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Full text of "Geographical surveying, its uses, methods and results"

UC-NRLF 

III 

$B EST blM 

ia\L COMMISSION OF 

: Cll. FRED. HARTT, CHTEF. 



;APHICAL SURVEYING, 



BE YEAUX CARPENTER, C 

Geographer to the Commission. 



FROM VAN NOSTKAND'S MAGAZINE 




NEW YORK: 

JSTOSTRAND, PUBLISHER, 

| MURRAY AND 2T WARREN STREET. 

1O K o 
O / O . 



VAN NOSTRAND'S SCIENCE SERIES. 



VAN NOSTRAND^UCIENCE SERIES. 

No. 17. WATER AND WATER SUPPLY, By 
PROF. W. H. CORFIELD, M. A., of the 
University College, London. 

No. 18. SEWERAGE AND SEWAGE UTILI- 
ZATION. By PROF. W. H. CORFIELD, 
M. A., of the University College, Lon- 
don. 

No. 19. STRENGTH OF BEAMS UNDER 
TRANSVERSE LOADS. By PROF. 
W. ALLEN, Author of " Theory of 
Arches." With Illustrations. 

No. 20. BRIDGE AND TUNNEL CENTRES. 

By JOHN B. MCMASTERS, C. E. With 

Illustrations. 
No. 21. SAFETY VALVES. By RICHARD H. 

BUEL, C. E. With Illustrations. 

No. 22. HIGH MASONRY DAMS. By JOHN B. 
MCMASTERS, C. E. With Illustrations. 

No. 23. THE FATIGUE OF METALS UNDER 
REPEATED STRAINS, with various 
Tables of Results of Experiments. From 
the German of PROF. LUDWIG SPANGEN- 
BERG. With a Preface by S. H. SHREVE, 
A. M. With Illustrations. 

No. 24. A PRACTICAL TREATISE ON THE 
TEETH OF WHEELS, with the Theo- 
ry of the Use of Robinson's Odonto- 
graph. By S. W. ROBINSON, Prof, of 
Mecha.iiical Engineering. Illinois In- 
dustrial University. 

No. 25. THEORY AND CALCULATIONS OF 
CONTINUOUS BRIDGES. By MANS- 
FIELD MERRIMAN, C. E. With Illustra- 
tions. 

No. 26. PRACTICAL TREATISE O^T THE 
PROPERTIES OF CONTINUOUS 
BRIDGES. By CHARLES BENDER, C. E . 

No. 27. ON BOILER ^INCRUSTATION AND 
CORROSION. By F. J. ROWAN. 



GEOLOGICAL COMMISSION OF BRAZIL, 

PROFESSOR CH. FRED. HARTT, CHIEF. 



GEOGRAPHICAL SURVEYING, 

ITS USES, METHODS Al RESETS, 



BY 



FRANK DE YEAUX CARPENTER, C.E, 

Geographer to the Commission. 



REPRINTED FROM VAN NOSTHAND'S MAGAZINE. 




NEW YORK: 



D. VAN NOSTRAND, PUBLISHER, 
23 MURRAY AND 27 WARREN STREET. 

1 8 78. 



Copyright ; 

18T8, 

By D. VAN NOSTRAND. 
"' 



PREFACE. 



CHAKLES FKEDERIC HAKTT, Professor 
of Geology in the Cornell University, 
and Chief of the Geological Commission 
of Brazil, died on the eighteenth of March 
last, in Rio de Janeiro, where he was 
engaged in preparing the reports of his 
Survey. 

His death and the dissolution of the 
Commission, of which he was the founder 
and director, have prevented the realiza- 
tion in Brazil of the plan of surveying 
proposed in the accompanying pages. 

F. D. Y. C. 

NEW YORK, July, 1878. 




GEOGRAPHICAL SURVEYING. 



IN this paper I shall present a scheme 
for the organization, the gradual develop- 
ment, and the prosecution of a geographi- 
cal survey in connection with the 
Geological Commission, which, in the 
efficiency of its results, will satisfy not 
only the present demands but also the 
future needs of the Empire of Brazil for 
very many years to come. In the rapidi- 
ty of its progress, this survey will be 
especially adapted to a country of so 
vast an area and comparatively sparse 
population, and as an adjunct to the 
above Commission, and in great part 
carried on by the members of the same, 
without interfering with the ends of 
that body, it can be maintained at an 
expense so moderate as to be in con- 
formity with the present desire for econ- 



6 



omy and retrenchment in the public 
service. 

THE PROPOSED PLAN OF SURVEY. 

The immense empire of Brazil is yet 
without reliable geographical maps. 
These are necessary to the national wel- 
fare. The question arises as to what 
kind of maps will be sufficient to satisfy 
the imperative needs of the country and 
of science. The plan of survey which I 
shall advocate is a mean between that 
system which takes cognizance of every 
house in a village and every little undula- 
tion in the landscape, and that want of 
system in which are represented whole 
mountain-chains that do not exist, or 
actual topographical features are delin- 
eated with gross inattention to accuracy. 
It is a judicious mean between the slow 
and laborious processes used, for in- 
stance, in the Ordnance Survey of Great 
Britain, and the sketchy and unreliable 
information gained by the early ex- 
plorers of the New World, from whose 
results our first maps were compiled. 



These last are scarcely more graphic and 
complete than our present maps of the 
moon, and in fact, speaking broadly, 
they are not so accurate as the latter, 
which are, in great part, photographs of 
the surface which they represent. With 
these mere hints of the geography of its 
country a people should not feel obliged 
to rest satisfied until it can sustain a 
minutely topographical survey. 

AN EVOLUTION IN CARTOGRAPHY. 

The demand for maps depends upon 
the population and civilization of a 
country. In the beginning a rough 
sketch will answer the purposes of the 
pioneer. As the region becomes inhab- 
ited better maps are wanted, and finally 
the people require the nearest possible 
approach to absolute accuracy in the de- 
lineation of topographical features. Map- 
making in every country must follow a 
regular evolution from the incomplete to 
the complete. 

Reviewing the origin and growth of 
the cartography of a country, we see how 
faulty it is liable to be. The first ex- 



plorer is the first contributor to the 
geography of a region. By way of il- 
lustration, let us follow one of these 
pioneers as he traverses Brazil from 
South to North. Following up a branch 
of the River Plate, he records the ap- 
proximate directions and distances of his 
journey, which he obtains, perhaps by 
the use of unreliable pocket instruments, 
perhaps by an occasional glance at the 
sun and his watch, or, more probably, 
by estimating at night the latitude and 
departure which he has made during the 
day. At a certain period of his march 
he finds a river entering from an easterly 
direction, whose volume he measures 
with a glance of the eye. Farther on, 
he encounters a tribe of Indians, whose 
village is situated upon the west bank of 
the river; he counts their houses, and 
makes the number of these a key to the 
extent of the population. At the fol- 
lowing night he camps at the foot of a 
cataract. Impressed by its grandeur, and 
also by a kind of optimism, common to 
early explorers, and which will not allow 



him to underrate any of the glories 
which he sees, he estimates its height to 
be at least twenty meters, when in reality 
it is but ten. 

At a certain point whose latitude and 
longitude he determines in a rude and 
hasty way with the sextant which he 
carries, he leaves the main stream and 
follows a tributary to its head in the 
highlands, where he crosses the divide be- 
tween the great Parana Paraguay basin 
and that of the Amazon. Upon the 
summit of the plateau he te'sts his alti- 
tude above the sea by noticing the tem- 
perature of boiling water, or by reading 
the indication of his single aneroid, un- 
reliable methods which have been known 
to give results even a thousand meters 
wide of the truth.* Continuing down 

* Gibbon's observations at the head of the Amazon, 
both the mercurial and thenno-barometer being used, 
show a discrepancy between the two which is equivalent 
to 300 meters of altitude. The height of Mount Hood, in 
Oregon, as given by one authority, who determined it by 
the boiling point of water, is almost 2,000 meters greater 
than that indicated by the cistern barometer and by tri- 
angnlation. In the writer's own experience he has en- 
countered an aneroid record, upon one of the peaks of 



10 

the Araguaya, he observes the trend of the 
mountain-range along his route, and, de- 
scending the Tocantins, he makes, a simi- 
lar survey extending to Para. 

We do not disparage the work of this 
man. Under the circumstances of hard- 
ship and peril by which he is surrounded 
he does all that is possible, and his re- 
port is really of great value until some 
more reliable exploration can be made; 
still, for all of that, it is none the less in- 
correct and incomplete. 

It is from such sources as this that the 
material for our first maps is drawn. In 
later revisions there may be introduced 
the results of desultory explorations of 
mines, railway routes and navigable 
waters, as well as the meagre topograph- 
ical data acquired by the land surveyor 

the Sierra Nevada Mountains of the United States, which 
made the height of this mountain to be 3,000 feet above 
its true altitude. It is a noteworthy fact that these pre- 
liminary determinations, made with the above faulty 
methods, resemble the estimates of the early explorers, 
inasmuch as they almost invariably give exaggerated alti- 
tudes ; perhaps the opinions and imagination of the ob- 
server are allowed to form, in some unaccountable way, 
a factor in these results. 



11 



in running boundary lines of private 
estates, but still, taken at its best, a map 
constructed in this way falls far short of 
its purpose as a picture of the conforma- 
tion of the earth's surface, or as a guide to 
the traveler, the geologist, or to the capi- 
talist who wishes to invest his money in 
the development and internal improve- 
ment of his country. 

FAULTS IN EXISTING MAPS. 

In his compilation of the scattered in- 
formation at his disposal the cartog- 
rapher finds that a certain district of 
country has never been entered by the 
engineer. He knows, however, that two 
rivers rise somewhere in this terra in- 
cognita, and he feels it safe to predicate 
a divide between them. He also thinks 
it safe to presume that this divide is a 
range of mountains, of greater or less 
height, and, in his desire to give an ap- 
pearance of finish to his chart, he does 
not scruple to insert at this place an 
ideal mountain system, and represent 
it as drained by the upper tributaries of 



12 

the two rivers, concerning|whose head- 
waters in reality nothing is known. 
These physical features soon come to be 
reproduced, with more or less variation, 
in other maps, and in this manner errors 
are grounded in the national geography, 
from which they can only be eliminated 
by a systematic geographical survey. 
Like national myths they stubbornly 
refuse to give way until eradicated by 
true scientific research. 

Supposing, on the other hand, that 
the compiler, accepting the report of the 
explorer, who claims to have discovered 
a range of mountains between the Rio 
Parana and the Rio Araguaya, wishes to 
represent them upon the map. He has 
no mathematical data to insure their 
position, and no sketches or other in- 
formation from which to draw their in- 
tricate topographical features, and so he 
evolves from his imagination an utterly 
impossible chain of mountains, out of 
place, artificial, conventional, and even 
mechanical in their regularity. These 
he depicts in that stereotyped form of 



13 

delineation, which is known in the 
modern geographical draughting-room 
as the " caterpillar " formation. 

THE RELATIONS OF GEOGRAPHY TO GEO- 
LOGY. 

Upon such an unfaithful map as this 
it is impossible to faithfully represent 
the geology of a country. If the geolo- 
gist attempts to lay down his conclusions 
upon a sheet of this kind, its' errors will 
continually clash with his truths. The 
configuration of the land, as it appears 
upon this erroneous drawing, might in- 
dicate that it belonged to a certain geo- 
logical age, and that, in fact, it could 
not be referred to any other; the geolo- 
gist, visiting and studying the country 
itself, finds that it is of a later and 
entirely different period. But if he 
paints it as it really is he publishes a 
glaring anachronism to the world, for 
the color which represents the rock of 
one geological epoch overlies, upon the 
map, the physical features which are 
peculiar to another age. As in the 



14 

artistic and true delineation of tbe 
human figure every feature must be the 
exponent of anatomical structure, so in 
topography, every representation of 
topography must be true to geological 
structure. Ranges of mountains mean 
disturbance or great erosion of certain 
strata, and each has its own characteris- 
tic features as sharply defined as those 
of an animal. This should be thoroughly 
understood, and those immense lines of 
sierras which are supposed to separate 
certain river basins, or are delineated in 
the very heart of regions of which we 
have no knowledge whatever, should be 
erased from the national maps until 
these districts can be explored. In the 
course of his travels the geologist may 
find some physical feature of great im- 
portance, which he wishes to portray, 
in area and position, upon his chart, but 
the best maps at his disposal represent a 
topography utterly at variance with 
geological structure, perhaps a sharp 
ridge of mountains where there should 
be a plain, and so they are of no use to 



15 

him. Or he may find himself obliged to 
color the top of a mountain peak with 
the tint conventional to the bed of a 
lake, and in this manner science is made 
ridiculous. 

To take an illustration nearer home, 
suppose that the group of mountains that 
abut into the sea in the vicinity of Rio 
de Janeiro have intervening valleys filled 
with alluvium, which is really the truth. 
Suppose that the limits of these mount- 
ains have never been accurately determ- 
ined, which is also true. In this case, it 
is easy to be seen that if the geologist 
lays down upon the map the alluvial 
deposits in their true extent, they will 
here and there encroach upon and over- 
lap the rugged masses of gneiss, and in 
places will extend far up the steep preci- 
pices of the mountain side. To avoid 
this absurdity the geologist is forced to 
be as inaccurate as those who have gone 
before him, and, in general, every error 
in the geographical map must be con- 
tinued and apparently sanctioned in the 
geological chart that is based thereon. 



16 

It becomes therefore absolutely neces- 
sary that the work of the geologist 
should be preceded by and based upon 
that of the geographer, and that he 
should work in conjunction with the lat- 
ter. In the exploration of a new coun- 
try the geological party should make its 
own topography ; and in the United 
States of North America, where the ex- 
periment has been most efficiently tried, 
this is always the case. 

A good geographical map would give, 
with sufficient completeness, all the lead- 
ing topographical features of the region 
explored, delineating with especial care 
those peculiarities of structure which are 
the keys to the different formations. It 
would display the shape and position of 
bodies of water, and show how the di- 
rection of a stream is changed and de- 
termined by the accidents of a broken 
and displaced stratification, and by other 
circumstances of its boundaries. If re- 
strained by canon walls its route would 
be angular; down a steep gradient it 
would be direct; and in the level allu- 



17 

vium near the sea its track would be 
tortuous and broken into bayous. This 
map would distinguish between the 
rounded slopes of a synclinal valley and 
the abrupt sides and angular cross sec- 
tion of an anticlinal cleft; and between 
the sharp edges of the volcanic rock and 
the eroded angles of the sand-stone. If 
there was exposed a great " fault " in the 
stratification, it would show it at a 
glance, with its precipitous bluff of ex- 
posed strata on one side, and, on the 
other, its gentle declivity of tilted sur- 
face rock. And, drawn in contour lines, 
it would reveal, not only the heights of 
peaks and passes and other vertical dis- 
tances from plane to plane, but also the 
various orographic forms, each of which 
is full of meaning to the geologist. 

ECONOMICAL USES OF THE PROPOSED 
MAPS. 

Aside from being quite indispensable 
to a scientific commission, in the various 
ways that have been mentioned, these 
maps can be made a graphic supplement 



18 

to their report in numerous other par- 
ticulars, and can be made to embody the 
stores of practical information which 
they gather incidentally to their regular 
work. Upon it they can display the 
valleys of arable land and the plains 
adapted to grazing. The forests of tim- 
ber can be laid down, and, from this 
drawing, their areas and values can be 
closely estimated. Advantageous sites 
for colonies can be noted here. The 
superficial contents of coal-beds and ore- 
deposits are given, and not only does a 
geological chart reveal where the 
precious and useful minerals are, or may 
be found, but it also furnishes that nega- 
tive information, equally valuable to the 
miner, which defines to him the larger 
districts in which it is impossible for 
them to exist, and in which, consequent- 
ly, it is a waste of effort to search for 
them; it is here that the science of 
palaeontology is especially useful. If 
any portion of the country lies at a great 
elevation, the altitude limits of the vari- 
ous forms of vegetable growth may be 



19 

traced, and also the limits of the possible 
culture of grain, coffee, cotton, and the 
other principal products. In this man- 
ner the map is made a general statistical 
report upon the value of the national 
domain. 

The economical ends served by a work 
of this nature in the development and 
settlement of a new country, cannot be 
too highly esteemed. Every stream of 
importance is surveyed, in all except 
those minor branches whose courses can 
be traced in from the adjacent mountain 
stations. The frequent tests for altitude 
along its banks determine the rapidity 
of its descent, the amount of water- 
power which it represents, and its value 
as a motor for machinery, and as an 
agent in hydraulic mining and diamond- 
washing. This profile of the bottom of 
the valley also decides the feasibility of 
railways or other lines of communication 
by this route, while the sketches of the 
adjacent hills show what room there is 
for such a road, and, in connection with 
this, the geologist's report will give a 



20 

general idea of the rock or other ma- 
terial with which the engineer will have 
to contend and work. In the survey of 
a range of mountains careful readings 
for altitude are made, not only on the 
summits of the peaks, but also at the 
passes, or low depressions in the divide, 
while the slope of the descent from the 
summit to the valley will be delineated 
in contour lines, drawn at such vertical 
distances as circumstances may require. 
It must be admitted that these contours 
will only approximate to their true 
places, yet their number will be correct, 
and their positions will be such that they 
will give with sufficient certainty the 
various gradients that occur in the as- 
cent, so that, by counting the meters of 
rise for every kilometer of horizontal ad- 
vance, as shown by the scale of the map, 
the engineer or capitalist, in his distant 
office, with this sheet before him, can 
form a very satisfactory idea of the 
practicability of a proposed railway, and 
can select the most advantageous route 
for the preliminary survey. 



21 

The meteorological data accumulated 
in the process of this work are valuable, 
not only in the determination of the ver- 
tical elements of the survey, but also as 
an illustration of the general laws of 
drought and excessive rainfall. At in- 
tervals throughout the country, the de- 
clination of the compass needle will be 
observed, and will be published for the 
guidance of land surveyors who may not 
be proficient in astronomical observation. 
The positions and supra-marine eleva- 
tions of all villages, important fazendas, 
medicinal and thermal springs, ancient 
ruins or other discoveries in archaeology, 
supplies of water in a dry country, or of 
pasture in a barren district, and all other 
places of interest to the traveler, will 
be determined. The roads and trails 
already in existence will be surveyed 
and mapped, while a leading object of 
this enterprise will be to find shorter and 
easier lines of travel. The explorer who 
opens a new pass through the mountains 
is a far greater benefactor to mankind 
than he who discovers and names a con- 
spicuous peak. 



22 

Many of the national surveys of 
Europe were founded on military 
necessity, that is, the necessity of having 
correct information to govern the move- 
ments of armies in time of war and the 
incessant transfer of troops in time of 
peace. In some of these countries their 
early maps were withheld from the 
citizen whose taxes had paid for their 
construction, and to as recent a date as 
1857, in one or two cases, they were 
kept secret for use in some contingent 
war. This argument of military necessi- 
ty will have but little weight in Brazil, 
whose rulers, knowing that a country 
strong in peace will also be strong in 
war, take the enlightened and advanced 
policy of encouraging the peaceful pur- 
suits of life, as the surest basis of nation- 
al strength. Still it must be acknowl- 
edged that these maps would be of 
excellent service in the administration 
of the affairs of distant provinces, in the 
transportation of military supplies, and 
in the garrisoning of frontier posts, 
although the country is to be congratu- 



23 

lated that, for every soldier to whom 
they would be useful, a hundred immi- 
grants would be benefited by them. 

THE INTENTS OF THIS ESSAY. 

While entertaining no wish to make 
this article popular, in the ordinary sense 
of the word, I shall seek to exclude from 
it all formulas, equations for computa- 
tion, and other material, purely mathe- 
matical, upon which the surveyor bases 
his work, and as far as possible I shall 
avoid those technical terms which would 
be embarrassing to the reader who is not 
an engineer. The fundamental princi- 
ples of geographical engineering are the 
same all the world over, and in every 
mathematical library there are books of 
reference which give all the laws and 
formulas necessary for a work of this 
kind. Therefore, nothing would be 
gained by their repetition here. Spe- 
cialists in geodesy, astronomy, and 
hypsometry have investigated their vari- 
ous branches, have published their re- 
sults, and these, in their purity, are 



24 

applicable to any quarter of the globe. 
One, for instance, has applied the theory 
of least squares to geodetic computa- 
tion; another has invented the zenith 
telescope for latitude observations; and 
a third has traced the horary curve in 
the barometric record. All of these dis- 
coveries fall within the comprehensive 
department of the geographer, who 
supplements these studies by utilizing 
their results in his labors in the Held 
and office; or, if he is about to write a 
brief exposition of the subject of geo- 
graphical surveying, it is his business to 
describe, in a straightforward manner, 
the way in which practical application 
of these truths is made. 

This paper will be, in general, a 
description of the most approved meth- 
ods, the economical devices, and the 
practical results of a successful geo- 
graphical survey, working in obedience 
to the directions of the chief of the 
commission to which it is attached, and 
covering such areas as may be designated 
by him as most worthy of geological 



25 

and geographical delineation. From 
time to time, as occasion may offer, and 
especially at the conclusion, the project 
will be adapted to the Empire of Brazil, 
as it is quite impossible to propose a 
plan of survey which will be applicable 
to all countries. Although, as has been 
stated heretofore, the general principles 
underlying this kind of work are the 
same wherever physical laws prevail, 
and the face of the country is wrinkled 
with mountains and valleys and furrowed 
with the river-bed and canon, yet there 
are physical conditions peculiar to every 
land, as well as circumstances of area, 
population, and wealth, which require 
that it should have its own type of geo- 
graphical survey, and not copy too ex- 
actly those of any other nation. 

THE BEST TYPE OF SURVEY FOR BRAZIL. 

Considering the circumstances of area, 
population, and wealth it is evident that 
the national surveys of Brazil should be 
" geographical " in a very liberal sense of 
the word; that is, that they should be 



26 

comprehensive in their scope, rapid in 
their execution, and sufficiently accurate 
without being too punctilious and too 
excessively minute. It is only within 
the present generation of engineers, and 
particularly in the western hemisphere, 
that there has grown up an important 
distinction between topographical and 
geographical surveying, and even now it 
is hard to define the limit between them. 
The latter is an outgrowth and extension 
of the former and an adaptation of it to 
the mapping of large domains at the 
least possible expenditure of money and 
time. 

DISTINCTION BETWEEN THE GEOGRAPHER 
AND TOPOGRAPHER. 

As one of the many points of differ- 
ence between the geographer and the 
ordinary topographer, we may mention 
that the former, in his travels and sur- 
veys, accommodates himself to the roads, 
trails, or other open and easy routes that 
already exist, and it is but seldom that 
he finds himself obliged to make a path 



27 

for his survey to follow. In the ascent 
of some mountains it may be necessary 
to cut a road, and in the measurement of 
the base line for his triangulation he may 
have to prepare the ground before him, 
but these are almost the only instances. 
The topographer, however, in tracing a 
contour line around the side of a mount- 
ain, or in making parallel profile sec- 
tions of the land, is not allowed to devi- 
ate therefrom, and if the way is not 
clear, he must wait, perhaps at great loss 
of time, until his assistants have removed 
the brushwood, or whatever other obsta- 
cles may intervene ; in this respect he 
resembles the railway engineer. Again, 
in the selection of the stations for his 
triangulation, the geographer makes the 
best possible use of the mountains 
of a country as he finds them, generally 
accepting them as they occur; though 
their arrangement, it may be confessed 
here, is not always in such well-condi- 
tioned triangles as he would desire. The 
topographer, on the contrary, delays his 
work by the establishment of arbitrary 



28 

stations where natural points are lacking, 
and by the erection of artificial signals 
on those mountain tops which the former 
observes without such aid. 

In the end it will be found that the 
topographer's notes are so numerous and 
in such detail that it may require several 
centimetres of map to represent one kilo- 
metre of the earth's surface; while to 
the geographer, who is satisfied with the 
general shape of a mountain- spur, the 
approximate width of a valley, and the 
more important bends of a stream, a 
scale of one centimetre to several kilo- 
metres may be sufficiently large for the 
portrayal of the earth as he finds it. But 
it will also be observed, by an economi- 
cal government, that while the topog- 
rapher consumes several years in the 
survey of a thousand square kilometres, 
the geographer will obtain a very satis- 
factory knowledge of thousands of 
kilometres in one year. And, in general, 
the superior accuracy, or rather detail, of 
the former, is purchased at an expendi- 
ture of time and money so great that 



29 

only the older and wealthier nations 
can afford the investment; while I hope 
to demonstrate that the geographer's re- 
sults are sufficiently complete for the 
needs of Brazil. 

THE GEOGRAPHER'S PROFESSION. 

The geographer's work is a peculiar 
and difficult one, and one for which his 
ideas must become enlarged by a special 
training. This is a branch of our pro- 
fession for which no training-school pre- 
pares its student and no text-book yet 
published can instruct him. This is a 
field in which the experienced topog- 
raphical engineer, fresh from his labors 
on park and landscape, or on the detailed 
surveys of thickly-populated Europe, 
finds himself unhandy and incompetent, 
for much of the experience and tradition 
that he brings with him is an incubus 
to retard him. To become efficient in 
this new service he must forget much of 
the rule and routine that he has learned, 
and accustom himself to taking broad 
and bird's-eye views of the country. 



30 

Strange as it may sound, he must 
make it a matter of duty and pride to 
overlook and neglect much that is near 
at hand, and remember that, although a 
mole-hill at a distance of a few feet sub- 
tends a greater visual angle than a 
mountain as many miles away, yet it is 
the mountain, and not the mole-hill, that 
deserves delineation upon his map. 
Hitherto he has been local and narrow in 
his range; he must now become geodetic, 
else he will accumulate a mass of minu- 
tiae, whose representation would be in- 
finitesimal on a map of the proposed 
scale, and which is hence but an incum- 
brance to his books, and even worse than 
cumbersome, inasmuch as its presence 
excludes other and more valuable data. 
In short, the topographer considers the 
earth minutely, and with a microcosmic 
view, but the geographer is a man of no 
such narrow horizon, and trains himself 
to look upon it as a macrocosm, or great 
world. 



31 



THE INSTRUMENTS USED. 

Of scarcely secondary importance to 
the men of a geographical corps, are the 
instruments with which they shall work. 
The tools which have been devised for the 
ordinary surveys of land and landscape 
must be left at home with the slow and 
tedious methods from which they cannot 
be divorced. In a work of geographical 
extent the spirit-level, chain, and tally- 
pins are out of place, and whosoever, 
making accuracy his plea, attempts to in- 
troduce them there, will find his own 
ends defeated by them. Once upon a 
time, for instance, an engineer was in- 
trusted with the survey of a large tract 
of new country. A certain sum of 
money and a limited period of time were 
given to him, a stated area of territory 
was assigned to him, and in return the 
authorities expected of him the most ac- 
curate and impartially complete map 
that his means would allow. 

The time and resources granted him 
would permit him to touch the country 
but lightly and by swift marches, but, as 



32 

this was intended to be only a reconnois- 
sance, nothing more was expected of him 
than to trace the conformation of the 
land in a general way. He was an 
honest and conscientious engineer, and 
so great was his zeal for accuracy, or 
nicety rather, that he was scrupulous to 
a fault. He abused the maxim which 
says that whatever is worth doing at all 
is worth doing well. For determining 
the altitude of stations along the route 
he used the spirit-level, and their inter- 
mediate distances were found by stadia 
measurements, which system, though 
considered incautiously rapid in topogra- 
phy, is too laggardly slow for the or- 
dinary purposes of geography. In this 
manner he crossed his territory with a 
few lines of march whose profiles were 
as trustworthy as those of a railway sur- 
vey, and far more accurate than the pub- 
lic interest demanded, while between 
them there were large areas untouched 
and unseen, and of these the public, 
whose agent he was, had commissioned 
him to obtain information. The failing 



33 

of this engineer was a common one; he 
neglected to distribute his resources 
fairly and impartially, and while half of 
his map is reliable the other half is con- 
jectural. 

It would be too long a task to de- 
scribe in detail all the instruments used 
in geographical work, or to rehearse all 
of the devices employed in its prosecu- 
tion; however, the most necessary and 
novel features will be noticed here. At 
the basis of the work is the transit, or 
theodolite, which, with compass-needle 
attached, is the engineer's constant com- 
panion, without which his occupation is 
gone, no matter in what field his labor 
may lie. As an appurtenance to this, 
not the chain nor the stadia, but the 
odometer wheel, has become the recog- 
nized means of linear mensuration in the 
survey of streams and the determination 
of those distances of route and detour 
which are so useful in filling in a trian- 
gulation chart. Instead of the level, the 
cistern barometer gives the heights of 
mountains, mines, passes, camps, vil- 



34 

lages, and other important positions, 
while the aneroid barometer, portable as 
a watch, and as easily read, will tell the 
altitude of minor points and give with 
sufficient closeness the data from which 
may be plotted the profile of the odome- 
ter's itinerancy. 

THE PERSONNEL OF A GEOGRAPHICAL 
CORPS. 

These are the three classes of instru- 
ments that are indispensable; the purely 
geographical party required to use them 
need consist of but three men, the en- 
gineer, the meteorologist, and the 
odometer recorder. To this corps it 
may be deemed advisable to add a fourth 
member to act as an assistant to the en- 
gineer, and, by personal obervation and 
experience acquire that facility in the 
practice of his profession which will fit 
him, in the course of a brief period of 
training, for the responsible position 
above him. Such a person should al- 
ready have the theoretical education of 
an engineer, and some skill in drawing. 



35 

If it is not practicable to make this ad- 
dition to the corps, it is well to choose 
as an odometer recorder one who pos- 
sesses the acquirements stated above, 
and to consider that position, whose 
appertaining duties are light, as prepar- 
atory to the grade of engineer. As for 
the meteorologist, his is an intricate 
science which cannot be studied too 
thoroughly, and barometric hypsometry 
should be regarded as a profession quite 
distinct from the engineer's, although 
necessarily subordinate to it. 

The various duties involved in the 
measurement of the base-line, at the 
opening of the season, may demand the 
services of a larger body of men than 
this, but, once in the field, any addition 
to the above number, except as muleteers 
and servants, will be superfluous, as far 
as the geographical work is concerned. 
One surveyor can see as far as two, and 
one man is able to take note of all of the 
country visible from his route of travel. 
No axemen are needed, for if there is a 
tree in the way, the line must yield to 



36 

the tree; the resultant error will be trif- 
ling and will not be apparent in a map 
which represents several kilometres of 
territory on one centimetre of space. 
Neither is there any necessity for rod- 
men, with rods of two targets for mi- 
crometer measurements or one target for 
levels, who would retard the corps by 
the long delays consequent upon their 
transfer from the stations in the rear to 
those in advance. This party travels as 
a unit, moving as fast as its animals can 
walk, and is never broken, a considera- 
tion which is of value in a country of 
hostile people. 

Of course the scope of the work may 
require the service of a great number of 
professional men, but its best progress 
demands that they should be divided 
into corps of the above size, which shall 
work in concord and under one general 
liead. This director will assign to each 
party its territory for the season, and 
tupon the borders of these areas, the va- 
rious engineers will make rendezvous 
from time to time, as circumstances may 



37 

admit, with their neighbors of the ad- 
joining fields, for the purpose of 
reorganization, exchange and issue of 
material, and especially for the compari- 
son of sketches and geodetic data, so as 
to insure the proper union of their sev- 
eral schemes of triangulation. In order 
to make the different systems of trian- 
gles interlock in one grand plan, the 
observer will frequently be obliged to 
read angles to stations which lie in an 
adjacent district, and which will be oc- 
cupied by his co-laborers for the purpose 
of reciprocal observations. It is there- 
fore necessary that they should meet in 
occasional conference for the mutual 
identification of those stations. 

THE STATIONS OF SURVEY. 

Guided by these thoughts, let us sup- 
pose that we have completed our organi- 
zation for a season in the field, and that 
we are now on the ground ready for 
work, at the place selected as the initial 
point of the survey. As with all surveys, 
this one will be executed from stations, 



38 

meaning thereby any points at which a 
tripod is planted and an instrument ad- 
justed, angles are read and sketches may 
be made. Of these we shall occupy 
four orders, of which, in importance, and 
consequently in accuracy, the astronomi- 
cal is first. Then comes the geodetic, or 
triangulation station; the topographical 
station, so designated for the sake of con- 
venience; and, finally, the odometric, or 
route station. In addition to the ends 
which they are especially intended to 
serve, each of these will be a meteorologi- 
cal station as well. These five classes, 
with the incidental details pertinent to 
them, will now be considered in the 
order named. 

THE ASTRONOMICAL STATION. 

Since the positions determined by tri- 
angulation, or other system of survey in 
which terrestrial objects alone are con- 
sidered, are only relative to each other 
and to the first station occupied, it is 
evident that a map may be completed, 
which, in itself, will have all of the ex- 



39 

actness of perfect truth, but whose place 
on a projected surface of the globe will 
still be uncertain. A map of a conti- 
nent may be made, and this may be of 
great use in the guidance of travelers 
across the continent, and for the local 
information of its inhabitants, but still 
it does not play its proper part in the 
grand plan of this earth's geography, and 
define the situation of this land relative 
to the other continents of the earth, 
until it is bound into place by the meri- 
dians and parallels, which are the warp 
and woof of the structure of geography. 
Therefore, in order to adjust our map, 
when made, into its true place, we must 
have the absolute determination of one 
or more of its positions. 

Now there is but one way of finding 
the absolute position of an object on the 
earth, and that is by going beyond the 
earth, consulting the stars, and ascer- 
taining its place relative to them. Hav- 
ing two triangulation stations thus 
located, the whole chart becomes ad- 
justed to its place. Or, having the lati- 



40 

tude and longitude of our initial point 
and the astronomical azimuth of a side 
of a triangle leading from this origin, the 
former serves to pin the plot to the pro- 
jected map, and the latter is instrument- 
al in orienting it into the area to which 
it belongs. 

POSITION OF THE ASTRONOMICAL STATION. 

For every base-line measured and 
developed there should be an astronomi- 
cal station occupied, and as a matter of 
convenience and co-operation they should 
be in the same vicinity, although it is 
not necessary that the station should be 
directly over either end of the base. 
Indeed, owing to great exposure to 
the wind, or to inconvenience of ap- 
proach, it may not be found practicable 
to locate the astronomical station at any 
of the points of the triangulation system, 
or, to secure proximity to the telegraph, 
whose office may be hidden in the heart 
of a town, or the bottom of a valley, it 
may be so secluded as to be quite in- 
visible from those points. 



41 

If so, it may be easily connected with 
them by running a careful linear survey 
from the astronomical station to the 
nearest geodetic station. If, owing to 
the disadvantageous nature of the 
ground, or other obstacles in the way, it 
may be impossible to measure the dis- 
tance directly between these two points, 
the engineer can connect them by a 
broken line, reading at the astronomical 
station the angle between the meridian 
mark, already fixed by the astronomer, 
and the direction of his first course, and 
afterwards referring the direction of each 
measured section of his traverse to that 
immediately preceding. From these re- 
sults he calculates, in meters, the differ- 
ence of latitude and departure between 
the two points, and then, transforming 
the meters into seconds of arc, he com- 
putes their difference of latitude and 
longitude. 

NUMBER OF ASTRONOMICAL STATIONS. 

For a commission of moderate size, in- 
cluding one, two, or three engineering 



42 

corps, the triangular development of one 
base will cover as much territory as can 
be surveyed by them in a single cam- 
paign, and therefore one astronomical 
position a season is all that this survey 
would require during the first year or 
two of its organization. A series of ob- 
servations extending through a couple of 
weeks, in favorable weather, or through 
a month at the farthest, will determine 
the geographical co-ordinates of our 
point of departure. These can be made 
by the astronomer while the engineers 
are measuring the base-line and develop- 
ing the same, the director is perfecting 
his arrangements, and the purveyors are 
preparing and distributing the supplies, 
instruments, and all of those numerous 
articles of equipment which are the fur- 
niture of a scientific field season. At 
the same time, the meteorologist, by a 
set of hourly barometric and psychro- 
metric readings accumulates data whose 
digest will give the vertical co-ordinate 
of this place with the possible error of a 
very few feet, and this completes the de- 



43 



termination of its position with reference 
to a system of co-ordinates whose origin 
is at the level of the sea at the point 
where the first meridian crosses the 
equator. 

For so short an annual term of service 
it might not be advisable to keep an as- 
tronomer constantly in commission, nor, 
at present, might it be well to go to the 
expense of the costly and elaborate in- 
struments requisite for the best astro- 
nomical observation, provided that the 
co-operation of the Imperial Observatory 
could be secured and an astronomer 
could be detailed from there for that 
purpose. In addition to the gratification 
to be derived from the warranted excel- 
lence of the results which would be fur- 
nished by the skilled assistants of that 
institution, this cooperation would be a 
matter of economy to the Government? 
and also, what is especially to be desired 
between any two scientific bodies, a 
means of friendly relation and inter- 
change of information which would cer- 
tainly prove of mutual value. 



44 



ASTRONOMICAL METHODS. 

For the determination of the latitude 
of our point of outfit the zenith tele- 
scope would be used; while the longitude 
would be found by the telegraphic ex- 
change of time signals, a method which 
has lately been so successfully introduced 
by the Astronomical Commission. The 
present wide-spread extension of lines 
of electric telegraph within the borders 
of Brazil is especially favorable for a 
survey of this nature, whose longitudes 
would be based upon telegraphic commu- 
nication with the national observatory. 
The lines along the coast afford a gen- 
eral connection with the northern and 
southern provinces of the Empire, while, 
by the numerous branches which accom- 
pany the railways into the interior, points 
which lie far to the inland could be re- 
ferred to the meridian of Eio de Janeiro, 
which, in its turn, has communication 
by cable with the observatories of Eu- 
rope. 

Thus it will be seen that the engineer 
need not be confined to any unfavorable 



45 

locality in the selection of the ground 
for his base line, nor need the chief of 
the commission be restricted in his choice 
of areas to be surveyed. From the 
railways either constructed or contem- 
plated it would probably be possible to 
reach any of the settled portions of 
Brazil without seriously overtasking the 
accuracy of the triangulation, and, if it 
were required to carry the survey still 
farther, longitudes determined by the 
method of moon-culminations would be 
sufficiently exact for the less important 
regions beyond. 

ORIGIN OF THE TKIANGULATION. 

An inland survey, based upon trigono- 
metrical methods, progresses most suc- 
cessfully from an initial source concen- 
trically outwards. The most fortunate 
location for the initial line is in the cen- 
ter of some broad valley or intermontane 
plateau, whose level expanse offers fair 
ground for the measurement of the base, 
and whose open field is favorable for the 
gradual and symmetrical development 



46 

of the same until it shall reach the lines 
of the remotest triangles, in which it be- 
comes a metrical standard for finding 
their length. In an extensive survey, 
lasting for years and covering broad ter- 
ritory, a series of bases are indispensa- 
ble. These act as checks upon each 
other, and the net-works of triangles 
emanating therefrom are dovetailed into 
each other, and, in their adjustment to 
fit, each to each, what little error they 
may have accumulated is reduced to a 
minimum. 

For instance, on each side of a range 
of mountains there is an open basin. In 
each of these an astronomical station is 
established and a base is measured. On 
the comb of the intervening sierra, one- 
hundred miles apart, stand two pre-emi- 
nent mountain peaks. The latitude and 
longitude of each of these, with the 
distance between them, is determined 
from the two origins independently. 
They check each other, verifying, in 
their agreement, the accuracy of both 
systems, or showing by their disagree- 



ment that there is an error somewhere^ 
and the long line, drawn by the labor- 
saving appliances of trigonometry, 
through a hundred kilometres of aerial 
route, a thousand meters above the val- 
leys and chasms which it spans, is now 
ready to be used as a new base in the 
primary triangulation. 

It may be difficult to find a favorable 
locality for the source of a triangulation 
immediately upon the sea-shore, as there, 
unless there are islands in the adjacent 
ocean, one side of the field is quite open 
and affords no stations to be occupied. 
If it were not for this objection it would 
seem best to measure a succession of 
bases along the coast of Brazil, and 
thence develop them westward. A tri- 
angulation is always most accurate in 
the vicinity of its origin, and as it be- 
comes more and more remote from its 
initial ground it becomes less reliable, 
owing not only to the continued multi- 
plication of the original error of the 
base, but also to the accumulation of in- 



48 

accuracy and mistake * from other 
sources. Now, the population of Brazil 
is thickest along the sea, and thence, into 
the interior, at least in many provinces, 
it gradually thins out. The importance 
of the country and the necessity of 
having truthful maps correspond to the 
density of the population. Add to this 
the fact that the most interesting geology 
of Brazil is on the sea-board, and, 
furthermore, the important considera- 
tion that the coast of a country, for pur- 
poses of navigation, demands a more 
rigorous geographical determination than 
the interior, and it will be seen that the 
triangulation upon which this delineation 
depends should not originate too far 
away. In a general survey of Brazil, 
therefore, the first series of astronomical 
stations and bases should be established, 
if not upon the sea-shore itself, at least 

* There is an important difference in the meanings of 
the terms "mistake" and "inaccuracy." If a man, 
carelessly reading a vernier whose indication is 38' 45", 
calls it 39' 45", he is guilty of a mistake. If from parallax 
or some defect in vision or judgment, he calls it 38' 40", 
he is inaccurate. Mistakes are due to want of care ; in- 
accuracy, to want of precision. 



49 

upon the first plateaus that are encount- 
ered between the mountains of the in- 
land. 

POSITION OF THE BASE-LINE. 

In its direction and position the base- 
line should bear judicious relations with 
certain hills, knolls, corners of terraces, 
or other prominent elevations in the vi- 
cinity, which may be selected as sites 
for the stations to be occupied in its de- 
velopment. The plans for its expansion, 
matured before its position is selected, 
should include two prominent peaks in 
the horizon, remote from the origin and 
from each other, whose distance apart 
this measured length will be instrumental 
in determining. The ground upon which 
it is to be measured should be as smooth 
and bare as possible. It should be free 
from brush, tall grass, or other vegeta- 
tion, and also from hillocks and gulches, 
which are serious impediments to a work 
of delicate mensuration. Whether it is 
level or not, provided its slope be grad- 
ual and even, is of secondary importance, 



50 

as corrections may be easily applied to 
cancel the effect of its gradients. 

LENGTH OP THE BASE. 

The length of the base may vary from 
two to ten kilometres. In the opinion 
of many engineers more than four kilo- 
metres of measured length is zeal gone 
astray, for the advantages of accuracy 
gained by such excess would be obtained 
more easily by devoting the extra time 
to a more elaborate trigonometrical de- 
velopment. No arbitrary rule can be 
applied here, however. All must depend 
upon the judgment of the engineer, who 
will consider his surroundings, and if 
they are favorable for a slow and pro- 
gressive development, a short base will 
answer; but if he is obliged to carry his 
triangulation from the base stations to 
the distant mountains by an abrupt 
transition, a longer one will be required, 
to prevent too great acuteness in those 
remote angles. 

INSTRUMENT OF MEASUREMENT. 

Since rapidity, as well as accuracy, is 



51 

an object, we use a steel tape, ten or fif- 
teen metres in length, as a measuring 
unit. In the swivel at one end of this 
there is a thermometer which tells the 
heat to which the tape is exposed at 
any time; there is also a micrometer 
screw, by which it can be lengthened or 
shortened in compensation for any possi- 
ble change of temperature; and there is 
a dynamometer attached to govern the 
tension applied, which should amount to 
three or four kilograms, being at every 
application the same as it was in the orig- 
inal test for length, to which the tape 
was subjected. 

Thus, as this apparatus is applied, in 
the process of measurement, it is under 
a constant strain, which preserves it 
from the error from sagging, to which 
all flexible cords are liable, and its length 
is always corrected to meet the contrac- 
tion and expansion which the metal is 
constantly undergoing as the tempera- 
ture varies. Should this micrometer be 
but incompletely graduated, so, for in- 
stance, as to be adjustable only for every 



52 

five or ten degrees of thermometric 
change, or should it even be wanting 
entirely, very good results can still be 
obtained with the steel tape by reading 
the thermometer at every application, 
and, in the final computations for length, 
making the necessary temperature cor- 
rections. Used carefully and with intel- 
ligence, this instrument is one of the 
most valuable adjuncts of the geograph- 
ical survey, and, in the hands of consci- 
entious and interested observers, it is 
capable of results that are very near the 
exact truth; the error ought not to ex- 
ceed one centimeter for every kilometer 
of measured distance. 

METHOD OF MEASUREMENT. 

The mensuration may be made on 
wooden plugs, with smooth, flat upper 
surfaces. These are driven firmly into 
the ground along the alignment at inter- 
vals equal to the length of the tape, and 
should be allowed to project above the 
earth sufficiently to permit this cord to 
swing clear of all inequalities in the 



53 

surface, or other obstacles between the 
two stations. Or, instead of these, little 
stools of plank may be used; these 
should have short, pointed iron legs, to 
be forced into the ground, so as to hold 
the wooden block firmly in position. 

When all things are ready a distance 
of one or two kilometers can be meas- 
ured in one day. But, on account of any 
possible inefficiency in the compensation 
for temperature, and also because even 
the best assistants are liable to a per- 
sonal equation in sticking the marking 
pin, some invariably inserting it to the 
right of perpendicular, and others the 
reverse, it is well that it should be 
measured several times, and by different 
persons, and a mean of the results taken. 
Then it should be leveled, in order that 
each tape-length may be corrected for 
its gradient, which is done by a simple 
trigonometric process, and finally it is 
reduced to its corresponding concentric 
arc at the level of the sea, when it is 
ready for use in the system of triangu- 
lation. 



54 



THE ASTRONOMICAL BASE. 

The method of base-measurement by 
astronomical observation is sometimes 
resorted to in geographical surveying, 
but this process will be noticed here 
only sufficiently to point out the serious 
objections that there are to its use. 
Having the latitudes of the two ends of 
the base and the azimuth of one from 
the other, it is a simple matter to com- 
pute their distance apart. This seems to 
afford an economy of labor, over the 
former method, that involves the determ- 
ination of the latitude and longitude of 
the first station, the azimuth of the i ase- 
line, and its length by direct measure- 
ment; this one requires the determina- 
tion of the latitude and longitude of the 
first station, the azimuth of the base- 
line, and the latitude of the second 
station. The latter is apparently the 
simpler and shorter task, and since both 
methods are based upon astronomical 
observation they would appear to be 
equally reliable. But they are not. 

Experience has long since taught the 



55 



scientific world that the probable error 
of any ordinary astronomical result is 
several meters at the very least, and that 
it is not safe to put absolute reliance in 
those reports which give a latitude down 
to a very small fraction of a second. 
Now, in that system of triangulation 
whose position is based upon the astro- 
nomical determination of one point only, 
an error of a few meters in the latitude 
of that point will not do material injury. 
It will simply displace the entire trian- 
gulation scheme, as a whole, so much to 
the north or the south, while, since the 
length of the base, or measuring unit of 
the proportions of * this scheme, was 
accurately found, there will be no error 
in these proportions. But, in the astro- 
nomical measurement of a base, suppose 
its two terminal points to be in their 
most favorable position, that is, on the 
same meridian. The latitude determina- 
tion of the southern station places it 
several meters too far to the south of 
its true position ; that of the other, per- 
haps, makes it an equal distance too far 



56 

to the north. Hence it follows that 
there is an error in the length of the 
base equal to the sum of the two astro- 
nomical errors, and this, in the develop- 
ment, is multiplied almost indefinitely, 
being repeated in any side of triangle as 
often as the length of the base is con- 
tained in the length of that line. This 
is supposing the base to be an arc of 
meridian; the greater its divergence 
from the meridian, the more seriously, 
for obvious reasons, will an error in the 
astronomical determination affect the 
length of the base. An astronomical 
base-line, therefore, should only be used 
when there are difficulties which make a 
direct measurement impossible. 

THE DEVELOPMENT OF THE BASE. 

In the early stages of the develop- 
ment, occurring, perhaps, on the level 
surface of the plain, it will be found 
necessary to use artificial signals. Great 
tripods of frame-work, ten or fifteen 
meters high, are constructed, leaving 
ample space within for the observer and 



5? 

his instrument. In erecting these, care 
must be taken that none of the legs of 
the tripod interfere with the view to- 
wards any of the proposed triangulation 
stations. Each of the signals terminates 
at the summit with a flag-staff, to which 
voluminous folds of white muslin are 
nailed, while the body of the steeple is 
wrapped with the same material and 
decked with loose tatters and streamers, 
which, by their ceaseless flutter in the 
wind, offer occasionally a surface from 
which the light is reflected to the eye of 
the distant observer. The same purpose 
may sometimes be better served by the 
use of glittering sheets of tin, or by a 
cone of the same material. These meth- 
ods all have one very great advantage 
over the more accurate heliotrope, that 
is, they are always in position, and ready 
for observations to be directed upon 
them at any time. The use of the re- 
fleeting mirror, however, unless there are 
a number of heliotropes in the field, in- 
volves the loss of much time, as the in- 
strument is transferred from one to an- 
other of the neighboring stations. 



58 

The development stations should be 
erected in conspicuous places, on high 
ground or the salient angles of bluffs, 
that the observer may know where to 
direct his instrument in searching for 
them, as it is extremely difficult to pick 
out the faint glint of a few yards of 
muslin on the broad light surface of a re- 
mote plain. As the development con- 
tinues and climbs from the foot-hills into 
the high and peaked mountains, these 
natural points are sharp and distinct 
enough, being projected against the sky 
beyond, and the labor of station-building 
ceases, except in cases that are very un- 
favorable. 

True, this triangulation by natural 
points is not so precise as it is in some 
geodetic surveys, and especially in the 
surveys of coasts, where even the phase 
of the conical signal is considered too 
important an element of error to be neg- 
lected; nor is it wise that it should be so, 
for a fault of a few meters in the posi- 
tion of a mountain-top in the remote in- 
terior of Brazil, located by this plan, is 



59 

at present of no practical consequence, 
and the nation cannot afford to purchase 
an accuracy imperceptibly greater than 
this by an expenditure that would many 
times exceed the cost of this method of 
survey. Considering a mountain as a 
land-mark by which travelers are assured 
of their place and are guided as they go, 
it will be seen that, to men who travel 
by land, a small fraction of a kilometer, 
in latitude and longitude, is a deviation 
which they cannot notice; to the voya- 
ger at sea, however, the exact site of the 
sunken rock which he shuns should be 
known to him, in order that he may cer- 
tainly avoid it. This is why the coast 
survey, in most countries, precedes that 
of the inland in the degree of accuracy 
which characterizes it, as well as in the 
amount of expense which attends it. 

TRIANGULATION BY NATURAL POINTS. 

It must not be inferred, however, that 
the use of natural points in triangulation 
necessarily involves a serious accumula- 
tion of error. In general, the engineer, 



60 

looking from one station to the next, can 
readily cover, with the thickness of the 
spider-line of his instrument, the highest 
ground of the distant mountain, and 
that point is selected as a correlative 
station, because that is the spot which 
can be most easily identified, either from 
a distance, or upon the ground itself. 
If this place is uncertain, as where there 
are a number of pinnacles of equal alti- 
tude, or not sufficiently prominent, as in 
a plateau summit, some peculiar object, 
as a solitary tree, or an isolated boulder, 
should be chosen as a center upon which 
to sight. If the profile of the mountain 
has but little curvature, its culminating 
point is usually determined by a pile of 
rock, a clump of vegetation, or other 
body upon its crest, which, although it 
may not be distinctly visible from a dis- 
tance, yet has the effect of increasing 
the apparent altitude at that precise 
locality. In the same way the useful- 
ness of a monument of rock, which a 
party should always leave behind it 
upon a mountain, as a signal to look 



61 

back upon, does not terminate at that 
distance at which it becomes apparently 
invisible. The eye will still be im- 
pressed with the superior elevation of 
the place where it stands. 

If the round top of a mountain is per- 
fectly bare, and offers none of these ac- 
cidental aids to the observer, it is well 
for him, in reading his first angle to it, to 
keep the horizontal cross-wire tangent to 
the surface, while he makes a careful 
and deliberate search for its highest 
point. Having decided upon this, he 
brings the vertical wire upon it, and then 
follows down the thread with his eye 
until he finds it bisecting some well- 
defined body in the field before him, 
such as a corner of rock or the trunk of 
a tree, and, in his repetitions of the 
angle he fixes the vertical wire always 
upon this object, while keeping the hori- 
zontal thread tangent to the surface. In 
this manner he secures to each of the 
following readings the advantages of the 
prolonged study given to the first, and 
not only are his results more accurate, 



62 

as a whole, but they also agree better 
among themselves, which is always a 
source of gratification to the engineer. 

THE MOUNTAINS OF BEAZIL. 

In those lands which are remote from 
the equator the summits of the high 
mountains, of an altitude of three thou- 
sand metres or more, are above all vege- 
tation and in the belt of perpetual snow, 
and their occupation is a work of great 
privation and exposure. The mountains 
of Brazil are exempt from that disad- 
vantage to triangulation, as the climate 
is never rigorously cold here, and the 
elevation of the highest land is less than 
three thousand metres. The only ob- 
stacles to be feared here are the oppo- 
site disadvantages of too much vegeta- 
tion, either hiding the tops of the peaks, 
or embarrassing the ascent to them, and 
too little height, whose result is liable to 
be a system of round, well-preserved, 
and insufficiently pointed mountains. 
But if those in the vicinity of Rio de 
Janeiro are to be accepted as a criterion, 



63 

nothing more could be desired in the 
way of natural aids to triangulation. 

PROGRESS OF THE TRIANGULATIOX. 

In some cases it may be absolutely 
necessary to send a party in advance to 
erect monuments of stone, or signals of 
timber upon proposed stations which are 
at the same time important and unfavor- 
able for observations ; or, should the 
mountain be covered with forest, it may 
be necessary to send axemen to clear 
away all but the largest and most cen- 
tral of these trees. Such action, how- 
ever, causes a vexatious delay on the 
part of the engineer, and is contrary to 
the fundamental principles of this 
method of survey, whose work should 
be a steady and unretarded progress, 
and should be reconnoissance and com- 
pletion in itself. 

From the top of his first high mountain 
station the engineer sees his allotted 
territory spread out before him, and he 
immediately begins to lay his plans for 
the coming season. He selects two dis- 



64 

tant peaks, which, with his present 
station, will form a grand triangle. Be- 
yond these, far in the distance, there is 
yet another, and these four constitute a 
great quadrilateral, the lengths of whose 
diagonals may each l>e determined by 
two independent sets of observations, 
checking each other. In like manner 
he makes the circuit of the horizon, util- 
izing, as best he can, the peaks which 
rise around him. 

Although, owing to the many obsta- 
cles and unforeseen difficulties which are 
experienced in traveling through an un- 
known country, he may be compelled to 
modify and alter his first plans very 
often, yet as soon as he abandons one 
feature of his scheme he immediately 
adopts a substitute to take its place. 
To be provided for such an emergency, 
if a distant peak, as,f or instance,one of the 
sharp pinnacles of the Organ Mountains, 
should appear impossible of ascent, he 
will select another in the same vicinity, 
and consider that as an alternate to the 
first, reading angles to it and treating it 



65 

in all respects as a regular station as 
long as such a reserve may seem neces- 
sary. 

In proceeding from one mountain to 
the next he surveys all of the interme- 
diate country, his course being governed 
by the advantages and obstacles whieh 
present themselves from day to day. 
His route should never be an arbitrary 
one, determined at a distance and weeks 
beforehand, but he should be free to act 
upon the spur of the moment, following 
a stream to its source here and stuvey- 
ing a lake there, according as these geo- 
graphical features may be encountered. 
If these features are depicted on maps 
already made, then there is no need of a 
second survey of the country; if they 
are not, he is not likely to know of their 
existence until he finds them. 

EQUIPMENT OF THE PARTY. 

Since the terminus of a day's survey 
cannot always be advantageously decided 
upon, even in the morning on which it is 
begun, it is especially desirable that th 



66 

party may carry with it its own equipage 
and supplies, so as to be prepared to 
camp anywhere that night may over- 
take it. As it is a part of the policy of 
geographical work that the engineer 
should never follow the same route 
twice, a survey carried on by daily ex- 
cursions from fazendas, settlements, or 
other fixed points of supply, returning 
to this base by the same road in the 
afternoon, would cost a great waste of 
time and energy. The necessary outfit 
of a scientific corps, consisting of instru- 
ments, clothing, cooking utensils, and 
provisions, can be carried by a train of 
pack-mules equal in number to the peo- 
ple whom they accompany. With this 
equipment the party are independent, 
and can camp anywhere that wood for 
fuel, forage for the animals, and a sup- 
ply of water are found. This arrange- 
ment is particularly necessary in the 
occupation of a mountain station, upon 
which, for successful observation, it may 
be imperative to arrive at an early hour 
in the morning and to remain through 



67 

the greater portion of one, two, or three 
days. From a camp near the summit 
this may be reached in an hour or two; 
but from a distant base almost the en- 
tire day would be consumed in the jour- 
ney to and fro. 

THE TRIANGULATION STATION. 

The mountain will be ascended by the 
engineer, the meteorologist, and such 
assistants as may be required to carry 
the implements of the work and the food 
and water necessary for the maintenance 
of the party, and to build the stone 
monument, which, if possible, should 
always crown the peak, to receive the 
records deposited here, to assist in the 
future identification of this station, and 
to serve as an object upon which to 
direct the telescope in subsequent ob- 
servations. One day will be a sufficient 
time of occupation for the ordinary 
triangulation station, provided the 
weather be favorable. To the more 
important ones, however, it may be 
advisable to devote two days, spending 



68 

one night upon the crest in astronomical 
observations for the determination of 
the azimuth of some line radiating from 
here; this will serve as a check upon its 
computed value, as derived from the 
original azimuth determination made by 
the astronomer at the base-line. In 
times of high wind, or cloudy and stormy 
weather, especially liable to occur upon 
the summits of peaks, it may be several 
days before satisfactory results are ob- 
tained, and therefore the party should 
always go well equipped for a prolonged 
stay in their mountain camp. 

PROFILE SKETCHES. 

As an economy of time, which is of 
the greatest value here, the observer 
should make all reasonable haste in his 
operations. Especially is this so in his 
sketches, over which he must not linger, 
which, if he is anything of an artist, he 
will be sorely tempted to do. He may 
see before him broader views and 
scenery more grand and impressive than 
ever was painted yet, but picturesque 



69 

effects are no business of his. To the 
geographer of artistic tastes there is 
great temptation to finish his sketch by 
inserting a pine-tree in the foreground, 
and, perhaps, an eagle's-nest in the tree; 
this is all very wrong, as such dalliance 
may cost the omission of that far distant 
peak, which is printed like a fine point 
against the horizon, and which, insignifi- 
cant and low as it appears, is yet of 
vital importance to his scheme. 

His sketch is perforce but the outline 
and skeleton of a picture. Two con- 
verging straight lines, with a few strokes 
of shading, hastily thrown in, are suffi- 
cient to represent the ordinary mountain 
peak. Yet, if the peak should possess 
any oddity or marked individuality of 
shape, this feature should be preserved 
and even magnified in the drawing, as a 
key to the identification of this point 
when seen from elsewhere at some other 
time. Since any mountain, from differ- 
ent points of view, presents phases that 
are quite dissimilar, it is one of % the 
greatest difficulties of triangulation to 



70 

make sure of the identity of a station 
previously occupied, or, where there are 
a number of observers in the field, to se- 
cure uniformity in the choice of the same. 

CONTOUR DRAWINGS. 

The expert geographer is proficient not 
only in rapid profile but also in contour 
drawing, and on every mountain station 
he executes a contour plot of that scope 
of country which he sees beneath his 
feet, and of whose conformation he is 
reasonably certain. But in the prepara- 
tion of this local plot he should not be 
too comprehensive, and go beyond the 
bounds of certainty into the outer limits 
of conjecture. Every mountain is sur- 
rounded by valleys, on whose farther 
side are other ranges perhaps as high as 
this, and they form the limit beyond 
which no contour sketch should presume 
to go, else it becomes conjectural and 
unreliable. It may include those en- 
virons of valleys, with a periphery of the 
foot-hills which are beyond them, and an 
indication of the canons which indent 
the same, but no more. 



71 

In the office a contour sketch is ac- 
cepted as truthful evidence of the ground 
as it really is, while a profile drawing is 
considered only a copy of the country as 
it appears to be, when uncorrected for 
the illusions of perspective, and is studied 
and deciphered accordingly. Looking 
abroad from this station, the successions 
of distant ranges, which are in reality 
separated by broad interspaces of valley 
and plain, are projected into a dense and 
circular wall, apparently unbroken by 
pass or intermission, whose serrated out- 
line is seemingly as continuous as the 
horizon. It is an error to which the 
human sight and judgment are subject, 
and so, in orographic delineation, the 
impressions of the eye are to be received 
with caution, and only the readings of 
the theodolite are to be accepted in full 
faith. 

PHOTOGRAPHS. 

As a supplement to the pencil of the 
engineer, the photographer's camera can 
often be used to good advantage in se- 
curing, in their true proportions, the 



72 

many details of geological structure 
which are necessarily omitted from a 
hasty sketch. In the best geographical 
delineation of a country, a series of 
photographs are almost indispensable, 
as, aside from affording much material 
for the filling in of a map, they reveal 
the nature of the surface which they 
represent, showing whether it is regular 
or broken, well-preserved or eroded, 
whether a cliff is impassable or easy of 
ascent, and whether a coast is smooth 
and sandy, or irregular and rocky. All 
of these conditions should be made to 
appear in every good map, whether in 
contour lines or hachures, and particu- 
larly so, when, as in this case, the map is 
intended as a basis for geological repre- 
sentation. 

READING THE ANGLES. 

The instrument of triangulation is a 
theodolite,- whose accuracy and weight 
increase with the minuteness of the 
graduation, but, in this work, in which 
rapidity and ease of transportation are 



73 

to be considered, there comes a limit be- 
yond which it is imperative to sacrifice 
nicety to portability. This is reached 
when the limb is graduated so as to dis- 
criminate to ten seconds of arc, between 
which divisions the observer may esti- 
mate to every intermediate five seconds. 
With this he reads and repeats the 
angles, singly and in combinations, that 
lie between the visible points of the 
triangulation scheme. It is advisable to 
make at least six determinations of each 
angle upon each of the two verniers of 
the instrument, amounting to twelve 
repetitions in all. The greater the num- 
ber of readings from which the mean is 
derived, the less will be the " probable 
error of observation affecting that mean. 
The observer may complete the repe- 
tition of each angle by itself, or, what is 
more convenient, he may read them in 
conjunction, by making six complete cir- 
cuits of the horizon. In either case the 
graduated limb of the theodolite will be 
turned 30 in azimuth at every return to 
the initial point. In this manner each 



74 

angle is read upon twelve different and 
equi-distarit divisions of the circle, and 
the faults arising from eccentricity or 
imperfect graduation are reduced to a 
minimum. 

The most opportune moments of the 
day will be devoted to this important 
task, and all other duties will be neg- 
lected for this. Successful triangulation 
demands perfect quiet and a clear hori- 
zon. In a dense and hazy atmosphere, 
or in a region of low clouds, the observer 
may find his opportunity in the evening 
or early morning, when the sun is be- 
hind the hills, and the rim of the earth 
is seen in" silhouette against the rosy 
background of the sky. 

SUBORDINATE ANGLES. 

Upon the triangulation station the 
engineer also reads angles for the direc- 
tion of the spurs which project from 
here and of the streams that debouch 
from here, estimating the distances of 
geographical features in his immediate 
vicinity. How far he may trust to his 



75 

judgment in this respect, will be determ- 
ined by the circumstances by which he 
is surrounded. It is the engineer's duty 
to make the best map of a country that 
is possible with the advantages at his 
command, and if he should see before 
him a tract of country, distant even ten 
or twenty kilometres, which he will 
never see again, he should take note of 
it on his contour plot; but if he knows 
that some future route of his will cross 
it, he can afford to neglect it now. 

In addition he takes readings to infe- 
rior elevations which, although they 
may never be occupied for reciprocal ob- 
servations, may yet be located by 
intersections from two or more triangu- 
lation stations. Some point, or "tit," 
standing on the edge of an abrupt bluff, 
where the rapid descent begins, is used 
as a means of marking the end of a 
neighboring mountain range. A solitary 
butte on the plain, insignificant in itself, 
is very useful in determining the locus 
of the stream which flows by the side of 
it. A promontory, jutting into the con- 



76 

fluence of two rivers, is instrumental in 
fixing the place of their union. Sights 
are also taken to the junctions of 
streams, the mouths of canons, and to 
the church or other central object of a 
distant village. A spot of green on the 
desert, evidence of a spring of water 
there, is located, for it will perhaps be 
camping-ground some day for himself or 
his co-laborers. A minute patch of 
white lake-bed, or red escarpment, or a 
solitary tree, is sighted upon, because on 
such a day he made an odometric sta- 
tion there, and this sight will serve to 
check his position. 

NOMENCLATURE. 

In his note-book and mind he has 
dubbed all of these things with graphic 
titles, or designated them by letters of 
the alphabet, and by these tokens he will 
know them when he sees them again. 
But this system of names is only a 
transient device for the assistance of 
himself and those who work in concord 
with him, and should not appear upon 



the printed sheet to the exclusion of tae 
native and established nomenclature of 
the country, which should be investigated 
as far as possible, and, upon the final 
maps, should be adopted in preference 
to the arbitrary naming of any one man. 
The usefulness of a map, as a guide to 
the traveler, is in a great degree invali- 
dated by a nomenclature which is at 
variance with that in use upon the ground 
itself. Perhaps the modern geographer 
is guilty of no more common and high- 
handed outrage against right, conven- 
ience, and beauty, than by ignoring the 
appropriate titles which abound in every 
country, however wild and uncivilized, 
and attaching his own, or by mutual and 
tacit agreement, the names of his com- 
rades, to the mountains of that land, 
thus announcing themselves to the world 
as nostrums are advertised on the pyra- 
mids. 

THE TOPOGEAPHICAL STATION. 

All of the preceding description that 
does not refer to the triangulation pro- 
cess is also pertinent to the topographical 



78 

tation. This term is applied to those 
isolated stations of survey, apart from 
the route of the odometer, and interme- 
diate to the points of primary triangula- 
tion. They are more numerous than the 
primary stations, being usually scattered 
over the country at intervals of not 
more than twenty kilometres, but are 
less important, since there is no great 
responsibility of accuracy resting upon 
them. The topographical stations cor- 
respond, in position and numbers, with 
the secondary triangulation stations of a 
more elaborate geodetic survey. 

A SECONDARY TRIANGULATION. 

Even here the topographical station 
may be made a point in a subordinate 
scheme of triangulation if its situation is 
elevated, distinct, and capable of recog- 
nition from a distance. Of course, it is 
desirable that every occupied station 
should subsequently be made an object 
of reciprocal observations, and the engi- 
neer should neglect no opportunity to 
confirm his position in this manner. 



79 

Each point thus fixed becomes the center 
of a plexus of triangles, of each of which 
the three angles have been observed; 
the total error of observation in these 
three angles becomes apparent, and the 
computer is enabled to distribute it judi- 
ciously among them before he proceeds 
to the computation of the sides. 

For this reason the observer upon any 
topographical station will make careful 
search for other points which he may 
have occupied or may contemplate oc- 
cupying, and will be more than usually 
cautious in reading angles to them. On 
his return to the office, at the end of the 
season, he will pick out from the multi- 
tude of his notes as many complete tri- 
angles as he may have observed, and 
these will be so much gain attained at a 
cost of but little extra labor. But if he 
makes it imperative upon himself to 
carry on a complete and systematic tri- 
angulation within the first, the additional 
refinement gained will by no means com- 
pensate him for the disadvantages of 
reconnoissance and delay which this in- 
volves. 



80 

It is safe to say that it is a longer and 
more laborious work to accomplish an 
unbroken secondary triangulation than 
a primary, as the stations are more nu- 
merous, less elevated and conspicuous, 
and oftener in the shadow. On the 
other hand, the results are by no means 
so valuable. The primary triangulation 
sustains the general and continued accu- 
racy of the survey; the secondary does 
little more than to insure the individual 
positions of its own stations. 

POSITION OF THE TOPOGRAPHICAL STA- 
TION. 

Although not necessarily a point in 
the triangulation proper the site of the 
topographical station must afford angu- 
lar data sufficient for the determination 
of its position by the three-point problem. 
After that, its predominant idea is that 
it is a means of local geography, or to- 
pography, and a center for a series of 
contour sketches. In addition to these 
detailed plots of the country in the im- 
mediate vicinity, profile drawings of the 



81 

more distant regions are made. Then, 
by lines of sight, which shall be intersect- 
ed by other rays from other topographical 
or triangulation stations, the most 
prominent features within a radius of 
twenty or thirty kilometres are crossed, 
and, as a precaution, angles are also read 
to all eminent points visible at a greater 
distance, even to the horizon, as they 
may come into use in some future di- 
lemma in map-drawing. 

While the site of the topographical 
station should be as elevated and marked 
as possible, yet any hill, however humble 
and inconspicuous, or even the level sur- 
face of a plain, may serve this purpose? 
provided that there be three triangula- 
tion stations, or other known points, visi- 
ble, and there is any useful information 
to be gained by lingering here. A few 
hours are usually enough for its occupa- 
tion, and the route between points of 
triangulation should be marked at regu- 
lar intervals by the monuments of these 
stations. It is a good plan for the en- 
gineer to make a practice of diverging 



82 

from his route at some point in each 
day's odometric survey, and, ascending 
a suitable eminence close at hand, make 
a topographical station there. As far as 
a general rule can be given for the oc- 
currence of mountain stations, it is advis- 
able for the party to advance by linear 
survey every second day, remaining in 
camp on each alternate day, while the 
engineer ascends some peak in the vicin- 
ity for the purpose of establishing a 
topographical or triangulation station 
there. 

The - large triangulation theodolite 
should be used in the more important 
topographical stations, or those which 
may possibly be treated as points in a 
secondary triangulation, but, for the sake 
of convenience, the small route transit 
must be made to suffice for those which 
are made in the course of the daily 
march. 

THE ODOMETRIC, OR MEANDER SURVEY.* 

The meander survey is useful as an 

* Note to the Portuguese Edition. This term, which is 
now firmly grounded in the technical language of 



83 

adjunct to the triangulation, filling up 
its skeleton with that 'detailed informa- 
tion which alone can give practical and 
popular value to a map. It determines 
the courses of valleys and streams, the 
routes of roads and trails, the peripheries 

geographical surveying in the United States, is a mis- 
nomer, and therefore, in introducing a corresponding 
one into the Portuguese, it will be well to adopt some 
more appropriate expression. For this reason " odomet- 
ric survey" will be used to designate line surveys in 
which the odometer takes part, and "route survey" 
(caminhamento) as a general term, to include not only the 
above, but also those in which distances are determined 
by time, by the chain where that method is employed, or 
by paces, whether of man or horse, and whether re- 
corded by the pedometer or by direct counting. 

As the meander survey is understood, where this ex- 
pression is used, it is simply any survpy following a zig- 
zag line, whose angles in general, are alternately salient 
and re-entrant, as the line accommodates itself to the 
route of travel. But this word " meander," having been 
derived from the river of the same name, in ancient 
Phrygia, which was celebrated for its winding, sinuous 
course, literally means "abounding in curves." It will 
thus be seen that the more a survey approaches to a true 
meander, the farther it departs from the first principles 
of accurate linear surveying, which dictate that it shall 
consist of straight lines and angles only. Since it is al- 
ways to be regretted when a survey is confined to a true 
meand*er line, as for instance, in tracing the course of a 
road along and up the Fide of a mountain range, so it is 
also a matter of regret that this word should have been 
introduced into the language of engineering, apparently 
sanctioning a faulty survey. 



84 

of lakes and basins, and the distances 
between springs of water, villages, areas 
of pasture, fords of rivers, and other 
points of interest to the future traveler. 
Finally, it is a commendable occupation 
for the engineer while on his way from 
one mountain station to the next, and, 
since it occasions no delay in the general 
progress of the work, as the engineer 
can, as a rule, meander as much road as 
his pack-train can travel in one day, its 
results are net gain to the survey. 

In the theoretical journey of this kind, 
the engineer would follow the edge of 
the dividing ridge from one station to 
the next, from which lofty promenade 
he could see the earth like an extended 
scroll beneath his feet, and make a sur- 
vey that would be exhaustive and 
complete. But in the real, hard prac- 
tice, he finds this path an impracticable 
one, for it is broken by precipices and 
blocked by abutments often a hundred 
metres or more in height. His easiest 
route of travel is by the side of flowing 
water, whose tendency it is to erode aft- 



85 

rupt cliffs and soften steep gradients 
into an average and even slope. Be- 
sides, along the streams there are trails 
made by the wild animals which come 
here for drink and covert, and by the 
people of the country who come hither 
to hunt and fish. Therefore, if the* de- 
tour be not too great, the most expedi- 
ent route from mountain to mountain, is 
down one valley and up another, and 
the geographer who traverses a valley 
without taking some sort of a survey of 
it, is culpably negligent of his duty. 
On the other hand, if in a block of 
mountains the pre-eminent peaks be oc- 
cupied, and the streams which emanate 
therefrom be meandered, nothing more 
is needed for a most excellent geograph- 
ical map of that country. 

THE MEANDER TRANSIT. 

It is supposed that all transportation 
of outfit, and all travel, even in the me- 
ander survey, is accomplished on the 
backs of horses or mules. Riding in 
the saddle, the surveyor can devote but 



86 

one hand to the grasp and protection of 
his instrument, the feet of whose tripod 
rest in a holster attached to the left 
stirrup. To facilitate his secure- hold, 
the members of the tripod are thirds of 
a cylinder, which fold into the smallest 
possible compass, and are easily held in 
the grip of one hand. 

The instrumental part of the meander 
transit is neat, solid, and compactly 
constructed. Its graduated limb is of 
small diameter, and its horizontal ver- 
nier reads to minutes only, which is all 
very well, since no smaller divisions can 
be plotted on the map. This graduation 
is used in the occupation of topograph- 
ical stations, at those meander stations 
where the view is extended enough to 
make it profitable to linger an hour or 
so in the accumulation of notes and 
sketches, and at all those which are 
three-point stations as well. But in the 
general survey, not the vernier-plate, 
but the compass needle, is used, on ac- 
count of its greater convenience. The 
compass box is graduated, from zero at 



8V 

the north, around by the left to 360 at 
the north again, so that a reading of 90 
corresponds to magnetic east, and 270 
to west. The field records are kept 
in this manner, and in the office the de- 
clination of the needle is first applied to 
each bearing^ after which it is reduced 
to its true direction, preparatory to the 
plotting. 

THE ODOMETEB. 

The distances from station to station 
of the meander are measured by the 
odometer, an implement of survey which, 
in some of its forms, has been long in 
use in Europe, and has of late years re- 
ceived especial attention and improve- 
ments in the reconnoissances and other 
geographical surveys carried on by the 
War Department of the United States 
of North America. In this service it 
has been adapted to the severe condi- 
tions of travel in a new country. It has 
been strengthened so as to withstand 
any shock or fall to which it may be 
subject. The recording apparatus is 



88 

made so compact and simple that there 
is no danger of disarrangement there. 
Instead of the old laborious process of 
pushing it by hand, the wheel has been 
fitted with shafts, so as to be drawn by 
a mule, and so efficient is the method of 
attachment that the odometer can follow 
any route, however rough, precipitous, 
or narrow, that will admit of the passage 
of a pack-mule. 

In its simplest and best form the 
odometer vehicle is a solitary wheel, a 
little more than a meter in diameter, or 
about the size of a light carriage- wheel. 
It is strongly constructed of the best 
material, and is braced by opposite in- 
clinations of alternate spokes, so as to be 
uninjured by the heaviest jars and col- 
lisions. A pair of shafts are attached to 
it, and into these a strong and steady 
mule is firmly harnessed by straps from 
above and underneath. The vehicle is 
close in the rear of the animal, and the 
shafts are made short and heavy, and in 
this manner the wheel is preserved in a 
plumb or upright position as it runs, not 



89 

swaying from side to side. The length 
of the circumference of the wheel being 
accurately known and the number of 
revolutions being recorded by the at- 
tached apparatus, it is a simple matter 
to learn the distance between any two 
points. 

The recording instrument hangs in a 
cylindrical box which is strapped to the 
wheel. It consists of a mechanical com- 
bination attached to a heavy block of 
metal, whose center of gravity is at one 
side of the axis to which it is suspended. 
As it is free to revolve upon this axis it 
always maintains a vertical position, 
while its box turns with the wheel, and 
the apparatus scores the number of 
revolutions, of which it is capable of re- 
cording 9900, or a distance of about 
forty kilometers, when it begins anew. 

USEFULNESS OF THE ODOMETEK. 

This detailed description of the odo- 
meter is in accordance with the promise, 
made in the early part of this article, to 
dwell upon the novel features of this 



90 

work, even to the exclusion and apparent 
neglect of others, already well-known, 
which are really of greater importance. 
Still it would be difficult to over-esti- 
mate the usefulness and practical value 
of this instrument. It requires but little 
technical knowledge to use it and to 
conduct the meander survey which ac- 
companies it, and any person educated 
in the simplest rudiments of surveying 
is competent for this kind of work. 

For this reason every party of scien- 
tific exploration and reconnoissance, 
every preliminary survey for railways, 
and every marching body of troops 
should consider its outfit incomplete 
without the implements of an odometric 
survey. Aside from the mass of notes 
and sketches that would be accumulated 
by them, and the itinerary maps that 
would result, in the item of distances 
alone the country would be more than 
repaid for the cost of these surveys. As 
a means of mensuration the odometer 
will determine distances en route, as the 
wagon travels, more truthfully than the 



91 

chain itself. These, being published, 
are of profit, not only to the ordinary 
traveler, but also to the general govern- 
ment, whose agents and officials, in one 
capacity or another, are constantly pas- 
sing to and fro. 

ERRORS OF THE ODOMETRIC SURVEY. 



is there any very great error in 
the ordinary surveys which the odome- 
ter is likely to be called upon to perform. 
Having the geographical positions of 
two towns forty kilometres apart, they 
may be connected by an odometric sur- 
vey, the plot of which can be adjusted 
between these two positions so that no 
intermediate points will be appreciably 
out of place on a map of the usual scale. 
Since this is a map for practical use and 
for the public good, it fulfills its pur- 
pose as well as if its distances had been 
measured by the most refined methods. 

The great objection to its use is the 
tendency towards the accumulation of 
error in an odometric meander, and the 
farther it is from the known point which 



92 



is its origin, the greater is the probable 
error of any position determined by it. 
Therefore, in a prolonged journey, or in 
a general survey of the country, the 
odoraetric position should frequently be 
verified, or checked and rectified, by con- 
nection with known points. This can be 
accomplished by making a station at 
some point on a railway, boundary, or 
other line of accurate survey ; by astro- 
nomical observation, which, however, if 
taken with a sextant, is often less relia- 
ble than the meander itself; or by mak- 
ing a meander station dependent upon 
the accompanying triangulation, by 
means of the three-point problem. The 
last method, which is by far the most 
reliable, will be explained further on. 

ERROR OF DIRECTION. 

The meander is affected by error of 
two kinds, of direction, and of distance. 
The former, in its most serious nature, is 
incurred in the survey of a tortuous val- 
ley, whose general course must be ac- 
cepted, or in crossing a timbered coun- 



93 

try, or a pathless plain, where the sur- 
veyor is in a constant state of uncer- 
tainty as to whither he is to go, or, tak- 
ing a back-sight, as to whence he has 
come. Sometimes the engineer is 
obliged to keep his eye on the sun and 
get a general idea of the course from 
that. Or, in traversing a dense forest, 
he may find himself compelled to resort 
to the paradox of sighting upon a sound; 
that is, he allows the pack-train to keep 
a certain distance in advance, and from 
time to time he directs his telescope to 
the tinkling of the bell which is carried by 
the horse that leads the train. It must 
be confessed that these make-shifts are 
loose methods of survey, but they are 
better than none, since they give the 
prominent directions and the distances 
between streams, divides, etc., and 
months afterwards, when the engineer 
comes to make the map and lay down 
upon it the trail of that day's march, he 
will find the poorest and most incom- 
plete notes more reliable than his present 
memory and judgment. 



94 

Even under the most favorable cir- 
cumstances it will seldom be possible to 
direct the telescope with greater pre- 
cision than to the nearest degree, nor, as 
a consequence, will it ever be worth 
while to record any fraction of a revolu- 
tion in the odometer. A road does not 
usually change direction by an abrupt 
angle, but by a gradual curve, and the 
bearing is made approximately tangent 
to that curve. Or, in the survey of a 
stream, it is not known on which side 
the trail will run at some point a kilo- 
metre in advance, and so the approxi- 
mate center of the valley is accepted. 
But if there should be a solitary tree, 
bush, house, rock, or other prominent 
object fortunately situated for a station, 
the course will be made closely tangent 
to that, a reading of instruments will be 
taken upon arriving there, and, going on 
to the next station, the engineer will 
take a back-sight to the same point. In 
general the system of back-sights will 
be found more satisfactory than that of 
foresights, as it is easier, on a strange 



95 

route, to tell whence you have corne than 
to decide where you are going. 

ERROR OF DISTANCE. 

This error of direction, it will be seen, 
is thrown by the law of chance alter- 
nately to the right and left of the true 
line, and so has a tendency in its elements 
towards mutual compensation, and in a 
measure it corrects itself. But not so 
the error of distance, which is always 
plus, and cumulatively so. The test of 
the odometer wheel, by which its num- 
ber of revolutions per kilometre is ascer- 
tained, is made upon a level surface and 
along a staked alignment, giving a re- 
sult almost absolutely correct. In prac- 
tice, however, the vehicle climbs acclivi- 
ties of every grade, tacks hither and 
thither as it follows the trail up the 
mountain, winds incessantly in its route 
through the forest, and is disturbed by 
frequent jolts and collisions along the 
rocky floor of the canon. In a theo- 
retical traverse the straight line between 
any two stations is determined, but in an 



96 

odometer survey the measuring imple- 
ment usually follows a beaten path, and 
the route distance, by road or trail, is 
rarely the shortest distance between two 
points. Hence an "overrun" in its 
record, which can only be remedied, and 
that approximately, by the judgment of 
the surveyor, who is taught by experience 
to estimate very closely the surplus in a 
given run, and who applies a correction 
accordingly. 

Still, to such perfection has the odo- 
meter survey been brought, that it is a 
common occurrence for a skilled worker 
to meander a closed circuit of. one hun- 
dred kilometres, and plotting the route, 
to find the plot also close within a small 
fraction of a kilometre. Even this error, 
being judiciously distributed in the pro- 
cess of adjustment, different weights 
being assigned to different runs, accord- 
ing to their probable accuracy," may be 
reduced so as to be practically imper- 
ceptible. 

OCCURRENCE OF MEANDER STATIONS. 

No general rule can be given for the 



97 

frequency of meander stations, but in 
ordinary country they will average per- 
haps one to the kilometre. In this all 
will depend upon local circumstances 
and exigencies. In the survey of a long 
and hidden valley, affording no opportu- 
nity for checks, especial care must be 
taken to preserve the integrity of the 
meander, and the stations must be espe- 
cially frequent; but in a survey by a 
direct line across the plain two or three 
stations a day may be sufficient. In a 
winding path up a mountain side a 
dozen stations may be necessary if there 
are no chances for checks; but if the 
ends of the trail, at the top and bottom 
of the mountain, can be located by the 
three-point problem, the intermediate 
route can be neglected, being, at most, 
sketched in by the eye. 

There are two considerations to govern 
the occurrence of stations; first, to pre- 
serve the continued accuracy of the sur- 
vey, and second, to note the local 
geographical features which may be 
encountered. For y the latter purpose 



98 

stations will be made at the center of 
every village, at every country-house of 
importance, at the crossing and diverg- 
ence of streams, roads and trails, at the 
opening of a valley, at the foot and 
summit of a mountain, and at the 
many other geographical vantage- 
grounds which the practical engineer 
will know how to select. But in this, as 
in the other departments of the survey, 
too punctilious zeal may defeat its own 
interests by causing delay, and the sur- 
veyor who is too scrupulously exact in 
the forenoon may have to virtually 
abandon his task in the afternoon, in 
order to reach a suitable camping-ground 
by night. 

SCOPE OF THE MEANDER SURVEY. 

The zone of country considered from 
a meander line may extend to the 
farthest visible point, as a series of sights 
upon a mountain even twenty-five kilo- 
metres away will give its position to a 
close approximation; but its principal in- 
tent is the preparation of a narrow route 



map, the areas encompassed by whose 
windings will be filled in from the topo- 
graphical stations. Since, from its nature 
and narrow scope, it is fuller and takes 
cognizance of objects more minute than 
can be noticed in the other systems, in 
this the engineer is liable to a charge of 
partiality, reproved in the early part of 
this article. But this is not partiality in 
one field at the cost of neglect in 
another, and the greater excellence of 
this work is so much clear gain. More- 
over, since the meander is usually by 
way of roads of frequent travel, and 
since a map is useful, and should be ex- 
cellent, exactly in proportion to the num- 
ber of people who are guided by it, it is 
well that the meander plot should excel 
in completeness those almost inaccessible 
parts which will never be seen except by 
the hunter or bandit. 

MAKESHIFTS IN THE SURVEY. 

In a forced march of forty kilometres 
or more, the meteorologist and odometer 
recorder, the safe carriage of whose im- 



100 

plements requires a slow and steady gait, 
may proceed at a walk after taking their 
readings at a meander station, which task 
will occupy them but a few minutes, 
while the surveyor lingers behind to make 
the necessary sketches and observations, 
and then, riding at gallop, overtakes his 
comrades before the next station is 
reached. Many such shifts as this are 
known to the practical and energetic 
geographer, who learns to emancipate 
himself from too close dependence on the 
text-books of surveying, some of whose 
rules are very common-place and pedan- 
tic, and brings into play his powers of 
ingenuity and invention, to adapt himself 
to the peculiar circumstances by which 
he may be surrounded. If he finds him- 
self alone, out on some trip of hasty 
reconnoissance, or on some hunting ex- 
cursion on which he could not carry both 
rifle and transit, he draws from his watch 
pocket an aneroid, and from his saddle- 
bags a pocket compass or an altazimuth, 
and his equipment for survey is com- 
plete; as for distances, he can estimate 



101 

them, or determine them by the time 
they take, calculating at the rate of five 
kilometres an hour, or, better still, by 
counting the steps of his horse and allow- 
ing six hundred double paces for a kilo- 
metre. 

In a geological survey of Brazil very 
much of the travel and exploration is 
necessarily done by water, as the outcrop 
of the various formations is most favora- 
bly shown upon the banks of the rivers, 
along which there is frequently no passa- 
ble route by land. Here the stadia may 
be used, provided there are two or more 
boats in the party, or, in the less import- 
ant instances, the methods of obtaining 
distances by estimation or by time would 
have to suffice. In either case the sur- 
veyor should lose no opportunity to 
emerge from the trough of the stream, 
or to ascend some eminence, and insure 
his position by observations upon three 
or more known points. Should these be 
wanting, he should resort to the sextant 
and to its use in astronomical determina- 
tions. 



102 

Since the attention of the geologist is 
in great- part absorbed in the duties pe- 
culiar to his profession, he cannot usually 
carry any but the lightest and most con- 
venient implements of survey, and since 
these are amply sufficient for his geologi- 
cal notes of dip, strike, trend, etc., it is a 
matter of expediency to make them an- 
swer for his geographical work as well. 
With the engineer, however, there rarely 
comes a necessity for being separated 
from his portable transit, which admits 
of being firmly set on its tripod, and from 
which angles, either horizontal or verti- 
cal, may be accurately read to the near- 
est minute. And in the general geo- 
graphical plan it is wise to deprecate as 
far as possible the employment of unreli- 
able pocket instruments, or of the devices 
for learning distances that have been de- 
tailed above. Since nothing is to be 
gained in time by their use, and very 
much may be lost in accuracy, the engi- 
neer should teach himself to consider that 
any method less complete than that of 
the portable transit and odometer is but 



103 

a temporary expedient and makeshift, 
serving an excellent purpose when all 
other means fail, but not to be relied 
upon as a permanent constituent of the 
survey. 

CO-OPERATION OF THE TRIANGULATION 
AND MEANDER. 

While the meander survey is an ex- 
cellent apprenticeship for the young en- 
gineer, it should not be despised, as an 
occupation, by even the director of the 
triangulation. Humble as it is, it per- 
forms a task in the geographical plan 
which no system of triangulation can be 
relied upon to perform in a rapid work 
of this nature. It enables the survey to 
reach any point, however remote and se- 
cluded, and to determine its positions; it 
makes the map complete in all of the 
details which are so useful to the trav- 
eler; and as an agent in what we may 
call the practical or economical branch 
of geography it is without an equal. 

It is dependent upon the triangulation, 
it is true, but then the dependence is 



104 

mutual. The full benefit of either can 
only be secured through the co-opera- 
tion of the two. As without the trian- 
gulation the map is unreliable, so with- 
out the meander it is incomplete. To 
use a homely illustration, the triangula- 
tion may be compared to the framework 
of the dwelling, and the meander to the 
intermediate filling of wall or other sub- 
stance which makes the house habitable, 
and is a shelter to the inmates. This 
frame, if its lines are true and its angles 
correct, is a beautiful thing for the arti- 
san to contemplate, but without its com- 
pletion of walls and furniture, it is of no 
real benefit to the world. In the same 
manner a bare triangulation scheme may 
be an interesting study to the geographer 
himself, but to the traveling public and 
the people at large, it possesses neither 
interest nor value. On the other hand, 
as the frame of the house is an absolute 
necessity to it, securing and sustaining it 
in its proper proportions, so is the trian- 
gulation the rigid frame work of the 
map and the skeleton to which the use- 
ful data of the meander are attached. 



105 

CHECKS BY THE THREE-POINT PROBLEM. 

Since the meander is from its very 
nature so hasty and loose, the system of 
frequent checks can alone make it relia- 
ble, and at intervals of every few kilo- 
metres, and especially at the crossing* of 
divides and other eminences from which 
there is a broad scope of country visible, 
connection should be made with the 
triangulation. Each of these stations 
then becomes a new initial point, at 
which the survey begins afresh and the 
error again begins to accumulate. 

This rectification is accomplished by 
the use of the three-point problem, a 
geodetic determination which, as a 
means of locating topographical stations, 
and as a connecting link between the 
meander and the triangulation, is of the 
highest importance in geographical sur- 
veying. Having three triangulation sta- 
tions in sight, and favorably situated, it 
is possible for the observer to determine 
his position in a few minutes of time 
and by the simple operation of reading 
the two angles included by those three 



106 

stations. From these and the data per- 
tinent to the triangulation stations he 
can compute his distance from them, and 
hence his present latitude and longitude. 
Or, plotting these angles from any cen- 
ter on a piece of tracing cloth, he can 
lay this upon the projected map and 
swing it around until each of the three 
plotted rays covers its proper triangula- 
tion point, when this center will indicate 
the position of the three-point station, as 
it is called. For this graphic determina- 
tion not only three points, but four, and 
even more, if they are visible, should be 
observed, as a greater number facilitate 
the operation and insure the accuracy 
of the result. 

This method of trilinear determinations 
cannot be introduced too often. A 
three- point station in the streets of a 
settlement, at the forks of a road, or at 
the end of a mountain range, will locate 
these important places, and in camp, 
even in the center of a broad and vacant 
plain, there is no more profitable man- 
ner in which the engineer can spend his 



107 

leisure time, before or after dinner, than 
by making a three-point station there 
and determining his position. Every 
camp thus fixed is a new and reliable 
origin at which the meander of the next 
morning will begin. 

A SURVEY BY THREE-POINT STATIONS 
ALONE. 

In some cases a successful meander 
may be carried on by three-point sta- 
tions alone, when all other means would 
fail. Take, for instance, the rugged 
shores of a lake or bay, which are inac- 
cessible except to a man on foot or in a 
boat. In the mountains on the other 
side of the water a series of triangula- 
tion stations stand up in full view. By 
means of these the engineer, working 
his way, transit in hand, from bay to 
bay, and from point to point, along the 
water's edge, makes three-point stations 
at all prominent changes of curvature, 
and, sketching in the intermediate shore, 
he determines its line by tangents and 
intersections, and thus secures a good 



108 

survey of the coast. If there are islands 
out in the water they may be surveyed 
in the same way. 

If the engineer was confronted with a 
piece of geography like the bay and 
islands of Rio de Janeiro, and if there 
were no roads along the beach to make 
direct linear measurements feasible, he 
could extend his triangulation to include 
all of the prominent peaks in the vicinity, 
and then, by means of three-point sta- 
tions, he could rapidly trace in the shore- 
line. As the surroundings of Rio are so 
broken and irregular, the triangulation 
points could be made so numerous that 
it would be difficult to find a spot on the 
beach of mainland or island so secluded 
that some three of these stations would 
not be visible from there. 

THE MEANDER PLOT. 

Every three-point station, as well as 
every other meander station, should par- 
take more or less of the nature of a regu- 
lar topographical station; that is, contour 
sketches should be kept constantly on 



109 

the plotted page as it progresses, and a 
continuous panorama of profile views, 
drawn in a separate portion of the book, 
should accompany the survey, so that, 
as some geographical features are left in 
the rear, others may be introduced in 
advance. 

As from one topographical station to 
its neighbor, so every distance from one 
meander station to the next should be 
considered a base to be used in the loca- 
tion of points useful in the structure of 
the map. The longer this base, the more 
distant may be the range of these views. 
In case several meander stations inter- 
vene between one observation and the 
following, this total intermediate dis- 
tance becomes what is called a broken 
base, but it is none the less useful for all 
of that. The above considerations will 
influence the engineer in his choice of 
stations, which will always be situated in 
such positions as may offer the best ad- 
vantages for the accumulation of what- 
ever information he most needs. 



110 

THE DECLINATION OF THE COMPASS 
NEEDLE. 

The variation of the compass needle, 
or, more properly, its declination, will be 
carefully watched throughout the sur- 
vey, and determinations of its angle will 
be made from time to time; these will be 
more than usually frequent wherever 
there is suspicion of some attraction im- 
mediately local, arising from the presence 
of magnetite or other ore of iron, basaltic 
rock, or other disturbing influence. These 
determinations are important, not only 
in the reduction of the meander notes 
taken in this vicinity, but also for the 
practical use, both present and future, 
of the country at large. In addition, their 
results will aid the general cause of sci- 
ence in its investigation of the laws of 
terrestrial magnetism, and in tracing the 
course of isogonic lines around the world. 

At every triangulation, topographical, 
and three-point station, the observer 
will note the direction of magnetic 
north, as indicated by the pointing of 
the compass needle. If his instrument 



Ill 

has a double movement in azimuth, as 
all should have, it is well, for the sake of 
convenience, to first set the zero of the 
graduated limb upon the same point of 
the vernier plate, by the upper motion, 
and then, by means of the lower move- 
ment, bring the north end of the needle 
to the zero of its circle. His initial 
entry in his note-book will then be 
" Magnetic North, 00' 00"." This 
direction of the telescope being referred 
to some line proceeding from here, 
whose true azimuth will be found by 
subsequent computation, the magnetic 
azimuth or declination of the needle at 
that place will be determined; it will 
simply be the difference between the true 
azimuth of the line, reckoned from the 
north point of the horizon, and its ap- 
parent azimuth, or the vernier reading 
which he enters in his notes. 

BY DIRECT ASTRONOMICAL OBSERVATION. 

The declination of the needle will also 
be determined directly by astronomical 
observation in the evening at camp. For 



112 

this purpose the engineer will select such 
nights, clear and still, as may appear to 
him most favorable, and such camping 
places as may most urgently require this 
information. A star as near as possible 
to the pole will be chosen, as, from its 
greater declination, an error in the lati- 
tude of the observer's place, and, from 
its slower motion, an error in the time 
of the observation, will result in less 
serious errors in the azimuth; and the 
smaller the polar distance of the star, the 
more convenient will be the observation 
and the computations which follow, and 
the more exact is the result likely to be. 
In the northern hemisphere a Ursce Mi- 
noris, or Polaris, is almost always used, 
as it is at present only about 1 20' from 
the pole, and it possesses the additional 
advantage of a brilliancy of the second 
order. But south of the equator there 
are no available stars so favorably situ- 
ated as this. The most southern one of 
any considerable size is ft Hydri, of the 
third magnitude, whose polar distance is 
a little more than twelve degrees. 



113 

This would have to be accepted in a 
survey of this nature in preference to 
any of the less brilliant stars of greater 
declination, as the observations would 
have to be made frequently by engineers 
of little astronomical experience, and 
with instruments not especially adapted 
to this kind of work. Indeed, it might 
be necessary at times to use the small 
meander transit for that purpose; arid it 
is seldom that the telescopes of even the 
theodolites for triangulation, as now con- 
structed, are provided with the hollow 
rotation axis requisite for a proper illu- 
mination of the diaphragm, without 
which it is difficult to see both cross- 
hair and star, unless the latter is of con- 
spicuous magnitude. 

Knowing, at least approximately, the 
latitude of the place, and also the decli- 
nation of the star and its hour angle at 
the time of observation, its azimuth 
angle from the south point can be com- 
puted. But as the hour angle depends 
upon the local time at that place, and 
there is great room for error there, the 



114 

observer, unless he has full confidence in 
his ability to make an accurate time-de- 
termination, should find the approximate 
minute of the star's greatest elongation, 
and follow it with the transit thread 
until it reaches the dead point in its 
azimuth motion, where it seems to stop 
a few moments between its advance and 
retrogression. Then, being at its 
greatest elongation, the sine of its azi. 
muth angle is equal to the cosine of its 
declination divided by the cosine of the 
latitude of the place. 

Should the star Hydri not arrive at 
its east or west point at a convenient 
hour, as at certain seasons of the year it 
will not, the star Canopus, differing in 
right ascension about six hours, or a 
Trianguli Australis, of about sixteen 
hours greater right ascension, may be 
employed. These are respectively of the 
first and second magnitude, and hence 
are very well adapted to this purpose, 
but, owing to their greater polar dis- 
tances, it would be necessary, in their use, 
for the observer to be especially sure of 
the correctness of his latitude. 



115 

The sun is not usually available for 
determinations of azimuth or time, as 
the engineer is generally upon the march 
throughout the day. The use of a star, 
however, admits of greater precision in 
the observations, while the resulting 
computations are less complicated, and, 
in the case of an azimuth determination, 
a south star is doubly convenient from 
the fact that its two daily elongations 
always come above the horizon, and 
whichever one occurs most opportunely 
may be used; or it may be possible at 
times to observe both, in which case it 
becomes unnecessary for the engineer to 
know his latitude. The same difficulty 
of latitude, may also be avoided by the 
method of equal altitudes of a star, taken 
at several hours before and after its 
meridian passage; the middle point be- 
tween the two corresponding azimuths 
will be upon the meridian. 

THE METEOROLOGIST AND HIS INSTRU- 
MENTS. 

In all of his travels the meteorologist 
will be the constant companion of the 



116 

engineer, so as to be prepared to take 
observations at any point that the latter 
may designate. At the beginning of the 
field season he will be furnished with, at 
least, two complete sets of meteorological 
instruments, to be carried by himself and 
by others who may be appointed to as- 
sist him. Each set will be composed of 
a cistern barometer, an aneroid, maxi- 
mum and minimum thermometers, pocket 
thermometers, and a psychrometer, con- 
sisting of two similar thermometers, one 
with its bulb capable of being moistened 
by the capillary attraction of a loose cord 
of cotton filaments leading to it from a 
cup of water, and the other dry, as in the 
ordinary instrument. 

Prior to taking the field he will com- 
pare these barometers by a series of 
readings extending through several days, 
with some standard barometer whose er- 
ror is known, in order to obtain the in- 
strumental errors of the instruments at 
hand. Throughout the season, also, he 
will lose no opportunity for comparisons 
with any reliable barometers that may 



117 

be encountered, as well as for frequent 
comparisons between these two. In this 
manner the time of any possible disloca- 
tion of the scale, or other source of error, 
will be determined. 

As in the rough and rapid travel of a 
geographical survey, there is great lia- 
bility to break the fragile glass tube 
which contains the heavy mercurial col- 
umn, an extra supply of barometer tubes 
and mercury should be transported with 
the party, and also an assortment of 
tools and material for the filling, boiling, 
and fitting of a fresh tube. This is a 
delicate and difficult task, but it is one 
in which every meteorologist should be 
proficient. As full instructions for the 
use and repair of meteorological instru- 
ments have already been prepared by 
the Commission, it is needless to repeat 
them here. 

METEOROLOGICAL OBSERVATIONS. 

At every station of the survey, the 
meteorologist will read from his instru- 
ments the data from which the elevation 



118 

of that point may be subsequently com- 
puted. Nothing more is then needed 
for the precise determination of that 
station's position. The engineer has fixed 
it in latitude and longitude; the mete- 
orologist, in its altitude above sea-level. 
The meteorological data will be more or 
less comprehensive and will be read from 
instruments more or less reliable, accord- 
ing to the geographical importance of 
the place at which they are taken. The 
more frequent the readings, and the 
more prolonged the series, the more 
trustworthy will the resulting mean be, 
and the less liable to be materially 
affected by errors of observation, and 
by those erratic fluctuations to which the 
barometer is subject, owing to the con- 
stantly varying atmospheric currents and 
other disturbing physical conditions to 
which it is exposed, and whose effect 
cannot be entirely eliminated by any 
formulas that it is possible to devise. 

Beginning at the point of outfit, 
which, on account of the work of pre- 
paration and the measurement of the 



119 

base-line, may be occupied some weeks 
or a month, hourly readings will be taken 
throughout the day and night for as 
long a time as possible. The cistern 
barometers will be read, as the height of 
the mercurial column is the basis upon 
which all barometrical determinations 
rest. The attached thermometer will 
be read, to learn the temperature of the 
mercury, and hence what correction 
must be applied to reduce it to the 
freezing point, at which all barometrical 
heights are compared. The isolated 
thermometer will give the temperature 
of the surrounding atmosphere, to be 
used in determining the mean tempera- 
ture of the stratum of air intermediate 
between this and the reference station. 
And the psychrometer will reveal the 
amount of aqueous vapor in the atmos- 
phere, and the influence of its pressure 
upon the height of the column of mercu- 
ry. In addition to these, note will also 
be taken of the direction and force of the 
wind, the condition of the sky, the proxi- 
mity of storms, and other atmospherical 



120 

phenomena, as this information may 
give the key to some abnormal baro- 
metric oscillation which would otherwise 
have to remain unexplained. 

HORARY AND ABNORMAL OSCILLATIONS. 

The hourly observations will be con- 
tinued throughout the day and night for 
the purpose of determining the amount 
of the horary oscillation at that place. 
This horary oscillation is a somewhat 
regular rise and fall of the barometer, 
occupying a period of twenty-four hours. 
The range of this fluctuation in some 
parts of the world is so great, that its 
effect upon the mercurial column may 
equal that which would be produced by 
a change of fifty meters in altitude. It 
is such that, if the successive heights of 
the column be represented graphically 
by a curve, this curve will show two 
daily maxima and minima, occurring at 
intervals of about six hours, the morning 
maximum being attained at about ten 
o'clock A. M. This horary curve, as it 
is called, varies with the latitude, alti- 



121 

tade, and climate of a place, as well as 
with the different portions of the year. 
The value of the horary variation for 
any hour of the day is revealed by a 
study of the prolonged series of observa- 
tions at that place, and may be assumed 
to be the same for all observations taken 
in the vicinity of that station and in the 
same season of the year. 

The barometer is also influenced by 
the abnormal oscillation, apparently re- 
sulting from the progress of great atmos- 
pheric waves across the country, affect- 
ing the mercurial column by a gradual 
rise of several days, followed by a period 
of subsidence of about an equal duration. 
The effect of this disturbance can be 
eliminated, approximately, by taking the 
difference of the barometric readings at 
the beginning and ending of any one day 
of its rise or fall, and considering this as 
its amount for that twenty four hours, a 
proportional part of which will be its 
value for one hour. 



122 

DETERMINATION OF HEIGHTS. 

To obtain the altitude of the first 
station of the survey, a mean of the cor- 
rected heights of the mercurial column 
is compared with a corresponding mean 
of the same hours of the same days at 
some permanent station, whose elevation 
above the sea is definitely known, as, for 
instance, the Imperial Observatory at 
Rio de Janeiro. This, by a process of 
computation, gives their difference of 
altitude, and hence the total elevation of 
the point in question. 

Now, making this point of outfit a 
reference station, at which an observer is 
left with meteorological instruments to 
be read at stated intervals throughout the 
day, the party takes the field, and the 
traveling meteorologist reads a series of 
barometrical and other observations at 
the first camp and at all others to which 
they may come during the season. 
These will be compared, as before, with 
synchronous* observations at the refer- 

* It is well to distinguish between the meanings, as now 
understood, of the two words " synchronous " and " sim- 



123 

ence station, and the differences of alti- 
tude will be calculated. At every topo- 
graphical station, and station of import- 
ance along the meander survey, such as 
villages, f azendas, mines, mountain passes, 
divides, etc., and at all other points that 
may be designated by the engineer, the 
meteorologist will read the cistern baro- 
meter, the watch, the thermometer, and 
the psychrometer, and, for the purposes 
of comparison, the aneroid barometer as 
well. These isolated observations will 
also be referred to the main barometrical 
station at a distance. 

But, on the occasion of the ascent of 
a mountain peak from a fixed camp, bet- 
ter results will be obtained by consider- 



ultaneous." The term " simultaneous " is applied to ob- 
servations which are made at the same absolute instant 
of time, as, for instance, upon the occultations and 
eclipses of the heavenly bodies. Synchronous observa- 
tions are taken at the same hour of the day, local time, 
irrespective of the difference of longitude between the 
two stations. Therefore, observations can be both sim- 
ultaneous and synchronous only when the observers are 
upon the same meridian. The word " simultaneous " 
belongs especially to the province of astronomy, whilst 
" synchronous " is most frequently used in connection 
with the phenomena of physical geography. 



124 

ing the camp a reference station in the 
determination of the altitude of the 
mountain. This ascent will necessitate 
the occupancy of the neighboring camp 
for two nights and a day at least, and 
perhaps longer, while the peak may be 
occupied only a portion of a day, during 
which time, however, there will be cor- 
responding hourly observations at camp 
and mountain-top. Hence the altitude 
of the mountain will be most truthfully 
ascertained by referring it, by these syn- 
chronous observations, to the camp, and 
then the camp, in a similar manner, to 
the distant reference station. 

HORARY CURVES AND REFERENCE STA- 
TIONS. 

Whenever the party, or a portion of 
it, remains stationary in camp for a few 
days at a time, hourly observations day 
and night will be taken to determine the 
horary curve at that place; the longer 
the series, the better will be the result. 
Since the horary variations are constantly 
changing with altitude, country and cli- 



125 

mate, it is important to have as frequent 
determinations of them as can practicably 
be made, so that no very great distance 
may intervene between the place where 
a table of horary corrections is construct- 
ed and the place where it is used. 

For a similar reason it may be deemed 
necessary to establish and sustain a sec- 
ond meteorological reference station, if 
the field of the season's survey should be 
a wide one, or if it should vary greatly 
in the atmospherical condition of differ- 
ent portions of its area. No comprehen- 
sive rule can be given to govern the num- 
ber of these reference stations; all must 
depend upon the judgment of the direc- 
tor of the survey, and the resources at 
his command. In general, the farther 
the place of an observation from its 
reference station, the less reliable will be 
its result. But, as an exception, let us 
take the example of a broad inland plain, 
separated from the sea and its influences 
by a wall of mountains, within which, 
upon the plain, the reference station is 
situated. In this case it may be more 



326 

justifiable to refer to this station a point 
on the plain, five hundred kilometres dis- 
tant, than one just over the mountains, 
only one hundred kilometres away. This 
is owing to the widely different climatic 
circumstances of inland and sea-coast, 
resulting in meteorological conditions so 
dissimilar that equal amounts of pressure 
cannot be relied upon as an indication of 
equal thickness of the atmospheric enve- 
lope. 

THE ANEROID BAROMETER. 

At the many stations of the meander 
survey that are comparatively unimport- 
ant, and that are occupied for a few min- 
utes only, it will suffice for the meteoro- 
logist to read only his aneroid, watch, 
and thermometer. Although the aneroid 
is not a reliable instrument, yet it serves 
an excellent purpose where rapid and ap- 
proximate work is sufficient. Since its 
principal use is in obtaining profiles of 
the meander routes, which will enable 
the engineer to properly distribute the 
contour lines upon his map, and since, 



127 

farther, the error of an aneroid will rare- 
ly exceed the vertical distance between 
two of these contours, the resulting inac- 
curacy upon the plot will be quite inap- 
preciable. 

The aneroid is to the cistern barometer 
what the meander is to the triangulation, 
that is, a means of filling in, which, 
while costing but little extra effort, 
is productive of very valuable results. 
The engineer who rejects the meander 
and the aneroid, because they are not 
rigidly exact in their functions, will find 
himself reduced to the necessity of 
tracing in the roads and streams of his 
map, locating many of the villages, cross- 
roads, etc., and drawing in the contours 
from his judgment and memory alone; 
and it is safe to say that the conjectures 
of the most able and trained topographi- 
cal intellect are by far less reliable than 
the figures of those humble instruments, 
the aneroid and odometer, when judi- 
ciously used. 

At every camp the aneroids are com- 
pared with the cistern barometer, their 



128 

scales are adjusted in compensation for 
any error that may have crept in, and 
the vertical element of the survey starts 
from a new and true datum plane when 
the march is resumed. At the end of 
the day's journey, also, they are imme- 
diately compared again, and the error 
accumulated throughout the day is 
noted, and, by a process of distribution 
along the day's profile, may be reduced 
to a minimum. Before and after every 
side trip, reconnoissance, or ascent of 
mountain, the aneroid is compared with 
the mercurial barometer, and thus, by a 
continual and careful watch over it, it 
may be relied upon to give results not 
seriously in error. But if left to itself 
and unchecked for any great length of 
time, or for any great distance of journey, 
or great change in altitude, this fickle in- 
strument may continue to go astray, by 
a shifting of its scale, exhaustion of its 
spring, or from other causes, until its 
readings are hundreds of metres too 
high or too low. Even then, however, 
it may be of use to the geographer in 



129 

drawing in the relief of the country, as 
the discrepancy is usually of gradual 
growth, and the relative altitudes during 
the progress of the survey, as, for in- 
stance, the height of a bluff above the 
neighboring valley, are sufficiently exact 
to be of much assistance to him in his 
plotting. 

BAROMETRICAL RESULTS. 

As to the reliability of altitudes de- 
termined by the cistern barometer, evi- 
dences and opinions differ, but those per- 
sons who are most thoroughly informed 
are generally the most lenient in their 
acceptation of results. Colonel Wil- 
liamson, of the United States Army, who 
has probably given more intelligent 
study to the barometer than any other 
man, has compiled a table of the maxi- 
mum errors which occur in numerous 
series of observations taken both in North 
America and Europe. Among these are 
many that exceed fifty meters in amount, 
and he assumes that the barometer under 
similar circumstances will be liable to 



130 

equal errors elsewhere. These, however, 
are not to be considered as representing 
the probable error of barometrical re- 
sults; they are rather the extreme limits 
of probable error, and may be taken as 
the error to which the barometer is liable 
under certain rare and very unfavorable 
conditions. While exact truth concern- 
ing altitudes is something which no 
barometer can be expected to tell, and 
while it is never safe to guarantee the 
accuracy of such a determination, even 
within many meters, yet when baro- 
metrical work is prosecuted judiciously 
and systematically, as it would be in this 
survey, and based upon formulas which 
represent the latest and most complete 
knowledge of meteorology, its tendency 
is to give results that are seldom more 
than a few meters wrong. 

It is often difficult for the popular 
mind to comprehend how an error of 
meters may be inevitable in some of the 
processes of barometric hypsometry. 
Since the scale of a barometer may be 
read to a thousandth of an inch, and that 



131 

amount of variation is supposed to cor- 
respond to a change of one foot in alti- 
tude, it would naturally be thought 
possible to determine the elevation of a 
place to the nearest foot. But this diffi- 
culty will be better understood when it 
is remembered that the barometrical 
measurement of the difference of altitude 
between two places depends upon the 
determination of the weights of a column 
of atmosphere at each of these stations; 
that this atmosphere is in a state of con- 
stant change and perturbation, its press- 
ure being modified by variations of heat 
and cold, storm and calm, and the 
absence and presence of moisture through- 
out different portions of its extent; and 
that, while some of these conditions are 
quite unknown to the observer, those 
that are apparent to him can be but in- 
completely compensated for. There- 
fore, since barometric hypsometry is not 
one of the exact sciences, but is affected 
by every change in the wind and 
weather, any determination of altitude 
that is true within a meter is as much 



132 

a source of surprise as of gratification to 
the meteorologist, who will be obliged 
to confess that this closeness could 
scarcely be possible without some coin- 
cidence and accidental equilibrium in 
the disturbing influences to which the 
barometer is subject. 

DIFFICULTIES IN BAROMETRIC 
HYPSOMETRY. 

At times men of little experience may 
have to be accepted as meteorologists. 
They work, perhaps, under the embar- 
rassments of exposure, fatigue, and a 
lack of appreciation of the responsibilities 
that rest upon them. It may be long 
before they can be taught to regard 
those niceties of barometrical work with- 
out which it cannot be truly successful; 
although there is but little hope of 
determining an altitude to the single 
foot, yet they have to learn that this is 
no reason for neglecting that thousandth 
of an inch which corresponds to a foot. 
Their instruments may be out of order, 
owing to the hardships of travel to which 



133 

they are exposed; the readings may have 
to be referred to a distant station of very 
dissimilar physical surroundings; or they 
may have been taken upon the top of a 
lofty mountain, in a belt of the atmos- 
phere with meteorological phenomena 
quite different from those properties of 
the lower strata of the air, for which 
our formulas were framed. 

These are some of the sources of error 
which may have conspired to vitiate 
those results which are fifty meters or 
more at fault. In Brazil, however, it is 
hardly necessary to anticipate discrepan- 
cies so great as this, since it is a country 
in which no very great change of alti- 
tude is possible, violent and phenomenal 
storms are not frequent, and the atmos- 
phere is of comparatively steady tem- 
perature, and not liable to sudden transi- 
tions from one extreme to the other. 

BAROMETRIC FORMULAS. 

Even if the observations have been 
made under the most favorable condi- 
tions of atmosphere, elevation and loca- 



134 

tion, and are perfect as far as human in- 
telligence can make them so, that is, free 
from all personal and instrumental er- 
rors, there yet remains a consideration 
which may materially affect the com- 
pleted altitude. The same observations, 
reduced by different formulas, will give 
results in some cases widely different, 
the discrepancy between the returns of 
two well-authorized methods of compu- 
tation frequently amounting to the sum 
of the real errors of both; this is ex- 
emplified in the following determination 
of the height of Corcovado, in which one 
system of reduction gives an altitude 
above the true one, and the other places 
it too low. 

The barometric formula is composed 
of several terms, each of which is a com- 
bination of some physical constants, such 
as the relative weight of air and mercury, 
or the variation of gravity with latitude, 
and some of the barometrical data, as 
the temperature or moisture of the at- 
mosphere. Of these formulas, there are 
two general classes, based upon the equa- 



135 

tions of Laplace and Bessel. Not only 
do they differ in those constant quanti- 
ties upon which all barometrical determ- 
inations must depend, but also in the 
presence or absence of an entire term, as 
the formula of Bessel has a separate fac- 
tor as a correction for the humidity of 
,the air, while Laplace includes the in- 
fluence of the aqueous vapor with that 
of temperature. 

Thus it will be seen that the formula 
of Laplace is more convenient, while that 
of Bessel is more complete. The scien- 
tific world has found it difficult to choose 
between them, and while Delcros, Guyot> 
and others have accepted the formula of 
Laplace, that of Bessel has been adopted 
by Plantamour, Williamson, and others. 
But it is admitted, even by those who 
are in favor of the former method, that 
the constants in use in Bessel's formula, 
as modified by the more recent arrange- 
ment of Plantamour, are later and more 
reliable than those accepted by Laplace, 
and there is also a prevalent opinion 
among scientists that some accuracy has 



136 

been sacrificed to convenience in La- 
place's method, a concession which it may 
sometimes be justifiable to make in the 
application of a formula, but never in 
its construction. 

The advocates of each system have 
published examples showing the close 
accordance of their results with altitudes 
determined trigonometrically or by spirit- 
level. But as the number of these re- 
markable coincidences is about equal on 
each side, and as in each instance the 
observations would have given results 
considerably wrong by the application of 
the other formula, they prove simply two 
things; first, that they are coincidences, 
and that to certain cases the method of La- 
place is more applicable, while to others 
that of Plantamour will yield better re- 
turns; and second 3 that it is quite impos- 
sible to devise any formula that will 
yield an accurate solution of all problems 
in the barometrical measurement of 
heights. 

Since there seems to be a preponder- 
ance of evidence and a growing disposi- 



137 

tion in favor of Plantamour's formula, it 
has already been adopted by the Geo- 
logical Commission as a basis for its 
barometrical work, and its several terms 
have been developed into tables for the 
convenient computation of altitudes. 
After the preparation of those tables and 
as a test example with which to prove 
their efficacy, the height of Corcovado 
Peak was determined barometrically 
with the following results: 

Metres. 

Altitude of Corcovado, by tables of the 
commission, based upon Planta- 
mour's formula 705 .84 

By Laplace's formula 702.15 

Determined by triangulation 704.74 

Metres. 

Error by Plantamour's formula +1.10 

" Laplace's " 2.59 

Discrepancy between the two 3.69 

The foregoing is a very creditable and 
satisfactory barometrical result, and is 
one more argument in favor of the use 
of Plantamour's complete formula. 

ALTITUDES BY VERTICAL ANGLES. 

As a supplement to the barometric 



138 

hypsometry, every theodolite, whether 
for meanders or triangulation, is fitted 
with a vertical circle, from which to read 
the angles of elevation and depression of 
those points which are located by inter- 
sections, in order to compute the heights 
of the same. From this angle and the 
horizontal distance between any two 
peaks, their apparent difference of alti- 
tude is obtained by a trigonometrical 
calculation, and then a correction is ap- 
plied for earth's curvature and refrac- 
tion. In the field these angles are 
recorded as plus or minus, according as 
the objective point is above or below the 
observer's station, whose altitude is in- 
variably determined by barometric read- 
ings. 

In this manner the heights of hund- 
reds of points throughout the field of 
survey are found with an accuracy 
nearly equal to that of the peak from 
which the angle is taken. Indeed, a 
mean altitude derived from the three 
angles of elevation, read from three 
different triangulation stations, will give 



139 

the altitude of the point of intersection 
with less probable error than that of 
either of the mountains from which it 
was derived. 

METEOROLOGY IN THE SOUTHERN HEMI- 
SPHERE. 

Brazil stands almost alone as a great 
civilized country lying in the Southern 
hemisphere. It is comprehensive in its 
latitude, reaching from north of the 
equator far into the south temperate 
zone. From this unique and favorable 
position upon the earth's surface, as well 
as from the liberal patronage bestowed 
by its government upon the de- 
velopment of science, it needs no 
prophetic eye to see that this em- 
pire is destined to become one of the 
busiest and most fruitful fields of scien- 
tific research. Especially is this the case 
in the investigation of those great ques- 
tions concerning the terrestial shape and 
dimensions, and those others, still more 
numerous, which from the form of the 
earth, or from other and unknown 



140 

causes, vary with geographical position. 
Important among the latter is the science 
of meteorology, whose general laws are 
not the same all the world over, but 
which are largely influenced by latitude 
and by proximity to either pole. 

The following extract from Colonel 
Williamson's valuable treatise on the 
barometer and its uses, will illustrate 
the absence and the need of meteorologi- 
cal observations south of the equator: 

" It has been determined by actual ob- 
servations, and confirmed by theory, that 
the sea-level pressure varies in different 
latitudes by a definite law, modified in 
practice by local peculiarities of climate. 
It has been found that the mean baro- 
metric pressure is less in the immediate 
vicinity of the equator, and it increases 
towards the north to -between latitude 
30 and 35 where it is greatest. It then 
gradually decreases to about latitude 60 , 
and from there towards the north pole 
there is a slight increase. In the south- 
ern hemisphere, where the observations 
have been less numerous, the mean 



141 

pressure seems to increase to between 
20 and 30 of south latitude, when it 
gradually decreases to about 42, and 
then commences a remarkable fall, so 
that towards the south pole, the mean 
pressure is said to be less than 29 
inches."* 

In the table of mean heights of the 
barometer at the sea-level, given in 
various works on meteorology, there are 
but two stations south of the equator; 
these are Rio de Janeiro and the Cape of 
Good Hope. In north latitude, however, 
the list comprises more than thirty 
places at which this determination has 
been satisfactorily accomplished, by 
years of observations, and these are 
favorably situated at intervals between 
the equator and the pole. 

Again, while the horary oscillation in 
the atmospheric pressure is greatest 
near the equator, and diminishes thence 
each way to the poles, the abnormal 
oscillation is least in regions of small 

* T36.6 millimetres. 



142 

latitude, and increases with the distance 
from the equator. As the latter is 
the more incomprehensible and less 
regular of the two, and consequently the 
greater source of error, it would appear 
that, in general, barometrical work would 
be most reliable in tropical regions, and 
hence this system of hypsometry would 
be especially applicable to Brazil. And, 
in addition to their immediate and prac- 
tical use in the construction of maps, the 
meteorological results of a survey of the 
proposed nature, taken at low and high 
altitudes, at the sea-coast and in the 
remote inland, with permanent stations 
at intervals where long series of obser- 
vations would be accumulated, would 
form a basis upon which to establish the 
general laws of barometric fluctuation 
throughout this vast portion of the 
Southern hemisphere. 

CONTINGENCIES IN THE SURVEY. 

The foregoing are the general divi- 
sions and some of the novel features of 
the geographer's work in the field. 



143 

While these are sufficient to carry the 
survey across any ordinary country, cer- 
tain districts may be encountered in 
which these methods may not be easily 
applicable. It is impossible, in a paper 
of this nature and length, to foresee and 
provide for all of the emergencies that 
may arise; it is necessary for the geog- 
rapher to first see his territory, and then, 
if he is a true engineer, he will be able 
to devise some means of survey which 
will be competent to meet the difficulties, 
however great they may be. 

For instance, it may be asked how a 
survey based upon triangulation can be 
carried across the smooth and unbroken 
table-lands of a country. The answer 
will be that the plains are not usually so 
broad that they cannot be spanned by 
the length of a triangle-side ; and, 
furthermore, if there are no eminences 
that can be used for triangulation points, 
so much less is there need for this system 
of survey. Over the smooth plain it is 
possible to travel in straight lines, such 
being the usual character of roads in a 



144 

level country, and since a meander by 
direct routes is reliable, the survey can 
proceed from one known point to the 
next with comparative accuracy, tracing 
in the rivers, lakes, and. other geographi- 
cal features as it goes. As a rough, 
mountainous country is*its own remedy, 
furnishing a great number of advantage- 
ous stations for the survey, so, with the 
absence of these mountains, vanishes in 
great part the labors and difficulties of 
this work. 

THE STADIA, OK TELEMETER. 

Although the stadia, or telemeter pro- 
cess, is too slow for the general prosecu- 
tion of a geographical survey, there may 
be occasional areas in which the previous 
methods will fail, and this will suffice. 
The direct linear survey of a river, by 
this means, has already been mentioned. 
As another illustration, take the case of 
a valley as, for instance, the valley of 
the Amazon which is so broken with 
lakes, swamps, and the many channels 
and arms of the river, that its islands 



145 

and shores cannot be reached and located 
by any means of direct measurement; 
and where, farther, the vegetation is so 
abundant and dense, that ordinarily no 
three fixed points are visible from the 
water's edge. Here the telemeter may 
be the only instrument by which the re- 
quired distances may be obtained. The 
observer, establishing his instrument in 
open ground, from which triangulation 
stations can be seen, sends his assistant, 
in a boat or otherwise, to such points 
along the water as may be in sight. 
These he locates by single observations, 
reading the distances from the rod held 
by the assistant. Thus the telemeter 
station is referred to the observer's posi- 
tion, which, in its turn, can be fixed by 
means of three- point observations upon 
the triangulation stations of the border- 
ing cliffs. 

In this simple and ingenious way of 
determining distances by single observa- 
tions, it is necessary that the diaphragm 
of the telescope of the observer's instru- 
ment should be fitted with two horizon- 



146 

tal cross-wires, and that his assistant 
should be furnished with a graduated 
rod, or telemeter. Then looking through 
the telescope, the projection of the cross- 
wires upon the rod includes a certain 
amount of the graduation. This is a 
chord subtending a certain constant 
angle in the line of collimation, and, by 
a principle in geometry, this chord in- 
creases directly with its distance from 
the angle which it subtends. 

THE PLANE TABLE. 

With the use of the plane table, there 
comes so great a temptation to go into 
the details of the work, to linger over a 
small area, and to finish the sheets with 
a topographical completeness, that its too 
general adoption will be found to retard 
the progress of a geographical survey. 
In addition, it is cumbersome in its 
shape, offering a broad surface of ex- 
posure, and for that reason is not well 
fitted for service upon high mountain 
stations, where the wind is strong and 
storms are frequent. In its favor, how- 



147 

ever, it must be said that this instru- 
ment has been successfully employed 
upon the extensive geological and geo- 
graphical surveys under Major J. W. 
Powell, of the United States, and that 
very favorable reports have been made 
concerning its usefulness. The incon- 
venience of its shape has been modified 
in this service, the table being composed 
of slats hinged together, so that it may 
be folded into a small compass for the 
purpose of transportation. 

When, in the course of a work of this 
nature, there is encountered a district 
where the importance of the field will 
justify a minute and laborious survey, 
the plane-table will serve an excellent 
purpose there. It is very useful in the 
mapping of a populous district, the 
suburbs of a city, a mining region, or in 
the representation on large scale of a 
piece of topography which is interesting 
as a type of geological structure. It is 
always an easy matter for the geogra- 
pher to accommodate himself and his 
methods to detailed surveys like the 



148 

above, and it is a mistaken idea to sup- 
pose that the exploration of a province, 
unfits an engineer for the topographical 
delineation of a parish. In all work of 
engineering there is a constant tendency 
towards greater accuracy, refinement, 
and detail, and it is not freedom which 
the geographer enjoys, in neglecting the 
minor features of the earth's surface, 
but rather a necessary restraint that is 
imposed upon him, to keep him from 
sacrificing the important to the unim. 
portant. 

THE OFFICE WORK. 

As for the computations and other 
reductions of notes which follow a field 
season of the survey, there is not space 
to discuss them here, nor is there any 
special need of such a discussion, as they 
do not differ materially from those 
which apply to geodetic work in general. 
Nor are the duties of the draughting- 
room greatly distinguished above the 
customary routine of such office work. 
This thing only, may be noticed, that 



149 

the hand-to-hand struggle which the 
field engineer constantly sustains with 
the forces and obstacles of nature blunts 
the delicacy of his touch, and makes his 
hand too heavy for the fine drawing 
necessary in a map finished for publica- 
tion, and there should be in every office 
a superior draughtsman who is accus- 
tomed to the use of no heavier imple- 
ment than the artist's pen. 

This artistic finish is bought by some 
sacrifice of accuracy, however, and be- 
tween the field engineer and the final 
draughtsman there should be few, if any, 
middlemen to compile and replot the 
work, because only the man who has 
seen the country can reproduce its physi- 
cal characteristics with truthfulness. 
In every copy that is subsequently made 
the face of the land grows more artifi- 
cial and ideal; each mountain loses its 
individuality of shape, and assumes a 
symmetrical regularity which it does 
not possess in nature; some of the nice- 
ties of truthful representation are mag- 
nified into exaggeration, and others are 



150 

overlooked and obliterated; the bed of 
every canon grows broader in each suc- 
cessive transcript; and the large hills 
grow larger as the smaller ones dwindle 
away. As in a popular parlor game, a 
whispered story, passing current from 
mouth to mouth throughout the round 
of a circle, grows strange and distorted 
beyond recognition, so in the successive 
reproductions of a map by strange 
hands, it loses its photographic truth of 
execution as the idiosyncracies of the 
various draughtsmen are wrought into 
the plan. Finally it comes to represent 
a country that is unnatural in its regu- 
larity, made not so much by the acci- 
dents of nature as by the design of 
man, and moulded by the rules of a uni- 
form and rigid geometry. 

PLOTTING THE NOTES. 

It is necessary that each engineer 
shall plot his own notes, as he alone is 
familiar with their arrangement through- 
out his books, and only he is able to de- 
rive the full benefit from them. There- 



151 

fore during the office season he will be 
engaged upon a contour plot of the area 
which he has surveyed during the pre- 
ceding half of the year. Here he will 
collect and compile in graphic shape all 
of x the information which lies scattered 
throughout the dozen note and sketch- 
books which represent his labors in the 
field. Upon this map fine drawing will 
not be so essential as truthful representa- 
tion and the utmost accuracy of position 
that can be attained from the material 
at hand; an inaccuracy that is barely 
apparent upon the paper will correspond 
to a very large error in the field, and so 
a moment's oversight in the office may 
invalidate the scrupulous care of a day's 
or week's work upon the survey. 

These sheets will be the basis of all 
the maps of the survey, no matter in 
what shape they may be published, and 
hence the urgency of having them correct 
in all of their positions, statements and 
figures, and so complete as to include 
every detail upon the pages of the 
sketch-books, down to the shape of a 



152 

mountain-spur or village, or the presence 
of a spring of water or dwelling place. 
As the expense of sustaining an engineer 
in the field is at least double the cost of 
his office-work, he should confine himself 
to what is absolutely necessary in the 
collection of his notes, and then utilize 
even the least of these in his subsequent 
plotting and development of them. 

CONTOUR PLOTS. 

The plots will be constructed in con- 
tour lines, as that is the only method in 
which the engineer can give precise ex- 
pression to his information and impress- 
ions concerning the heights, slopes, and 
forms of the country that he has sur- 
veyed. While a map executed in 
hachures would be more artistic and 
more pleasing to the eye, it cannot be 
made so mathematically invariable in its 
conveyance of ideas, that is, it cannot be 
made to convey the same ideas to all 
persons; the bluff that would seem high 
to one observer would seem low to 
another, and the depth of shade that 



153 

would represent a steep gradient to one 
draughtsman would stand for a moderate 
declivity to another, according to their 
peculiarities of judgment, or to the 
different schools of drawing in which 
they had been educated. The most 
skilled cartographer, with one of the 
best of hachure maps before him, would 
find it difficult to estimate the angle of 
any mountain slope, or to tell which of 
two neighboring peaks was the highest, 
unless their heights were given in figures. 
In a glance at a contour plot, however, 
he could count the excess of lines in one 
of these mountains, and so compute its 
superior altitude; or note the number of 
lines in a centimeter of space, and so 
determine the gradient of the earth's 
surface there. For this reason the con- 
tour plot is the only true basis from 
which subsequent maps can be made; 
then, no matter how many field engi- 
neers may contribute to this work, their 
reports will all come to the compiler and 
final draughtsman, written in the uniform 
language of lines at regular vertical in- 



154 

tervals. Otherwise, if the plots were in 
hachures, this draughtsman would find 
it well-nigh impossible to so assimilate 
them that his finished map would not 
reveal traces of the many different hands 
from which it originated. 

FINAL MAPS. 

Unless the contour lines are so numer- 
ous and close together as to produce 
striking contrasts of light and shade as 
the slope varies, this map has no mean- 
ing to the popular eye. The ordinary 
observer sees in it only a maze and con- 
f vision of lines, of whose design and 
importance he is ignorant, and so it is of 
no assistance to him. Therefore, since 
maps are usually published for the in- 
formation and guidance of the people at 
large, it is wise that they should be 
drawn with hachure shading, which 
gives a more intelligible but less precise 
picture of the country. In the construc- 
tion of this, the contours of the engineer's 
plot are so many guide-lines to the 
draughtsman, who graduates the light 



155 

and darkness of the shade to accord with 
the divergence or approach of these 
wavering lines. 

In addition to these a map in contours 
may also be issued for the use of engi- 
neers, the projectors of railways, and, 
more especially, as a basis of the geo- 
logical and resource charts, to which 
this system is peculiarly adapted, as its 
lines of equal level are of great assist- 
ance in determining the extent of the 
various formations, and for depicting 
those areas of vegetable growth which 
are bounded by fixed limits of altitude. 
The dip and strike of a bed of uniform 
slope being given at any one point of its 
outcrop, it is an easy matter to trace 
upon this map its line of reappearance 
upon the farther side of a mountain- 
range, or at any other point at which it 
may be exposed again. Or, by counting 
the lines of vertical equi-distance, the 
geologist learns the thickness of the vari- 
ous strata, the extent of a fault, or any 
other fact in geological dimensions. 



156 

REVIEW OF THIS METHOD OF SURVEY. 

In this paper the writer is at a disad- 
vantage in appearing to advocate inac- 
curate methods, and perhaps, at times, 
actuated by a desire to give a perfectly 
frank and honest expose of the subject 
under discussion, he has magnified the 
amount of inaccuracy to which the 
operations described in these pages 
would be liable; at all events he has 
been very liberal in his allowance for 
probable error. Indeed, to those who 
have been in the habit of reading, and 
believing, barometrical altitudes that are 
given down to the tenth of a foot, or 
sextant determinations to the hundredth 
of a second, it may appear unpardomibly 
liberal to allow for an error of meters or 
seconds in these classes of work, and 
perhaps to some it may seem indicative 
of professional unfitness in the engineer 
who would acknowledge the liability of 
such. But while results like the above 
are frequently published, their authors 
would be either sciolists or charlatans if 
they were to claim that they were abso- 



157 

lately reliable down to those small 
fractions; it is often the custom among 
the most conscientious and intelligent 
engineers to make their reports in that 
elaborated form, since those are the 
figures at which their computations 
finally arrived, and hence there are cer- 
tain weights of probability in their 
favor. 

In like manner, in the computations of 
a survey of the proposed nature, it would 
never be allowable to neglect or throw 
away any odd figure or fraction, on the 
plea that it was probably exceeded by 
the error of the whole. By following 
this system, not only are habits of accu- 
racy inculcated and sustained among the 
assistants of a survey, but the closest 
possible approximation to the truth is at- 
tained. 

In the ordinary branches of his profes- 
sion, habits of rigid precision, at what- 
ever cost of time and money, are the 
best recommendations for an engineer. 
In a geographical survey, however, to 
enforce this rule beyond .the triangula- 



158 

tion, upon which the integrity of the 
whole depends, and to continue it in full 
force throughout all of the subordinate 
branches of the work, would be to make 
such a survey impossible in Brazil, owing 
to the enormous expense that would at- 
tend it. Viewed theoretically, the best 
of maps, even those produced by the 
tedious processes of the European topo- 
graphical surveys, are but approxima- 
tions to the truth; the question now 
arises as to how close it is profitable to 
bring this approximation. Viewed prac- 
tically, the maps that would result from 
the proposed system of survey would be 
seldom, if ever, in error to a perceptible 
degree, and it would seem that this is 
the limit of accuracy bayond which this 
country cannot well afford to go. 

To condemn a method of surveying 
because it is not absolutely accurate 
would be to condemn all of the survey 
of the world, and especially all of the 
systems of ordinary land surveying, 
which are so faulty that it is very sel- 
dom that a purchaser of land does not 



159 

get either considerably more or less than 
he pays for. Still, that has not been 
deemed sufficient reason why all buying 
and selling of real estate should cease 
until its boundaries could be determined 
by the instrumentality of such rods, com- 
pensated for temperature or packed in 
ice, as are used in the measurement of 
geodetic base-lines. In one respect the 
proposed system is far superior to the 
land survey, as it is founded upon the 
principle of triangulation, which, secur- 
ing it in its true proportions, prevents 
any great accumulation of error. In the 
United States of North America, where 
surveys of this nature are in active and 
successful operation, it has been earnestly 
advocated that the triangulation of the 
geographical survey should be made the 
basis of the land survey, the different 
triangulation stations serving as initial 
points from which to run the land bound- 
aries, and it is very probable that, with- 
in a year or two, this plan will be 
adopted there. 
There are different degrees of accu- 



160 

racy, each adapted to the end which it is 
intended to serve; this degree, explained 
here, is sufficient for the rapid prepara- 
tion of a very useful and complete 
geographical map. It would not suffice 
for the measurement of an arc of the 
meridian r such as has been proposed for 
this empire. That is a work in which 
no error, however small, that is not be- 
yond the cognizance of the human 
senses and judgment, can be excused or 
overlooked. To publish a wrong result 
here would be not only a national dis- 
grace, but a misfortune to the whole 
world, as it is upon the shape and dimen- 
sions of the earth that many of our 
geodetic and other scientific formulas 
rest, while it is from the same source 
that the world derives its standard unit 
of length, by which the interests of all 
civilized people are affected. Or, if 
Brazil were prepared to enter into that 
honorable rivalry in geodetic work, in 
which some of the older nations are en- 
gaged, each seeking to produce instru- 
ments, methods, results, discoveries, and 



161 

developments that may be in advance of 
everything hitherto achieved, this sys- 
tem of survey would not be recom- 
mended. It is not impossible, however, 
that, from this as a beginning, there 
might grow, keeping pace with the gen- 
eral progress of the country, a geodetic 
institution that would be equal to the 
best. 

ORIGIN OF THIS SYSTEM. 

The writer by no means pretends to be 
the inventor of the combination of 
methods described in these pages, al- 
though hitherto there has been but little 
description of them in print. An effi- 
cient system of survey cannot be the in- 
vention of any one man; it must be the 
outgrowth of years of practical expe- 
rience, resulting in the gradual accumu- 
lation of ideas and improvements con- 
tributed by those who have been en- 
gaged upon it. This one is the result of 
a growth of at least a quarter of a cen- 
tury, and therefore is not open to the 
serious objection of being new and un- 



162 

tried. During that length of time, the 
enterprise of geographical surveying 
has been receiving more and more en- 
couragement from the government of 
the United States, which has wisely 
adopted that plan, in connection with 
geological and other scientific research, 
as a means of opening and illustrating 
its vast public territory. 

At the present day there are actively 
engaged upon this duty in that country 
three important commissions of survey. 
That of Dr. F. V. Hayden, geologist in 
charge, is known throughout the world 
by its extensive and important work, not 
only in geology and geography, but in 
all their kindred sciences as well. A 
second is under Major J. W. Powell, the 
intelligent geologist and intrepid ex- 
plorer who was the first to descend the 
great canon of the Colorado River. An- 
other, more strictly geographical in its 
nature, is under the auspices of the War 
Department, and is conducted by Lieut. 
George M. Wheeler, an officer of envia- 
ble reputation in the United States Corps 



163 

of Engineers. While the general plan 
is much the same throughout these 
three commissions, it is especially to his 
former associates, the geographers and 
officers of the last-named organization, 
that the writer wishes to acknowledge 
his indebtedness for whatsoever of value 
there may be in this paper. 

BRAZIL AND THE UNITED STATES. 

Although, as has been stated hereto- 
fore, it is not wise for any nation to copy, 
blindly, and without adaptation to its 
own peculiar needs, the system of sur- 
vey employed by any other country, yet 
it would seem that the processes that are 
fitted to the United States would require 
but little modification to be adapted to 
use in Brazil, so analogous are the two 
countries in many respects. They have 
equal amounts of territory as near as 
may be, but, peopling this territory, 
there are four times as many inhabitants 
in the United States as there are in 
Brazil; thus it would seem that the me- 
thods that are deemed sufficient for the 



164 

former would certainly suffice for the 
latter. In each country the population 
diminishes from a thickly-settled sea- 
coast back into an uncivilized and almost 
unknown interior. In each of these 
there is a great amount of wild land 
which the government is anxious to open 
to colonization and cultivation. To ex- 
pose and popularize the natural wealth 
of this public domain, the U. S. Govern- 
ment resorted to the plan of scientific 
surveys, to which the Geological Com- 
mission of Brazil is very similar in all 
respects, and so efficiently have they 
accomplished their purpose that it has 
become a noticeable fact in the cartog- 
raphy of the United States that its maps 
of some of the remote and unsettled dis- 
tricts of the Rocky Mountains are 
superior to those of its oldest and richest 
States, and, therefore, there are now 
plans on foot looking to the extension of 
these geographical surveys over the en- 
tire surface of the country. 

As the American manner of railway- 
building, more expeditious and involving 



165 

less first cost than the European methods, 
has been found practicable in Brazil, in 
some instances, in which all other plans 
would fail, so with this question of geo- 
graphical surveys, it may prove to be the 
American system or none. 

RESULTS OF THIS SYSTEM. 

Considering now the results that could 
be expected from such a geographical 
survey of Brazil, this question can be 
best answered by referring to areas sur- 
veyed in the same manner in the United 
States. From Lieut. Wheeler's annual 
report, which the writer has before him, 
it appears that in six years' continuance 
of his commission an approximate extent 
of 800,000 square kilometres has been 
surveyed. Allowing an average of five 
parties in the field during that time, the 
season's work of one engineer reduces 
itself to about 25,000 square kilometres. 
Allowing proportional returns from the 
various other geographical surveys at 
present in commission, or that have been 
in existence during the last ten years in 



166 

the western portion of the United States, 
it appears that one-third of the area of 
that great country has been thus sur- 
veyed in that period. 

This is at a total expenditure which, 
while including the cost of all other 
concomitant scientific labors, to which 
the geographical work has been in large 
part incidental and tributary, has never 
exceeded four hundred contos ($ 200,000) 
per year. There is probably no other 
department of public enterprise which 
has yielded so extensive and valuable re- 
turns for an equal amount of money. 

AN ESTIMATE FOR ONE SEASON. 

In general, an area of from 10,000 to 
30,000 square kilometres, varying ac- 
cording to the geographical nature of 
the country, is assigned to each party 
for a season of four, five, or six months, 
and its ability to satisfactorily cover 
that district in that time is conceded. 
To illustrate the possibility of such rapid 
progress, let us take a typical area of 
20,000 square kilometres and see what 



167 

can be done with it by one party and 
one geographer in one season's work of 
six months in duration. Of this time 
the first month will be consumed in the 
measurement and development of the 
base, and in other preparation. Of the 
remaining period one month more will 
perhaps be lost in unavoidable delays 
resulting from storms or other causes. 
There will then remain four months, 
which, at twenty-five available days in 
each, will afford one hundred days for 
active service in the field. 

Allow one half of these days for the 
meander survey, and the other half for 
the occupation of mountain stations. 
Fifty mountain stations will thus result, 
and, in addition to these, there will be a 
topographical station either upon or 
adjacent to each day's meander. So 
there are one hundred triangulation and 
topographical stations distributed at 
judicious intervals over this territory. 
That is, there is one for every two 
hundred square kilometres of ground, or, 
typically, they are but about fourteen 



168 

kilometres apart, and the piece of coun- 
try to be sketched in contours need not 
extend more than seven kilometres in 
each direction; this estimate ignores the 
meander surveys, to which fifty days of 
the season will be devoted, and by which 
these stations will be separated and sur- 
rounded. 

At twenty-five kilometres a day, a very 
reasonable allowance, the total distance 
of meander route will be 1250 kilometres. 
This distance would reach across our 
area nine times, cutting it into strips of 
sixteen kilometres in width. Hence, in 
order to include the entire country from 
this survey, the typical zone of each 
meander would not reach more than 
eight kilometres on either side of its 
path; but, since it would be superfluous 
to sketch from this base the country in 
the immediate vicinity of the mountain 
stations, these plots en route need never 
extend more than four kilometres from 
the central line. Of course, in practice, 
these surveys will not be thus distributed 
in straight lines at equal distances apart, 



169 

but will communicate, intersect, and 
duplicate in every possible way. Still 
the meander will serve its original pur- 
pose of penetrating those regions and 
traversing those border-lands that are 
remote from the mountain stations, and 
will trace out the roads, trails, and im- 
portant streams, whose entire length in 
this area will not be likely to exceed 
1250 kilometres. 

Returning to the office at the end of the 
season, the engineer will have material 
enough to make a plot of the country on 
a scale of one centimetre to the kilo- 
metre (100*000)? or one-half a centimetre 
to the kilometre (^-oSror)' Or, to put 
this statement with more precision, he 
will have so much and so detailed mate- 
terial,that he will not be able to portray 
it conveniently and intelligibly on a scale 
of less than 3-^-^0 o- But when the 
final draughtsman comes to copy these 
plots, he may condense them, if it be 
thought expedient, to proportions of 
TToVsr* or even smaller. On the other 
hand, portions of this area may be plot- 



170 

ted upon a much larger plan than any 
here noticed, should such be found nec- 
essary for the clear and complete geo- 
graphical and geological representation 
of the same. 

EUROPEAN SURVEYS. 

Now, in contradistinction to the above 
showing, let us take up the reports of 
some European surveys. In Prussia, 
12,000 square kilometres, a little more or 
less, are surveyed annually, at a cost of 
800,000 marks, or, as near as may be, 
four hundred contos of Brazilian money,* 
exclusive of the salaries of military as- 
sistants; notice that in the United States, 
with a total annual appropriation not 
greater than this, at least 300,000 square 
kilometres are geographically surveyed 
each year, this territory being studied at 
the same time by the geologist, the 
chemist and the naturalist. 

Upon the Ordnance Survey of Great 
Britain there were over 1800 assistants 

* A conto of reis, in Brazil, is equal to about five hun- 
dred American dollars, or a hundred pounds sterling. 



171 

and employes engaged during the year 
of 1874; the total area surveyed by them 
was not more than 8,000 square kilome- 
tres. With the methods in use in Austria 
an experienced topographer can survey 
in one field season of six months five 
hundred square kilometres at the farthest. 
In Switzerland the topography is in large 
part done by contract, and it alone, ex- 
clusive of triangulation and publication, 
costs 700 or 800 francs per square stunde, 
or about twenty-two mil reis* per square 
kilometre. So with the surveys of Italy, 
Spain, Sweden, and the other European 
countries of comparatively small extent; 
they are so slow, detailed, and withal so 
expensive as to be inapplicable to the 
great empire of Brazil. 

AX ADVANTAGEOUS DEVELOPMENT. 

So vast is the extent of this empire 
that the idea of a geographical survey 
of its territory, as a whole, is an astound- 
ing one, and is liable, in itself, to forbid 
all further consideration of the subject. 

* Eleven American dollars. 



172 

But this plan does not necessarily imply 
the regular extension of this survey over 
the whole country, irrespective of popu- 
lation and wealth. On the contrary it 
would devote itself at first to such areas 
as, from geological or other economical 
reasons, might most urgently require it, 
and a region of especial interest to the 
geologist would be surveyed first and 
with especial care, to the neglect or even 
exclusion of those great stretches of 
country whose structure is unvaried and 
monotonous. In a few conditions of its 
plan, as, for instance, in the system 
adopted in the projection of its maps, it 
might provide for any possible ultimate 
extension, but in other respects it could 
operate with equal facility, in whatever 
districts might be assigned to it. 

Nor does this plan imply the necessity 
of any great outlay at the beginning, but 
would ask to start upon a small scale at 
first, with a view to gradual growth as it 
proved itself worthy of encouragement. 
As the aim of this project would be not 
only the production of much-needed 



173 

maps, but also the introduction of these 
methods of survey from abroad, and the 
training of Brazilian engineers in the use 
of the same, any very extensive initial 
basis would prove not only embarrassing 
at first but also probably disastrous in 
the end. A survey inaugurated upon a 
grandiose scale is too liable to exhaust 
the patience and liberality of its official 
patrons before it can exhibit results ap- 
parently equivalent to the expenditure 
that it has caused, and the frequent fate 
of such enterprises is that they are dis- 
continued at about the time when, their 
organization being successfully com- 
pleted, they are prepared to enter upon 
an area of efficient and fruitful labor; 
hence, all of the expense of organization 
and other preliminaries becomes a total 
loss to the government. 

On the other hand, some of the rm>st 
important surveys of the world have 
arisen from humble beginnings. Such an 
enterprise educates its own members, the 
assistant engineer of one season becom- 
ing the engineer of the next, and so on. 



174 

It develops gradually and with a healthy 
growth, perfecting its own methods, and 
always experimenting upon a small scale, 
so that it is never liable to serious disas- 
ter. And, above all, by its early pro- 
duction and exhibition of results com- 
mensurate with its size, and with its 
cost, which is insignificant at first, it 
buys the right to be continued, en- 
couraged and increased from year to 
year. 

A GEOLOGICAL AND GEOGRAPHICAL SUR- 
VEY. 

There are two very good arguments 
for such a geographical survey in connec- 
tion with the Geological Commission of 
Brazil ; first, its necessity to the geologi- 
cal survey, as explained in the early part 
of this paper; and second, because in 
sudh a connection it can work most 
economically and profitably. With a 
combination of these elements comes 
much valuable co-operation between the 
representatives of the various branches 
of science, and this is constantly acting 



175 

to lessen the expense and increase the re- 
turns of such a survey. For instance, as 
the meteorologist of the engineering 
corps, an assistant with some acquaint- 
ance with geology, could be chosen. As 
his meteorological duties upon the march 
would be but light, he could devote 
much of his time to a geological study 
of the road, leaving the regular geologist 
at liberty to go from camp to camp by 
any other route that he might select. 
Again, the meteorologist, or even the en- 
gineer himself, may make strati graphical 
sketches upon every mountain, and bring 
specimens of rock from the same, while 
the geologist is away upon some detour 
to regions of interest in another direc- 
tion. 

Or, reversing this illustration, the 
geologist, whose profession is so closely 
allied to that of the geographer, is con- 
stantly making notes of direction, dis- 
tance, slope, and altitude, which are of 
the highest importance and use in the 
construction of a map. These are lost 
to the world if there is not an accom- 



176 

panying geographical survey into whose 
plots they may be assimilated. 

In witness of the sympathy with 
which the present members of the Geo- 
logical Commission regard geographical 
work, and of their skill in the prosecu- 
tion of the same, the writer would men- 
tion their intelligent and extensive sur- 
veys of the valley of the Amazon, from 
Monte Alegre westwards, and of its 
tributary, the Trombetas; of the island 
of Fernando de Noronha; and of many 
localities along the Atlantic coast and 
elsewhere in the empire. These are evi- 
dences of a willingness and an ability to 
collect geographical information, which, 
in themselves, assure the success of a 
system of geographical surveying in 
connection with the Geological Commis- 
sion of Brazil. 




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CLARKE. DESCRIPTION OF THE IRON RAILWAY 
BRIDGE Across the Mississippi River at 
Quiucy, Illinois. By Thomas Curtis Clarke, 
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graphed flans. 4to, cloth, . . . $7 50 

ROEBLING. LONG AND SHORT SPAN RAILWAY 
BRIDGES. By John A. Roebling, C. E. 
With large copperplate engravings of 
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DUBOIS. THE NEW METHOD OP GRAPHICAL 
STATICS. By A. J. Dubois, C. E., Ph. D. 
60 illustrations. 8vo, cloth 2 00 

EDDY. NEW CONSTRUCTIONS IN GRAPHICAL 
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Ph. D. Illustrated by ten engravings in 
text, and nine folding plates. 8vo, cloth, 1 50 

BOW. A TREATISE ON BRACING with its ap- 
plication to Bridges and other Structures 
of Wood or Iron. By Robert Henry Bow, 
C. E. 156 illustrations on stone. 8vo, cloth, 1 50 

STONEY. THE THEORY OF STRAINS IN GIRDERS 
and Similar Structures with Observa- 
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Practice, and Tables of Strength and other 
Properties of Materials. By Bindon B. 
Stoney, B. A. New and Revised Edition, 
with numerous illustrations. Royal 8vo, 
664 pp., cloth, 12 50 

HENRICI. SKELETON STRUCTURES, especially in 
their Application to the building of Steel 
and Iron Bridges. By Olaus Henrici. 8vo, 
cloth, 1 50 

KING. LESSONS AND PRACTICAL NOTES ON 
STEAM. The Steam Engine, Propellers, 
&c., &c., for Young Engineers. By the late 
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AUCHINCLOSS. APPLICATION OF THE 

VALVE and Link Motion to Stationary, 
Portable, Locomotive and Marine Engines. 
By William S Auchincloss. Designed as 
a hand-book for Mechanical Engineers. 
With 37 wood-cuts and 21 lithographic 
plates, with copper-plate engraving of the 
Travel Scale. Sixth edition. 8vo, cloth, $3 00 

BURGH. MODERN MARINE ENGINEERING, ap- 
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Consisting of 36 Colored Plates, 259 Practi- 
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Descriptive Matter, the whole being an ex- 
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lowing firms: Messrs J. Penn & Sons; 
Messrs. Maudslay, Sons & Field; Messrs. 
James Watt & Co. ; Messrs. J. & G. Ren- 
nie. Messrs. R. Napier & Sons- Messrs J. 
& W. Dudgeon: Messrs. Ravenhill <fc 
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Mr J. T. Spencer, and Messrs. Forrester 
& Co. By N P. Burgh. Engineer. One 
thick 4to vol., cloth, $25 00 ; half morocco, So 00 

BACON. A TREATISE ON TIIE RICH ARD'SSTEAM- 
ENGINE INDICATOR with directions for 
its use. By Charles T. Porter. Revised, 
with notes and large additions as devel- 
oped by American Practice; with an Ap 
pendix containing useful formula^ and 
rules for Engineers. By F W. Bacon, M. 
E. Illustrated Second edition. 12mo. 
Cloth $1.00; morocco, ..... 1 5 

ISHERWOOD ENGINEERING PRECEDENTS FOR 
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ST1LLMAN. THE STEAM ENGINE INDICATOR 
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and Vacuum Gauges their utility and ap- 
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JJ. VAN NOSTRAND'S PUBLICATIONS. 
MacCORD. A PRACTICAL TREATISE ON THE 

SLIDE VALVE, BY ECCENTRICS examining 
by methods the action of the Eccentric 
upon the Slide Valve, and explaining the 
practical processes of laying out the move- 
ments, adapting the valve for its various 
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cloth $3 00 

PORTER. A TREATISE ON THE RICHARDS' 
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McCULLOCH A TREATISE ON THE M>^TANI- 

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cloth, . . 3 50 

VAN BDREN. INVESTIGATIONS OP FORMU- 
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STUART. How TO BECOME A SUCCESSFUL EN- 
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SHIELDS A TREATISE ON ENGINEERING CON- 
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WEYRAUCH. STRENGTH AND CALCULATION OP 
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STUART. THE NAVAL DRY DOCKS OF THE 
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TUNNER. A TREATISE ON ROLL-TURNING FOR 
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GRUNER. THE MANUFACTURE OF STEEL. By 
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BARBA. THE USE OF STEEL IN CONSTRUCTION. 
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BELL. CHEMICAL PHENOMENA OF IRON 
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WARD. STEAM FOR THE MILLION. A Popular 
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CLARK. A MANUAL OF RULES, TABLES AND 
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DODD. DICTIONARY OF MANUFACTURES, MIN- 
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VON COTTA. TREATISE ON ORE DEPOSITS. By 
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8vo, cloth, .... ... 4 00 

PLATTNER. MANUAL OF QUALITATIVE AND 
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o the Royal Saxon Mining Academy. 
Translated by Professor H. B. Cornwall. 
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PLYMPTON. THE BLOW-PIPE : A Guide to its 
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JANNETTAZ. A GUIDE TO THE DETERMINATION 
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G. W. Plympton, Professor of Physical 
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12mo, cloth, $] 50 

MOTT. A PRACTICAL TREATISE ON CHEMISTRY 
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ties, Weights and Measures, etc., etc., etc. 
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HVO, cloth, , . 6 00 

PYNCHON. INTRODUCTION TO CHEMICAL PHY- 
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copious experiments, with directions for 
preparing them. By Thomas Ruggles Pyn- 
chon, D. D., M. A., President of Trinity Col- 
lege, Hartford. New edition, revised and 
enlarged. Crown 8vo, cloth, . . . 3 00 

PRESCOTT. CHEMICAL EXAMINATION OF ALCO- 
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ed Liquors of Commerce, and their Quali- 
tative and Quantitative Determinations. 
By Alb. B. Prescott, Prof, of Chemistry, 
University of Michigan. 12rno, cloth, . 1 50 

ELIOT AND STOKER, A COMPENDIOUS MANUAL 
OF QUALITATIVE CHEMICAL ANALYSIS. By 
Charles W. Eliot and Frank H. Storer. Re- 
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NAQUET. LEGAL CHEMISTRY. A Guide to the 
Detection of Poisons, Falsification of Writ- 
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and Examination of Hair, Coins, Fire-anna 
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by J. P. Battershall, Ph. D. ; with a Preface 
by C. F. Chandler, P^. D., M. D., LL. D. 
Illustrated. 12mo, cloth, . . . . $2 00 

PRESCOTT. OUTLINES OP PROXIMATE ORGANIC 
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gan. 12mo, cloth, . . . 1 75 

DOUGLAS AND PRESCOTT. QUALITATIVE CHEM- 
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Prescott ; Professors in the University of 
Michigan. Second edition, revised. 8vo, 
cloth, 3 50 

RAMMELSBERG. GUIDE TO A COURSE OF 
QUANTITATIVE CHEMICAL ANALYSIS, ESPE- 
CIALLY OF MINERALS AND FURNACE PRO- 
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ler, M. D. 8vo, cloth, 2 25 

BEILSTEIN. AN INTRODUCTION TO QUALITATIVE 
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Third edition. Translated by I. J. Osbun. 
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POPE. A Hand-book for Electricians and Oper- 
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DAVIS AND RAE. HAND BOOK OF ELECTRICAL 
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HASKINS. THE GALVANOMETER, AND ITS USES. 
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LARRABEE. CIPHER AND SECRET LETTER AND 
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GILLMORE PRACTICAL TREATISE ON LIMES, 
HYDRAULIC CEMENT, AND MORTARS. By 

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GILLMORE. COIGNET BETON AND OTHER ARTIFI- 
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GILLMORE. A PRACTICAL TREATISE ON THE 
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GILLMORE. REPORT ON STRENGTH OF THE BUILD- 
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HAMILTON. USEFUL INFORMATION FOR RAIL- 
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STUART. THE CIVIL AND MILITARY ENGINEERS 
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ERNST. A MANUAL OF PRACTICAL MILITARY 
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SIMMS. A TREATISE ON THE PRINCIPLES AND 
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HOWARD, EARTHWORK MENSURATION ON THE 

BASIS OF THE PRISMOlDAL FORMULAE. 

Containing simple and labor-saving meth- 
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ed. 8vo, cloth, 1 50 

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CLEVENGER. A TREATISE ON THE METHOD OF 
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MINIFIE. A TEXT-BOOK OF GEOMETRICAL 
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MINIFIE. GEOMETRICAL DRAWING. Abridged 
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FREE HAND DRAWING. A GUIDE TO ORNAMEN- 
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AXON. THE MECHANIC'S FRIEND. A Collec- 
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relating to Aquaria Bronzing Cenients 
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connected with the Chemical and Mechan- 
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12ino, clotu. 300 illustrations, . . . 1 50 

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JOYNSON. THE MECHANIC'S AND STUDENT'S 
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of General Machine Gearing. Edited by 
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RANDALL. QUARTZ OPERATOR'S HAND-BOOK. 
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cloth, . . $2 00 

SILVERSMITH. A PRACTICAL HAND-BOOK FOR 
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BARNES. SUBMARINE WARFARE, DEFENSIVE 
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War. Methods of Ignition by Machinery. 
Contact Fuzes, and Electricity, and a full 
account of experiments made to deter- 
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under Water. Also a discussion of the Of- 
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Iron-clad Ship systems, and influence upon 
future Naval Wars. By Lieut.-Com. John 
S. Barnes, U. S. N. With 20 lithographic 
plates and many wood-cuts. 8vo, cloth, 5 00 

FOSTER. SUBMARINE BLASTING, in Boston 
Harbor, Mass. Removal of Tower 
and Corwin Rocks. By John G. Foster, 
U. 8. Eng. and Bvt. Major General U. S. 
Army. With seven Plates. 4to, cloth, 3 50 

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WILLIAMSON. ON THE USE OF THE BAROME- 
TER ON SURVEYS AND RECONNAISSANCES. 
Part I.-Meteorology in its Connection with 
Hypsometry. Part II. Barometric Hyp- 
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Col. U.S.A., Major Corps of Engineers. 
With illustrative tables and engravings. 
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WILLIAMSON. PRACTICAL TABLES IN METE 
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8. Williamson, U. S. A. 4to, flexible cloth, $2 50 

BUTLER. PROJECTILES AND RIFLED CANNON 
A Critical Discussion of the Principal Sys 
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U-. S. A. 36 Plates. 4to, cloth, . . 7 50 

BENET. ELECTRO-BALLISTIC MACHINES, and 
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MICHAELIS. THE LE BOULENGE CHRONO- 
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4to, cloth, . . . ... 3 00 

NUGENT. TTEATISE ON OPTICS ; or Light and 
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PEIRCE. SYSTEM OF ANALYTIC MECHANICS. By 
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CRAIG- WEIGHTS AND MEASURES. An Account 
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ELLIOT. EUROPEAN LIGHT-HOUSE SYSTEMS. 
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wood-cuts. 8vo, cloth, $5 00 

SWEET. SPECIAL REPORT ON COAL. ByS. H. 

Sweet. With Maps. 8vo, cloth, . . 3 00 

COLBURN. GAS WORKS OF LONDON. ByZerah 

Colburn. 12mo, boards, . ... 60 

WALKER. NOTES ON SCREW PROPULSION, its 
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U.S. Navy. 8vo, cloth, .... 75 

POOR. METHOD OF PREPARING THE LINES AND 
DRAUGHTING VESSELS PROPELLED BY SAIL 
OR STEAM, including a Chapter on Laying- 
off on the Mould-loft Floor. By Samuel 
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8vo, cloth. 5 00 

SAELTZER. TREATISE ON ACOUSTICS in connec- 
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250 illustrations. 8vo, cloth, . . . 1 50 

SCHUMANN. A MANUAL OF HEATING AND VEN- 
TILATION IN ITS PRACTICAL APPLICATION 
for the use of Engineers and Architects, 
embracing a series of Tables and Formulae 
for dimensions of heating, flow and return 
Pipes for steam and hot water boilers, flues, 
etc . etn By F Schumann, V. E., U. S. 
Treasury Department 12mo. Illustrated, 
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WANKLYN. MILK ANALYSIS. A. Practical 
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its Derivatives, Cream, Butter, and 
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S. 12rno, cloth, . . . . $1 00 

RICE & JOHNSON. ON A NEW METHOD OF OB- 
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S. Navy, and W. Woolsey Johnson, Prof, of 
Mathemathics, St. John's College, Annap- 
olis. 12mo, paper. . 50 

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