206 
PRESTON. 
We have only to compare the methods of today with those 
hitherto employed to realize the phenomenal advance in the 
practice of surveying. The precision attainable in the astro¬ 
nomical determination of a point on the earth’s surface has 
certainly increased fivefold in the last fifty years. It is not 
to be expected that the fathers of our Republic should fore¬ 
see all of the necessities growing out of the proposed “ survey 
of the coast.” Nothing in the original act of Congress gives 
authority for the observation of terrestrial magnetism, unless 
such authority is implied in the words “ together with such 
other matters as may be deemed proper; ” yet no civilized 
nation today would undertake a trigonometrical survey with¬ 
out determining the variation of the magnetic needle. There 
would seem to be at first sight no intimate connection be¬ 
tween the measurements of the force of gravity and a trigo¬ 
nometrical survey of a country, nor between the temperature 
and density of the Gulf of Mexico and the hydrographic con¬ 
ditions along our eastern coast; yet both the law of falling 
bodies and the subocean currents are now T regarded as a legit¬ 
imate and necessary study in connection with a survey of the 
national domain. 
Every trigonometrical survey of great extent has been con¬ 
fronted with the question, “ What is the size and shape of 
the earth?” and every nation within the measure of its 
ability and opportunity has added something to our knowl¬ 
edge on the subject. It is evident that those countries whose 
domain is extended in the direction of the meridian possess 
unusual facilities for contributing data to the solution of the 
problem. England, France, and Russia have thus far been 
the most active governments in this respect, and have to¬ 
gether measured nearly ninety degrees of latitude. Less 
than ten degrees have been measured in the southern hem¬ 
isphere. The United States have measured an oblique arc 
of 22 degrees, several smaller ones running north and south, 
and have just completed theTongest parallel arc ever under¬ 
taken by a single government. Not content with this, work 
has already begun on the ninety-eighth meridian, which is 
