Polytechnic Association. 727 



theories of steam boiler explosion, replacing vague conjecture and 

 crude hypothesis with exact experimental facts, and, by thus narrow- 

 ing the field for the search of truth, has made its discovery more 

 probable. 



All of which, together with drawings of the boilers experimented 

 with, are respectfully submitted by, sir, 



Your obedient servants, 



B. F. Isheewood, 



E. S. De Luce, 



Sidney Albert, 



Chief Engineers U. S. Wavy. 

 Hon. George M. Robeson, 



Secretary of the Navy. 



To the conclusions contained in this report, Prof. Thurston added, 

 9. That a boiler may explode at a pressure lower than the hydro- 

 static test to which it has been subjected. 



Adjourned. 



December 22, 1871. 



Prof. S. D. Tillman in the chair ; Robert Weir, Secretary. 

 The President read the following scientific notes : 



I. A Solar Explosion. 

 Prof. Young, of Dartmouth College, on the 7th of September last, 

 at 12.30 p. m., was examining, by means of his spectroscope, an enor- 

 mous flame or hydrogen cloud, on the eastern border of the sun, 

 about 100,000 miles long and 54,000 miles high, its lower surface 

 being at least 15,000 miles above the visible border of the sun to 

 which it was connected by three or four bright columns. Such was 

 its appearance when he left the telescope. On returning, within half 

 an hour, he was surprised to find this vast projection had been lite- 

 rally blown to shreds by some inconceivable force from beneath. In 

 place of the quiet cloud, the air, to use his expression, was filled with 

 flying debris — a mass of detached, vertical, fusiform filaments, which 

 continued to rise with a motion almost imperceptible until the upper- 

 most were more than 200,000 miles above the solar surface. As they 

 rose they gradually faded away like a dissolving cloud, and at 1.15 p. m. 

 only a few filmy wisps, with some lighter streamers low down near 

 the chromosphere, remained. In reference to the supposed disturb- 



