Supplement to NA T URE of May 21,1938 909 Then why do we have heating For the same same statistical results as the hard plus soft radiation reason that life on the earth needs the radiation of The following result was obtained Out of every the gun.But this does not exist on the incident 100 particles of the hard radiation,41 give no visible energy,for the latter apart from a negligible amount effect.18 tracks were found in section I,21 in II, is re-radiated,just as a man,in spite of continual 22 in III and 23 in IV.Thus the hard radiation absorption of nourishment,maintains a constant gives considerably less secondaries than the hard body-weight. Our conditions of existence require a determinate 2 degree of temperature,and for the maintenance of this there is needed not addition of energy but addition of entropy. As a student, read with advantage a small book by F. Wald entitled "The Mistress of the World and her Shadow" These meant energy and entropy. In the course of advancing knowledge the two seem to me to have exchanged places. In the huge manufactory of natural processes,the principle of en. tropy occupies the position of manager,for it dictates the manner and method of the whole business,whilst the principle of energy merely does the book- keeping, balancing credits and debits. R.EMDEN. Kempterstrasse 5, Zurich. plus soft radiation. Assuming now that the 30 Secondary Effects of the Hard and Soft Components particles without visible secondary effect in the first of Cosmic Rays experiment all belong to the hard component,we shall find,in agreement with experiments,that the Ir has been shown in a previous paperi that the soft component amounts to about 27 per cent of the major part of the electron showers produced in a lead total radiation at the earth's surface. plate are formed by a'cascade process'in accordance In order by these calculations to get a correct with the shower theory proposed by Bhabha and value of this distribution factor,we are furthermore Heitler:and Carlson and Oppenheimer3.Our experi- forced to assume that the quantities of hard particles ments have been made with an automatic cloud being transformed into soft particles in the filter chamber.Four lead plates of 3 cm.thickness are are negligible. On this assumption,we can now placed inside the chamber in a distance of 5 cm.A caleulate the statistical distribution of secondaries cloud chamber divided up in this way offers good for soft rays alone.We will find that practically all opportunity of studying the way in which the the soft rays give visible secondary effects,and as showers are generally produced. distinet from the hard rays the number of secondaries Fig.I shows a typical 'cascade process'. In later increases rapidly from one section to the other in the experiments two counters were used to detect the downwards direction.The number of secondaries passage of the particles through the cloud chamber. stated in this way seems to be in good agreement One was placed above and the other below the with the electron absorption theory of Bhabha and chamber in such a position that any ray passing Heitler. straight through both must also go through the The theory has been proposed that the hard rays chamber and the four lead plates.The intention was are electrons having an energy higher than some to study the production of secondaries when the critical energy above which the quantum absorption primaries pass the lead plates and to make statistical theory is not valid.If this be correct,we shall have investigations of their frequency in the various to assume that the iron filter will decrease the energy sections.Figs.2 and 3 show some track photographs of some of the hard particles and in this way produce made in this way.Secondary,not ionizing,light a new soft radiation component.Our experiments quanta are here seen to have produced ionizing seem,however,to show that this cannot be the case. particles near the main ray. and consequently we shall have to conclude that the A statistical examination of results,obtained with. hard particles cannot be electrons. out screening the chamber,gives the following result As to the secondary effect of the hard rays,it Out of every 100 particles (hard plus soft radiation) might be mentioned that the secondaries most fre- passing the chamber,30 were without visible quently form a branch of the main rays,as shown secondary effect.26 tracks were found in section I, in Fig.4.Secondaries-electron pairs and single 35 in II,44 in III,and 45 in IV,the sections being rays-among which are found strongly ionizing numbered from above.The cloud chamber was then nuclear particles,may,however,also appear at some screened with an iron filter of 33 em.in order to distance from the main ray according to the effects absorb the soft radiation.In this way it was possible shown in Figs.5 and 6.Such cases show that the to ascertain whether the hard radiation gave the hard radiation also may be accompanied occasionally 1938 Nature Publishing Group© 1938 Nature Publishing Group