2122 Journal of Applied Microscopy 



mination is concerned, if it were not tiiat it is carried out on a single level 

 with clear-story windows, which contributes also skylight to the general 

 illumination. 



Even under the circumstances given, the illumination of the National Museum 

 is not wholly satisfactory, in fact at points is very poor. The limits of time in 

 which there is good lighting are shortened in all single-story roof-lighted build- 

 ings, where the walls are very high and the skylight is replaced by clear-story 

 windows, or the skylight has insufficient slope. In regard to the unfavorable 

 condition produced by the combination of high walls and skylights, it has been 

 fouad that a gradual increasing of the height of the wall greatly diminishes the 

 li<yht. There are in this connection obvious modifications of the shape of a 

 skylight to be considered, according to the latter"s length, for architectural effect, 

 viz., a long skylight should not have too steep a slant, and a short one not 

 too low. ' 



The light at this latitude varies significantly in the different seasons, and upon 

 the two opposite aspects (north and south) of a building. In summer the sun 

 reaches at the solstice the extreme northern latitude of 23)4°; in winter it is 

 never vertical, and the inclined rays in the morning and evening then issue from 

 a point approaching tangentiality with our latitude. The contrast of the north 

 and south sides of a building in illumination is very noticeable from December 

 until April, and hence the meridional position — the flank exposure — is so much 

 to be preferred. To secure the maximum illumination at all seasons, the fiat or 

 one storied museum with skylight, clear story, etc., has been devised. It is 

 always best shown in the great exhibition halls of the different World's Fairs, 

 where the possibility of the largest possible public inspection is desired. This 

 result was well attained in the Government Building at the Centennial in Phila- 

 delphia (1876), and at the Mines and Mining, Transportation, and Horticultural 

 Buildings at Chicago. In such buildings extreme height must be avoided. 



The Manufacturers' and Liberal Arts Building at Chicago was covered, in 

 its skylight, with eleven acres of glass, but its enormous height of 210 feet pre- 

 cluded the full effect of its upper stories and covering of windows. One-storied 

 canopied buildings, if low, are defective in appearance, and they are diffuse and 

 expanded, covering a good deal of ground, while they furnish insufficient isola- 

 tion, unless cut up into rooms and halls, producing thereby a tangled and con- 

 fusing labyrinth, interfering with other aims of arrangement. 



The museum building can be carried upward to any height, and where space 

 cannot be easily obtained in a north or south line, rather than grow sideways 

 let the museum structure rise upward with additional stories. This has never 

 been tried because it interferes with architectural pretense, but it will keep the 

 museum in the best plane for light as explained above. It is perfectly feasible, 

 and not necessarily ugly. A sixteen or twenty storied bank of halls would, when 

 the very best position had been selected, form an admirable and almost perfect 

 museum structure. The possibilities of ascensional arrangement would permit 

 a very philosophical development of ideas in system and classification, from 

 inorganic through organic to human subjects. 



