INTRODUCTION. 
Explorations of the wild interior, for the purpose of ascertaining the most economical and 
practicable route for a railroad to the Pacific, are reconnaissances* rather than surveys. They 
are engineering studies of routes, or belts of country, often of two hundred miles in breadth, of 
two thousand miles in length, extending from the verge of the eastern border to the Pacific, of 
which the characteristics are to he known regarding railroad construction. 
Routes are not lines; several lines might occupy relative positions on a single route. 
The lineal section, rapidly placed by the labors of a single season, and presented as the result 
of a Pacific railroad exploration, must not always he presumed to be a profile of the preferable 
or the very best trace for location, existing upon the division examined. From the limited time 
prescribed for making these examinations, and from the vast extent of country explored, the 
first line of barometric levels does not always occupy the best position of the route to which 
applied. 
The engineering features of the whole broad division passed over are connected with this base 
line, and stated in the form of opinions or convictions forced upon the mind of the engineer by 
former experience of the necessities of location in all varieties of country. 
The study of reconnaissance is not, however, confined to single divisions. In its broadest 
application, it compares routes rather than lines ; states their relative merits, and, by a sim¬ 
plified system of hurried field service, restricts the costly and tedious labors of elaborate instru¬ 
mental survey to the preferable division ; and, even upon that division, to a limited section of 
surface. 
Thus, distinct knowledge of extreme, or nearly impracticable obstacles, upon routes involving 
deep national interests, the existence of which may lead to the abandonment or neglect of 
important termini, or to the repeated and expensive application of instrumental survey to solve 
what nature made insurmountable, directs the attention of reconnaissance beyond the narrow 
limits of sectional location. 
And as reconnaissance directs reconnaissance ; as the labors of survey are pursued as its 
results, and are involved and tedious in their deferred conclusions, the developments of the first 
important service cannot he too speedily continued to their limit when tending to prevent more 
costly expenditure by anticipating proposed surveys by additional information, which changes 
their direction.f 
In all reconnaissances of location for the selection of the route or the line of a route of a rail¬ 
road, some requisition to be answered must be present in the mind of the engineer. The interro¬ 
gation, For what am I here seeking? should he evident to his senses and aid his study. 
There are different classes of railroads ; different plans of construction. 
** Railroad reconnaissance. —To look, to view ; the study of country with limited use of instruments, to procure information 
of its characteristics regarding railroad construction. 
Report of reconnaissance. —To describe and submit conclusions from inferences drawn. 
Railroad survey .—Instrumental examinations, by which surfaces are measured. 
Report of survey. —To state by accurate deductions from data gained. 
f 1 shall again refer to this brief definition in giving the reasons why the exploration, of which this report is the result, 
was conducted at an unfavorable season of the year, by private means, and was endorsed by unanimous resolutions of the 
legislative assembly of Washington Territory. 
