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The chemical action of ultraviolet rays
700
Book
REVIEWS.
[J. F. I.
with illustrative experiments, associated with such mathematical explanations as are necessary to the preservation of the proper relation between theory and fact. Undoubtedly, teachers and research workers will differ much on what this proportion should be. Professor Eucken, as already noted, leans to a very large allowance of the mathematical phase. He alludes to the difference of opinion on this question that has been manifested by some of his colleagues, but he asserts, that when " i t is desired to make accessible to students the resources of physical chemistry, which are so useful for practical purposes, the task is made more difficult instead of easier for both teacher and pupil in the attempts to avoid mathematics." The validity of this assertion will depend much upon the teacher's ability to make clear the mathematical demonstration (not by any means a universal ability) and the pupil's preliminary training in mathematical abstraction. The translators have done their work well. They understand the subject and have had the direct assistance of the author. The text is in excellent English. They have added a very large amount of additional statements. There is, however, no little conflict between the statements in the original work and these annotations, so that one gets the impression that some qf the " fundam e n t a l s " of physical chemistry are in a rather " colloidal" form. The book is well worth attention by the advanced worker in physical chemistry. HENRY LEFFMANN. THE
CHEMICAL ACTION OF ULTRAVIOLET RAYS. By Carleton Ellis and Alfred A. Wells, assisted by Norris Boehmer. 362 pages, 85 illustrations, 8vo. New York, The Chemical Catalog Company, 1925. Price, $5. This is one of the most interesting books that the reviewer has seen for some time. Dealing a s it does with a peculiar and comparatively unfamiliar field of physico-chemical phenomena, it presents a vast mass of facts in a clear and comprehensive form. The Newtonian discovery gave information as to the composite nature of white light and enabled scientists to explain the color phenomena in nature. Some of the Greek philosophers supposed that the rainbow was due to the effects of rain-drops on light, but in the absence of any knowledge of the composite nature of light.they could give no explanation. It is curious to note the contrast between the Jewish and the Greek minds in relation to the rainbow. Early Jewish literature presents no speculation as to the nature of the bow; the word by which it is mentioned in the book of Genesis means " the weapon," and the significance of the appearance is that the deity has hung up the weapon as an earnest of the cessation of warfare against man. The Greek did not speculate on the teleologic significance of the appearance, but tried to discover its nature. Newton was unaware of the existence of invisible rays, and since he used a rather large opening for the admission of the beam of light to the prism, he also overlooked the numerous dark lines, which cross the solar spectrum and indicate missing waves, so that solar light is really imperfect. In the early part of the nineteenth century, it was discovered beyond the violet and below the red are a long series of waves invisible to human eyes, but having noticeable chemical and physical effects. The work in hand is limited to the study of the chemical action of the rays beyond the violet. It seems that the infra-red field
Nov., I925.]
BOOK R E V I E W S .
701
is generally neglected, possibly because the phenomena to which the rays give rise are not so spectacular or so widely applicable to practical uses. To any one who wishes to learn the information now at hand concerning the nature and effects of the ultra-violet rays, this book can be cordially recommended. A chapter on sources gives many ways in which the rays may be obtained. The important and striking uses, including therapeutics and hygiene, to which the rays have been put, have stimulated inventive talent and several excellent generators are now on the market. They are unfortunately still quite expensive. The most familiar depend on electrical discharges for action. High tension sparks from iron poles and discharges in mercury vapor are two of the most familiar. Inasmuch as the rays are almost all stopped by even very thin layers of ordinary glass, quartz tubes must be used and this adds considerable expense. Uviol glass which passes a considerable proportion of the rays is noted, but the glass lately introduced by the Corning works, which is dark purplish and cuts out almost all visible rays, thus transmitting a nearly pure beam of ultra-violet, seems to be not mentioned. The improvements in the manufacture of quartz glass are progressing encouragingly, and it is to be hoped that before long a complete quartz train for camera and photomicrographie work will be available at reasonable cost. There is a certain amount of ultra-violet light of comparatively long waves emitted from the sky. It is stated in this book that the short waves emitted by the sun are mostly scattered and absorbed before reaching the garth, but the clear blue sky is generally a sufficiently abundant source of the rays as to require the use of yellow screens in taking pictures on Lumi6re plates. Wood showed that many leaves reflect large amounts of infra-red, and later observers have discovered that many flowers reflect notable amounts of ultra-violet that are present in ordinary outdoor light. There is possibly such a difference between these two reflections that the contrast between the flower and leaf is intensified to any insect which is capable of " seeing" the two classes. This book deserves wide circulation. It is to be hoped that some one will take up the burden of writing a similar work on infra-red, thus bringing before the general scientific world the story of the "invisible lights." HEI~'RY LEFF MANLY'.
A SURVEY OF PHYSICS, a collection of lectures and essays. By Max Planck, translated by R. Jones and D. H. Williams. viii-I84 pages, 7 ~ × 5 inches, cloth• New York, E. P. Dutton and Company, no date. Price, $2.4o. There is a small body of celebrated investigators who are at the forefront in the development of modern physical theories. Professor Planck is an outstanding figure among them. His studies in radiation and evolution of the quantum theory are now widely adopted as a satisfactory working hypothesis for certain phenomena for which the laws of Newton and those of Maxwell have proved inadequate. Both on account of a commanding position in a new path in physical science and an otherwise established leadership in the fields of mathematics and physics, his " s u r v e y " will meet with a warm welcome by all who are interested in the fundamentals of the subject. The title plainly states the purport of the work. The volume embraces the collection in chronological order of eight lectures given on several occasions
Book
REVIEWS.
[J. F. I.
with illustrative experiments, associated with such mathematical explanations as are necessary to the preservation of the proper relation between theory and fact. Undoubtedly, teachers and research workers will differ much on what this proportion should be. Professor Eucken, as already noted, leans to a very large allowance of the mathematical phase. He alludes to the difference of opinion on this question that has been manifested by some of his colleagues, but he asserts, that when " i t is desired to make accessible to students the resources of physical chemistry, which are so useful for practical purposes, the task is made more difficult instead of easier for both teacher and pupil in the attempts to avoid mathematics." The validity of this assertion will depend much upon the teacher's ability to make clear the mathematical demonstration (not by any means a universal ability) and the pupil's preliminary training in mathematical abstraction. The translators have done their work well. They understand the subject and have had the direct assistance of the author. The text is in excellent English. They have added a very large amount of additional statements. There is, however, no little conflict between the statements in the original work and these annotations, so that one gets the impression that some qf the " fundam e n t a l s " of physical chemistry are in a rather " colloidal" form. The book is well worth attention by the advanced worker in physical chemistry. HENRY LEFFMANN. THE
CHEMICAL ACTION OF ULTRAVIOLET RAYS. By Carleton Ellis and Alfred A. Wells, assisted by Norris Boehmer. 362 pages, 85 illustrations, 8vo. New York, The Chemical Catalog Company, 1925. Price, $5. This is one of the most interesting books that the reviewer has seen for some time. Dealing a s it does with a peculiar and comparatively unfamiliar field of physico-chemical phenomena, it presents a vast mass of facts in a clear and comprehensive form. The Newtonian discovery gave information as to the composite nature of white light and enabled scientists to explain the color phenomena in nature. Some of the Greek philosophers supposed that the rainbow was due to the effects of rain-drops on light, but in the absence of any knowledge of the composite nature of light.they could give no explanation. It is curious to note the contrast between the Jewish and the Greek minds in relation to the rainbow. Early Jewish literature presents no speculation as to the nature of the bow; the word by which it is mentioned in the book of Genesis means " the weapon," and the significance of the appearance is that the deity has hung up the weapon as an earnest of the cessation of warfare against man. The Greek did not speculate on the teleologic significance of the appearance, but tried to discover its nature. Newton was unaware of the existence of invisible rays, and since he used a rather large opening for the admission of the beam of light to the prism, he also overlooked the numerous dark lines, which cross the solar spectrum and indicate missing waves, so that solar light is really imperfect. In the early part of the nineteenth century, it was discovered beyond the violet and below the red are a long series of waves invisible to human eyes, but having noticeable chemical and physical effects. The work in hand is limited to the study of the chemical action of the rays beyond the violet. It seems that the infra-red field
Nov., I925.]
BOOK R E V I E W S .
701
is generally neglected, possibly because the phenomena to which the rays give rise are not so spectacular or so widely applicable to practical uses. To any one who wishes to learn the information now at hand concerning the nature and effects of the ultra-violet rays, this book can be cordially recommended. A chapter on sources gives many ways in which the rays may be obtained. The important and striking uses, including therapeutics and hygiene, to which the rays have been put, have stimulated inventive talent and several excellent generators are now on the market. They are unfortunately still quite expensive. The most familiar depend on electrical discharges for action. High tension sparks from iron poles and discharges in mercury vapor are two of the most familiar. Inasmuch as the rays are almost all stopped by even very thin layers of ordinary glass, quartz tubes must be used and this adds considerable expense. Uviol glass which passes a considerable proportion of the rays is noted, but the glass lately introduced by the Corning works, which is dark purplish and cuts out almost all visible rays, thus transmitting a nearly pure beam of ultra-violet, seems to be not mentioned. The improvements in the manufacture of quartz glass are progressing encouragingly, and it is to be hoped that before long a complete quartz train for camera and photomicrographie work will be available at reasonable cost. There is a certain amount of ultra-violet light of comparatively long waves emitted from the sky. It is stated in this book that the short waves emitted by the sun are mostly scattered and absorbed before reaching the garth, but the clear blue sky is generally a sufficiently abundant source of the rays as to require the use of yellow screens in taking pictures on Lumi6re plates. Wood showed that many leaves reflect large amounts of infra-red, and later observers have discovered that many flowers reflect notable amounts of ultra-violet that are present in ordinary outdoor light. There is possibly such a difference between these two reflections that the contrast between the flower and leaf is intensified to any insect which is capable of " seeing" the two classes. This book deserves wide circulation. It is to be hoped that some one will take up the burden of writing a similar work on infra-red, thus bringing before the general scientific world the story of the "invisible lights." HEI~'RY LEFF MANLY'.
A SURVEY OF PHYSICS, a collection of lectures and essays. By Max Planck, translated by R. Jones and D. H. Williams. viii-I84 pages, 7 ~ × 5 inches, cloth• New York, E. P. Dutton and Company, no date. Price, $2.4o. There is a small body of celebrated investigators who are at the forefront in the development of modern physical theories. Professor Planck is an outstanding figure among them. His studies in radiation and evolution of the quantum theory are now widely adopted as a satisfactory working hypothesis for certain phenomena for which the laws of Newton and those of Maxwell have proved inadequate. Both on account of a commanding position in a new path in physical science and an otherwise established leadership in the fields of mathematics and physics, his " s u r v e y " will meet with a warm welcome by all who are interested in the fundamentals of the subject. The title plainly states the purport of the work. The volume embraces the collection in chronological order of eight lectures given on several occasions