AN EXPERIMENTAL STUDY OF FIELD METHODS WHICH 
WILL INSURE TO STADIA MEASUREMENTS G-REATLY 
INCREASED ACCURACY. 1 
LEONARD SEWAL SMITH, B. 0. E. 
Instructor in Engineering , University of Wisconsin. 
INTRODUCTION. 
The collection of data on this subject was begun during the 
field work of the International Boundary Survey between United 
States and Mexico, 1892-3, merely as a study of a certain phe¬ 
nomenon familiar to engineers under the name “boiling of the 
air.’’ In the summer and fall of 1894, this systematic study 
was continued in Wisconsin, but was made to include an experi¬ 
mental study of the effect of this boiling upon the accuracy of 
stadia measurements. 
It has been found that the boiling and other related disturb¬ 
ances do not differ greatly either in character or amount, even 
in such extreme latitudes as New Mexico and Wisconsin. 
When this study was begun, it was thought that this unstead¬ 
iness of the atmosphere, called boiling, exercised a governing 
influence on the accuracy of stadia work, but while the investi¬ 
gation proves that this is not so, it has been the means of dis¬ 
covering what that governing factor really is. 
It is generally admitted that theoretically the only errors to 
which the stadia method is subject are compensative errors; but 
it is as generally known that practically the actual results of 
all stadia measurements have been bristling with large syste¬ 
matic errors, so large as often to cover up the accidental 
errors. 
1 This paper is a resume of a thesis offered to the Faculty of the Uni¬ 
versity of Wisconsin for the degree of Civil Engineer, and published in 
the Engineering Series of the University Bulletin. 
For an explanation of the theory of stadia measurements see ap¬ 
pendix. 
