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The comets and their origin
Book reviews
Book LYTIZETON,
R. A:
reviews
The Comeb sad their Origin.
Cembridge
University
Press, 1953. 26s. net.
In this book the author gives 8n account of his new theory of the origin of the comets; the mein part is rather technical, but since the author is of the opinion thet the fe8turea of cometa are not too well known even to astronomers, he begins by describing the dyn8mical end physical properties of comets as established by observation81 astronomy. These first two chapters of the book, which are enlivened by a gre8t number of Carefully chosen photograph& of comets, c8n rep&e some of the earlier books on comets which 8ppe8led to 8 lerge circle of readers owing to the interest these unusual celestial objecta &rouse. The two subsequent chapters distinguish this book from all those previously written; here 8 new expl8n8tion for the origin snd formation of comets 8nd their tails is given which c8n claim to be a scientific theory, open to quantitative examination. The principel idea is briefly that the sun, during paesagea through galactic dust clouds, by its gmvitational action c&uses the aggregation of dust particles; these clusters will revolve round the sun and, under favourable conditions, become visible to us aa comets. It will be for astronomers to teat how far this new theory can explain 8il the strange observations made on comets throughout the centuries. It bee the Advantage of not introducing like most of the earlier comet theories new and unfounded hypotheses as for instance ejection of the cometary material from the sun or the planets, or pulverization of en aeteroid. For the existence of dust clouds, on which the author’s theory is based, there is smple evidence, and his views are also in full 8grecment with other recent cosmological theories which were developed without reference to the problem of comets. One point may be of special interest to reeders of this journal. Since SCHIAPARELLI’S wnrk we know that at least some periodic meteor swarms are genetically related to comets, and this assumpt.ion has sometimes been extended by astronomers to meteorites because it seemed simplest to consider meteors and meteorites 8s essentially the same celestial bodies, differing only in Lize. It is to the credit of geologists to have insisted that objects like meteorit,es can only have their origin in 8 celestial body akin to our earth, and not ti 8 comet. Dr. LYTPLETON’S inference that comets must be composed of em811 p&ticles confirms this view. It is of course possible, and even likely, that some meteorites are so smell that they are completely consumed during their flight through the terrestrial atmosphere and it may not be feasible, by watching the luminous effect in the sky, to distinguish them from meteors. But a meteor, of cometary origin, c8n never have the size, end even leas the structure, of the meteorite specimens of our museums. If we make use of CWMBE~LIN’S distinction between the “two solar families”, planets 8nd comets (end their relatives), then the meteors-at leclst those connected with comets-belong to the second family, but meteoritea to the first. F. A. PANETH
C#&eine und Minerallager&U&m, Band II, Exogene Geateine und biinerallagersttiiten by Par-~ NIGGLI in collaboration with ERXST NIQ~LI, Verleg Birkhiiuser, Basel, 657 pp., 181 figs., 1952. Price (bound in linen) 49.40 Swiss francs, (in paper) 46.26 Swiss fmncs. Volume II of Gesteine und Miner&@er8t&%?n is 8 comprehensive treatment of the rocks of sedimentary origin and of t,he sedimentary ore deposits which they contain. The book is divided into two parta: Part I concerns the autochthonous deposits end rocks formed by weathering and Part II treats the sediments. Each of these mrrjor divisions is subdivided into sections. Part I (117 p8ges) discussea weathering and soils. P8I% II (416 p8ges) covers A: Fragmental, claatic rocks; B: Pelite. gelite, hum&e, and related rocks; C: Carbonate rocks; D: Sedimentary phosphate deposits; E: Sulphate 8nd chloride rocks end related s8lt deposits; E: Sulphete and chloride rock sand related ealt deposits; F: Snow and ice; G: Petrographic provinces of sedimentary sequencea. These sections are further subdivided into six subsections. Extensive bibliographies 8re given at the end of each subsection.
243
Book LYTIZETON,
R. A:
reviews
The Comeb sad their Origin.
Cembridge
University
Press, 1953. 26s. net.
In this book the author gives 8n account of his new theory of the origin of the comets; the mein part is rather technical, but since the author is of the opinion thet the fe8turea of cometa are not too well known even to astronomers, he begins by describing the dyn8mical end physical properties of comets as established by observation81 astronomy. These first two chapters of the book, which are enlivened by a gre8t number of Carefully chosen photograph& of comets, c8n rep&e some of the earlier books on comets which 8ppe8led to 8 lerge circle of readers owing to the interest these unusual celestial objecta &rouse. The two subsequent chapters distinguish this book from all those previously written; here 8 new expl8n8tion for the origin snd formation of comets 8nd their tails is given which c8n claim to be a scientific theory, open to quantitative examination. The principel idea is briefly that the sun, during paesagea through galactic dust clouds, by its gmvitational action c&uses the aggregation of dust particles; these clusters will revolve round the sun and, under favourable conditions, become visible to us aa comets. It will be for astronomers to teat how far this new theory can explain 8il the strange observations made on comets throughout the centuries. It bee the Advantage of not introducing like most of the earlier comet theories new and unfounded hypotheses as for instance ejection of the cometary material from the sun or the planets, or pulverization of en aeteroid. For the existence of dust clouds, on which the author’s theory is based, there is smple evidence, and his views are also in full 8grecment with other recent cosmological theories which were developed without reference to the problem of comets. One point may be of special interest to reeders of this journal. Since SCHIAPARELLI’S wnrk we know that at least some periodic meteor swarms are genetically related to comets, and this assumpt.ion has sometimes been extended by astronomers to meteorites because it seemed simplest to consider meteors and meteorites 8s essentially the same celestial bodies, differing only in Lize. It is to the credit of geologists to have insisted that objects like meteorit,es can only have their origin in 8 celestial body akin to our earth, and not ti 8 comet. Dr. LYTPLETON’S inference that comets must be composed of em811 p&ticles confirms this view. It is of course possible, and even likely, that some meteorites are so smell that they are completely consumed during their flight through the terrestrial atmosphere and it may not be feasible, by watching the luminous effect in the sky, to distinguish them from meteors. But a meteor, of cometary origin, c8n never have the size, end even leas the structure, of the meteorite specimens of our museums. If we make use of CWMBE~LIN’S distinction between the “two solar families”, planets 8nd comets (end their relatives), then the meteors-at leclst those connected with comets-belong to the second family, but meteoritea to the first. F. A. PANETH
C#&eine und Minerallager&U&m, Band II, Exogene Geateine und biinerallagersttiiten by Par-~ NIGGLI in collaboration with ERXST NIQ~LI, Verleg Birkhiiuser, Basel, 657 pp., 181 figs., 1952. Price (bound in linen) 49.40 Swiss francs, (in paper) 46.26 Swiss fmncs. Volume II of Gesteine und Miner&@er8t&%?n is 8 comprehensive treatment of the rocks of sedimentary origin and of t,he sedimentary ore deposits which they contain. The book is divided into two parta: Part I concerns the autochthonous deposits end rocks formed by weathering and Part II treats the sediments. Each of these mrrjor divisions is subdivided into sections. Part I (117 p8ges) discussea weathering and soils. P8I% II (416 p8ges) covers A: Fragmental, claatic rocks; B: Pelite. gelite, hum&e, and related rocks; C: Carbonate rocks; D: Sedimentary phosphate deposits; E: Sulphate 8nd chloride rocks end related s8lt deposits; E: Sulphete and chloride rock sand related ealt deposits; F: Snow and ice; G: Petrographic provinces of sedimentary sequencea. These sections are further subdivided into six subsections. Extensive bibliographies 8re given at the end of each subsection.
243