People should go to the works and experience them. Because just having an idea or picture in mind is absolutely not the experience that's necessary. Even just landing in Albuquerque or Salt Lake City or Las Vegas was immediately part of the experience. And then you'd get in a car from the airport and take these very long trips - in Michael Heizer's case, it was three hours by car to get to his work. And then there's walking around and into the piece and seeing it from different angles. The kinetic experience of being a part of it physically was very important for me.

I think Michael Heizer and Walter De Maria had a love-hate relationship because they both had a lot in common. But inevitably one would get more publicity than another. Of course, Robert Smithson's gotten so much attention through the years. One of the reasons is not only that his work is quite wonderful, but the fact that he was a writer himself.

I remember very vividly. I was here in New York. Nancy Holt called me and - I feel unhappy thinking about it - she said that Bob Smithson had died. I said, "Oh, Nancy, what will we do without Bob?" He was a very good friend.

I think the four land artists I showed all worked within a few years of each other. And they were standard bearers, I suppose, for land art. They each did very separate things. Apparently, later in California, a lot of artists started working in that medium and there was something of a rush of earthworks. But I wasn't involved with that.

I remember when I went to a gallery in Paris at one point, they had drawings of earthworks set in different places. I asked the person sitting at the gallery desk where these works were - where in France they could be found. She looked at me in horror as if I'd asked something completely insane. She said, "Well, of course, these works don't actually exist. They're concepts."

What's happening in the larger world always influences art. When I first started the gallery in 1959, one of the first things I learned was that most people assume artists know one thing and one thing only - that they were idiot savants. I found very quickly that most artists were very informed and very aware of what was happening in the world around them. So all of those things go together, especially for earthworks. And at that time there was such an intense interest in American art. So there was a great deal of attention paid to where it was going.

I didn't know Michael Heizer until I was preparing for my "Earthworks" show in 1968, and somebody called and told me to look at his work. Heizer had already made land art before any of the others and was deeply into it. But he was very young and working out West, so I wasn't aware of his work until he came and showed it to me.