OF ARTS AND SCIENCES. 427 



Eight hundred and tvrenty-first Meeting. 



April 10, 1889. — jMoxthly Meeting. 



The President in the chair. 



Letters were read from Messrs. Bradford, Cheever, Ernst, 

 Fitz, Knight, Lyman, Peabody, Schwamb, Stephenson, and 

 "Wendell, accepting Fellowship in the Academy ; also, from 

 Messrs. Johnston and Stockwell, acknowledging their elec- 

 tion as Associate Fellows. 



The President, having stated that the special business of 

 the meeting was the presentation of the Rumford Medals, 

 made the address printed among the papers of this volume, 

 on the numerous investigations which had been made on the 

 velocity of light, and their relation to the theories of optics 

 and delicate questions in astronomy. He then addressed 

 Professor Michelson in these words : — 



Professor Michelson, — It is now my duty and privilege to pre- 

 sent to you, in the name of the Academy and in the presence of these 

 members, here assembled to administer Count Rumford's Trust, the 

 gold and silver medals which together constitute the Rumford Pre- 

 mium. Be pleased to receive with these medals my congratulations, 

 and those of all the other members of the Academy, for the intelU- 

 gence, ingenuity, and perseverance with which you have labored to- 

 wards the solution of problems of the greatest concern to more than 

 one of the physical sciences. 



Professor Michelson, having received the medals, made the 

 following reply: — 



Mr. President and Gentlemen of the Academy, — I wish 

 to thank you sincerely, and to express my appreciation of the high 

 honor you have just conferred upon me. These medals I shall always 

 regard as a token of your encouragement and approval ; but in addi- 

 tion they will, I trust, be a strong incentive for the future to do the 

 best that is in me to justify this expression of your kind ai^preciation. 



The following paper was presented by title : — 

 Classification of the Atomic Weights in two Ascending 



Series, corresponding to the Groups of Artiads and Perissads. 



By W. R. Liverraore. 



