26

The foot plates were found to make the best turning points on dirt or macadam
roads, or when crossing long stretches of sand, gravel, or farm lands. The method
of using the foot plate is simply to set it down and press it firmly into the soil; when
the rod is set on the plate, it is kept there until the rodman leaves his station; that
is, he is not allowed to raise his rod, and then replace it.

The foot pin is made of hard steel, having a broad head with a spherical cavity
for receiving the foot of the rod, the same as the foot plate. The pins are driven
with a mallet and are very useful when running over grassy soils, through wooded
country, and on very steep grades.
 

h^-^-H
 

Xo.
 

-Foot Plate and Foot Pin.
 

The method used in taking and recording the observations on the Board of Esti¬
mate leveling is the one so successfuly applied by the U. S. Coast and Geodetic Survey
since 1900. This method is defined by the instructions given to the precise leveling
parties of the Coast Survey*; these instructions were, however, slightly modified to
adapt them to the particular requirements of city work.
 

General Instructions for Precise Leveling.

1.    Except when specific instructions are given to proceed'otherwise, all lines are
to be leveled independently in both the forward and the backward direction,

■ These instructions were prepared by Mr, J. F, Hayford, E.vpert Computer and Geodesist.    Some
minor changes have been made since  1900,   making the  instructions more  complete.