced the normal death-rate to below 1.5 per cent.

　　技术革新和工业革命促进了食品生产，控制了传染病的流行，这使人口正常死亡率降到1.5％以下。（to below是双重介词，reduce.……tobelow，“降到……以下”。）

　　64.There are a few specially designed homes that are heated primarily by the sun but there is no practical and economic means for converting solar energy directly into that great convenience，electricity.

　　现在已有一些专门设计的住宅主要利用太阳能取暖，但还没有一种实用和经济的办法把太阳能直接转化为便于使用的电能。（介词短语for.……electridty用来修饰means.，oonverting.……into，“把……转化为……”。）

　　65.A balance consists of an arlTl balanced at its middle，　with known weights hung on one hand and the object whose weight is to be found on the other.

　　天平由一个在中央平衡的臂组成，已知重量的砝码挂在平衡臂的一端，而把要称出重量的物体挂在平衡臂的另一端。　（分词短语balanced at its middle用来修饰arm.with……weights hung…是介词复合结构，用来对balance作补充说明，过去分词known作定语，修饰weights.hung是hang的过去分词。）