THE LECTURE ROOM, SMITHSONIAN INSTITUTION. 113 



from the accompanying drawing, ■whicli exhibits a plan of the second 

 story of the main building. In this, G, F, F, represent the rear, and 

 M, M, M, the front towers. The lecture-room is 100 feet in its great- 

 er dimension, 64 feet from I to C, and 88 feet to the extremity of 

 the upper gallery F, F, The curved dotted line represents the 

 front of the gallery, which is in the form of a horse shoe. The dot- 

 ted line in the rear tower represents the extension of the gallery into 

 this space. 



The second illustration exhibits a perspective view of the lecture- 

 room from the west side under the gallery ; and, when viewed along 

 with the ground plan, shows better than any description could do, how 

 well the second requisite has been accomplished : that everv person 

 should have an opportunity of seeing, as well as of hearing distinctly. 



The speaker's platform is placed between two oblique walls. The 

 corners of the room which are cut off by these walls afford recesses 

 for the stairs into the galleries. The opposite corners are also parti- 

 tioned off, so as to afford recesses for the same purpose. The ceiling 

 is twenty-five feet high, and, therefore, within the limit of percepti- 

 bility. It is perfectly smooth and unbroken, with the exception of an 

 oval opening nearly over the speaker's platform, through which light 

 is admitted. The seats are arranged in curves, and were intended to 

 rise in accordance with the panoptic curve, originally proposed by Pro- 

 fessor Bache, which enables each individual to see over the head of the 

 person immediately in front of him. The original form of the room, 

 however, did not allow of this intention being fully realized, and there- 

 fore the rise is a little less than the curve would indicate. 



The walls behind the speaker are composed of lath and plaster, and 

 therefore have a tendency to give a more intense, though less prolong- 

 ed sound than if of solid masonry. They are also arranged for exhib- 

 iting drawings to the best advantage. 



The general appearance of the room is somewhat 'fan-shaped, and 

 the speaker is placed as it were in the mouth of an immense trumpet. 

 The sound directly from his voice, and that from reflection immedi- 

 ately behind him, is thrown forward upon the audience ; and as the 

 difference of distance travelled by the two rays is much within the 

 limit of perceptibility, no confusion is produced by direct and|reflected 

 sound. 



Again, on account of the oblique walls behind the speaker, and 

 the multitude of surfaces, including the gallery, pillars, stair-screens, 

 &c., as well as the audience, directly in front, all reverberation is 

 stopped. 



VOL. III. H 



