OF ARTS AND SCIENCES : APRIL 25, 1865. 495 



Five hundred and fiftieth Meeting. 



April 11, 1865. — Monthly Meeting. 



The President in the chair. 



Mr. Alexander Agassiz read a paper on the young of a spe- 

 cies of Planaria. 



Five hundred and fift^-first Meeting. 



April 25, 1865. — Special Meeting. 



The President in the chair. 



Professor Lovering presented a report from the Rumford 

 Committee, recommending that the Rumford Premium be 

 awarded to Professor Daniel Treadwell for improvements in 

 the management of heat, and the subject of the report was 

 assigned as tlie special business of the meeting on the second 

 Tuesday of May. 



Professor Cooke made the following communication : — 



An accident to one of the large turbine wheels employed by the 

 Merrimack Manufacturing Corporation of Lowell has furnished a most 

 remarkable illustration of the modern mechanical theoiy of heat, and 

 through the kindness of Mr. Isaac Hinckley, the accomplished agent of 

 the Corporation, I have the pleasure of bringing tiie facts to the notice 

 of the Academy. I cannot do better than to begin by reading Mr. 

 Hinckley's own statement, in a letter addressed to me, dated December 

 30th, 1864. The specimens referred to in the letter I have placed on 

 the table for the inspection of the Academy. 



" In accordance with your request, I herewith send you five pieces of 

 metal, once portions of one of our turbines. I have placed these pieces 

 in the box in the same relative positions which they occupied when they 

 made a part of the turbine. To make my statement clear to you, I 

 would refer to Plate I. of Mr. Francis's admirable work, ' Lowell Hy- 

 draulic Experiments,' which you will find in the College Library. Our 

 turbines are similar to the Tremont turbine therein shown. 



" The turbine of which these pieces were a part is one of 250 H. P., 

 under a fall of 32 feet, using 75 cub. ft. of water per second. The wheel 

 is of 58^ inches diameter, with depth of float of 6 inches, and a velocify 



