168 LECTURES. 



"been led to the conclusion that the restrictions which the state of the 

 walls and the time for applying his plans in this building necessarily 

 imposed on him, universal diffusion through a porous floor was the only 

 scheme of supply that met the realities of the case. This arrangement 

 for the supply he introduced accordingly ; and, for fifteen successive 

 years, after which the building was pulled down in consequence of the 

 progres of the new works, the government and the House uniformly sup- 

 ported it, notwithstanding some obvious disadvantages that were met 

 by peculiarities of details. The House of Peers, also, after it had been 

 sustained for three successive years, requested that similar arrange- 

 ments should be introduced into their chamber ; but the means 

 allowed for this purpose did not permit the views to be applied as 

 completely as in the House of Commons — the progress of the new 

 works leading the authorities to expect that they would soon be en- 

 abled to occupy the new House of Peers. 



Tables were then presented, showing the observations that had been 

 made every hour during the sittings of the House of Commons for 

 fifteen successive years. Large diagrams were also shown explana- 

 tory of all the peculiarities of the arrangements adopted in the late 

 House of Commons, and of the experimental buildings previously con- 

 structed by the Lecturer at Idinburgh in reference to the ventilation. 

 In the temporary House of Peers arrangements were made that 

 enabled a large movement to be tested whenever the weather gave a 

 suitable temperature, according to which fresh air was permitted to 

 descend from one part of the ceiling and ascend to another. This 

 was independent of the usual arrangements adopted there. A similar 

 movement had also been in use in his lecture-room at Edinburgh from 

 the time it was constructed in 1833 ; but there he did as he pleased, 

 and gave a supply and discharge by a large aperture having an area 

 of several hundred superficial feet. The wall of one side was left out 

 in reality, so that air descending from the contiguous apartment 

 moved in one broad current to the class-room. A movement of sup- 

 ply and discharge by the ceiling requires a very large amount of 

 apertures, otherwise much of the air passes from the aperture of 

 supply to the aperture of discharge without doing any good to the 

 ventilation of the lower part of the room, where alone it is essential 

 to have fresh air. Again, there are cases where a direct descent is 

 preferable to all other movements. These occur principally where 

 there are peculiar difficulties connected with the supply and the con- 

 dition of the floor. At one period he (Dr. Eeid) was under the impres- 

 sion that such a movement might have been the best for the old House 

 of Commons ; but, on investigating the circumstances that led to this 

 view, it was found that the whole arrangements for the ventilation 

 had been improperly changed and neglected during his absence, 

 and, with the sanction of the government and the members of the 

 House of Commons who attended the investigation, everything was 

 restored to its former position. 



Descending ventilation could be rendered perfectly successful even 

 in a crowded assembly, but never without a much larger supply than 

 was requisite with an ascending movement. He had made the exi^eri- 

 ment repeatedly with individuals, and in a room specially constructed 



