1917.] The Fourth Indian Science Congress. clxix 



On the Theory of the Periodic and Cyclical Vibrations of 



Bowed Strings. — By C. V. Raman. 



The author has found that, in a considerable variety of cases, the 

 motion of a bowed string instead of being periodic, becomes cyclical in 

 character. Some photographic records illustrating this fact will be shown 

 as Ian tern- slides, and the theory of these cases will be discussed in the 

 light of the corresponding theory for the periodic forms of vibration. 



On Discontinuous Wave-Motion. — By C. V. Raman and 



Ashutosh Dey. 



Continuing the investigations described in the Phil. Mag. for Jan. '10 

 jointly by C. V. Raman and S. Appaswami Aiyar, it has been found 

 possible by the authors to obtain, experimentally, wave forms containing 

 two equal or unequal discontinuities, of the same sign or opposite signs, 

 in each period. The resulting vibration forms are found to be of consider- 

 able interest in acoustics. 



The Cause of the Abnormal Displacements in the Sun's 



Spectrum. — By T. Royds. 



Difference of vapour density in the sun and arc has been suggested 

 to account for the abnormal displacement of certain lines in t ie sun' 

 spectrum, and though no objections have been raised against this hypo- 

 thesis, attempts at direct experimental proof have failed. 



Types of Electric Discharge.— By D. N. Mallik and A. B. 



Das. 



In this paper, the authors use vacuum tubes of ordinary pattern 

 (electrodes consisting of thin rods of aluminum) and show, that the dis- 

 charge passes through the various stages previously obtained with a De 

 La Rive tube, * showery,' ' band,' and ' glow,' so far confirming the 

 theory worked out in their former papers on the subject. In accordance 

 with that theory it is during the second stage that the discharge should 

 behave like a flexible wire carrying current. This is verified by experi- 

 ment. When the discharge is striatory, the effect of the magnetic field 

 due to a rectangular coil of wire with two of its sides parallel to the 

 electrodes and carrying current has been studied. This is likely to lead 

 to a theory of striatory discharge, on which the authors are now engaged. 

 The effect of the length of a discharge tube on the change in the types 

 of discharge is most marked. But anything like a complete explanation 

 of it is impracticable at present. 



The Cathode fall from different metallic Cathodes.— By H. E. 



Watson 



which was given at the last 



This work, a preliminary account of which was given at the last 

 Science Congress, has been continued. A large number of detailed ob- 

 servations have been made with regard to the conditions under which the 

 cathode fall is the same as the total potential across the tube 



The cathode fall has been measured in differ ent ga^ t^ atout ; d 

 metals, and it has been found that for most of these it is almost constant 

 within the limit of experimental error. A few metals, however, are ab- 



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normal, and these are separately discussed. 



