320 Geographical Notices. - ow 
of Tolteks, Chichimeks, Nahuatleks, and Azteks wandered, be- 
tween the sixth and twelfth centuries, through southern tropical 
Mexico, partially peopling it. The work will consist of sixty or 
seventy sheets in quarto. 
The sixth volume of the surveys is a report by Lieut. H. L. Ab- 
bot on the expedition originally commanded by Lieut. R. 8. Wil- 
liamson for determining a route for connecting the Sacramento 
Valley and Columbia river. The surveys were made in 1850 
Of this volume, ‘Part I. contains the general report, divided into 
seven chapters; of which the first contains a general description 
of the different regions traversed during the survey. This syn- 
opsis has been prepared partly to enable those wishing merely 
to obtain a general idea of the country, to dispense with reading 
a mass of details, and partly to render the railroad report more 
intelligible. The second chapter is devoted entirely to a discus: 
sion of the facilities offered for the construction of a railroad near 
the lines of survey. The third, fourth and fifth chapters con- 
tain a narrative and itinerary of the expedition. An attempt 
has been made to give, in this portion of the report, a detailed = 
description of the nature of the country examined ; of the sup- 
of wood, water, and grass near the trails; of the character 
of the Indian tribes; and of various other matters, interesting 
to those who wish to thoroughly understand the character of the 3 
regions explored, The sixth chapter contains a statement 0! Ne — 
method used in computing altitudes from observations taken 
with the barometer. The seventh chapter eontains an ac of 
of a former exploration of Lieut. Williamson, near a portion © 
our line of survey. | 
“Parts II, II, and IV, contain Srologacet botanical, ue 
oom the astro 
deduced — 
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ae 
from them by computation 
a Tw 
