>73 The Microscopic Technique
    Each advance in microscopic technique has provided scientists with new perspectives on the function of living organisms and the nature of matter itself. The invention of the visible light microscope late in the sixteenth century introduced a previously unknown realm of single celled plants and animals. In the twentieth century, electron microscopes have provided direct views of viruses and minuscule surface structures. Now another type of microscope, one that utilizes x rays rather than light or electrons, offers a different way of examining tiny details; it should extend human perception still farther into the natural world. The dream of building an x ray microscope dates to back 1895; its development, however was virtually halted in the 1940's because the development of the electron microscope was progressing rapidly. During the 1940's, electron microscopes routinely achieved resolution better than that poss ible with a visible light microscope, while the performance of x ray microscopes resisted improvement. In recent years, however, interest in x ray microscopes has revived, largely because of advances such as the developmen t of new sources of x ray illumination. As a result, the brightness available today is millions of times tha t of x ray tubes, which, for most of the century, were the only available sources of soft x rays.The new x ray microscopes considerably improve on the resolution provided by optical microscopes. They can also be used to map the distribution of certain chemical elements. Some can form pictures in extremely short times; others hold the promise of special capabilities such as three dimensional imaging. Unlike conventional electron microscope, x ray microscope enables specimens to be kept in air and in water, which means that biological samples can be studied under conditions similar to their natural state. The illumination used, so called soft x rays in the wavelength range of twenty to forty angstroms (an angstrom is one ten billionth of a meter), is also sufficiently penetrating to image intact biological cells in ma ny cases. Because of the wavelength of the x rays used, soft x ray microscopes will never match the highest resolution possible with electron microscopes. Rather, their special properties will make possible investigations that will complement those performed with light and electron based instruments.

    显微技术
    显微镜技术的每一个进步都给科学家提供了看待生物体的功能和其性质的新 观察方式。 16 世纪晚期可视光显微镜的发明引入了一个以前一无所知的单细胞植物和动物 的领域。 20 世纪电子显微镜提供了对病毒和极微物体的表面结构的直接观察。 现在一种 新的显微镜，利用 X 光而不是自然可见光或电子，为观察微小细节提供了不同的观察方式， 它将扩展人类对自然世界进行的更深入的认识。 研制 X 光显微镜的梦想可追溯到 1875 年； 但它的发展却在 20 世纪 40 年代实际上停止了，因为电子显微镜的发展进行很快。 在 40 年代，电子显微镜毫无例外地比可见光显微镜获得了更好的分辨能力。 然而 X 光显微镜的 表现却没有改进。 但近年来，对它的兴趣又复活了，这很大程度是因为例如 X 射线在新光 源上的发展的结果。 结果，今天可得到的亮度是大半个世纪以来唯一可得到的 X 光源-X 光 管的几百万倍。 新的 X 光显微镜相当大地提高了电子学显微镜提供的分辨能力。 它们也 可用来给某些化学元素绘制分布图。 某些 X 光显微镜可以在极短的时间里成像。 另一些可望具备三维成像的特殊功能。 与传统的电子显微镜成像术不同，X 光显微镜成像术可使 分析样本保留在空气或水中。 这就意味着生物样品可以在与它们自然环境相近的条件下被 观察研究。 其使用的照明度，即所谓的软性 X 射线，其波长在 20 到 40 埃之间(1 米的 100 亿分之一为 1 埃)。 在许多情况下也能够穿透完整无缺的生物细胞并成像。 由于使用的 X 射线的波长使软性 X 射线显微镜永远比不上电子显微镜可能具有的最高分辨力。 不过他们 特殊的功能将可能补充那些用自然光和电子仪器所进行的观察。
  >74 The History of Chemistry
    Chemistry did not emerge as a science until after the scientific revolution in the seventeenth century and then only rather slowly and laboriously. But chemical knowdedge is as old as history, being almost entirely concerned with the practical arts of living. Cooking is essentially a chemical process; so is the melting of metals and the administration of drugs and poisons. This basic chemical knowledge, which was applied in most cases as a rule of thumb, was nevertheless dependent on previous experiment. It also served to stimulate a fundamental curiosity about the processes themselves. New information was always being gained as artisans improved techniques to gain better results. The development of a scientific approach to chemistry was, however, hampered by several factors. The most serious problem was the vast range of material available and the consequent difficulty of organizing it into some system. In addition, there were social and intellectual difficulites, chemistry is nothing if not practical; those who practice it must use their hands, they must have a certain practical flair. Yet in many ancient civilizations, practical tasks were primarily the province of a slave population. The thinker or philosopher stood apart from this mundane world, where the practical arts appeared to lack any intellectual content or interest. The final problem for early chemical science was the element of secrecy. Experts in specific trades had developed their own techniques and guarded their knowledge to prevent others from stealing their livelihood. Another factor that contributed to secrecy was the esoteric nature of the knowledge of a alchemists, who were trying to transform base metals into gold or were concerned with the hunt for the elixir that would bestow the blessing of eternal life. In one sense, the second of these was the more serious impediment because the records of the chemical processes that early alchemists had discovered were often written down in symbolic language intelligible to very few or in symbols that were purposely obscure.

    化学的历史
    化学在17 世纪的科技革命后才成为一门科 学，其发展是缓慢而艰难的。 但化学知识却象人类历史一样古老，与人们实际生活密切相 关。 做饭基本上是一个化学过程。 同样，金属熔炼、使用药品或毒剂也是如此。 人们在 大多数情况下只是粗糙地运用这些基本化学知识，但这些基本知识的确是来自于前人的实 验。 它们同时也激发了人们对化学本身的兴趣。 匠人们利用新技术来改良工艺，就增加了 对化学的了解。 但是，化学科学方法的发展却有许多阻碍的因素。 其中最严重的问题就是 要把浩如烟海的物质归纳为若干系统确实很困难。 此外，还有社会和知识的原因。 离开实 际用途，化学就毫无价值；研究化学的人必须亲自动手，这就要求他们要有很强的动手能力。 但在许多古代文明中，动手的活都是奴隶的行当。 思想家与哲学家与此劳碌决不沾边，因 为在他们看来，实际操作技能低智而乏味。 最后，还有一个原因妨碍早期化学的发展，那 就是保密。 某个行家一旦发现了新技术，就竭力保密以防被人偷了饭碗。 另一个原因加剧 了知识封锁这是因为炼金术士的知识的神秘性。这些术士们要么想他便宜的金属变成黄金， 要么期望找到一种长生不老药。从某种意义上说，这第二个因素带来了更严重的阻碍，因为
早期术士们的研究成果记载于鲜为人知的或故意让人不懂的符号中。