THE TRANSIT 

 Notes may be kept as follows: 



85 



Caution. In transit surveying, where angles are read, 

 each line is referred to the one that goes before, and in 

 consequence an error in reading one angle is perpetuated 

 throughout the survey. Further than that, some of the 

 errors arising from lack of adjustment of the instrument 

 are multiplying errors, increasing as the work proceeds, 

 and unless every precaution is taken they may, though 

 individually small, mount up to a very considerable size 

 in the course of a survey. 



With compass surveying, on the other hand, though 

 bearings cannot be read with great exactness and single 

 angles are not so accurately determined as with the transit, 

 yet errors have not the same opportunity to accumulate 

 because each course in the survey is referred anew to the 

 meridian. 



The man who is not in constant practice, therefore, will 

 be likely to find that he attains better results with the 

 needle than by turning angles, and in that case, unless the 

 telescope is wanted for stadia measurements, the compass 

 is the instrument to use. The matter of cost is, in woods 

 conditions, strongly on the side of the compass, for it is 

 usually expensive to cut away for the long, clear sights 

 requisite to the running of a reliable transit line. 



Typical examples of stadia surveys such as the woods- 

 man may have occasion to perform are as follows: 



Stadia Survey of a Pond as carried out on the ice. 

 The needle was relied on in this case, but it will readily be 

 understood that angles might be read instead of bearings 

 and the survey so rendered independent of the magnetic 

 needle. If the survey were to be made in summer, points 



