10 CPXSTRUCTION OF NEW READING-ROOM, &C. 



between the external covering and brick vaulting, the object 

 being the equalization of temperature during extremes of 

 heat and cold out of doors; the other chamber, between the 

 brick vaulting and the internal visible surface, being intended 

 to carry off the vitiated air from the Reading-room. This 

 ventilation is effected through apertures in the soffites of the 

 windows, and partly by others at the top of the dome ; the 

 bad air passmg through outlets provided around the lantern. 

 In order to obviate the effects of condensation, all tlie sky- 

 lights, lanterns, and windows throughout the building are 

 double. The quantity of glass used amounts to about 

 60,0U0 supcrticial feet. In order to guard against the con- 

 sequences of an avalanche of snow falling from the dome on 

 to the surrounding libraries, the building h;us been carried 

 up outside perpendicular to such a height above the spnng 

 of the arch as to form a gallery nine feet in width, provided 

 with proper outlets, by which the snow is intercepted. 



" This Reading-room contains ample and comfortable ac- 

 commodation for .'5oO readers. Each person will have allotted 

 to him a space of 4 feet .'5 inclies long. He is screened from 

 the opposite occupant by a longitudinal division, which is 

 fitted with a hinged desk graduated on sloping racks, and a 

 folding shelf for spare books. In the space between the 

 two, which is recessed, an inkstand is fixed, having suitable 

 penholders. Thus the whole table-top is free from writing 

 implements or other embarrassments, and every precaution 

 is taken to preserve the books if the readers will but use 

 common care. 



" The framework of each table is of iron, forming air-dis- 

 tributing channels, which are contrived so that the air may 

 be delivered at the top of the longitudinal screen division, 

 above the level of the heads of the readers, or, if desired, 

 only at each end pedestal of the tables, all the outlets 

 being under the control of valves. A tubular footrail also 

 passes from end to end of each table, which may have a 

 current of warm water through it at pleasure, and be used 

 as a footwarmer if required. 



