changed glances； and went downstairs to look。
The console screen was slowly printing out letter groups。
CQX VDX MOP IM
〃Is that Jerry？〃 Norman asked。
〃I don't think so；〃 Harry said。 〃I don't think he would go back to code。〃
〃Is it a code？〃
〃I would say so； definitely。〃
〃Why is it so slow？〃 Beth said。 A new letter was added every few seconds in a steady； rhythmic way。
〃I don't know；〃 Harry said。 〃Where is it ing from？〃
Harry frowned。 〃I don't know； but the transmission speed is the most interesting characteristic。 The slowness。 Interesting。〃
＇＇276＇＇ Norman and Beth waited for him to figure it out。 Norman thought： How can we ever get along without Harry？ We need him。 He is both the most important intelligence down here； and the most dangerous。 But we need him。
CQX VDX MOP LKI XXC VRW TGK PIU YQA
〃Interesting；〃 Harry said。 〃The letters are ing about every five seconds。 So I think it's safe to say that we know where it's ing from。 Wisconsin。〃
Norman could not have been more surprised。 〃Wisconsin？〃
〃Yeah。 This is a Navy transmission。 It may or may not be directed to us； but it is ing from Wisconsin。〃
〃How do you know that？〃
〃Because that's the only place in the world it could be ing from；〃 Harry said。 〃You know about ELF？ No？ Well； it's like this。 You can send radio waves through the air； and； as you know； they travel pretty well。 But you can't send radio far through water。 Water is a bad medium； so you need an incredibly powerful signal to go even a short distance。〃
〃Yes 。。。〃
〃But the ability to penetrate is a function of wavelength。 An ordinary radio wave is short…shortwave radio； all of that。 The length of the waves are tiny； thousands or millions