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demonstrate. You put this on like you work a vacuum cleaner. It was the same principle - you sucked it out. You did it at the point of operation where the drill was going down and where the dust was rising. You could stand by any foundation operation and see this dust rising.

They tried having men work with masks on. In the first place, the men won't wear masks. It's really true, and we finally agreed, that wearing a competent mask, which is a prone pressure mask, no man could do eight hours' work. It was too exhausting and too heating. The other little masks are of just no account at all. They don't collect enough dust to make it worthwhile.

So it had to be something at the point of operation and this man had hit it. It was very good. I asked the Turner Construction Company if they would let him make a demonstration. We would put a set of physicians in there to examine the men regularly and a number of industrial hygienists to count the dust exposure, number of particles per square foot and so forth. It so happens that Rockefeller Center was the big foundation that they were working on. I used to go up almost every day and observe it. It was so fascinating. They put this contraption on every one of the jack hammers and let him make full experiments. One of the problems then came to be, “What do we do with the dust?” They collected