and Laboratory Methods. 



2419 



(1) lighting from one side, (2) lighting from both or all sides, (3) lighting from 

 both or all sides without reservation of wall space. Taking the first, it is evi- 

 dent that if the hall is wide the windows should be high and frequent, in order 

 that the opposite wall may be reached. They should, in a hall sixty feet wide, 

 extend almost to the ceiling, and their ratio of aggregate width to the remaining 

 wall space, on the same side, be little or no less than one-half. In narrower 

 halls their height can be diminished, but the ratio of window and wall space 

 should undergo but a slight reduction. The object in view, naturally, is to allow 

 light from the windows to reach perhaps two-thirds of the way to the opposite 

 cases in the middle of the forenoon and in the middle of the afternoon in winter, 

 and so far at noon, taking the summer altitude of the sun, as by reflection from 



Fig. o2. — Mineralogical Hall, Natural History Museum, London. 



the floor, and general diffusion, to fully illuminate them. In this respect, viz., 

 when one side of the hall is pierced with windows, north and south halls are less 

 advantageously conditioned than east and west halls, and of east and west halls 

 it is also obvious that those facing south are better off for light under this con- 

 dition than those facing north, it being understood that the /air side carries the 

 windows. 



The unpleasant effect, if some should so regard it, of having tall windows 

 can be sensibly improved by dividing the window apertures into a long lower 

 section, and a short upper section, with transom-like partition between both. 

 The width and number of windows and their disposition is a subject of choice, 

 but a safe rule is to have few and broad windows, rather than many and narrow 

 windows. Windows should not be less than five feet wide. 



