Abstract :
Percy H. Thomas: There are two principal conclusions or principles in these papers which we should carefully distinguish. First, where solid dielectrics are combined with air in the insulation of terminals of any kind, advantage is gained if the solid insulator is shaped in a particular way; that is, if the outline of the solid material follows what may be called a line of electrostatic force extending from the positive to the negative terminal. Second is the intelligent control of the static potential at all points between the two terminals. This principle is illustrated by the so-called “condenser” transformer terminal. Instead of applying 100,000 volts between two terminals and allowing the potential to take its own natural distribution, Mr. Fortescue inserts a number of conductors at various points between the terminals, and then impresses on each particular intermediate conductor the potential he thinks it ought to have. The net result is a gain of three or four hundred per cent in the voltage which can be withstood by the same length of air gap. The advantage comes about in this way — we get a relatively high voltage resisted by a definite air gap, when the fall of potential is distributed equally through the whole length of the air gap. By devising some scheme which will make every portion of the air gap work to its maximum limit, we succeed in getting the greatest effectiveness that is possible out of the available separation.
