Excerpt from Studies in Spherical and Practical Astronomy A method of reduction which is the same for both types of level, and which is in most cases more convenient than the above, is as follows: In the square array of numbers which constitute the observed readings of the level, take the diagonal differences. The mean of the two diagonal differences is the inclination of the line in half divisions of the level. That end of the line is the higher which is ad jacent to the greatest single reading. If the level readings have been correctly made the two diagonal differences will be the same, and the reduction thus serves as a check upon the accuracy of the record. Thus, from the readings given above, we see at a glance that in the first case 2 half divisions and the readings have been correctly made. In the second case z half divisions and there is a discrepancy of div. In the readings. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.