within this fractured mass , within all of these different impressions of the crawler-half-blinded but still triangulating through my other senses-i thought i saw a darker shadow of an arm or a kind of echo of an arm in constant blurring motion , continuously imparting to the left-hand wall a repetition of depth and signal that made its progress laboriously slow-its message , its code of change , of recalibrations and adjustments , of transformations .