200 ANNUAL REPORT SMITHSONIAN INSTITUTION, 19 3 5 



What can they tell us of the conditions in other parts of the uni- 

 verse, both at their place of origin and in the interstellar spaces 

 they traverse? What are the effects of their bombardment on our 

 own planet? Many problems present themselves for investigation. 

 The field is a new one to science and, like Aladdin, we wonder what 

 new mysteries are about to be revealed. One must not be impatient, 

 for the revelation is slow and involves many difficulties. Some 

 progress, however, has already been made, particularly in regard 

 to the problem of the nature of the radiation. 



To understand what cosmic rays are, involves knowledge of their 

 electrical charges, their masses, and their energies. These are the 

 quantities which play the significant roles in determining the be- 

 havior of a ray. Are the rays electrically neutral or are they 

 charged? If charged, are they positive or negative, and how much 

 charge do they carry? How much inertia do the rays possess and 

 do their masses correspond with any known particles? How much 

 matter would have to be converted into energy in their production, 

 or through what differences of electric potential would the rays 

 have to fall to gain their energies? The questions are not only 

 interesting in themselves, but their answers will be helpful clues 

 in tracing down the places and processes of origination. 



5. METHODS FOR ANALYSIS OF THE COSMIC RADIATION 



With the technique in hand for detecting cosmic rays and measur- 

 ing their intensity, methods of analysis have developed. For many 

 years after their discovery the cosmic rays were commonly sup- 

 posed to be photons, similar in character to the X-rays, the gamma 

 rays, or the light rays. Experience had shown that rays of this 

 type were more penetrating than corpuscular rays of equal energy 

 and it was natural to assume that the extremely penetratmg cosmic 

 rays were also photons. Even on this assumption it was necessary 

 to postulate energies far in excess of anything known, to account 

 for their great depths of penetration through matter. 



A more discriminating method for the analysis of radiation than 

 that of the studies of penetrations consists in determining the deflec- 

 tion when the rays are passed through a magnetic field. If the ray 

 carries an electric charge it constitutes an electric current and is 

 subject to the same kind of force as is exerted on the wires of the 

 armature of an electric motor. Under the action of this force 

 charged rays may be bent into circular paths, the direction of curva- 

 ture depending upon the sign of charge. Positive rays are curved 

 oppositely to negative rays, and neutral rays pass through unde- 

 flected. Moreover, the radius of curvature determines the resistance 



