10 COXSTRUCTIOX OF NEW READING-ROOM, &C. 



between the external covering and brick vaulting, the object 

 b«ing tbe 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 passing through outlets provided around the lantern. 

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

 lights, lanterns, and windows throughout the building are 

 double. The quantity of glass used amounts to about 

 60,000 superficial 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 has been carried 

 up outside perpendicular to such a height above the spring 

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

 with proper outlets, by which the snow is intercei)ted. 



** This Eeading-room contains ample and comfortable ac- 

 commodation for 300 readers. Each person will have allotted 

 to him a space of 4 feet 3 inches long. He is screened from 

 the opposite occupant by a longitudinal division, which is 

 fitted with a hiaged desk gi-aduated on sloping racks, and a 

 ; folding shelf for spare books. In the space between the 

 I 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 

 j common care. 



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

 t tributing channels, which are contrived so that tlie air may 

 ' be delivered at the top of the longitudinal sci-een division, 

 I 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 o/ valves. A tubular footrail also 

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

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

 I as a footwarmer if required. 



