Report on the causes of error affecting levelling

The International Association 6f Geodesy and also the International Commission of Levelling, since its foundation, has performed much w o r k of high value to elucidate the errors appear ing in precise levelling. Special attention has here been paid to the mathematical aspect of the matter. The treatment of the errors of precise levelling will, however, acquire its final shape only when the manner of occurenee and the effect ot' all, or at least of all the essentiel errors will be fully explained. For this reason, I venture to call the attention of the members of the Section of Levelling to the fol lowing qualities of the errors (most o~' them already known today) oeeuring in precise levelling.