PHILOSOPHICAL SOCIETY OF WASHINGTON. 99 



ventive. They further found that the activity of the Teredo was ? 

 to a certain extent, dependent upon meteorological conditions since 

 the years 1720, 1755, 1782, 1820, and 1850, were seasons of great 

 drought, and consequent increase of salinity of the sea-water along 

 the coast, and in those years the destruction caused by the Teredo 

 was unusually great. 



Respecting the geological age of the Teredo, Mr. White exhib- 

 ited to the Society fossilized wood from the cretaceous formation 

 showing Teredo borings. 



Mr. Billings then presented to the Society a communication 



ON THE VENTILATION OF THE HOUSE OF REPRESENTATIVES, 



which was unfinished when the hour of adjournment arrived, and 

 went over to the next meeting. 



Adjourned. 



215th Meeting. April 8, 1882. 



President Wm. B. Taylor in the Chair. 

 Forty-eight members and visitors present. 



Mr. Billings then continued the presentation of the communica- 

 tion begun at the last meeting 



ON THE VENTILATION OF THE HOUSE OF REPRESENTATIVES, 



of which the following is an abstract : 



The difficulties to be overcome, and the means used for this pur- 

 pose were explained, and plans and sections of the Hall of the 

 House of Representatives at the Capitol, in Washington, were 

 shown. The amount of fresh air required is about one foot per 

 second per person, if an approach to perfect ventilation is de- 

 sired. The imperfect form of ventilation by dilution requires from 

 forty to fifty feet per minute. When a hall is occupied only one 

 or two hours, the cubic space is important, but in long sessions it 

 is the supply rather than the space that must be looked to. 



To produce the requisite movement of the large amount of air 

 used, special force must be supplied. This may be propulsion — the 

 plenum method, or by aspiration — the vacuum method, or a com- 

 bination of the two. The effect of wind and rain on aspirating 



