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I was very happy to learn that Plenum Press has decided to publish an English edition of Chemistry of the Ionosphere. I will be pleased if publication of the book in English will as sist in removing some of the currently existing ambiguities in basic problems of upper atmosphere chemistry.

The problems of the classification of rocks, particularly igneous rocks, and of the nature and genesis of ores are obviously chemical and, by the mid- 19th century, chemistry was in a state where rocks could be effectively analyzed, and a classification built up depending partly on chemistry and partly on the optical study of thin specimens.

However, applications of radiography in the earth sciences and in the related field of soils engineering have, until recent ly, been slow to develop. Gradual ly, radiography was applied to other tests including those on footings, compaction of soils, strain in sand, effects of pile penetration, and displace ments under moving wheel loads.

In its classical sense "epigenesis" refers to all geological processes originating at or near the surface of the earth.

Recently there has been growing interest in the physical properties of rocks. v vi FOREWORD At present, while research into the mechanical properties of rocks (relating to the problems of geophysics, geochemistry, geology, and mining) is pressing forward on a wide front, much less work is being done with electrical properties.

The user of this valuable compilation owes a debt of gratitude to that Society, to the Diamond Alkali Company which donated countless hours of Mr. Lefond's time, and above all, to author Stanley Lefond.

The adjectives have retained their Russian case endings in the process (masculine -yi or -ii, feminine -aya or -'ya, neuter -oe) and this may occasionally lead to some slight confusion, for example, when the author calls a given feature Severnyi Volcano at one point and Severnaya Mountain at another.

For agriculturalists and other land users, perhaps the most important part of soil science is the description of soils and the capacities of such soils to maintain crops, and this is reflected by the fact that soil science is usually treated ima highly descriptive manner, with soil classification being one of the main efforts.