The reading of measurements from a linear scale, as is done on conventional instruments, has been shown to be neither as reliable nor as speedy as those taken from a number counter.

The \"Harpenden\" range of anthropometric instruments, which have been developed in close collaboration with the University of London Institute of Child Health, are counter recording and they give accurate and direct readings to the nearest millimetre. \"Harpenden\" instruments are so effortless in operation as to make possible a control of measurement unrealisable with conventional anthropometric instruments.