In view of the fact that doctors practicing at moderately high altitudes are being told repeatedly by their patients that they must leave the country on account of their health and the influence the altitude has on their condition, a series of readings was taken to see if a change of from 1,400 to 1,700 feet would be of any importance on the blood-pressure.
The Homestake Mining Company, through whose courtesy this work was carried on, is a gold mining concern whose underground workings are naturally ventilated. This is accomplished by having shafts in different gulches, widely separated from each other, the current of air in some of them being downward, in others upward. The mine is quite free from gases because the character of the rock does not generate any per se. A small amount of carbon dioxid is present, due to the decomposition of dynamite, the