You put a counter into that tank, that would be totally useless. No, instead of that, you collect the argon which is a rare gas and a noble gas does not interact chemically and remains a gas, while your carbon chloride is a liquid, and so you collect the argon gas. How do you do that? You flush it with helium, which is a much more available noble gas, you pump that through the tank and out comes the helium together with the argon, and then you condense the argon by freezing it, and fill a counter with that and then you observe counts in that counter. Well, what do you observe? You observe a few counts a month coming from this very elaborate experiment. And so Davis proved in this way that indeed neutrinos do come from the sun and this proved maybe even better by the Japanese experiment which was done in an old mine in Japan in Kamioka, it's known as the Kamiokande Experiment, Kamioka Neutron Detector Experiment. That used a different method.