The atmosphere in the city is often trying in the summer months because of the excessive humidity, and extraordinary measures were resorted to in the construction of the building to minimize this unpleasantness on the crowded floor, where the presence of a large number of men in a greater or less degree of physical animation but adds to the general discomfort. To meet this condition an air-cooling plant was provided--the first and the foremost example of its kind in existence, both in point of magnitude and in the exacting demands involved. By means of this remarkable triumph of mechanical skill, outer air at a temperature of say 90° is taken into the basement, eighteen hundred pounds of water (humidity) are squeezed out of it per hour, it is purified and cleansed through many walls of cheesecloth, the temperature is refrigerated down to 60°, and then, after again raising it to a point at which no dangerous results may affect a member passing in and out of the room, it is finally supplied to the great floor and again exhausted by methods that obviate drafts or dangerous currents of any kind. Aside from the members and attendants, the only person having access to the floor is the chief engineer who controls this remarkable air-cooling plant. A wizard in a way, it is curious to watch him threading in and out of the busy crowds, tasting and feeling the air which, under the black art of his necromancy, turns intolerable conditions into others quite delightful. The history of the New York Stock Exchange has been written many times, and need be but briefly referred to here. Something approaching an organization was effected May 17, 1792, when, under a tree which stood opposite what is now 60 Wall Street, twenty-four “Brokers for the Purchase and Sale of Public Stocks” signed an agreement to charge not less than a commission of ¼ per cent. It was a day of small things; the national debt was but $17,993,000; there was but one bank in the town. Through the fragmentary data that has survived, we learn that occasional meetings of the brokers were held during the next twenty-five years at the old Tontine Coffee House, at Wall and Water streets. In 1817 the formal organization was effected and the meeting-place fixed at the Merchants’ Exchange, later the site of the Custom House, and now the property of the National City Bank. In 1853 the Stock Exchange moved to Beaver Street and in 1865 to its present situation. The “Open Board of Brokers,” a rival organization, was absorbed in 1869, and ten years later the “Gold Board” also joined forces with the parent body.