In 1955 Houot and Willm gave their account of bathyscaph experiences and achievements in 2000 Fathoms Down (Dutton) using the FNRS 3, which was originally a Piccard invention. Here Professor Piccard's son, with Dr. Dietz of the Office of Naval Research, U.S., tells the story of the FNRS 2, 3, and of their successor the Trieste; of the project begun in 1939, delayed by the war, and first successful in 1948; of the delays and financial holdups, and of the tests and trials in 1953, which resulted in a two mile dive. With 1955 and Dr. Dietz' unqualified enthusiasm, Piccard and the Trieste won international friendships in a summer of a tight diving schedule in 1957 ; then came her purchase by the U. S. and her work off San Diego; finally came the Big Dive off Guam, in the Mariana Trench, into The Challenger Deep, where, beyond her tested capabilities, the Trieste touched bottom at 37,800 feet. Piccard's story makes certain the importance of an ultra-deep submersible -- in oceanography, in the extension of submarine knowledge, in the future uses of information gained; it is most expressive of the scaph's dependability and of the acoustic, biological and other scientific data acquired; and his view of what is to come for further depth exploration persuades and convinces. In the field of deep ships and scientific applications in oceanography this will have stature, while general readers following these lines will find tremendously interesting material here. There is an appendix of technical description of the Trieste, tables of her dives off Italy and under the Office of Naval Research and photographs.