Egg shell deformation: Field comparison of two measurement devices1

Abstract
Two devices for measuring shell deformation were compared. One was the original Schoorl and Boersma apparatus, the other a device developed by Voisey and Foster. It was found that the two machines were of similar precision but gave different absolute values for the same egg. This was thought to result from a systematic error in the Schoorl and Boersma machine. The Voisey and Foster machine was found to be easier to use but the time required to take each measurement was 2 1/2 times that for the Schoorl and Boersma apparatus.