TRANSACTIONS OF SECTION A. 593 



WEDNESDAY, AUGUST 15. 



The following Papers were read : — 



1. On the Displacements of the JHotational Axis of the Earth. ^^ Professor 

 W. FoRSTER. — This Paper was ordered by the General Committee to 

 be printed in extenso. See Reports, p. 476. 



2. A Lecture-room Experiment to illustrate Babinet's Principle. By Pro- 

 fessor A. CoRNU, F.B.S. — This Paper was ordered by the General Com- 

 mittee to be printed in extenso. See Reports, p. 480. 



3. A New Explanation of the Wave-movements of a Stretched String. 



By Wm. Barlow. 



The writer begins by setting out the commonly received explanation which 

 attributes to the string when disturbed the properties of a cord slipping through a 

 bent tube at a velocity such as to make the pressure on the tube arising from the 

 centrifugal force just balance the pressure caused by the tension.' 



He then argues that this course involves the fallacy that a wave-movement is 

 supposed to take place spontaneously in the disturbed cord, whereas all that the 

 argument offered proves is that if a wave is set up and travels at a certain rate in a 

 given direction, it toill have a constant form. 



He further shows that the conditions laid down do not suffice to determine the 

 direction of the wave ; that the direction is perfectly arbitrary. 



He then suggests another explanation of the wave-movements in question. 



This is based on the observed behaviour of a highly elastic cord, and he attri- 

 buted the wave-movement to the successive orientation of segments of the stretched 

 string caused by a difference of tension due to inertia, the spot at which the 

 difference makes itself felt travelling along the string, now in one direction, now 

 in the opposite, as the string swings from side to side of its normal position. 



6. On Lunar Curves of Mean Temperature at Greenwich, and the 

 Heat of the Moon. By J. Park Harrison. 



The great heat experienced in 1893 led the author to tabulate the mean tem- 

 peratures of the day at Greenwich for that year, according to the age of the pioon, 

 to see how far a curve derived from ihem corresponded with the model curve for 

 618 lunations, which was exhibited by him on the last occasion when the British 

 Association visited Oxford. Whilst closely following the curve alluded to, the 

 maximum temperature showed itself two days earlier in the lunation ; but the 

 same abrupt fall in temperature occurred immediately after the first quarter, and 

 continued below the average of the year from that period until the second day after 

 last quarter. The difference between the maximum on the fourth day of the lunation 

 and the minimum on the day of full moon was 6^ Fahr. for twelve complete 

 lunations. 



> See Art. ' Wave,' Enc. Brit., p. 416. 



1894. Q Q 



