THE MANIPULATION OF THE TELESCOPIC ALIDADE 
IN GEOLOGIC MAPPING 
KIRTLEY F. MATHER 
INTRODUCTION 
The ability to use the telescopic alidade in plane-table mapping 
is absolutely indispensable to the geologist engaged in investi- 
gating oil and gas resources of any region. Even though he 
may be assisted by an ^ instrument man/’ to whom is entrusted 
the actual operation of alidade and table, final responsibility 
for the accuracy and speed of the work rests with the geologist. 
No geologist bent upon applying the principles of geology to 
the search for, and production of, petroleum may consider his 
training complete until he has had considerable experience using 
plane-table and telescopic alidade. Manipulation of the alidade 
is sufficiently simple to permit the tyro to grasp quickly its more 
obvious details, but at the same time offers opportunities for 
ingenuity and resourcefulness sufficiently complex to be worthy 
the mettle of the most expert. 
It is the purpose of this paper to assemble in convenient form 
certain of the more successful methods of manipulating the 
alidade, which have been developed during the last few years 
by many of the workers with this instrument. It is hoped that 
this presentation will be sufficiently simple to enable the be- 
ginner to make use of it, and at the same time sufficiently 
comprehensive to be a desirable reference work for even the in- 
strument man of wide experience. The paper does not include 
a description of field methods of mapping, either by traverse or 
triangulation; for such a description reference should be made to 
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