This is where Anderson and his balloons come in. Knowledge of the stratosphere, the home of the ozone, is at this point primitive, and the experiments he is doing should shed light on how much ozone is still there and how it is affected by various chemicals.

"Everyone is waiting with bated breath. His information will be absolutely critical," says Myron Uman, executive secretary of the environmental studies board of the National Research Council. Anderson's findings are expected to provide crucial information for the government on a host of environmental questions, including limits on aerosol cans.

Anderson's basic research interest is to get an idea of what the stratosphere looks like, and what are the chemical reactions going on within--no simple task. Predicting the stratospheric gas mixtures is comparable to predicting the chemical composition of water somewhere in the midst of an ocean, a job that can not be done from the ground. So Anderson must bring his lab to the stratosphere.

Years ago, Anderson would send his balloons about 140,000 feet up and then drop packages of measuring instruments by parachute, allowing them to take readings of the chemical composition in the air as they hurtled back to earth. Anderson says that although the experiments yielded useful information, the results were prone to error and difficult to test for accuracy since each experiment was a one-shot deal.

To remedy the problem, Anderson devised the "reel-up, reel-down" technique, whereby his instruments are hung over the side of the balloon and reeled up and down through the stratosphere as needed. The device not only allows his experiments to be repeated, says Anderson, but it permits numerous readings at various altitudes.

The gigantic yo-yo consists of a platform weighing more than a ton and hanging under the side of the balloon, an eight-mile cable and a 130-pound "monkey."

The monkey contains the instruments and goes up and down in the stratosphere; it consists of three elongated hollow "doughnuts" which fire a beam of light through its center hole as stratospheric gasses pass through. The light absorbs oxygen and measures the concentration of atmospheric gasses.

While Anderson has some suspicions about the extent of the danger to the ozone, he is treading very carefully, mindful of the enormous caution with which the government is approaching the issue. Clamping down on the production of certain types of gasses in, for instance, the aerosol industry could draw a backlash from businessmen.

"Our understanding is still primitive. We know the process is significantly altering the composition of the stratosphere, but nothing should be passed until we get more scientific information," says Anderson, who has testified before Congressional committees on the matter.

He adds, "We're at the stage where we have to build evidence like a lawyer in court. We can't talk about free radicals and tell people to shut down their plants until we can show a definite cause-and-effect relationship. We must show we understand what we're talking about." Legislation limiting certain kinds of chemical emissions simply is not warranted now, because researchers do not yet know enough about their effect on the ozone layer, he and other scientists say.

"It may seem to be fence-sitting, but we can't really make an honest evaluation yet," says Baird Professor of Science Dudley R. Herschbach. "There appears to be a long-term danger, but we still can't tell the extent of it."

Scientists, though, are irritated by a series of recent government reports down-playing the dangers to the ozone. One study has it that fluorocarbons will reduce the ozone content by only two to four percent by the end of the century; previous estimates put the figure at as high as 16 percent.

Experts fear that such conclusions will reduce the impetus to finding a solution to the problem. This in turn, they say, could further excerbate the current trend to less funding for atmospheric research, which would be disastrous to long-term efforts in the area.

Anderson says that research done by him and Michael B. McElroy, Rotch Professor of Atmospheric Science, indicates that the "fluorocarbon situation is much worse than we believed it to be few months ago. We think we have only five to 10 years to establish our case." And so it is back to the balloons.