256 
PRESTON. 
With these safeguards thrown around our procedure, we may 
with confidence draw conclusions that are both legitimate 
and sound. 
II. Methods of Determining the Earth’s Figure. 
t 
The size and shape of the earth may be found either from 
two meridional arcs or two longitudinal ones, or finally from 
a simple oblique arc. The first method was exclusively em¬ 
ployed during the last century, because it was possible to 
determine latitudes with more precision than longitudes; 
but in recent times the electric telegraph has so simplified 
the determination of the latter and has given such increased 
accuracy to the result that the last two methods may now be 
employed with entire success. All three are comparatively 
simple in their conception, although the problem considered 
in detail becomes an intricate and troublesome one. The 
individual steps are these: For the first case we have only 
to measure the length of two lines running north and south 
and observe the latitudes of the extremities. From this data 
the flattening is first found and afterwards the absolute 
length of the earth’s axes. This method was used in the 
work which gave us our first knowledge of the relative 
lengths of the polar and equatorial diameters of the earth, 
and the arcs of Lapland and Peru, which have become clas¬ 
sical in geodetic literature, were utilized in this way. These 
measurements have now little more than historic value. 
Nevertheless, their great importance when executed may be 
judged from the fact that on' their testimony the great ques¬ 
tion was decided as to whether the poles were nearer the 
center of the earth than the equator. This is a query that 
every schoolboy will answer today, but as late as the middle 
of the last century no one knew, and thousands of dollars 
were spent by the French in their efforts to solve the prob¬ 
lem once for all. The arctic and the equatorial work decided 
the question, and with this contribution to our knowledge it 
may be said that their usefulness ceased, although the result 
