4:>(i Scientific Intelligence. 



was independent of the nature of the particles. From this fact, 

 the conclusion is drawn that the maximum potential difference 

 through which each set of particles had fallen is the same. These 

 rays are called " primary " rays. 



The second type of curve is differentiated by the property of 

 radiating from the point on the negative which is struck by rays 

 which have experienced neither magnetic nor electric deflection. 

 The portions of the curves near this " origin " are straight lines 

 when the magnetic and electric fields are coterminous. If the 

 magnetic field overlaps the electric field on the side nearer the 

 sensitive plate the curves are concave towai'ds the horizontal 

 axis. This fact is interpreted as meaning that the curves repre- 

 sent "secondary" positive rays produced by the passage of pri- 

 mary rays through the gas on the way to the photographic plate, 

 and that the parts of the curve near the origin, which are pro- 

 duced by particles which have suffered only small deflections, 

 were produced by rays which had not traversed the whole of the 

 magnetic and electric fields, but had been generated towards the 

 ends of these fields. On the other hand, curves which are con- 

 cave towards the vertical axis correspond to primary rays which, 

 after passing through the cathode, have lost their charges as 

 they were passing through the electric and magnetic fields. In 

 this case, the parts of the curves near the origin would be due to 

 rays which had lost their charges near the beginning of the elec- 

 tric and magnetic fields. 



For sake of brevity Thomson calls the ratio of mje for any 

 ray to the value of mje for the atom of hydrogen, the " electric 

 atomic weight " of the particle forming the ray. Primary rays 

 in hydrogen were found to have electric atomic weights 1 and 2 ; 

 in oxygen, 16 and 32 ; in carbon dioxide, 12 and 47 ; in marsh 

 gas, 16 and 28 ; in cyanogen, 26 ; etc. 



Many intei*esting and important facts concerning the secondary 

 rays are recorded in the paper, but since an entire page is 

 required for a synoptic table it will not be possible to quote the 

 details in this place. Suffice it to say that the electric atomic 

 weights have the following values : 1, 1*4, 2, 3, 6, 7, 12, 16, 26, 

 36, 48, 72-78, 96, 100, 200 and 800. The last three numbers per- 

 tain to mercury vapor. — Phil. Mag. (6), xxi, 225. h. s. tj. 



5. Focal Isolation of Long Heat - Waves. — Rubens and 

 Wood first tried to take advantage of the selective refraction of 

 quartz in the manner described in 1899 by Rubens and Aschki- 

 nass, which was to employ quartz prisms of small refracting 

 angles in conjunction with a suitable spectrometer. The energy 

 finally emergent in the apparatus was found to be too small a 

 fraction of the incident radiation, and hence the experimenters 

 were led to devise another and more efficient form of apparatus 

 with which they were able to obtain heat waves of greater length 

 than had ever been measured before. 



The source of energy, a Welsbach mantle, was placed in line 

 with a circular aperture in a double screen of tin plate. This 



