THE rubber diving dress evolved by Siebe a hundred years ago extended the useful range of human activities to rather more than a hundred feet below the surface of the sea, and for several years engineers and physiologists have been striving in their respective spheres to double or treble this working depth. Much progress has been made, and as an example of the most advanced methods now in use we reproduce, by courtesy of Messrs. Siebe, Gorman and Co., Ltd., two illustrations (Fig. 1) of the Davis submersible decompression chamber already described in these columns (NATURE, March 15, p. 415; 1930) and to the British Association at its Bristol meeting last year. The diver on finishing his work ascends not to the salvage ship but to this chamber, and, clambering in, finds an attendant waiting to divest him of the helmet and lead weights; the two men close the bottom door, and the chamber, retaining air at any desired pressure, is hoisted on board the salvage ship, which is then free to manœuvre or explode blasting charges while the diver is being slowly decompressed. Within his range the rubber-suited diver will always be supreme, but for objectives still beyond his reach another system is being developed.