The reader's guide to the Encyclopaedia Britannica

by Inc. Encyclopaedia Britannica

While the student will doubtless be interested equally in each of these departments, the general reader will be especially interested in the historical development which—it is worthy of note—is almost the only concise account of geological history hitherto published in English. Especially interesting is the question, fully discussed, of the age of the earth. Lord Kelvin (Vol. 11, p. 653) declared some few years ago that the time “was more than twenty and less than forty millions of years and probably much nearer twenty than forty.” But the trend of later investigations, and especially the study of radio-activity, has led to the belief that the period must have been much longer. Sir Archibald Geikie sums up the evidence as follows (Vol. 11, p. 653): “In the present state of science it is out of our power to state positively what must be the lowest limit of the age of the earth, but we cannot assume it to be less, and it may possibly have been much more than one hundred millions of years.”

Geological Formations

The general reader will find of interest, too, the table (Vol. 11, p. 670) representing the geological record or order of succession of the formations of the earth’s crusts from the earliest Archean, through Cambrian, Silurian, Devonian and Carboniferous to the Post-glacial or Human of to-day. A separate article is to be found on each of these different formations, namely: Archean (Vol. 2, p. 360); Cambrian (Vol. 5, p. 86); Silurian (Vol. 25, p. 109); Devonian (Vol. 8, p. 124); Carboniferous (Vol. 5, p. 309); Permian (Vol. 21, p. 176); Triassic (Vol. 27, p. 258); Jurassic (Vol. 15, p. 567); Cretaceous (Vol. 7, p. 414); Eocene (Vol. 9, p. 661); Oligocene (Vol. 20, p. 81); Miocene (Vol. 18, p. 565); Pliocene (Vol. 21, p. 846); Pleistocene (Vol. 21, p. 835); Recent, Post-glacial or Human under article Quaternary (Vol. 22, p. 718).

Full local geological information is found in geographical articles. See, for instance, in the article United States, the section on Geology (Vol. 27, pp. 624–632), by Professors R. D. Salisbury and T. C. Chamberlin of the University of Chicago; the section Geology in the article England (Vol. 9, pp. 415–416), by H. R. Mill, editor of The International Geography; the section Geology in the article Africa (Vol. 1, pp. 323–325), by Walcot Gibson, author of Mineral Wealth of Africa, etc. These special treatments are accompanied by sketch maps. Similarly, the articles on each of the different states of the Union has a section giving information on the geology, the flora and fauna, the climate, and the geography of the state. And in such articles on geographic topics as Great Salt Lake, Niagara, by G. Karl Gilbert, and Grand Canyon, by R. S. Tarr, there is valuable geological information.

Other important articles which the reader should consult are Petrology (Vol. 21, p 323), equivalent to 40 pages of this Guide, largely illustrated, by Dr. J. S. Fleet, petrographer to the Geological Survey of Great Britain; Mineralogy (Vol. 18, p. 509), equivalent to 25 pages of this Guide, by L. J. Spencer, editor of the Mineralogical Magazine; Mineral Deposits (Vol. 18, p. 504), equivalent to 15 pages of this Guide, by James F. Kemp, professor of geology of Columbia University, and geologist to the United States and New York Geological Surveys; Crystallography (Vol. 7, p. 569), equivalent to 60 pages of this Guide, also by L. J. Spencer; Mining (Vol. 18, p. 528), equivalent to 40 pages of this Guide, by Henry Smith Munroe, professor of mining, Columbia University, New York; Palaeontology (Vol. 20, p. 579), profusely illustrated, equivalent to 35 pages of this Guide, by Prof. Henry Fairfield Osborn of Columbia University, and president of the American Museum of Natural History of New York; Palaeobotany (Vol. 20, p. 524), profusely illustrated, equivalent to 100 pages of this Guide, written by three of the leading geological writers of the day: Dr. D. H. Scott, president of the Linnean Society, author of Studies in Fossil Botany; A. E. Steward, professor of botany of the University of Cambridge; and Clement Reid, author of Fossil Flora of Tegelen.

Of more popular interest are the three articles, Earthquake, Seismometer and Volcano. The article Earthquake is in two parts. The first (Vol. 8, p. 817) is an historical account telling of the extent and damage done by many earthquakes, including the terrible San Francisco earthquake of April 18, 1906, and that of Calabria and Sicily, December 28, 1908, by F. W. Rudler, president of the Geologists’ Association; the other part (Vol. 8, p. 820), by Dr. J. Milne, late professor of geology in the Imperial University of Tokio, deals with the physical theory of earthquakes. The article Volcano (Vol. 28, p. 178), equivalent to 45 pages of this Guide, is by F. W. Rudler, and gives us the reasons for and the history of volcanic disturbances. It is of interest both to the scholar and to the casual reader. Thus we learn that “while Herculaneum was buried beneath a flood of mud swept down from Vesuvius” in 79 A.D., Pompeii “was overwhelmed in great measure by loose ashes, capable of removal with comparative ease.” Nearly everyone of middle age remembers the famous eruption of Krakatoa in 1883 and the famous sunsets of that year. Concerning this the Britannica article tells us (p. 180):

Enormous quantities of dust ejected from Krakatoa in 1883 were carried to prodigious distances, samples having been collected at more than a thousand miles from the volcano; whilst the very fine material in ultramicroscopic grains which remained suspended for months in the higher regions of the atmosphere seems to have enjoyed an almost world-wide distribution, and to have been responsible for the remarkable sunsets at that period.

The article Dust (Vol. 8, p. 713), by John Aitken, inventor of the machine for counting particles of dust, explains the mechanical causes of this suspension. Besides there is much concrete information about volcanoes in articles on volcanic regions: for instance, on volcanoes in the possessions of the United States, see articles Hawaii, Alaska, Philippines.

The student should read also the articles on the different minerals, many of them long and important and all by well-known authorities. Thus the article Diamond (Vol. 8, p. 158), illustrated, equivalent to 20 pages of this Guide, is by Henry Alexander Miers, editor of the Mineralogical Magazine. Besides dealing with the general character of this stone, the article pays particular attention to diamond mining in South Africa, the text being illustrated by plates showing the Kimberley and DeBeers workings. The article Gem (Vol. 11, p. 560), is equivalent to 25 pages of this Guide. The article Gem, Artificial (Vol. 11, p. 569) is by the well-known chemist and physicist, Sir William Crookes. It tells of the changes induced by radioactive emanations and of the artificial production of the diamond, ruby, sapphire, Oriental emerald, amethyst and topaz. The reader will be interested, too, in the article Lapidary and Gem Cutting (Vol. 16, p. 195), by Dr. George F. Kunz, gem expert for Messrs. Tiffany & Co., New York.

There are special biographical articles in the Britannica on all the well-known geologists, and in these articles special stress has been laid on the part played by the subject of the memoirs in promoting the science. This is well shown, for instance, in the articles Agassiz (Vol. 1, p. 367); Hutton (Vol. 14, p. 16) and Lyell (Vol. 17, p. 158).