Proceedings of the Michigan Engineering Society (Paperback)

This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1883 edition. Excerpt: ...becoming most westerly at 2 P. M., and the needle returning to its mean direction about 6 P. M. The greatest difference is found in clear weather and when the air is in the condition we call bracing. The duller the weather, the less is the variation, and it is least in dull, drizzling or rainy days. At times of light thunder showers I think I have observed a disturbance of from 15 to 30 minutes, in a few minutes of time, but, as there was no regularity, I could not repeat observations so as to be certain of the amount. ' ' 4. After taking the first bearing of a line, should the surveyor be governed by the back-sights or by the needle in running the line? Answer.--The needle can never be depended upon to do good work; it should be superceded by the transit where correct lines are required, and all angles measured by the transit. At any time thereafter, as long as two points on any one line of the survey can be ascertained, the bearing of the remaining lines can readily be located. The needle-is very useful for approximate work, where great accuracy is not 'cal1ed_ for, but is liable to change from so many causes that it is impossible to guard against them. (Adopted). 5. In surveying fractional sections and establishing"quarter corners in the same, should the lines be divided pro-mta, according to the Government notes, or should the east or south quarters be made full and all excess or deficiency be allowed on the west or north quarters of the fractional sections? Answer.--Where any two points on a section line can be ascertained, the-distance between them must be assumed to be exactly what the Government notes call for, and no more; if we find, by measuring it-with our chain, that it is longer or shorter, we must assume, for that...