1. Probably the first example of such a large system was the million-volt x-ray tube of C. C. Lauritsen at the California Institute. The “cyclatron” and the high frequency x-ray tube of Lawrence and his collaborators at Berkeley, the high voltage x-ray tubes of W. D. Coolidge, the large ion accelerating tubes of Tuve at the Bureau of Terresterial Magnetism, of Lauritsen and Crane at Pasadena and of Cockcroft and Walton at Cambridge are all excellent examples of the trend. Huge vacuum systems for spectroscopy have been constructed at Massachusetts Institute of Technology. Probably the largest high vacuum system in point of volume is that of John Strong used at California Institute of Technology for coating the 100-inch Mount Wilson Observatory Reflector.