Comments on "Evidence of Quarks in Air-Shower Cores"

McCusker and Cairns have published data on cloud-chamber tracks which they claim to be less ionizing than would be possible for singly charged particles, thus giving positive evidence for the existence of quarks of charge $\frac{2}{3}$. They neglected the effects of the relativistic rise of ionization in the gas of their cloud chamber and we believe they underestimated the errors of their drop count. Considering the fluxes of known particles in the cosmic rays it is concluded that their results can be explained as due to statistical fluctuations.