Metallic Dust
The "deposits" on the floor of the subway in Diagram E are diagrammatic representations of one of the very interesting facts which was developed by the reports referred to, namely: "That it is a matter of official information that the loss of weight in brake shoes has amounted to one ton per mile per month." The iron so ground up into powder and so deposited, or remaining in suspension in the air of the subway, probably now amounts to more than 900 tons! Obviously this metallic dust either remains in suspension to be breathed in by the passengers or is too heavy and falls to the floor of the subway there to remain until the suction of the train sets it into motion. Either of these assumptions is another strong reason for frequent and positive flushing out of the entire contents of the subway.
Suggested Remedies
Before one leaves this stage of the investigation, it is interesting to note that on Sept, 19, 1906, Charles S. Churchill, Member of the American Society of Civil Engineers, submitted a paper to his society upon "The Ventilation of Tunnels" which paper was discussed by Reginald P. Bolton, George S. Rice and the author himself. In this paper distinct issue is taken with the methods pursued, or not pursued, in the attempt to ventilate the subway; and reference is made to the suggestions of Mr. Churchill in 1904 preceding the opening of the subway, in which he called attention to the absolute necessity of employing mechanical ventilation, i.e. fan ventilation. It is worthy of note that it was in this discussion that Engineer Rice called attention to the possibility of the presence of smoke in the subway and its dangers, and that it was also in this discussion that Mr. Bolton suggested "agitators" within the cars—a suggestion which obviously cannot add one iota to the ventilation of the subway but merely stirs up the foul and heated air within the cars themselves. In this discussion it was also brought out that the air in the Boston subways was figured to be renewed six times per hour, or once every ten minutes, which, if duplicated in the New York subways, would unquestionably result in excellent conditions.
On March 15th, 1906, Prof. Soper read a paper before the New York Academy of Medicine in which he says, in conclusion, "I should say that I think the subway as a whole is sufficiently ventilated and free from conditions injurious to health except as to presence of metallic dust, lack of sanitarv care, and conditions inseparable from overcrowding."
The Arnold Investigation
Leaving now the subway as "ventilated" by Prof. Soper and Chief Engineer Rice, we pass over the year 1907 to Aug. loth, 1908, when, as
