Electrostatic generators, now produced commercially for a variety of scientific medical and industrial users, depend for their successful operation upon good-quality solid insulation. For the most compact generators, in which the solid insulation is continuously under a stress of over 60 KV per inch d.c., the structure is immersed in nitrogen or other inert gas at a pressure of 400 pounds/square inch, and great attention must be paid to the electrostatic field to ensure that stress is everywhere uniformly distributed.