Roentgen Rays and Phenomena of the Anode and Cathode

Edward P. Thompson

Roentgen Rays and Phenomena of the Anode and Cathode

Published by Good Press, 2022

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EAN 4066338085429

Table of Contents

PREFACE.

INTRODUCTION.

CHAPTER I

CHAPTER II

CHAPTER III

CHAPTER IV

CHAPTER V

CHAPTER VI

CHAPTER VII

CHAPTER VIII

CHAPTER IX

CHAPTER X

CHAPTER XI

CHAPTER XII Miscellaneous Researches on Roentgen Rays.

CHAPTER XIII A few Typical Applications of X-rays in Anatomy, Surgery, Diagnosis, etc.

CHAPTER XIV Theoretical Considerations.

PREFACE.

Table of Contents

In addition to the illustrated feature for exhibiting the nature and practical application of X-rays, and for simplifying the descriptions, the book involves the disclosure of the facts and principles relating to the phenomena occurring between and around charged electrodes, separated by different gaseous media at various pressures. The specific aim is the treatment of the radiant energy developed within and from a discharge tube, the only source of X-rays.

Having always admired the plan adopted by German investigators in publishing accounts of their experiments by means of numbered paragraphs containing cross-references and sketches, the author has likewise treated the investigations of a large number of physicists. The cross-references are indicated by the section sign (§). By reference, the analogy, contrast, or suggestiveness may be meditated upon. All knowledge of modern physics is based upon experiments as the original source. Inasmuch as many years may be expected to elapse before the innumerable peculiarities of the electrical discharge will be reduced to a pure science, and also in order that the contents of the book may be of value in the future as well as at present, the characteristic experiments of electricians and scientists are described, in general, by reference to their object, the apparatus used, the result, the inferences of the experimenter, and the observations of cotemporaneous or later physicists, together with a presentation here and there of theoretical matters and allusion to practical applications.

The classes of reader to which the book is adapted may best be known, of course, after perusal, but some advance intimation of the kind that the author had in view may be desired. Let it be known that, first, the student and those generally interested in science ought to be able to comprehend the subject-matter, because experiments are described, which are always the simplest means (e.g., in a popular lecture) for explaining the wonders of any given scientific principles or facts. Thus did Crookes, Tyndall, Thomson (both Kelvin and J. J.), Hertz, etc., disseminate knowledge—by describing their researches and reasoning thereon.

In view of the tremendous amount of experimenting which has been carried on during the past few years in connection with the electric discharge, it was difficult to determine just how far back to begin (without starting at the very beginning), so that the student and general reader, whose object is to become acquainted especially with the properties of cathode and X-rays, might better understand them. The author realized that it was necessary to go back further and further in this department of science, and he could not easily stop until he had reached certain investigations of Faraday, Davy, Page, and others, which are briefly noticed in an introductory sense. Take, for example, the inaction of the magnet upon X-rays in open air. § 79. Of course, it would be of interest for the student to know about Lenard’s investigations relating to the action of the magnet upon cathode rays inside of the observing tube. § 72a. It would follow, further, that he would desire to know about Crookes’ experiment relating to the attraction of the magnet upon cathode rays within the tube. § 59. In order that he might not infer that Crookes was the first to investigate the action of the magnet upon the discharge, it was evident that the book could be made of greater value by relating the experiments of Prof. J. J. Thomson as to the discharge across and along the lines of magnetic force, § 31, and Plücker’s experiment on the action of the magnet upon the cathode column of light. § 30. The interest became increased, instead of diminished, by noting De la Rive’s experiment on the rotation of the luminous effect of the discharge by means of the magnet. § 29. Being now quite impossible to stop, Davy’s electric arc and magnetic action upon the same had to be alluded to, at least briefly. § 28. On the other hand, the very earliest experiments with the discharge in rarefied air are not described—occurring as remotely as the eighteenth century—so ably treated of in Park Benjamin’s work. Those facts that have some mutual bearing are brought forward to serve as stepping-stones to the investigation of cathode and X-rays.

Secondly, the author often imagined that he was writing in behalf of the surgeon and physician and those who intend to experiment, especially when he found in his investigations of recent publications descriptions in detail of the electrical apparatus employed in experimenting with X-rays. He improved the opportunity of repeating the statements of the difficulties, and how they were overcome; also, the precautions necessary to be taken, and, besides, the kind of discharge tubes and apparatus best adapted for particular kinds of experiments. The chapter on applications in diagnosis and anatomy, etc., is of especial interest to physicians.

Thirdly, as the discovery of the Roentgen rays has established a new department of photography, those who are interested in this art may be benefited by the results and suggestions disclosed in connection with photographic plates, time of exposure, adjuncts for best results, precautions for obtaining sharp shadows, and steps of the process, from beginning to end, for carrying on the operation.

Fourthly, expert physicists and electricians, professors, etc., need something that the above classes do not, and this is the reason why the author has not assumed the burden of carrying any line of thought or theory from the beginning to the end of the treatise, nor has he made the book in any way a personal matter by criticising experiments, nor even by favoring the views of one over the other, unless it is in an exceptional case here and there; but in each instance the investigator’s name is given, and that of the publication in which the account may be found, so that the scientist may refer thereto to test the correctness of the author’s version of the matter, or to learn the nature of the minute details and circumstances.

The author suggests that the study of the phenomena of the discharge tube would not be amiss in scientific schools and colleges. He argues that in view of all experimenters in this line having been made enthusiastic and fascinated by reason of (1) the beautiful effects, (2) the field being always open to new discoveries, (3) the direct practical and theoretical bearing of the peculiar actions upon other departments of electricity, light, heat, and magnetism, (4) the pleasure in attempting to obtain results reported by others, and especially the large amount of valuable theoretical and practical instruction resulting therefrom, by repeating the experiments or studying them, and (5) the possible applications of the discharge tube in connection with electric lighting and in the new department of sciagraphy by X-rays, and for other good and valuable considerations—it follows that students who have been through or who are studying a text-book of physics and electricity would be greatly benefited by a course in the discharge-tube phenomena.

In view of the large amount of dictation necessary in order to complete the work in such a short period, and in order that the subject-matter might involve the treatment of the latest work of the French and German as well as of the English and American, and inasmuch as the journals of the latter did not always contain complete translations and, for better service in behalf of the readers, the authorship was shared with others, and, therefore, much credit is due to Prof. Anthony for final chapter, to Mr. Louis M. Pignolet for assistance in connection with French periodicals and academy papers (§ § 63a, 84, 99, 101a, 103a, 112a, 124a, 128, at end, 139a, 154, 155, 156, 157, 158, and 159); to Mr. N. D. C. Hodges, formerly editor and proprietor of Science, who obtained some pertinent accounts, (§ 97a, 97b, 99A, B, C, D, to 99T, inclusive) by investigations of recent literature at the Astor Library, New York; and also to Mr. Ludwig Gutmann (Member American Institute of Electrical Engineers) for a few translations from the German.

Credit is given in each instance to all societies and publications by naming them in the respective paragraphs herein. In nearly every case the author prepared his material from original articles and papers contributed by the investigators to the societies or periodicals.

The author has prepared himself to withstand, with about half as much patience as he expects will be required, all criticisms based upon disappointments which may be experienced by the true, or the alleged true, first discoverer of any particular property of the electric discharge not duly credited. He has been particular in presenting knowledge as to physical facts and principles, but not equally, perhaps, as to the originator of the experiment, or as to the actual first discoverer, for the simple reason that the book is in no sense a history not a biography. Where the paragraph has been headed, for example, Swinton’s Experiment, it means that that party (according to the article purporting to be written by him) made that experiment. Some one else may have made exactly the same experiment previously, yet the instruction is equally as valuable as though the researches of the first discoverer had been related. On the other hand, the author has never had any intention of giving credit to the wrong party. The dates in the captions indicate the general chronological order in behalf of those thus interested. With this explanation, it is thought that the claimants will be much more lenient in their criticisms concerning priority of discovery. While the developments have generally followed each other historically, as well as appropriately for the purpose of instruction, yet now and then it was preferable to place the description of a comparatively recent experiment in conjunction with some description of an experiment made at a much earlier date. For this reason, also, the book is not of a chronological nature. The subject-matter, as usual, is divided into chapters, but the sections are to be considered as subordinate chapters, having different shades of meaning, and the one not necessarily bearing a direct relation to the contents of its neighbor, but as, in a novel or a treatise on geometry, having its important part to play in conjunction with some later or preceding section.

Edward P. Thompson.

Temple Court Building, New York,

August, 1896.

CHAPTER XI.

CHAPTER XII.

Total number of sections to this place, 199.

CHAPTER XIII.

CHAPTER XIV.

INTRODUCTION.

Table of Contents

The new form of energy, for which there are two names—to wit, the Roentgen ray and the X-ray—is radiated from a highly exhausted discharge tube, which may be energized by an induction coil or other suitable electrical apparatus, such as a Holtz or a Wimshurst electrical machine. § 106. The principle underlying the construction of the usual induction (or Ruhmkorff) coil is disclosed in the subject-matter of § § 1, 2, and 3, and is represented in diagram in Figs. 1 and 2 on page 17. It would be well for the amateur or general scientific reader to study these sections carefully, for then he will have all the knowledge that is necessary for understanding the apparatus by which the discharge tube is energized. Of course, he will not comprehend the various mechanical details, nor the many electrical and mathematical relations existing in connection with an induction coil, but he will gain sufficient knowledge to appreciate what is intended when such a device is referred to here and there throughout the book. Since the time of Faraday, Page, and Fizeau induction coils of very large dimensions have been constructed, but none of them probably ever exceeded that built by Spottiswoode, during or about 1875, which was so powerful as to produce between the two electric terminals, in open air, a spark of 42 in. in the secondary current with only 30 small galvanic cells of the Grove type in the primary circuit. The cells are seldom used in this connection at the present time, the same being replaced by the dynamo, and the current being conveniently obtained from the regular incandescent-lamp circuit which may be found in almost any city. Those, therefore, who intend to become better acquainted with the details of the electrical apparatus should study in conjunction with this book some elementary treatise relating particularly to dynamos and electric currents.

The essential element in connection with the generation of X-rays is not the coil nor the dynamo, but the electric discharge, especially when occurring within a rarefied atmosphere, provided within a glass bulb, called the discharge tube throughout the book, but which has usually been called by different names, for example, the receiver of an air pump, or a Geissler tube, when the air is not very highly exhausted, or a Crookes tube (see picture at § 123) when the vacuum is definitely much higher by way of contrast. It has also been called a Hittorff tube, the Lenard tube, and by several other names, according to its peculiar characteristics.

Fig. 1.—Head.

Fig. 2.—Broken Arm, Overlapping.

(Due to defective setting.)

Fig. 3.—Ribs.

Fig. 4.—Knee, Knickerbocker Buttons, Bullet in Femur.

FROM SCIAGRAPHS BY PROF. DAYTON C. MILLER. § 204.

For those who are not acquainted with the nature of the electric charge and discharge, nor with the peculiar and exceedingly interesting phenomena which various investigators have discovered from time to time, nor with the variety of effects according to the nature and the pressure of the atmosphere within the glass bulb, it is exceedingly difficult to understand with any degree of satisfaction the properties, principles, laws, theories, and manner of application of cathode and X-rays. Consequently, the greater part of the book treats of the electric charge and discharge in conjunction with certain kindred phenomena. Primarily, the meaning of the electric discharge may be derived by referring to Fig. 2, page 17, where there is shown an electric spark, indicated by radial lines between the terminals of a fine wire forming the long and fine coil or secondary circuit. Imagine that the wires are at great distances apart. Let them be brought closer and closer together. By suitable tests it will be found, for example, that no current passes through the wire, but when the points are brought sufficiently close together a spark will occur between the two terminals. § 2. Sometimes instead of what is understood as a spark, a brush or glow takes place (§ § 10 and 11), and in fact a numerous variety of effects occur, a general name for all being conveniently termed an electric discharge. Even if no sudden discharge takes place, yet, as when the terminals are far apart, there may be a charge or a tendency, or, as it is technically called, a difference of potential, between the two electrodes, one of which is the cathode and the other the anode. This is comparable to a weight upon one’s hand, tending continually to fall, and always exerting a pressure, and it will fall when the hand is suddenly removed. This is in the nature more of an analogy than of an exact correspondence. A discharge through open air, while adapted to produce a great many curious as well as useful effects, does not act as a generator of X-rays. § 136. Another class of phenomena is obtainable by exhausting the air to a certain extent from a discharge tube, thereby obtaining what is usually called a low vacuum. Such bulbs have been called Geissler tubes. Neither can X-rays be generated therefrom to any practicable extent, but only feebly if at all. § 118. Hittorff, Varley (§ 61a), Crookes (§ § 53 to 61, inclusive), were the first to discover and study the different phenomena that are obtained by diminishing the pressure within the discharge tube to a decrement of several thousand millionths of an atmosphere. This will explain why so many allusions have been made to the Crookes tube, for when