As the rate of the metronome is increased, we cannothelp reading into the succession of strokes a more or lesscomplicated rhythm. At first, with rates that are still fairly slow,the beats group themselves into twos or threes, and the attentionis still adequate to six impressions, — six rhythmical units of two beats (twelve beats in all) or six rhythmical units of three beats (eighteen beats in all). 这段怎么翻译?或者给出最后一句的翻译也可以~