Average airspace CO2 concentrations for the week just ended were 993, 1179 and 1224 ppm for the low-, intermediate- and high-concentration experimental units.  Averaged over both weeks, however, their mean CO2 concentrations were 1221, 1266 and 1253 ppm, demonstrating the virtue of starting the experiment in the alternative manner we suggested last week.  Nevertheless, we shall continue with what we have begun and see where it takes us.