145 
then passed on to make some remarks on the Pleiads men- 
tioned by the Greek Poets sometimes as six, sometimes as seven, 
and concluded that the uncertainty of the number was due to 
the above fact. 
Professor KENNEDY made some TeTLEILE on the derivations 
of the name Pleiad. 
Professor CHALLIS thought that one of the stars might be 
a variable one. 
Mr Porrer made a few remarks on ihe appearances pre- 
sented by the blood vessels in the eye. 
Professor MILLER said these could well be seen on waking 
suddenly. 
Mr TROTTER mentioned that, as shewn by some experiments 
lately made at Heidelberg, the focus centralis took a longer 
time to receive the impression of objects, but retained it longer. 
Dr Pacer thought the matter required further experiments, 
and mentioned ways in which it would be desirable to test it. 
Some further conversation occurred, in which the MASTER 
oF Trinity, Mr W. C. Green, and the above took part. 
(2) On new and general Equations for the Equilibrium 
of Flexible Surfaces. By Ricuarp Porrsr, A.M. 
[ Abstract. ] 
In a paper on the “curve linteariz” of John Bernoulli which 
the author read in May 1868 before the Society, he stated 
that he believed the equations which Poisson had investigated 
in his “Mémoire sur les surfaces élastiques” read before the 
French Institute on the Ist August 1814, might be brought to 
comprehend all the ordinary cases to which we wish to apply 
them, by restoring a factor which M. Poisson had struck out. 
Soon after reading the paper he came to a different conclusion, 
and undertook to investigate the equations for the equilibrium 
of flexible surfaces, from mechanical rather than mathematical 
