250 



Popular Science Montlily 



At left, view of aerial screen system and secondary apparatus for collecting charges. At 

 right, public demonstrating screen suspended thirty feet above ground by four poles 



At left, spectators experimenting with apparatus. One boy is waving a vacuum tube. 

 At right, Prof. Thordarson examining his one million-volt, sixty-cycle transformer 



Engineers are of course interested in 

 the details of construction of such a 

 transformer, and some of the facts have 

 been generously given by Mr. Thordar- 

 son himself and by his assistant and 

 o[)erating expert, Mr. A. S. Lindstrom. 

 The laminated iron magnetic circuit is 

 arranged on the "core" t\pe, with both 

 primary and secondary windings grouped 

 upon one leg only. Horizontal members 

 are 120 ins. in length, the vertical ones 

 40 ins., their section being 16 ins. by 

 16 ins. Primary winding consists of 

 122 coils of 44 turns each of copper 

 ribbon, .020 in. by .281 in. in section, 

 i)iing the ef|ui\alent of a No. 12 romul 

 wire. These coils are i)laced >4 in. 

 apart, pairs being connected in series, 

 lluii the 61 groups connected in parallel 

 lor receiving the 2,20o-\-olt supiil)'. 

 When assemi)led, the primary portion 

 lormed a cylinder 67 ins. long, 23 ins. 

 inside diameter, 28 ins. outside diameter. 

 As a jirotection from i-iectrostatic surges 



the junctions between the pairs were 

 connected to a heavy copper bar that 

 was thoroughly "grounded" to frame 

 and earth. Over the primary coils was 

 a specially prejiared paper c>linder 

 92 ins. long, inside diameter 29^2 ins., 

 outside 41 '2 ins., therefore 6 ins. thick. 

 For the high \-oltage secondary wind- 

 ing 190 separate coils were used, each 

 adapted for 5,300 volts, being all 

 connected in series. Each coil consists 

 of 212 turns of aluminum foil, .008 in. 

 L>y -135 ''i-' with three thicknesses of 

 .006 in. paper between turns, and when 

 finalK' assemliled forming a tube 71 ins. 

 long, 43 ins. inside tiianieter, and 51 ins. 

 outside diameter. The construction ot 

 this secondary was of course the crucial 

 |)art of the whole experiment, anil the 

 ingenuity that was brought out to cope 

 with the different problems is of the 

 greatest credit to the designer and 

 builder. In gciur.il, the principle of 

 construction atlopted, that of breaking 



