LECTURES. 165 



vitiated air prevailed in the upper portion of different buildings. 

 There vitiated air was prone to ascend by passages and staircases from 

 other apartments, and if the roof or ceiling of the attics had no adequate 

 discharge, the moisture of respiration was condensed during the cool of 

 the night, though the warmth of the sun gave an elevated temperature 

 to this space during the day. He had seen numerous houses where dry 

 rot from vitiated air had entirely destroyed floors in the attics, while 

 the lower floors were comparatively sound. In public buildings the 

 same tendency was equally manifested under parellel circumstances. 

 An example was cited of a church in Scotland, near Edinburgh, 

 where the upper part of a long ladder was found so completely de- 

 cayed that it was broken with facility by the hand, while the wood of 

 the lower portion was perfectly sound. This church had been venti- 

 lated apparently by apertures in the ceiling, but there was no dis- 

 charge above in the roof, so that they were totally useless, except in 

 so far as they permitted the air in the roof to add its volume to that 

 below ; but at night the moisture of respiration condensing on the 

 timbers of the roof, which were finally entirely destroyed by the dry 

 rot. In London a very marked case occurred in the new post office, 

 where, a few years after it had been occupied, large quantities of a 

 brown fungus were found in the roof extending in branches sometimes 

 ten, twelve, or sixteen inches long, and as thick as a man's finger. 

 The products of respiration and of the gas lamps below had formed the 

 food that supported the growth of the fungus. 



The ventilation of public buildings was the next subject of consid- 

 eration. The same principles were applicable there as in the ventilation 

 of individual habitations ; but the numbers crowded in a given space,, 

 the fixed position and comparative restraint that necessarily accompa- 

 nied many of the duties of official life, the long sittings of a judge in 

 court, of a member of the legislature, according to the public business 

 transacted, the ever-varying numbers present, and the changes of the 

 external atmosphere during long protracted investigations and de- 

 bates — all conspired to render a degree of control and power of venti- 

 lation requisite that was not needed in ordinary apartments. Further, 

 in public buildings, large halls, corridors, and passages were often 

 necessary, besides numerous individual apartments applied to very 

 various purposes, and subsidiary to the principal assembly rooms for the 

 transaction of public business. These varying in number from one 

 or two to hundreds, and sometimes covering several acres of ground^ 

 in many cases required to be ventilated in unison with the principal 

 assembly rooms ; and without the adoption of some general system for 

 the whole, the warming and ventilating would be equally defective and 

 incongruous with the architectural character of the building were 

 the different portions of il. erected without reference to any general 

 plan. 



The first point to determine, in the construction of a large building, 

 in reference to warming and ventilating, was the number of apart- 

 ments, halls, and passages that were to be used in such a manner, or 

 so arranged that they must be subject to one system of ventilation to 

 rciaintain uniformity of action. Then came the determination of the 

 question, how far it was necessary or desirable to unite the varied 



