jj-thompson the corpuscular theory of matter

THE CORPUSCULAR THEORY OF MATTER J. J. THOMSON, M.A. F.R.S. D.Sc. LL.D. Ph.D. PROFESSOR OF EXPERIMENTAL PHYSICS, CAMBRIDGE, AND PROFESSOR OF NATURAL PHILOSOPHY AT THE ROYAL INSTITUTION, LONDON. LONDON ARCHIBALD CONSTABLE & CO. LTD. 10 ORANGE STREET LEICESTER SQUARE W.C. 1907 3) %^^l^ 3f BRADBURY, AftNEW, & CO. LD.^PRINTERS, LONDON AND TONBRIDGK. PREFACE This book is an expansion of a course of lectures given at the Eoyal Institution in the Spring of 1906. It contains a description of the properties of corpuscles and their application to the explanation of some physical phenomena. In the earlier chapters a considerable amount of attention is devoted to the consideration of the theory that many o' the properties of metals are due to the motion of corpuscles diffused throughout the metal. This theory has received strong support from the investigations of Drude and Lorentz ; the former has shown that the theory gives an approximately correct value for the ratio of the thermal and electrical conductivities of pure metals and the latter that it accounts for the long-wave radiation from hot bodies. I give reasons for thinking that the theory in its usual form requires the presence of so many corpuscles that their specific heat would exceed the actual specific heat of the metal. I have proposed a modification of the theory which is not open to this objection and which makes the ratio of the conductivities and the long-wave radiation of the right magnitude. The later chapters contain a discussion of the properties of an atom built up of corpuscles and of positive electricity, the positive electricity being supposed to occupy a much larger volume than the corpuscles. The properties of an atom of this kind are shown to resemble in many respects those of the atoms of the chemical elements. I think that a theory which enables us to picture a kind of model atom and to interpret chemical and physical results in terms of vi PEEFACE. such model may be useful even though the models are crude, for if we picture to ourselves how the model atom, must be behaving in some particular physical or chemical process, we not only gain a very vivid conception of the process, but also often suggestions that the process under consideration must be connected with other processes, and thus further investigations are promoted by this method ; it also has the advantage of emphasising the unity of chemical and electrical action. In Chapter VII. I give reasons for thinking that the number of corpuscles in an atom of an element is not greatly in excess of the atomic weight of the element, thus in particular that the number of corpuscles in an atom of hydrogen is not large. Some writers seem to think that this makes the conception of the model atom more difficult. I am unable to follow this view ; it seems to me to make the conception easier, since it makes the number of possible atoms much more nearly equal to the number of the chemical elements. It has, however, an important bearing on our conception of the origin of the mass of the atom, as if the number of corpuscles in the atom is of the same order as the atomic weight we cannot regard the mass of an atom as mainly or even appreciably due to the mass of the corpuscles. I am indebted to Mr. G. W. C. Kave for assisting in revising the proof sheets. J. J. Thomson. Cambridge, July 1 5, 1907. CONTENTS I. Introduction — Coepuscles in Vacuum Tubes . . 1 II. The Origin of the Mass of the Corpuscle . . 28 III. Properties of a Corpuscle 43 IV. Corpuscular Theory of Metallic Conduction . 49 V. The Second Theory of Electrical Conduction . 86 VI. The Arbangement of Corpuscles in the Atoii . 103 VII. On the Number of Corpuscles in an Atom . . 142 INDEX 169 [...]... the methods described in connection with the cathode rays to determine the value of e/vi for the particles in the canalstrahlen The contrast between the results obtained for the two rays is very interesting In the case of the cathode rays the velocity of different rays in the same tube may be these rays is independent different, but the value of e/m for of the velocity as well as of the nature of the. .. deposited in the form of a number of small drops all of the same size thus the number of drops will be the volume of for ; the water deposited divided by the volume of one of the Hence, if we find the volume of one of the drops drops we can find the number the charged particles If which are formed round of drops the particles are not too numerous, each will have a drop round it, and we can thus find the number... weight of the element a multiple, and not a large one, of the atomic weight of the element If this result is right, there cannot be a large number of corpuscles and therefore of units of positive it is an atom of hydrogen, and as the mass of a very small compared with that of an atom of hydrogen, it follows that only a small fraction of the mass of the atom can be due to the corpuscle The bulk of the mass... 10* one of these bands the maximum FIG 10 is 10*, while for the other it is 5 X 10^ In helium we also get two bands as in Fig 11, but while the maximum value of e/m in one of these bands is 10*, the same as for the corresponding band in hydrogen, the value of e/m maximum We see value of from e/ni in the other band this that the ratio of the is masses only 2'5 X 10^ of the carriers FIG 11 in the two... effect of the water if we supposed the mass of the sphere to be increased in the way indicated If we suppose the lines of electric force proceeding from the charged body to set the ether in motion and assume the ether has mass, then the origin of the increase of mass arising from electrification would be very The increase in analogous to the case just considered when + M+ mass due the intrease in the. .. presence of the radium hardly increases the small amount of cloud I now discharge the — THE COEPUSCULAE THEOEY OP MATTEE 14 and on making the expansion the clond plates, is so dense as to be quite opaque We can use the drops to find the charge on the particles, when we know the travel of the piston we can deduce the amount of supersaturation, and hence the amount of water deposited when the cloud forms The. .. determinations of the made by this method are very interesting, that however the cathode rays are values of ejm it is found produced we always for same value of ejm for all the particles in the may, for example, by altering the shape of the discharge tube and the pressure of the gas in the tube, pro- get the rays We duce great changes in the velocity of the particles, but unless the velocity of the jparticles... that it is of quite a different order of magnitude Before the cathode rays were investigated the charged atom of hydrogen met with in the electrolysis of liquids was the system which had the greatest known value for ejm, and in this case the value is only 10*; hence for the also of the kind of gas in the tube ; corpuscle in the cathode rays the value of e/in is 1,700 times the value of the corresponding... one of the bricks of which atoms ever it is found it ; are built up Magnitude of the Electric Charge carried by the Corpuscle I shall now return to the proof that the very large value compared with that for the atom of hydrogen is due to the smahness of m the mass, and not We can do this by to the greatness of e the charge actually measuring the value of e, availing ourselves for this purpose of a... storage cells The until there , pressure in the tube is very low You will notice that the rays are very considerably deflected when I connect the plates with the poles of the battery, and that the direction 6 THE COEPUSCULAE THEOEY OF MATTEE of the deflection shows that the rays are negatively charged We can also show the effect of magnetic and electric force on these rays if we avail ourselves of the discovery . of the same size ; thus the number of drops will be the volume of the water deposited divided by the volume of one of the drops. Hence, if we find the volume of one of the drops we can find the number. Arbangement of Corpuscles in the Atoii . 103 VII. On the Number of Corpuscles in an Atom . . 142 INDEX 169