HIGH VOLTAGE — COMPTON 265 



for operation in air, tlie limitation being placed by the size of the 

 house in which it must operate. The largest place available was a 

 dock built for a Goodyear dirigible on the estate of Col. E. H. R. 

 Green at South Dartmouth, Mass, and which Colonel Green kindly 

 put at the disposal of the Institute. Ten million volts was selected 

 as the highest voltage that could be used in a building of this size 

 without excessive loss of current through the air to the roof and walls. 

 For this voltage, therefore, there has been built a generator with 

 15-foot spherical terminals made of welded aluminum, mounted on 

 24-foot textolite insulating columns in the form of 6-foot cylinders, 

 and carried on large fabricated steel trucks, running on a 14-foot 

 gage railway track in order to vary the position of the terminals 

 when desired. 



In this construction the Research Corporation gave invaluable 

 aid through assistance in the engineering drawings and through a 

 grant of $10,000, which defrayed approximately half the cost of the 

 generator. 



Plate 1 is a photograph of this generator, taken on the day before 

 Christmas. In using this generator for experimental purposes it is 

 planned to use the inside of the spheres as laboratory rooms, and to 

 mount the discharge tube, suitably designed for producing high speed 

 ions, between two spheres. 



Every feature in the construction and operation of this large gen- 

 erator has gone as expected, and a few days ago the first belt was 

 put into operation and voltage generated as expected. This belt is 

 made of paper 3 feet wide and running at about 5,000 feet per minute. 

 The initial trials gave an output of 600 microamperes, and previous 

 experience indicates that with the proper adjustments this output 

 may be increased to a milliampere. The design of the apparatus is 

 such that a large number of belts may be made to operate in parallel, 

 so that there will be no difficulty whatsoever in securing an output of 

 between a tenth and a hundredth of an ampere if such large currents 

 become desirable. It will be noted, however, that if currents as 

 large as a tenth of an ampere are used at 10 million volts, the gen- 

 erator will be delivering 1,000 kilowatts. 



The enormous possibilities of this machine become evident when 

 we compare a possible input of 1,000 kilowatts in the form of 10- 

 million-volt electrified particles, with the sources which up to the 

 present have been available for experiments on atomic disintegration 

 and which have been principally small amounts of radioactive 

 material. 



We come now to a very interesting aspect of this type of generator, 

 namely, the influence of the surrounding insulating medium. If the 

 generator is placed in some medium whose electrical break-down 



