of the Catskill Mountains. 431 
mostly embodied in a map, now engraved* which is believed 
to furnish the first accurate delineation of these mountains. A 
few words on the manner in which these results have been ob- 
tained may not be amiss here. 
The map, of which Plate XIX gives a reduced sketch, was 
drawn by my assistant, EH. Sandoz, and engraved on the scale 
of one inch for three miles. It covers a surface of about 
4000 English square miles, of which the mountainous part 
proper occupies somewhat more than one half, or about 2400 
Square miles. The position of all the mountain peaks was ob- 
The Hydrography was taken from the most recent county 
and township maps of Greene, Ulster, Delaware and Scho 
harie counties and has been regulated by the position of the 
mountains. 
The altitudes have been measured by mercurial barometers 
with the aid of assistants, all trained by myself; in only a few 
of the less important points tke aneroid was used to obtain a 
Proumidary measurement. Among my most useful assistants 
must mention E. Sandoz for all the Northern Catskills, Wm. 
Libbey, Jr.,-for observations and computations in the Southern 
Catskills, John eid and Samuel E. Rusk for the eastern por- 
ions. Most of the aneroid observations I owe to H. Kimball, 
the most indefatigable and skillful mountain climber of the 
Catskills. 
The formula used in the computations is, as in my other 
measurements, that of Laplace, in connection with a table of 
Corrections for the influence of the hour of the day and the 
barometrical coefficient, which I have derived mainly from the 
elaborate reduction of the meteorological observations of Ge- 
neva and St. Bernard by Plantamour 
The altitude of five points, not more than ten miles apart, 
was determined with great care from the Hudson River and 
the Delaware and Ulster Railroad, and each served as a base for 
* The map is for sale by Charles Scribner's Sons, and B. Westerman, New 
York City. 
