THE SMITHSONIAN INSTITUTION. 



15 



with the exception of an oval opening above to admit light on the platform. It 

 thus powerfully reflects the sound of the speaker's voice to the hearers, and being 

 so low, this reflection blends with the original sound and simply re-enforces it. 

 The general form of the room is fan-shaped, the speaker being near the handle 

 of the fan, on one side of the room. The walls behind and near him are smooth 

 lath and plaster, giving a powerful but short resonance, which strengthens 

 his voice. Not being parallel, they reduce the reverberation, but send the sound 

 out from the speaker, to increase the volume of his voice until it reaches the fur- 

 thest part of the gallery. The multitude of surfaces directly in front of the 

 speaker — gallery, pillars, stair-screens, and the seats of the audience — prevent 

 reverberation. The seats are curved, so that each spectator faces the platform ; 

 and the floor is also curved, so that the back seats rise above the front — not 

 quite so much as is required by the panoptic curve of Professor Bache, but as much 

 as the size of the room will allow. The gallery is in the form of a horse-shoe. The 

 architecture of this room is due to Captain Alexander, of the corps of Topo- 

 graphical Engineers, who va- 

 ried the plan until the required 

 conditions were, as nearly as 

 possible, fulfilled. The room 

 will seat fifteen hundred persons^ 

 and when crowded will contain 

 upwards of two thousand. Prof. 

 Henry presented a valuable 

 paper on acoustics to the Ameri- 

 can Association for the Advance- 

 ment of Science, at its meeting 

 in Albany, August, 1856. It 

 gives an account of the princi- 

 jjles on which the Smithsonian 

 lecture-room was constructed, 

 and the result of the observations 

 made by Capt. Meigs, Prof. 

 Bache, and Prof. Henry, in rela- 

 tion to the new rooms in the 

 extension of the Capitol. It 

 was published in the transac- 

 tions of the Association, and 

 in the Smithsonian Report for 

 1856. 



The room in the second story 

 of the south tower is used for the 

 meetings of the* Board of Re- 

 gents. The ofiices of the Secre- 

 BEOENTs' ROOM. tary are in the north tower, im- 



