11-1 PROCEEDINGS OF THE AMERICAN ACADEMY 



Explanation of Lettering. 



a, anus. f brachiolar arms. 



0, oesophagus. /", odd brachiolar arm. 



m, mouth. /', branch of water-tube leading 



d, digestive cavity. /'", surface warts of/". [into /. 



c, alimentary canal. s, actinal region. 



w, water-tube. [body, r, abactinal region. 



iv', water-tube leading to madreporic t, tentacles. 



w w\ point of junction of m; and to. t\ odd terminal tentacle of star-fish. 



ft, madreporic body or suture of the e, eye of star-fish. 



arms. [laria. v, vibratile chord, anal part. * 



e', e", e'", e"", e*, e*, arms of Brachio- v\ oral portion of vibratile chord. 



Professor Peirce and Mr. Winlock made a communication 

 upon the remarkable auroral arch seen on Thursday evening, 

 the 9th instant. 



Professor Lovering made the following communication 



On the Velocity of Lights and the Sun^s Distance. 



Foucault's recent experiment on the velocity of light, though of 

 a less popular character than his celebrated pendulum-experiment to 

 prove the earth's rotation, will, nevertheless, attract even more attention 

 among men of science. If its results are placed beyond doubt, they 

 vpill affect Astronomy to a degree not possible for the pendulum-experi- 

 ment, unless it had come as early as the time of Galileo. I shall exam- 

 ine Foucault's investigation on the velocity of light : 1st, as it influences 

 the science of Optics ; and 2d, as it tells upon one at least of the vexed 

 questions in Astronomy. 



In the circle of the sciences the centre may be placed anywhere, and 

 the circumference will be everywhere ; such is the natural dependence 

 of each upon all the rest. The child even may become father of the 

 man. After the science of Optics had furnished Astronomy with the 

 telescope, the astronomer discovers with it the satellites of Jupiter and 

 the aberration of light, and with the help of these phenomena assigns 

 the value of the velocity of light, and thus repays to Optics the debt 

 incurred by his own special science. Now for the first time the sci- 

 ence of Optics has relinquished the guardianship of Astronomy ; ascer- 

 tained by direct experiment one of its own fundamental data, and 

 thereby, possibly, put Astronomy under a new obligation, to be can- 

 celled doubtless, with interest, hereafter. 



