LECTURES. 177 



scene. In this respect the pure white wax candle, with its hrilliani 

 flame, was unrivalled, except by the small gaslight burning with 

 similar lustre. But he did maintain that the best style of lighting 

 is that which t(dd least on the nervous system and on the health of 

 those who were engaged in public assemblies, and one that was, at the 

 same time, the best for the transaction of public business. The light 

 itself should be altogether concealed, or at least very considerably out 

 of the direct line of vision. He would only add that light trans- 

 mitted through ground glass was very oifensive to some, and that a 

 smoother and opalescent material gave it a softness of tone that could 

 never be commanded by the ground glass. Light radiated from 

 invisible burners, and, falling upon convex plaster of Paris surfaces 

 and solid flowers made of the same materials, and tinged to any 

 agreeable tone, gave a very pleasing and diffused radiation, with which 

 any desirable amount of illumination could be obtained for public 

 buildings. 



SEVENTH LECTURE. 



In this lecture Dr. Keid commenced with an explanation of the 

 manner in which fire-proofing interfered with the ventilation of some 

 public buildings, and the method of obviating the defects arising from 

 this source. The whole question of fire-proofing required revision. 

 An examination of the construction of different buildings said to be 

 fire-proof would exhibit a great diversity in the standard aimed at, 

 and in the amount of security given against fire. Ventilation re- 

 quired the ingress and the egress of air. Some systems of fire-proof- 

 ing contemplated the entire prevention of such movements when not 

 in actual occupation, and therefore valves (doubled, if necessary, for ad- 

 ditional security) were requisite to cut off all communication with the 

 air flues. The importance of separating contiguous rooms or buildings 

 by fire-proof walls and floors was universally recognized. But the great 

 point desirable in public buildings was to use no combustible mate- 

 rials, or a portion so small that even if on fire it could not do any 

 material injury. These also could be charged with chemicals of 

 different kinds, so as to diminish their ready accendibility. Various 

 experiments were then made illustrative of the action of alkaline and 

 earthy salts in preventing or retarding the combustion of wood, 'cloth, 

 and other inflammable substances used in building or for furniture. 

 Many fires originated not merely from carelessness, but from an 

 ignorance of the first principles of chemistry. In the present state of 

 society, in v^'hich the extension of art and science had introduced the use 

 of so many new materials, it was essential that the chemistry of daily 

 life should be made an elementary branch of general education. 



A number of special facts were then mentioned in illustration of 

 this position. It would give increased power and facility in con- 

 ducting o{)erations of art, and in dealing with combustible and ex- 

 plosive materials. To illustrate this^ a portion of gunpowder was placed 

 in a small copper cuj), and covered with oil of turpentine. The oil 

 of turpentine was then inflamed. It continued to burn above the 



12 s 



