The first, and more conventional, way is to start at the beginning and to read through to the end, which gives a coherent and thorough picture of the subject and opens a resource of basic information that can be returned to for rereading and reference.
The second allows the book to be used as a library of information presented subject by subject, which the reader can consult piece by piece as required.
All articles are prepared and presented so that the subject is equally accessible in either way. Topics are arranged in a logical sequence, outlined in the contents list. The index allows access to more specific points.
Within an article scientific terms are explained in the main text where an understanding of them is central to the understanding of the subject as a whole. Fact entries giving technical, mathematical, or biographical details are included, where appropriate, at the end of the article to which they relate.
There is also an alphabetical glossary of terms at the end of the book, so that the reader's memory can be refreshed and so that the book can be used for quick reference whenever necessary.
All articles are relatively short, but none has been condensed artificially. Most articles occupy two pages, but some are four, or occasionally six, pages long.
The sample two-page article opposite shows the important elements of this editorial plan and illustrates the way in which this organization permits maximum flexibility of use.
(A) Article titlegives the reader an immediate reference point.
(B) Section titleshows the part of the book in which a particular article falls.
(C) Main textconsists of approximately 850 words of narrative information set out in a logical manner, avoiding biographical and technical details that might tend to interrupt the story line and hamper the reader's progress.
(D) Illustrationsinclude specially commissioned drawings and diagrams and carefully selected photographs, which expand, clarify, and add to the main text.
(E) Captionsexplain the illustrations and make the connection between the textual and the visual elements of the article.
(F) Annotationof the drawings allows the reader to identify the various elements re ferred to in the captions.
(G) Theme images,where appropriate, are in cluded in the top left-hand corner of the left-hand page, to emphasize a central el ement of information or to create a visual link between different but related articles. In articles about the major groups of ele ments, for example, the theme images re late the elements being discussed to their neighbors in the periodic table.
(H) Fact entriesare added at the foot of the last page of certain articles to give additional information relating to the article but not essential to an understanding of the main text itself.
Color photographyrelies on subtle light-induced reactions that are the province of photochemistry, a fast-growing specialized branch of the science of chemistry.
For 4,000 years chemistry has been essential to the development of mankind. Since the beginning of the Bronze Age, people have used chemical processes in smelting and glassmak-ing; early medicine and alchemy were intimately related; and chemistry played a key role in the reawakening of scientific interest during the Renaissance and in the Industrial Revolution. But above all, it is in the last 100 years that the influence of chemistry has exploded, so that it now touches every aspect of scientific knowledge and civilized living.
Most of the familiar products around us depend on the chemical industry. Modern transportation relies on synthetic rubber, refined metals, and high-energy fuels. The construction industry needs paints, pigments, alloys,
cements, glasses, plastics, and ceramics. Our clothing and fabrics are increasingly manufactured from artificial fibers such as nylon and polyesters, colored by synthetic dyes, and cleansed by synthetic detergents and solvents. Fertilizers, antifreezes, disinfectants, pesticides, cosmetics, adhesives, and drugs are just a few of the other products of synthetic chemistry.