Now, though I had observed large numbers of transient echoes when I first turned on this equipment in the middle of December 1945, it was still uncertain as to what they were. The only evidence was from Hey's memorandum, which was still classified secret, which he sent me, when he was ordered to try to locate the V2 rockets. He gave false warnings because of these transient echoes, and it was he who had referred to the work of Schaeffer and Goodall in America, who had also observed these echoes, and had rather loosely associated them with the ionisation caused by meteors burning up in the 80-100 kilometre region of the atmosphere. So the problem still really existed as to whether, in fact, amongst this mass of echoes, there were any of any kind of durational strength, which might be what I was looking for, that is, the ionisation from the very large cosmic ray air showers. And I think, for the first month or so, when we were working from the Park Royal in this new situation, I made quite a long list of the echoes and the various types of echoes, still hoping that some of them might be associated with the cosmic ray air showers.

And then, at about that time, Blackett, who had recovered a bit from his quarrel with the inner Cabinet, over the atomic energy problem, he arrived one day, and said, 'Oh, by the way, you might like to read this letter.' Now, this letter was from TL Eckersley, who was the chief scientist of the Marconi Company, and now Eckersley was one of the great authorities on the ionosphere. The letter to Blackett, which I believe is now in the archives, said that he had been interested to read the paper by himself and me in the Royal Society in 1942, and he agreed with the calculations, but would he suggest to Lovell that he looked into the possible effect of the damping factor? Now, the extraordinary thing is that I thought that Blackett had just received this letter, but in fact, when I looked at it, it was dated 1942, so Eckersley had written this letter to Blackett in the hectic time of the war, in 1942, and Blackett, naturally, who was then, I think, the Scientific Advisor to Coastal Command, just put it in his pocket and forgot about it. Understandable, I mean, if he'd given it to me then, I would not have recognised it, because I was deeply involved in other matters.

Now, I of course knew nothing about damping factors, and hastened to the library to try and find out what Eckersley was referring to. And that led to a very great shock because the problem was in effect, in essence, a very simple one, that Eckersley said the movement of the electrons would not execute a simple harmonic motion in the atmosphere, they would collide, and the rate of collision would depend on the height in the atmosphere, and would vary, a greater damping at 80 kilometres than 100 kilometres, and the effect of this would be to lessen the... to make it even more difficult to detect the showers because it would reduce the intensity of the reflection from this stream of electrons. The trouble, I found out, was that on the frequency, which I was working then, about four metres, the effect was really colossal, and it depended on what assumptions one made about the nature of the shower, and the altitude at which the shower was developing, but it was a very large factor. I think something at least of 1,000 or more. And that set the tone for the developments, which then occurred at Jodrell.