beneficial to the caverns' air. It would be trite to dwell on the advantages of lime as a purifier and disinfectant.
Again, we find no organic matter in the caverns undergoing decomposition, and have on every hand the beautiful, clean, limestone walls and draperies being corroded and reformed by the constant action of myriads of water courses (see Fig. 5). Can we arrive at any other conclusion than that here we have the purest and cleanest atmosphere that can anywhere be found?
Mr. Northcott 's control of the temperature and humidity conditions is a feature over which the thoughtful visitor must grow enthusiastic. The temperature of the caverns registers from 54° to 56° F. throughout the year, and the relative humidity varies but a fraction of a per cent, from 87. In the hottest summer weather the sanitarium temperature
ranges from 70° to 74° F., and the relative humidity is reduced to 70 per cent, or less, merely by the expansion in volume incident to an increase in temperature from 56° to 70°. In the winter the air is easily raised in temperature from 54° to 70°, and the problem of humidity, while somewhat more complicated than in the summer, is perfectly controlled. As seen in Fig. 1, the air is sent through a boiler-like box of sheet iron (B) and comes in contact with a wide surface of iron tubing, the opposite surface of which is exposed to the cold air outside. This one box failing to reduce the humidity sufficiently, there was built a long sheet-iron passageway (D) over the summer air corridor, and by placing a closed door (R) the air is forced through this accessory condenser to be still further robbed of its moisture.
