Topographic instructions of the United States Geological Survey

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DEPARTMKNT OF THK INTERiOR

UNITED 2;ftTE5 GEOLOGICAL SURVEY

TOPOGRAPHIC INSTRUCTIONS

UNITED STATKS GEOLOGICAL
SURVEY

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r

CONTENTS.

Page.

Prefatory note 9

General instructions 11

Administration 11

Organization 11

Relations to the Government 11

Relations to vState surveys 12

Relations to the public 12

Information to the press , 13

Organization and management of field parties 14

Personnel 14

Classification 14

Appointment 14

Traveling expenses 14

Field insurance 15

Camp subsistence and management 15

Subsistence 15

Camp administration 16

Camp equipage 18

Storage >....>. 19

Reports :•>'•:••• '-^-y^ /• . y ".ar

Instruments ' . /...'. ..'.."... 22

Delivery and return : v^ ; . .^:.. /. *a2

Requisitions . '.'.•'...: . i2i»

Responsibilitv •■ . . v^. ^ .^ . ; . • "idf*

Transfer 1 ...: : .% .;. . ^

Return 22

Types 23

List 23

Care in specification 24

Accessory articles 26

List 1^

Bench-mark posts or tabl^Vs

4 CONTENTS.

Page.

General instructions — Continued.
Instruments — Continued .

Care 27

Cleaning 27

Protection against weather 28

Transportation 28

Adjustment 30

Precautions 30

General adjustments 30

Telescopic alidade 32

Y level 32

Locke level 34

Rod level 34

Transit 34

Theodolite 36

Suggestions to computers 39

Primary control 42

General conditions 42

Primar>' tri angulation 43

Field work 43

Personnel and outfit of party 43

Preparatory work 44

Observing and recording 49

•: ;•• % : x:dtnMf'XtiiiAs 56

' : %,: PrimM-^^nra^litsiJ 74

•'•. * • .;^?W:*1^^^ 74

^ ^l *•**•! Pcifconncl and outfit of party 74

• / •- • ..• .♦l^jeparatorv work 75

V V: :.\ V: •;,*T^v;?^ 76

' **Of)sefving and recording 78

Computations 82

Primary and precise leveling 87

Distribution of primary-level control 87

Bench marks 88

Primary leveling with Y level 91

Primary leveling with yard rod and prism level 94

Vec/se leveling 100

imputation and adjustment oi \eve\ citcuVts vsfe

» e • * *

CONTENTS. 5

Face.

Secondary control iz3

Plane-table triangulation zi3

General instructions iia

Choice of station 113

Observing and recording 113

Three-point method 115

Plane-table traverse 116

Methods 116

Stadia traverse 118

Wheel traverse 123

Tape traverse 123

Foot traverse 124

Use of aneroid 124

Use of Baldwin solar chart 125

Explanation 125

Object 125

Preparation of chart for use 126

Orientation of plane-table . . . . i 128

Errors 129

Time correction ' 130

Map construction 131

Field work 131

General character of atlas sheets 131

Preliminary instructions 131

Preparatory work 131

Names 133

Mapping of cultural features 135

Mapping of hydrographic features 144

Mapping of topographic features 146

Contours 146

Delineation 147

Mapping of land-classification data 149

General requirements 149

Agricultural data 151

Water-supply data 154

6 CONTENTS.

ICap construction — Continued. Page.

Ofl&ce work 159

Preparation of topographic field sheets for engraving 159

Inking 159

Culture i6o

Bench marks and elevation figures 161

Hydrography 162

Topography 164

Lettering 166

Preparation of river-siurvey maps for photolithography 169

Size of sheets 160

Plans 169

Profiles 170

Drafting 170

Proof reading, inspection, editing, and transmission . 171

Order of procedure 171

Proof reading 172

Editing 174

Supplementary data 175

Medical and surgical attention 175

First aid in emergency 175

Surgical attention 177

Medical and surgical outfit 178

Pack transportation 180

Pack-train equipment 180

Organization of pack train 181

Carrying capacity of pack train 181

Marches 182

Care of pack animals 182

United States system of public-land surveys 183

Township units 183

Principal meridians and base lines 183

Standard parallels and guide meridians 184

Township exteriors 185

Section lines 187

Meanders 188

'^ng lines 189

king comers 189

CONTENTS. 7

Supplementary data — Continued. Page.

Requisitions 19a

Stationery 193

Instruments 199

Fountain pens aoa

Miscellaneous articles aoa

Conventional signs 205

Index 229

ILLUSTRATIONS.

Paie.

Plats I. Marks used for control stations 46

II-III. D. H. Baldvnn solar chart for plane-table orienta-
tion ia6

FlouRS I. Diagram showing arrangement of triangles 60

3. Diagram showing method of adjusting a level net . . 109

3. Diagram showing solution of three-point method . . 116

4. Diagram illustrating correction of base laa

5. Pattern and s3mibols for designation of forest land . 151

6. Patterns and symbols for designation of arable land. 153

7. Pattern and symbols for designation of grazing

land 153

• I

PREFATORY NOTE.

The instructions relating to the topographic work of the United
States Geological Survey issued as part of the general Survey instruc-
tions of 1903 are now in many respects obsolete, although revised
portions of them have from time to time been issued as circular
letters or printed leaflets. The need for a single book containing the
latest and most approved information on the subjects treated has
become so urgent that it has been deemed advisable to rewrite the
instructions in the form herein presented.

The several parts of this book were prepared by the members
of the topographic branch best qualified for the task and after being
assembled and revised by the geographers in charge of divisions were
critically examined by the chief geographer. It is desired to make
these instructions complete so far as the technical work of map
making is concerned and to reduce to a minimum the necessity of
personal instruction. The present edition is preliminary, and any
criticisms or suggestions for its improvement should be sent promptly
to the chief geographer.

R. B. Marshall,

Chief Geographer.

Approved.

Geo. Otis Smith, Director.

Washington, D. C, November q, igi2.

Instructions to Topographers of the
United States Geological Survey.

GENERAL INSTRUCTIONS,
ADMINISTRATION.

ORGANIZATION.

The topographic branch is organized under the direction of a chief
geographer into five areal divisions (Atlantic, Central, Rocky Moun-
tain, Northwestern, and Pacific), each of which is in charge of a
geographer. The members of the technical force are graded as
chief geographer, geographers, topographic engineers, topographers,
assistant topographers, junior topographers, topographic aids, and
draftsmen.

RELATIONS TO THE GOVERNMENT.

Loyalty on the part of every member to the Survey as an organiza-
tion is essential to its continued efficiency and high standing. The
enviable position which the organization now holds in the esteem
and confidence of the public is a most valuable asset, and each
member should feel that he is personally responsible for maintaining
and bettering that standing. The personality or the work of other
members of the topographic branch or of other branches of the
Survey or of other Government bureaus should never be publicly
criticiied. If criticisms seem necessary they should be communi-
cated through the proper official channels to the responsible officer,
who will give them full consideration.

The topographic branch cooperates with other branches of the
Survey, and to render such cooperation effective the interests of the
Survey as a whole must be kept in mind, rather than the s|)ecial
interests of any particular branch or division.

Members of the topographic branch should keep themselves
informed regarding Survey work in general and topographic work

12 INSTRUCTIONS TO TOPOGRAPHERS.

in particular. Ihey are referred in this connection to the leaflet
"Nature and use of the topographic maps of the United States
Geological Survey," and to Bulletin 227, "The United States Geo-
logical Survey, its origin, development, organization, and opera-
tions."

The topographic branch is frequently called upon to cooperate
with the General Land Office, the Forest Service, the Bureau of
Soils, the Reclamation Service, and other Government bureaus.
Topographers assigned to such work should familiarize themselves
with the regulations and methods of procedure of the cooperating
bureau and should conform to them.

RELATIONS TO STATE SURVEYS.

it is essential to efficiency and economy that cordial relations
exisrt between the United States Geological Survey and the State
surveys. When formal cooperation with a State is in force, topog-
raphers submitting expense vouchers should first familiarize them-
selves ^vith the State methods of accounting, so as to avoid confusion
and delay in settlement of vouchers. It should be clearly under-
stood that the Federal and State surveys are not competitors
occupying the same field, but that each organization has a province
of its own fmd that each supplements the work of the other.

RELATIONS TO THE PUBLIC.

Courtesy to the public is enjoined on every member and employee
of the typographic branch. Discourtesy to the public will not be
tolerated, and chiefs of party will be expected to discipline or
discharge employees for flagrant neglect to conduct themselves with
politeness and propriet>'. When persons make serious inquiry con-
cerning work that the Survey is carrying on, time should be taken
to give th^m the information; and when Federal and State Govern-
ments are cooperating. Survey employees will be expected on. all
proper occasions to make known to citizens the relations of the State
to the woik which is being done.

Objection is sometimes made to entry on private property by

members of the Survey engaged in official work, but it is believed

V objections may generally be overcome by an explanation

GENERAL INSTRUCTIONS. 1 3

of the public character of the work. Laws enacted b}'- the legis-
latures of Arizona, California, Illinois, Maine, Montana, New York,
Ohio, Pennsylvania, and Washington grant authority for sucn entry
to officials of the United States Geological Survey.

INFORMATION TO THE PRESS.

It is desirable that information concern in^ the progiess of Survey
work and matters of public concern in connection therewith shall
be supplied to representatives of the press. Such information is
usually given through the weekly press bulletin, and it is expected
that members of the Geological Stu^ey will utilize this in matters of
routine importance. It is sometimes advisable, however, for a mem-
ber of the Survey to give information direct to a newspaper man; in
such cases it is of the utmost importance that all statements shall be
well considered and that they shall be correctly reported. The
tendency among a certain class of newspaper men to wrongly inter-
pret or to recklessly color a verbal expression in order to produce a
"good stor}'" necessitates the adoption of safeguards which shall be
automatic in operation and general in application.

No statement relative to official matters may be given to the press
without previous authorization from the Director. Whenever any
member of the Survey is asked for a statement regarding any public
matter, he must, before giving it, ascertain by confiultation with the
Director whether authorization has been granted. No interview is
to be given without securing from the person soliciting the same a
promise that he will, before submitting his manuscript to his pub-
lication office, present a copy of it to the Director for approval. If
any such promise is violated, the incident will be made a matter of
record, and future interviews will be denied to the person guilty of
such violation.

These restrictions arc regarded as essential to the continued wel-
are of the organization, and must apply to all employees in the
field, as well as in Washington, with the exception that field men
may make general statements to representatives of the press regard-
ing their own field plans or work accomplished

No statements touching upon the policy of the Surveyor any other
Government bureau should be made txc^xA. \tv 'Ccl'^: tkscncsrx. '^icsss^^
outlined.

i

14 INSTRUCTIONS TO TOPOGRAPHERS.

ORGANIZATION AND MANAGEMENT OF FIELD PARTIES.

PBRSONNBL.

CLASSIFICATION.

The letter of assignment issued to the party chief specifies the
number and class of field men who are to make up his party, and
their compensation. Field men are graded as follows: (i) Topo-
graphic aids; (2) grade i: recorders, rodmen, chainmen, etc.; (3)
grade 2: laborers, including teamsters, packers, and cooks.

APPOINTMENT.

Topographic aids. — Topographic aids are selected from a list of
eligibles furnished by the United States Civil Service Commission.

Applications for employment. — Persons desiring temporary' employ-
ment on the field force in grade i must file application, on the form
provided for that purpose, with the chief geographer in Washington.
Laborers (grade 2) will be employed in the field by chiefs of parties
as necessity may arise, and no applications for such employment
will be received or filed in Washington. All persons are ineligible
for employment if they are suffering from any contagious or other
disease, and, in grade i, if they are imder 20 or more than 40 years
of age, or if they are students pursuing a college course, tmless they
bind themselves to remain with the party until their services are no
longer needed. Preference is given to applicants from States in
which the work is to be done; and in case of residents assigned to
parties working in Western States, the age limit for rodmen, recorders,
etc., may be waived, provided that no such employee is to be less
than 18 years of age.

Employment contracts. — Before entering upon his field duties every
employee must sign a contract specifying the terms of his employ-
ment and containing an agreement to remain with the Survey tmtil
the close of the field season, provided his services are satisfactor>'.

TRAVELING EXPENSES.

In addition to compensation, necessary living and traveling

expenses incurred diuing employment will be refunded to topo-

lids and to employees in grades z and 2. They must report

ft 0/ beginning of &eld work, however, atUVi^vc orvncL^xi^ense.

MANAGEMENT OF FIBI/D PARTIES. 1 5

FIELD INSURANCE.

As no leave is given to temporary employees in the field, whether
employed by the month or day, their pay stops immediately if they
become incapacitated by reason of accident or sickness. In order
that other members of a party may not be called on to bear the
expenses entailed by sickness or accident of one of its members,
chiefs of party are instructed to m'ge all employees to take out insur-
ance. To provide this at the lowest possible rate, a mutual benefit
association has been formed by members of the Geological Survey
and other Government bureaus. This association exists solely for
the purpose of giving health and accident insurance to field men at
cost and of preventing unnecessary burdens from falling on the
immediate associates of those disabled. Information concerning
membership can be obtained from chiefs of party.

CAMP SUBSISTENCE AND MANAGEMENT.

If camp outfits are used their character should be determined b}'
the size of the party, the means of transportation, and the nature of
the work. They should contain the essentials for efficiency and
comfort. Unnecessary hardships should be avoided as much as
unnecessary luxur}-, as both lower efficiency.

SUBSISTENCE.

Rations. — Economy in the purchase of supplies is expected, but
the supply should be ample and of good quality. The subjoined
ration list is recommended as a general guide. Experience has
shown it to be ample in amount as regards all essential articles.

Ration list for topographic field parties.^

loo rations.

Fresh meat, including fish and poultry loo pounds.

Cmed meat, canned meat, or cheese 50 pounds.

I/ard IS pounds.

Flour, bread, or crackers 80 pounds.

Commeal, cereals, macaroni, sago, or cornstarch 15 pounds.

> The following substitutions may be made: 8 eggs for x pound of meat; 5 pounds
of frah meat for a pounds of cured meat; 5 quarts of fresh for x can of condensed mUk.\
S poMiHlf of fresh fruit for i pound of dried fruit-, ^ poMii*^% «A \\«^ ^^siS»aficJ«s.Ns«^
2 pooftd of dried vegetables.

i6

INSTRUCTIONS TO TOPOGRAPHERS.

loo rations.

Baking powder or yeast cakes S pounds.

Sugar • 40 pounds.

Molasses x gallon.

Coffee 12 pounds

Tea, chocolate, or cocoa 2 pounds.

Milk, condensed 10 cans.

Butter 10 pounds.

Dried fruit 20 pounds.

Rice or beans 20 pounds.

Potatoes or other fresh vegetables 100 pounds.

Canned vegetables or fruit 30 cans.

Spices 4 ounces.

Flavoring extracts 4 ounces.

Pepper or mustard 8 ounces.

Pickles 3 quarts.

Vinegar i quart.

Salt 4 pounds.

Ration for stock, — For stock the following ration may be used as a
basis for estimate:

Daily ration, in pounds j for stock.

Heavy horses.
Mules

Oats.o

12
10

Com.o

IS

Z2

Hay.

24

20

a The rations of oats and com are substitutes for each other.

CAMP ADMINISTRATION.

Discipline. — In camp the chief should insist on punctuality, order,
and neatness. Proper discipline is absolutely essential to efficiency.
It should be remembered that the Siurvey is judged generally
throughout the coimtry by its field representatives, and they should
do it credit in personal appearance as well as in other ways.

A United States flag and a Survey pennant must be displayed over
each camp.

Camp sites should be carefully selected and the tents arranged in

de&u'te order and not at random. Wagons and other vehicles should

*^ parked on one side: Harness, saddles, etc., should be kept off

MANAGEMENT OF FIELD PARTIES. 1 7

the groirnd and either hung on racks or placed in the wagons. Ani-
mals should be corralled at sufficient distance from the tents to
prevent them from interfering with comfort and sanitation. The
camp should be kept neat at all times; no loose articles, papers, or
refuse should be allowed to litter the grounds.

Topographers are by nature of their work called upon to sojourn
in many different regions and to adapt themselves to changes of
climate and environment. Their work frequently takes them to
remote localities where medical aid is not readily obtainable, and it
is therefore especially important that they should be personally
familiar with and should habitually conform to the laws of hygiene
and diet. It is especially important that all chiefs of party should
be conversant with such matters, as it is a necessary part of their
professional equipment. Promiscuous drinking from streams, faitoe
to use boiled drinking water, carelessness in selecting camp sites,
inadequate provision for the disposal of refuse, failure to observe
sanitation in the arrangement of toilet facilities, insufficient screen-
ing from flies, and failure to use mosquito netting in malarial districts
are responsible for most of the sickness in camp. All chiefs of party
should formulate sanitary regulations for camp administration
adapted to the locality and should see that they are rigidly enforced.

Typhoid-fever prevention. — Field men are more liable to contract
typhoid fever than any other disease. It is therefore urged that
everyone who has not already had that disease protect himself against
it by inoculation with antityphoid serum or "vaccine" as prepared
and administered by the United States Army.

The experience of the United States and foreign armies proves
conclusively that the vaccine is an almost infallible preventive of
the fever and that its effects last for several years.

Sufficient of the prophylactic for the complete treatment and a
copy of instructions for its use may be obtained by any member of
the field or office force of the United States Geological Svu^ey on
official request addressed to the Director. It will be necessary for
each person to employ at his own expense a physician to admin-
ister the serum, which is given as hypodermic injections in the
arm in three doses, lo days apart.

66512 — 13 2

1 8 INSTRUCTIONS TO TOPOGRAPHERS,

Farmers' Bulletin No. 478 of the United States Department of
Agriculture gives valuable data on the prevention of typhoid fever
and the use of the prophylactic for its prevention.

Entertaining persons in camp. — Chiefs of party and all other em-
ployees of the Survey are cautioned, when on field duty, against
entertaining in camp any persons, whether acquaintances, friends,
or relatives, in a manner to interfere with public business. Instru-
ments, outfit, and supplies are provided at Survey expense for offi-
cial purposes only and should be used solely to advance official
work. Members of the Survey are required to give their time and
labor strictly to official business.

Personal baggage. — The bulk and weight of camping outfits should
be kept as low as is compatible with comfort. To this end, personal
baggage should consist of essentials only. It should be carried in
canvas bags chiefly, and in pack outfits is limited to one bag for
each man. Trunks should not be taken to camp, except where they
may be readily transported by rail. Each man is expected to fur-
nish his own bedding and canvas bed cover. Folding cots are fur-
nished for permanent employees only. Mattresses are too cumber-
some for convenient transportation, and should not be used.

CAMP EQUIPAGE.

In order to facilitate field work in regions where camping is neces-
sary or desirable, parties will be furnished with complete camp
equipage, including tents, stoves, camp fumittue, mess and cooking
outfits, as well as means of transportation, such as wagons and other
vehicles, harness, riding saddles, packsaddles, and necessary acces-
sories.

Care of public property. — Chiefs of party will be held strictly re-
sponsible for the public property intrusted to their care and are
expected to see that it receives no rougher usage than conditions
necessitate. They should instill their men with a feeling of respon-
sibility for the property and induce them to take pride in keeping
it in good serviceable condition. As wear results mostly from care-
lessness in packing, loading, and transporting when camp is moved,
party chiefs should take pains to instruct their assistants as to proper

MANAGEMENT OF FIELD PARTIES. 1 9

methods. Tents should receive particular care in transportation, for
the best of them may be worn through or rendered leaky by a few
hours' chafing against boxes or wagon bed. They should, therefore,
be loaded with care, and should never be transported without being
wrapped in some protective covering; the heavy tarpaulins used for
tent floors are convenient for this piu"pose. In transporting tents by
pack train special pains must be taken to keep them from contact
with the animal 's body, as they will be permanently ruined if per-
meated by its sweat.

Wagons and harness should be kept in repair. Wagons should be
kept painted, as without such protective covering their woodwork,
more especially that of the running gear, will not last. Harness
should be oiled and blacked as frequently as is necessary to keep it
in good condition. The teamster should be required to give proper
attention to these details.

Purchase of property in field. — Every article of property which
appears on a voucher as having been purchased and which is not
expendable must be accounted for on the returns of the custodian.
In cooperative States such articles must be submitted for payment
on a separate Federal voucher. Those in direct charge of property
should be prepared at all times to make a statement to the custodian
as to its condition and the amount on hand.

Tents, wagons, and other property of considerable value should
not be purchased without authority from the division geographer.

Lost or stolen property. — When public property has been lost or
stolen, without negligence on the part of its user, reasonable charges
for recovering it are allowable.

When field property is condemned or has been lost, a certificate
to that effect, approved by the Director, must be furnished and filed
with the custodian.

STORAGE.

Storerooms. — In arranging for the care of field property at the close
of a season, efforts should be made to store it near a main line of
railway, if possible in a brick building or other substantial structure.

Storing and pasturing . — Storing is something more than mere stow-
ing away in haphazard fashion ; it should be done with order ^xjA's^'s.-

f

20 INSTRUCTIONS TO TOPOGRAPHERS.

tern. The materials should be placed in boxes, the boxes numbered,
and lists made of the articles in each box. The boxes should be
securely packed and nailed, so that, if necessary, they may be in
condition to be shipped by rail. In the case of wagon outfits the
Ixixes may be left (m the wagons ready to haul away. Precautions
must be taken to protect the property against dampness and rodents.
Tents, harness, blankets, etc., must be thoroughly dried before
packing, otherwise they will be ruined by mildew. Axles of vehi-
cles must be cleaned with coal oil and well covered with axle grease.
Cooking utensils and tableware must be thoroughly cleaned and
dried and must never be packed unwashed.

No faod should be stored.

Chiefs of party must exercise great care in selecting proper locali-
ties and responsible caretakers for public animals to be placed in
pasturage. Shelter, water, and character of forage, as well as the
reliability of the caretaker, are the factors which should govern
selection . All shoes should be removed and an inventory and a com-
plete dcscrii)tion of all animals should be made before they are
delivered to the caretaker.

Signed agreements must be executed in triplicate with all persons
taking charge of Government property. Two copies must be sent
to the Survey in Washington and one retained by the caretaker.
Similar agreements should be signed when animals are placed in
pasturage.

Employees will be held personally responsible for neglect to
comply with these instructions.

Inventories. — When nonexpendable propert}' is stored a detailed
inventory, stating the condition of each article, must be made and
forwarded to the chief geographer. Similarly, on withdrawing prop-
erty for field use, each party must take an inventory of the same and
promptly forward it to the chief geographer, with the date of with-
drawal indicated. The last party to draw upon a storeroom should
send to the division geographer an inventory of the material left

An inventory or invoice, finally, of each shipment of property
should be made in duplicate. One copy should be sent to the con-
signee and another to the chief geographer.

MANAGEMENT OF FIELD PARTIES. 21

REPORTS OF FIELD PARTIES.

A monthly report is required from each chief of party on the topo-
graphic, primary control, or level work done under his direction;
also, from each levelman in charge of an independent level party.
Reports should be made out in duplicate and one copy sent to the
chief geographer, the other to the division geographer; and it is
absolutely essential that they be complete in every detail. They
should be mailed not later than the 3d day of each month and
should in no case reach the Washington office later than the 9th.

The regular monthly form is to be used for topographic, triangula-
tion, and level work. A separate sheet must be used for each quad-
rangle and State, in order that the division geographers may be able
accurately to apportion the cost of the work. Thus, where a party
has worked on three quadrangles in one montli, the chief of party
should apportion the amount of work and the cost among the three
as nearly as practicable, for he can do this better than the division
geographer. The total for the three should be accurate, though the
details of each may necessarily be approximate.

When a party is engaged in several classes of work, a separate dia-
gram should be used for each. Thus one diagram should show the
area controlled by plane-table or traverse (distinguishing between
kinds of traverse); another, the area leveled; and a third, the area
mapped. The work of the current month should be given most
prominence on the diagram; preferably, it should be indicated in
ink, different colors being used where necessarj-. Previous work
should be indicated in pencil.

A weekly report must be transmitted by each levelman and each
field assistant doing traverse work to his immediate part>- chief,
using the report blanks in card form that are provided for each class
of work. As the data from these weekly reports are incorporated
by the party chief into his monthly report, levelmen and field assist-
ants should so time the sending of their last weekly report for each
month as to avoid delaying the party chief's monthly report.

An employment report stating the names of the field assistants of
grades i and 2 employed, and the length of their sers'ice, is required
from all party chiefs. This report is to be made out quarterly, during

22 INSTRUCTIONS TO TOPOGRAPHERS.

the field season; that is, on July i for the months of April, May, and
June, and on October i for the months of July, August, and Septem-
ber. During the remainder of the year it is to be made out monthly.
One copy only, to be transmitted promptly at the close of the month
to the chief geographer, is required.

INSTRUMENTS.

DELIVERY AND RETURH.
REQUISITIONS.

Threefold forms are provided for requisitions for instruments;
these, when properly filled in and signed by the division geographer,
are to be transmitted to the chief geographer. When the instruments
called for are shipped, one of the three sheets is retained as the office
record; the other two are sent to the consignee, who upon receipt of
the shipment will sign and return to the custodian the second sheet,
retaining the third for his own use.

RESPONSIBILITY.

All persons to whom Siu^ey instruments are issued will be held
personally responsible for them and will be required to replace or
repair loss or injuries resulting from carelessness. In case of loss,
a certificate on the prop>er form must be furnished to the chief
geographer.

TRANSFER.

When instruments are transferred from one employee to another,
a threefold transfer card must be made out; one card must be sent to
the chief geographer, another card mailed to the consignee, and the
third card retained as a memorandum by the party transferring. It
does not suffice merely to state the number and kind of instruments
transferred. The list number stamped on each piece must also he given,

RETURN OF INSTRUMENTS.

When instruments are shipped to the office, a letter or card of noti-
fication should be mailed to the Director, stating the number of
bundles shipped and giving an invoice of the contents of each. Sv^h
invoice is not complete without the numbers stamped on the instruments,
^ facr should be attached to each instrument returned, listing defects
rs needed. Special tags are provided lot \ivvs pMr^se.

• INSTRUMENTS. 23

TYPES OF INSTRUMENTS.

LIST.

The following instruments are kept in stock and will be supplied
on requisition :

Alidades. Bulgine, 12-inch ruler.

Alidades, open sight, brass; length, 6, xo, and z8 inches.

Alidades, open sight, Burkland type; on boxwood scales graduated to all field

scales.
Alidades, telescopic; length of ruler, x8 inches. 25 inches.
Alidades, telescopic, with Beaman attachment.
Alidades, telescopic, with micrometer eyepiece.

Aneroids, graduated to altitudes of 3,000, 5,000. 10.000. 15,000. and 16.000 feet.
Baldwin solar chart.
Compasses, box.
Compasses, pocket.
Compasses, prismatic.
Counters, hand.

Dies, letters, and figures, standard size for bench-mark tablets.
Glasses, field, for triangulation or level parties.
Levels, circular.
Levels, hand.

Levels, plumbing, for New York rods.
Ircvels, plumbing, for stadia rods.
Levels, prism.
Levels, Y, 20-inch.
Levels, Y, is-inch.
Odometers.

Pins, marking, sets of 11, plain or loaded.
Pins, turning point, for precise levels.
Pins, turning point, for primary levels. 6-inch and lo-inch.
Plane-table boards. 24 by 3 x inches (full size), with wooden or leather cases.
Plane-table boards. z8 by 34 inches (half size), with wooden or leather cases.
Plane-table boards, x 5 by 15 inches (traverse size), with oilcloth cases.
Plane-table boards, 9 by 9 inches (for foot traverse).
Rods, precise leveling, marked in yards.
Rods, New York.
Rods, Philadelphia.
Rods, paper stadia.
Scales, boxwood, graduated to 1/50, 1/80, and i/ioo inch: also 1:24.000. 1:31.680.

1:48,000, 1:96,000, 1:125,000, and 1:240,000, in decimals of miles on one edge, in

feet on the other; also 1:48,000. in decimals of miles on one edge, chains on

the other.
Scales, triangular, steel, for plotting geographic coordinates Oa't.v<.>afiSL^

longitude).
Scribes, timber.

24 INSTRUCTIONS TO TOPOGRAPHERS.

Tapes, invar, 300 feet.

Tapes, metallic, 50 and 25 feet.

Tapes, steel, 300 feet.

Tapes, steel, 100, 50, and 25 feet.

Tapes, steel, 6 feet, pocket size.

Theodolites, 8-inch micrometer.

Thermometers.

Transits.

Transits, solar.

Tripods, traverse, Bumstead type.

Tripods, Johnson.

Tripods, for levels, theodolites, transits, etc.

CARE IN SPECIFICATION.

General rule. — Pains should be taken to make requisitions distinct
and specific, so there may be no doubt on the part of the custodian as
to the class or type of instrument desired. When several types of
instruments are available, the particular type desired should be
clearly specified, and, if necessary, the use for which it is intended
should be stated.

Thus, in ordering open-sight alidades, specify whether the brass or
the Biu-kland type is desired; if the former, state length of ruler; if
the latter, state the scale. The vanes of the Burkland alidade are
light and are readily fitted to any flat boxwood scale.

Prismatic eyepieces. — Prismatic eyepieces can be supplied for any
telescopic alidade if requested before the instrument is shipped from
the office.

Aneroids. — In ordering aneroids it should be remembered that
they are easily strained and rendered unreliable if carried to alti-
tudes much exceeding the limit for which they are graduated. It is
wise to allow a liberal margin.

Plane-table boards. — Plane-table boards 24 by 31 and 18 by 24
inches will be provided with plates to fit the Johnson tripods.

Traverse boards, — Traverse boards 15 by 15 inches may be had either
with or without box compass attached; also with plates for either
Johnson or Bumstead tripods.

Exchangeable parts, — Extra parts for standard telescopic alidades
are kept in stock and may be obtained on requisition. To insure
proper fit the size of part and the number of instrument should be
care/uJJy stated.

INSTRUMENTS. 25

Extra bubbles. — Each telescopic alidade, when issued, will be
provided with an extra bubble for the striding level . Whenever this
extra bubble is put into service on the instrument, requisition should
be immediately made for a new one. Before inserting the extra
bubble measure its over-all length and diameter, for these two
dimensions must be specified in ordering the new one.

Stadia rods, — ^A few stadia rods with standard saw-tooth gradua-
tions are kept in stock at the Washington office for use by near-by
parties not in camp. Photographs with specifications of the ap-
proved style of rods will be supplied on request. The specifications
are as follows:

Rods are to be of clear, straight-grained, well-seasoned white or
sugar pine, 4 inches wide, J/i inch thick, and 13.2 feet long, hinged
at the 6.6-foot mark with two 4-inch strap hinges bolted or riveted in
place. An extra handhold strip ^ by 3 by 27 inches is to be bolted
to upper end so as to project 15 inches beyond rod when closed; the
ends are to be protected with J^ by J^ inch strap iron screwed on.
The entire rod to be painted with two coats of flat white paint, and
to be subdivided by saw-tooth mark into tenths; the X-^oot marks
being made -^ foot and the tenth marks 1^ foot in height. The
even foot marks and figures are to be painted with scarlet vermilion
flat paint; the other marks with black flat paint. Figures are to be
2X tenths foot in height; V is to be used for 5 and X for 10; 6 is to be
made with straight upper stem; 9 with curved stem. About -j^
foot from the top a piece of thick leather about X i^ch by 2 inches
must be attached to keep painted faces from rubbing together when
rod is closed. A 14-inch by >^-inch leather strap with buckle may
be attached to back near bottom to hold the parts of rod in place
when folded. If desired to fasten rod open, a plate staple may be
bolted on the inside of the hand strip near its lower end so as to pro-
ject through a slot in rod; a wooden pin through this will hold rod
open.

For some classes of work rods without hinges are to be preferred.

Full-size paper prints of the stadia rod face will be furnished on
request; these, when attached to a piece of board, with varnish
make very serviceable rods.

Plumbing levels should be used when necessary.

26 INSTRUCTIONS TO TOPOGRAPHERS.

ACCESSORY ARTICLES.

LIST.

In addition to the instruments listed on page 23, the following
accessory articles may be obtained from the custodian. Requisi-
tions for them must be kept separate from stationery requisitions,
as the latter go to another division. (See also pp. 192-203.;

Abridged nautical almanac.

American ephemeris and nautical almanac.

Bags, noteboc^.

Bench-mark posts.

Bench-mark tablets.

Bench marks, temporary, copper nail and washer.

Branding irons.

Bubbles, level, extra.

Cans, paint, with brush inserted.

Canteens.

Celluloid, white sheets. 15 by 15 inches, or z8 by 24 inches.

Cement, in half-pint cans.

Circular letters, regulations, and instructions.

Cloth, tracing.

Computation tables, logarithmic. 5 place and 7 place.

Computation tables, natural sines and cosines.

Computation tables, stadia.

Computation tables, vertical angle elevations.

Crayons (keel), red or blue.

Drafting instruments, triangles, straightedges, ruling pens, plain dividers,

spacing dividers, scales.
Flags. United States, Survey ensign.
Paper, plane-table, double-mounted (34 by 31 inches, 35 by 36 inches, and 18

by 34 inches).
Paper, plane-table, single-motmted, in rolls of xo yards, width 58 inches and

73 inches, cut to plane-table sizes.
Paper, tracing (vellum), in so-yard rolls, cut as wanted.
Paper, tracing, in sheets, size 33 by 38 inches.
Paraffin, i-pound cakes.
Plaster of Paris.
Rubber stamps.
Shellac, liquid.
Tapes, cloth, in 400-yard spools.

BENCH-MARK POSTS OR TABLETS.

IVhen ordering bench-mark posts or tablets to be used in ooopera-
vorAr, the name of the cooperating State must be given, as such

CARE OF INSTRUMENTS. 2/

mailcs ar« eqiecially stamped with the name of the State. The same
style "Of tablet or post serves for triangulation stations, primary-
tra^werse stations, and bench marks.

CARE OF INSTRUMENTS.

Too much emphasis can not be laid upon the importance of care
in the handling and transportation of instruments. Every emplo3ree
imtrttsted with instruments in the field will be expected to keep
them clean and in adjustment, to protect them from imdue wear,
and to return them to the custodian in fit order for use.

CLEANING.

General rule, — Instruments having working parts exposed to air
and diist require cleaning from time to time. Such exposed parts as
the threads of tangent screws and the cups of Johnson tripod heads
are particularly liable to collect dust and grit and should be wiped
frequently with an oily rag, then rubbed dr>'.

Tapes. — Steel tapes should be cleaned and oiled after use. All
moisttue or grit must be wiped from them each time they are reeled,
or they will deteriorate rapidly. Special precautions must be taken
in this regard in work on the seacoast or in semitropical regions of
h^h humidity.

Arts and verniers, — ^Most graduated arcs and verniers are made of
silver and are therefore readily scratched and defaced. They
should be cleaned by wiping lightly with chamois skin dipped in
weak ammonia. A high polish on either an arc or a vernier is a dis-
advantage rather than an advantage in reading.

Telescope lenses. — ^The object glass and eyepiece of every telescope
&oidd be periodically dusted with a camel's-hair brush or wiped
wilh a piece of silk or soft tissue pai)er. They should never be
rtibbed with rough cloth or with the fingers, as the glass may thus
be (Knnanently scratched.

Alcohol should not be used for cleaning object glasses, as it may
penetrate between the lenses and dissolve the cement that holds
them together. The lenses should never be removed from the cell
that holds them nor separated from one another.

PROTECTION.

It should be a strict rule with everyone u?»\tv^ ^ <:avK^^iSB»\aX>&x
the needle from the center pin immediaieXy ajlet use. \lixv.^^^ ^»si ox

28 INSTRUCTIONS TO TOPOGRAPHERS.

cumstances should a compass ever be carried from one station to
another with the needle resting on the center pin. Party chiefs
should lay special emphasis on this when instructing new field
assistants.

When in camp instruments, plane-table boards, tripods, and rods
should never be allowed to ren^ain outside overnight, exposed to
dew or rain. It should be the regular practice in every field party
to place all instruments under shelter as soon as they are brought in
at the end of the day.

Pains should be taken to protect instruments from dampness or
rain when in use. Cross wires in telescopes may sag when damp,
and in that condition may introduce serious errors. Tripods and
rods warp or twist and may acquire a permanent set. Though such
wooden articles are usually well varnished or painted, some moisture
will penetrate these coatings, and too much dependence should not
be placed on their protective efficiency.

TRANSPORTATION.

Pack trains. — In mountains where pack trains are the sole means
of conveyance the triangulator's outfit is most conveniently carried
in a pair of canvas pack bags (alforjas), which must be properly
balanced. The tripod, * umbrella, and wind screens should be
placed lengthwise on top, lashed to the saddle, and further balanced
by properly disposing them on either side of the center. A canvas
pack cover should be thrown over the whole and tucked in on all
sides.

A plane-table outfit is best packed by hanging the plane-table in
its wooden case on one side, flat against the animal, and balancing it
with the alidade and other minor paraphernalia in a pack bag on the
other; the tripod goes on top, lashed to the saddle, head forward. A
leather or rope harness, with loops for hanging on the packsaddle,
should be provided for the plane-table case. As with the triangula-
tor's pack, a pack cover is a valuable protection.

Judgment should be used in selecting the animal for the instrument
pack. It need not be stout (for the pack is seldom heav}') but must
be well broken, intelligent, and sure-footed. In difficult places the

CARB OF INSTRUMENTS. 29

judgment and coolness of the animal must largely be depended Uf)on;
the more reliable the animal, therefore, the safer the pack. It is to
be kept in mind that the instrument pack is the most important and
valuable in the entire pack train; it should be constantly under the
eye of a competent packer, and the animal bearing it should be led
if necessary.

Freight or express. — In shipping instruments by freight or express^
the following rules must be strictly obeyed :

Telescopic alidades, spirit level, transit, and theodolite boxes
must be filled in with paper or cloth, so that if any part of an instru-
ment should jar loose during the journey, it may not roll around in
the box and damage the others. No heavy articles, such as box
compasses, aneroids, or other small instruments, should ever be
inclosed. The micrometers of theodolites should be wrapped
tightly with cloth, as they are easily jarred loose. The same pre-
caution should be taken when these instruments are to be transported
by pack train.

On no accotmt should any of the above-mentioned instruments
ever be shipped by express or freight in its own case only. A wooden
box, large enough to permit a generous packing of excelsior, hay, or
other padding, should always be provided.

Level rods, besides being protected by their canvas covering,
should have their targets and clamp screws protected with excelsior
or other packing. Strapping them to a board helps materially to
prevent them from being strained or bent in transport. Precise-
level rods should not be shipped except in the box provided for them.

Tripods should have their heads protected by sacking and by
excelsior or hay packing.

All instruments exceeding 4 pounds in weight should be shipped
by express, or by freight when returning them to the office from
distant points in large quantities, at the end of the field season.
From points near Washington, express rates are about as cheap as
freight. Small instruments which with packing weigh less than
4 pounds should, as a rule, be sent by registered mail, sealed, as
first-class matter. Domestic parcel-post rates do not apply to oflScial
mail, dnd packages weighing more than 4 pounds can not be mailed
by the Survey.

According to deoiaion ot '^%>0T\).%r3 'iaA'^'^^'

the weitf ht limit of omo\©.\ TCi%.\\ ^©^"^ \i»S^«^

tanked )ab«l is raiBeA fvoin ^ ^.^^.^^ x^o-^-^^^

30 INSTRUCTIONS TO TOPOGRAPHERS.

ADJUSTBCBRT OF ntSTRUMSNTS.

PRECAUTIONS.

The object glasses and eyepieces of all instruments must be piO|>-
erly focused. The cross wires projected against a distant object
should appear immovable when the eye only is moved. Befoce the
adjustments are commenced the instruments must be finnly set up
and leveled. An instrument may at times appear to be out oC ad-
justment because some part is loose. The object glass may be
partly unscrewed or an adjusting screw may be only partly tightened.
Level bubbles or cross wires occasionally become loosened; there-
fore, before commencing the adjustment of an instrument look out
for such defects. X^lien it is thought that an adjustment has been
completed, always test it before using the instrument. All adjusting
screws should be screwed tight enough to hold, yet not so tight as
to injure the threads or put a severe strain on any other part.
Especial care should be taken not to strain the cross-wire screws. Ad-
justments should be made in the order given, for some adjustments
depend on the acctu'acy of others previously made, and a change in
any one may affect the others.

GENERAL ADJUSTMENTS.

Setting of bubbles. — For setting level bubbles a small supply of
plaster of Paris should be kept on hand. For use the plaster should
be mixed with water to the consistency of a thick paste. If plaster
is lacking, strips of paper may be used, but these should never be
jammed ia very tight, as the pressure may distort the glass and thus
vitiate the bubble reading by an appreciable amotmt. A reflecting
surface of colored paper should be placed under the bubble in order
to make the graduations more readable; a subdued green or blue
tint is recommended.

Mounting of cross wires. — For mounting cross w^ires a small bottle
containing shellac dissolved in alcohol, a pinch of beeswax, and a
pair of dividers or a forked stick are needed. The best spider web is,
of course, a freshly spun one from a small spider, for this will be both
clean and elastic; but as spiders are not always available, it is
Hv// to keep on hand a spider cocoon. Such a cocoon will furnish

ADJUSTMENT OF INSTRUMENTS. 3 1

webs enough to last for years, although with age the threads become
stiff and brittle and therefore more liable to break from a jar to the
instrument. Most webs taken from grass or bushes are rough, coarse,
and dirty. The most convenient way to prepare a web is as follows:

To draw the reticule from the instrument, unscrew and remove
the eyepiece slide; then take out two opposite capstan-headed
screws and loosen the other two. Using the latter two as handles,
revolve the cross- wire ring 90**, insert a pointed stick through the
end of the telescope tube into a screw hole in the ring, and, using it
as a handle, remove the other capstan screws and draw out the ring.
To replace it in the telescope, reverse this procediu-e. When in
place, the cross wires should be on the side of the ring toward the
eyepiece.

Having pressed a bit of beeswax to each prong of the dividers or
forked stick, let a small web fall from the end of one of the prongs,
or pick with it from a cocoon a single thread, pressing the thread into
the beeswax, stretch the thread moderately, and attach to the wax
on the other prong. If an old web is used, it should first be damp-
ened by dipping in water for a few seconds. In place of the dividers
or forked stick, small sticks or lumps of wax may be attached to the
web about 2 inches apart. Place the web across the reticule, using
a magnifier to insure its coinciding exactly with the marked lines.
Put a small drop of shellac on each end and leave until dry.

Instruments such as the prism level, dumpy level, and transit,
which are not provided with wyes or similar devices for adjusting
the cross wires, may be put in close adjustment by means of impro-
vised wooden or metal rings.

For the prism level, the body of which has a cloth finish, remove
the object-glass cap and run the eyepiece slide part way out as though
focusing for a near-by object. Provide a Y of wood or metal large
enough to go over the object-glass end of the telescope where the cap
usually fits. Take a second Y of a size suitable to inclose the eye-
piece slide near the main telescope tube. Fasten these Ys securely
to a box or some other object, rest the telescope in them, and sight a
distant point cut by the cross wires; revolve the telescope and adjust
the cross wires in the usual way. A final adjustment must be made
for such instrumeats as this by the regular met\vod^. i^^ "^^ - "iiV^N
and 96.)

32 INSTRUCTIONS TO TOPOGRAPHERS.

Some instruments, such as Y levels, have eyepiece slides separate
from the telescope tube which must be adjusted independentlv of
each other. After the cross wires are adjusted, center the eyepiece
on them by tiuning the four screws under tl:e cover, adjusting by
estimation only, an exact centering not being necessar\'.

TELESCOPIC ALIDADE.

But two adjustments are ordinarily required for the telescopic
alidade — ^for level and for coUimation^ These should be tested dail}-.

Level. — Clamp the telescope, bring the bubble to the center of the
tube with the tangent screw, lift up the level carefully, reverse, and
replace it on the telescope. If the bubble runs away from the center,
bring it halfway back by means of the tangent screw and the other
half by the adjusting screw imder the end of the level tube. Repeat
this operation till the bubble stays in the center after reversal.

Collimaiion. — Test the verticality of the vertical wire by raising
and lowering one end of the telescope, the cross wires having been
set on a near-by point; loosen the screws and twist the cross- wire
ring if necessary, or by a slight shift in the position of the cross-
wire ring make the vertical wire parallel to the vertical comer of a
building or a pltmib line. Point the telescope on a small but well-
defined object about half a mile distant, and while watching this
through the telescope revolve the telescope i8o° in its supporting
sleeve. If the intersection of the cross wires remains centered on
the object, the adjustment is perfect; if not, change the cross wires
for half the error and repeat the operation until they stay on the
point selected.

Ruler. — So long as but a single alidade and but one edge of the
ruler are used, it makes no difference in the results whether the edge
of the ruler is parallel to the line of sight or not, except for use with
the Baldwin solar chart, when a correction must be applied if
appreciable. (See p. 128.)

Y LEVEL.

All instrumental errors of the Y level can be eliminated by exactly
equalizing fore and back sights, but as this is seldom possible the
e of coJJimation and the level should be kept as nearly in adjust-
t as practicable.

ApjUSTMENT OF INSTRUMENTS. 33

Collimation. — Having the instrument carefully leveled, note ^
ssfMll object about 300 feet distant that one end of a honzfrntad ccojss
wire touches, turn the instrument on its vertical axis a few degrees,
a^vt note whether the pther end of the cross wire cuts the point; if it
does and the Ys are not badly out of adjustment, the wire is horizontal.
With the clips up, focus on a small object 300 or 400 feet dista^^t;
watcji this through the telescope while revolving it 180^ in the Ys;
i^ the iatersectipn of the cross wires moves away from the ppiiit>
bring it halfway back by means of the cross- wire adj.usting screws;
repeat the test and adjustment until there is no movement of the
cross wires away from the point.

Jj^el. — ijaving the instrument carefully leveled, loosep the clips,
lifjt the telescope out of the Ys, reverse it end for end, and replace it
in the Ys; if the level bubble has moved away from the center, brii}|;
it Jjajfway back by means of the adjusting screws at oije en4 of ^he
level tube and the other half by the lower leveling screws. Repeat
this operation until the adjustment is perfect. With the bubble in
tlje centef, rock the telescope back and forth in the Ys about 25°
a]'Qun4 its axis; if the bubble moves away from the center, bring it
b^ck with the side adjusting screws.

Object-glass slide. — It is seldom necessary to adjust the object-glasj
slide, as it is usually fixed by the maker, but when required make
the collimation adjustment as above described ; then an error in the
adjustment of the slide will appear as an error of collimation when
tested on a near-by point, say 50 feet distant. To correct the error
remove the ring near the middle of the telescope and with a screw
driver turn the screws found underneath so as to bring the cross- wire
intersection halfway back to the near-by point selected.

Eyepiece slide. — The adjustment of the eyepiece tube so that the
ciiQSS wires will appear in the center of the field, though not essential
to the accuracy of the work, may be ejffected by means oi the screws
tuEulemeath the ring just back of the cross-wire screws. Iposen one
and tighten the opposite one of these screws with a screw dfiv^f
until the wires appear centered.

Ys. — After each of the foregoing adjustments have been mafjle*
the adjustment of the Ys is made liy turning the telescope and level
66512—13 — ^3

34 INSTRUCTIONS TO . TOPOGRAPHERS.

i8o° on its vertical axis; if the level bubble, which was at first in the
center, moves away from it, bring it halfway back by changing the
large nuts under one Y.

" Pey method/' — In the ordinary Y-level adjustment it is assumed
that the two rings on the telescope tube which rest in the Ys are
circular and exactly equal by construction.

The level and line of collimation can be made parallel independ-
ently of the rings and Ys by the "peg method" described under the
heading "Prism level'* (p. 96).

LOCKE LEVEL.

The adjustment of the hand level, or Locke level, is most easily
tested by sighting along a horizontal line determined by a Y level
or alidade, but when no such line is available a modified form of the
"peg method" must be used. Hold the level on a fixed point and
sight a second point 300 or 400 feet distant which appears by the level
being tested to have the same elevation as this point. Take the
level to the second point and with the bubble centered over the cross
wire sight the first point; if it appears to be on the horizontal line,
the level is in adjustment; if not, correct for one-half the difference
by turning the small screw at one end of the level box.

ROD LEVEL.

The leveling or stadia rod to which levels are attached should be
carefully plumbed with string and plumb bob. The level bubbles
should then be brought to the centers by means of the proper adjust-
ing screws.

TRANSIT.

Plate levels. — With lower plate clamped and upper plate loose, level
carefully; revolve the instrument 180° on its vertical axis and bring
each level bubble halfway back to the center of the tube by means
of the screw at one end.

Collimation. — Level carefully, sight on a point about 500 feet
distant, raise or lower the telescope slightly, and note whether the
vertical wire remains on the point; if not, loosen the capstan-headed
and turn the cross-wire ring till the vertical wire will remain

^

.«y^rv»i«r

ADJUSTMENT OF INSTRUMENTS. 35

on the point when the telescope is raised or lowered. Clamp the
instrument, set the vertical wire so that it cuts the point selected,
transit the telescope by revolving it i8o° on its horizontal axis, and
select a second point 500 feet distant in the opposite direction from
the first. Unclamp the upper plate, turn the transit 180° on the
vertical axis, set it on the point first selected, and again clamp the
plate. Transit the telescope, and if the vertical cross wire exactly
bisects the second point its adjustment is perfect; if it does not,
bring it one-quarter of the way back to the second point by turning
the two capstan-headed screws on the sides of the telescope.

Standards. — Set up the transit near a tall building or other high
object; after leveling carefully, point the telescope so that the vertical
wire intersects a definite point about 60° above the horizontal,
depress the telescope and select a Second point near the ground.
Unclamp the upper plate, revolve the telescope and plate 180° on
the vertical axis, clamp the plate with the vertical wire again cutting
the upper point, and depress the telescope; if the cross wire inter-
sects the lower point, the standards are in adjustment; if it does not,
correct for one-half the error by the screw underneath one end of the
telescope axis.

Object-glass slide. — If an adjustment for the telescope object-glass
slide is possible, it is made as follows: First make the coUimation
adjustment for a point about 300 feet distant, then focus on a point
1,000 feet or more distant and again on a point only 10 or 15 feet away,
transit the telescope, unclamp the plate, tiun it 180° on the vertical
axis, and reclamp. If the cross wire still cuts the distant and near
points the slide is in perfect adjustment, but if it does not, correct
half the error by means of the side screws which hold the slide ring
in place. Next repeat the regular coUimation adjustment and again
test for the slide error; repeat both adjustments until no errors appear.

Eyepiece tube. — ^The eyepiece may be put into position over the
cross wires by ttuning the screws which hold the eyepiece ring tmtil
the cross wires appear in the center of the field; an exact centering
is not required.

Telescope level. — If there is a level attached to the telescope it may
be adjtisted by the "peg method** after all the other ad\usfcDD«s!&&'asfc
made, as follows: Level the transit andbTm%\k<t\i>3Ja\i\t\a^5iEv^^^is^^

3i6 rxsTEucnoNS to totogbafbeks^

ol the tabc coder Uic icksQope. Take a readai^ on a Icvdii^ lod or
pole ^oo<7r 400 icct disuaA, vldch is WdoK « stake set findj in the
pocdd. Rrvofirc the Uaasit i%ai^ on the Tccfeical sns and after
bffiasnif the buhfale to the coBSer act a anonl stake at fht
distance at the §nt and at tpdh aneleratian that the rod or
pole icadins » the nine as on the icat stake. The teps of tiie tna
tfakcs will then be at tiw sane elmtioaL Move ^e tianBt 25 gt 5s
feet back oC one stake and on a line nidi the odter. Mbke the telc^

scope as nearly hotiaonlai as poasAife by means of the sttnched level,
clamp it, and then take a leading oft the nd hekl on the near atake
and another reading on the distant stake. If the tno lendrnga s^iee
the telescope is horiao nt al; if they do not agree tnm the tangrat

soew so as to bring the csoBS wire while set on the distandt nd neviy
to an agreement; repesi the ope ra tion till an agrecnwnt is reached.
The telescope is then level and the adjnsting auls si the end of ths
level tube should be turned till the bid>ble is btonglit In the center.
Vertical circle or <mc. — ^The screws holding the Temier lor the
vertical arc should now be l oosene d and the Temier mofved yyyt*!
the reading is 0° while the telescope is still level.

THSODOUTS.

Striding 2rtv/.— Place the levri in the proper position on the
telescope axis. Level carefully with the horiaontal plates clamped
and lock the level slowly back and forth till the foot pieces steike.
If the bubble leaves the center, bring it back by means of the side
adjustii^ screws near one end of the tube.

Reverse the level and bring the bubble halfway back to the center
by raising or lowering one end of the tube with the screw at that end,
and the other half with the leveling screws. Repeat these operations
till the adjustment is perfect.

Standards.— -After the striding level is in adjustment with the
lower horizontal circle clamped, level the instrument in two positioBS
4t 90* from each other. Turn on the vertical axis 180® from one
position; if the bubble runs away from the center bring it halfway
back by loosening one of the large capstan-headed screws underneath
the Mtaadards and tightening the other. Test the adjustment and
itepeat it if necessary.

At>jUSTMeNT OF THEbEk>LlTE. 3f

Plate levels. — Level itistruttient with the striding level only, theti
bring the bubbles of the plate levels to the center of their tubes by
ttiesois of the end adjusting screws; or the method described fbr
adjusting the transit plate levels may be used for the theodolite alst>.

Micrometers. — Each micrometer consists of three concentric tubes;
the upper and lower ones slide in the central one. The lower tube,
which holds the object lens when in proper position, is clamped td
the middle one by means of the capstan-headed screw in the lo^et
part of the ]-shaped support. These two tubes may be moved
together or the lower one moved alone by loosening the proper screws.
The upper tube contains the eyepiece lenses and is held in place by
friction only.

Focus the eyepiece on the two parallel movable threads and do not
change it afterwards. With the eye in position for setting the
micrometer, tighten one and loosen the other of the two screws that
liold the ]-shaped microscope support to the main frame of the
theodolite, until the figures and graduations on the plate appear to
be in the center of the field.

Clamp the plate and by turning the micrometer screw set the two
movable threads over a long graduation. Examine carefully to see
whether they appear exactly parallel to it. If they are not parallel,
loosen the two capstan-headed screws which clamp the micrometer
tube and twist the tube until the threads and mark appear parallel.
Clamp the side screws lightly.

Set the movable cross wires on a division to the apparent left of the
field of view as for a regular angle reading; read the micrometer head
aud record the reading. Turn the graduated head about five turns,
gtopping when the threads are set on the next lo'' division to the right;
fead and record. Repeat this operation several times. If the meail
of the left-hand readings is the same as the mean of the right-haiid
readings, or within cme division c5f it, the adjustment may be accepted
as satisfactory. Afi actual count of full revolutions should be made
at least once; otherwise the adjustment might wrongly be thought
perfect for 4}^ or 5X te volutions.

When the space covered by the two parallel micrometer threads,
firioived by exactly five rcvolutious of the micrometer screw, appears
to be longer than one 10'' space on the 9;caud\i^<&^ cvxcX^, Vi'^'^^^^V'^

38 INSTRUCTIONS TO TOPOGRAPHERS.

into adjustment make the distance between the micrometer box and
graduated plate longer by raising the middle part of the tube; but
when the space is shorter than a lo^ space make that distance shorter
also — ^that is, consider as connected or dependent the length of the
thread space covered by an even five revolutions of the micrometer
screw and the distance between the micrometer box and the gradu-
ated plate. When the former is longer than it should be, the latter
should be made longer, if an adjustment is desired, and vice versa.

To make the adjustment, loosen the small capstan-headed screws
which clamp the microscope tube; then, if the thread space is long,
twist the middle part of the tube (including the micrometer box)
back and forth and at the same time pull it upward, thus lengthening
the distance to the graduated plate. When by estimation it has
moved far enough, which can be roughly determined by the amount
of blurring that results from the lower lens being thrown out of focus,
clamp the upper capstan-headed screw. The lower part of the micro-
scope tube holding the objective lens must now be twisted and gently
pushed downward till the graduations again appear in focus. If the
movable threads and graduations are not then parallel, the upper
screw must be again loosened and the tube turned far enough to make
them parallel, after which both screws must be tightened. Test the
adjustment by again measuring a lo^ space with the micrometer. If
it is still out of adjustment, repea^ these operations till it is satisfac-
tory. When the adjustment has been completed, a scratch may be
made on the tube below each support and used as a guide in future
adjustments.

The opposite micrometers may be placed i8o° apart by setting one
at a reading of o° c/ c/\ with the comb scale exactly centered. Then
center the comb scale of the other micrometer over the i8o° mark by
means of the capstan-headed screw at the left-hand end of its box.
Bring the micrometer threads over the i8o° mark also; then, while
holding the screw firmly in place, turn the graduated ring till it reads
zero.

When setting the micrometer wires on a graduation, it is very

important that they be moving toward the right when the turning of

the screw is stopped. Should they be moved the least bit too far to

the r/jgrht, turn back not less than half a revolution of the screw and

SUGGESTIONS TO COMPUTERS. 39

then bring them forward again. In general, when a setting is made
by means of a screw working against a spring, the spring should
always be undergoing compression when the motion stops.

Cross wires, — ^The vertical wire should be truly vertical ; otherwise
an exact adjustment of the cross wires is not essential .

After the striding level has been adjusted and the horizontal axis
of the telescope carefully leveled, sight a distant point, raise and
lower the telescope through an angle of 5° or io°, and note whether
the cross wires follow the point. If not, loosen the cross-wire ring
and twist slightly; repeat the adjustment if necessary.

Hold the striding level on the telescope parallel to the optical axis
and, with the bubble in the center of the tube, set the intersection
of the cross wires on a distant point and clamp both plates; lift the
telescope out of its supports and turn 180° around its optical axis;
set it again on the selected point. If the striding level when placed
on top of the telescope is horizontal and the vertical wire still cuts
the point, the adjustment is complete. If not, shift the cross wires
in either direction by means of the capstan-headed screws for one-
half the apparent error. Repeat the test till the error is nearly all
eliminated. Finally readjust the vertical wire, if necessary; or both
wires may be put in place by means of temporary wooden Y supports,
as explained on page 31.

SUGGESTIONS TO COMPUTERS.

Do not crowd your work; paper is cheap.

Do your work in a systematic manner. If it permits tabular
arrangement, always use the forms approved by other computers
imless you can convince them that yoiu^s are better. The Survey
has printed forms for many purposes; these should be used whenever
possible, for by their use the work is made more mechanical, and the
more mechanically the work is done the less chance there is of error.

A computer who is inexperienced or out of practice should check
his work in every way possible. He should check logarithms either
of numbers or of circular functions by using first a tabular value for
a quantity less than the given one and then a greater tabular value,
so that the differences in one case may be added and in the other
subtracted. This operation may be reversfed >nVv^ti \?cvfe Vi'^^<^^^£^^sv
is given and numbers or angles are required.

40 INSTRUCTIONS TO TOPOGRAPHERS.

Many errofs are made by faking out the first tHttt figures of a
logairithni frota the wrohg line Where a dash over the fourth 6gufe
indicates that th^ first three should come ffbm a lower line.

As the algebraic signs of eoSiries ahd sines are so fret[ueritly Re-
quired, the rules governing them should be firmly fixed in the mind;
as an aid to this remember the general rule that distances measured
Upward or to the right on the conventional plat of the quadrants of
tlie circle are considered positive, others negative. The wrong trge
di signs l^ a very commbh source of error.

Where the function of an ^gle over g6*^ is desired, instead of sub-
tracting 90** or iyd° ftoin the angle to find the argument, add the
%tires in the tens and htmdreds of degrees places together and pre-
fix the suin to the unit degree figu^, dropping the sum if it is 9.
thus 121° gives 1+2=3, ^^^ 31° ^s the argument; 184° gives
i+8=9, drop it, leaving 4° for the argument; 290° gives 9+2=11,
dtop 9 ftom the 11 or add the two figufxis a sedond time, giving an
^irgiinient of 20°.

Bach step in a long computatioh, if it is hot at once automatically
checked, should be checked by repeatihg the computation.

Check the copying of angles, distances, etc., takefi from adjusted
results for use in new computations; also check figures carried ffoiti
page to page.

Gross errors are sometimes made by using the sine when a cosine
is required, or by writing a product in the wrong column, as east for
west in primary traverse computations.

Placing the decimal point in the wrong place is a common mistake.
This may in many cases be corrected by a mere inspection of the
quantity to see whether it appears of proper value.

Good judgment should be exercised in the degree of accuracy
sought for a given result. For the preliminary computation of
geodetic positions, for example, six-place logarithms will probably
suffice; these can be taken from a seven-place table with only a
rough interpolation. A four-place logarithm can often be used to
advantage. The accuracy of the results obtained should equal the
requirements; more than this involves a waste of time.

TTie loot, yard, and mile are the tmits adopted for all Geological
""y Held work, but for geodetic computations meters are used.

SUGGESTIONS TO COMPUTERS. 4I

The best conversion tables for metric and English measures are
those published by the Bureau of Standards, edition of 1910. In
using these all changes from one system to another should be checked
by reversing the operation. The logarithms for the interchange of
these measures are given in "Geographic tables and formulas," ^
page 301.

When computers are duplicating work and a difference is found,
e&ch should recompute the result before correcting either, as errors
have frequently been made by changing the correct figures.

When two persons are comparing a copy with the original, if the
reader occasionally calls out a wrong figure or word intentionally
and notes whether the error is caught up, it tends to keep the listefier
more intent on the work.

* Bull. tJ. S. Geol. Survey No. 234, 1904, t>. 296.

PBIMABY OMITRGU
GEHERAL COHDITIOHS.

The btmndsuy lines of all regular United States Geological Survey
maps are parallels of latitude and meridians of longitude. In order
that these shall be pcoperty located and that intermediate points shall
be placed in correct positions, some S3rstem of horizontal control is
required. The method to be adopted for linear control shoidd be
fixed by the character of the country-, the requirement being that
all control work shall be so accurate that no errors will be apparent
in maps several times as large as those to be published. In moun-
t^nous regions or in hilly, partly timbered areas horizontal control
is effected by a system of triangulation, the whole area being divided
up into triangles whose apexes are represented by stations established
on prominent points several miles apart. The angles between each
station and all others visible from it are carefully measured with a
theodolite graduated to read angles by micrometer to two seconds of
arc or by estimation to fifths of a second. One side of one oi the tri-
angles, called the base line, must be carefully measured with a steel
tape, account being taken of slope of the line, elevation above sea,
temperattu'e of the tape, and other essential details, and for at least
one station the exact latitude and longitude and also the azimuth of
one of the lines must be determined by astronomic observations.

In heavily timbered areas, where it is diflScult to see from any point
more than a mile or two in any direction, horizontal control is best
obtained from distances actually measured on the grotmd with a
300-foot steel tape, a record being made of angles measured with a
transit at each bend in the line. Such control, called primary trav-
erse, must begin and end at points whose positions have been
previously determined and must be carried around the edge of each
quadrangle and once across its center east and west.

Because of the great expense involved in base-line measurements
arrd the fixing of astronomic positions, it is generally advisable to
42

TRIANGULATION FIELD WORK. 43

connect triangulation systems or traverse lines with positions pre-
viously determined, even though they may be a long distance away.
There are now but few localities in the United States that can not
conveniently be connected with known positions and distances, and
therefore, before horizontal control work is begim, the records of the
Coast and Geodetic Survey, the Lake Survey, the United States
Army Engineers, and other Government organizations should be
examined in order to ascertain what positions in the area surveyed
have been determined and are available for use in the work on hand.
The results of triangulation or primary traverse by the Geological
Survey can always be obtained by anyone having occasion to use
them by applying to the Director, United States Geological Survey,
Washington, I?. C.

PRIMARY TRIANGULATION.

FIELD WORK.

PERSONNEL AND OUTFIT OF PARTY.

Each party usually consists of a chief of party, who acts as observer,
and a recorder; also a cook and a teamster (or packer) when camping
is necessary. Additional men are required for heliotroping, one for
each heliotrope station, and local laborers may be employed to clear
timbered summits or to erect large signals.

The following instruments and books are used in primary triangu-
lation:

One S-inch theodolite, with leather carrying case and shoulder straps.

Two i>airs field glasses.

One prismatic compass. '

One protractor (6-inch celluloid, full circle).

One boxwood scale, graduated to inches and tenths.

One 50-loot steel tape, meters on back.

Two electric hand lamps.

One 6-foot steel tape.

Heliotropes.

One plumb bob.

Triangulation tablets or i)osts, according to requirements of country.

Cement, cans.

Signal notices, printed on cloth.

Climbing irons, for use in wooded regions.

44 INSTRUCTIONS TO TOPCteRAPHlSRS.

sua. tanbreUalFor use in r^ions wliere iatpMvis«d Sim tiiad wind shelters

Wind screeh j cftn not readily be built.

Triangulation field note? (9-912).

C6hii}iitation of geodetic distances (9-901).

Comtnitation of geodetic coordinates (9-903).

Commutation book, blank (9-9S9).

Nautical almanac (abridged).

Geographic tables and formulas.

Seven-place logarithm tables.

A iood Watch must be provided by the chief of party.

iTie following additional articles may be purchased in the field;
Ax, hatchet, saw, nails, tacks, signal cloth, guy wire, stone drills
(i)^-inch bit), drill hammer, post-hole digger, wire cutter, brace
and bits.

PREPARATORY WORK.

Amount of control. — At least three serviceable stations must be
established in each quadrangle aiid as many more as may be nee
essary to afford adequate control. In addition, a number of sec-
ondary points — siich as church spires, wiildmills, water tanks, trees,
and in high mountain regions some of the more prominent summits —
tQust be located by intersection and checked by angles trom one or
fibre stations or by the " three-jxjint method.*' Where no siich
dejects afe available, at least two points should be flagged tot ifitet-
^ctiok if practicable. These poiiits are ilitended to affbrd siipijl^-
mental control for the topographer and should be selected wttii
spet^lal refetehce to the it usefulness in that cohliectiori.

The observer is also expected to locate, when practicable, eith^f
by direct measurement from his stations or by the three-point
method, conspicuous objects, marks on State and county boundary
lines, and township and section comers. Especial attention should
be given to township and section comers because of their recognized
value in the control of the land-line net.

Reconnaissance. — Stations should be selected and signals built

before any observing is done , and to this end the triangulator and his

assistant should make a reconnaissance over the area to be controlled.

Such reconnaissance should disclose evefy practical scheme of trian-

£Ti)at'ion, the angles at each point selected being mea^uted with a

/prismatic compass and platted with the protractor so that the size and

pfopprtipns oi the figures may ]be ascertained . All preparatory i^tqfk ,
SNcb 9S tbe setting ctf tablets axid posts, the erectly of sign^s 994
aca|Eol<ls, the cl<sarui^ of lin^ gl sight, and the securing ooo^eiit of
owner if on private Iw^* should b^ completed during this reooa;-
Q^ss^ce, sp th^jt tl^ ^aal ot^aerviug may be performed with e«)0i»*
pmy aiiAd disi>atch. The rjeopujaaissance afords the trianguhrtOT
Qpportui^ty l¥» ^qu^iftt himself with the ^prtes^t rput^s of ti;»yel>
th& best stopping i^j^ces, i^e available c^mp sites, w^ter \^fi^,
|i^Ui:e3, au4 ifV\»* ?p4 ^ ^^ routes fosr Sjcalipg each p^ak t» ln^
occupied: ?nd it ^n^bl^ him to gain a fi^miliarity with th^ sp^<M
character of e9^)i sta^tipn a^d its signal which will be iny^naj[)h$ tx)
him in ident^ying the points wh^n he eights them l^ter on. A9
station nam^S ^re to be published, efforts ^ould be made to seli^ct
those which have local significance.

Figures. — ^The most desirable groups of triangles consist of either
quadrilaterals with both diagonals sighted or central point figvm
with four to ^(^ven sides. The triangles composing these dgUT!^
sfips^ld be well proportioned, angles me^uring not l^ss than 50^
nor mpre th^ 120^ each. The scheme should not be allowed to
dwindle down to simple, unsupported triangles, and especial car^s
should be t^k^n to connect the work done with other work by means
of well-proportioned triangles. Overlapping figures or an exeeas
of observed lines beyond those necessary to insure a double deter-
mination of each length are undesirable, although a diagonal through
some figure may occasionally be valuable as a check. Additional
lines of this kind only complicate the main scheme without mate-
rially adding to its strength, and the numerous observations made lot
them are discarded by the computers as superfluous. Judgment is
to be used in this matter, however, for in many regions the atmos-
pheric conditions are exceedingly uncertain and the observer qan
not always count on being able to see in both directions over every
line that may be essential to the main scheme. In such regions it i^
well to err on the safe side and to obtain too many data rather than
too few.

Angles should be read to all prominent points outside of the are.i|
for use in future expansion, even though they are witl\o>\\. ^^^g^s^^
or are not sharply defined.

46 INSTRUCTIONS TO TOPOGRAPHERS.

Secondary points. — In cutting in secondary points for topographic
control it should be remembered that locations which depend on
two sights only, even if the angles are of adequate size, are likely to
be of doubtful value, because of the absence of any check on possible
gross errors in observing or computing, or because of mistakes in the
identification of the points. An endeavor should therefore be made
to obtain at least three sights to every secondary point, even if the
triangles are not of the best shape. Observers are especially cau-
tioned not to slight the location of secondary points merely because
they happen to be of no importance in their scheme of figures. The
topographer may find it expedient to start his control from a secon-
dary point, so that a blunder in the location of such a point may result
in his starting with an erroneous base and having to make corrections
at a great cost.

Consent of owner. — Before a site for a station on private land is
selected, the written consent of the owner should be obtained, if
practicable, for establishing a permanent station mark and erecting
the required signal. If a summit must be cleared of timber, or if
lines of sight must be cut, the value of the timber to be cut should
be definitely fixed and agreed upon with the owner before cutting
is begun. Payments on this account should be made and sub-
vouchers taken before the station is left. A suggested form for word-
ing these vouchers is as follows:

Received from the sum of in full payment for

timber cut on hill (or mountain), in

County, State of , in connection with the establishment and occupation

of triangulation station [give name oi station] [date].

When it is necessary to clear away timber and the owner or agent
for the groimd can not be reached without great delay, three resi-
dents of the locality should be asked to appraise the value of the
timber cut and to sign a written statement regarding it. This state,
ment should be forwarded to the office of the Survey for consideration
should a claim for damage be filed.

Station marks. — Primary triangulation stations must be perma-
nently marked by either standard iron bench-mark posts or by
tablets, each tablet to be set in rock in place or in the top of a concrete
<^r stone pier. (See PI, I and also fourth paragraph, p. 88, for instruc-

■;h:- ;;i:, a ygrk

uiiLiC library!

ASTOR, LEMOX
TILDE N FOUNDATiONB

]

.' J.

TRIANGUI.ATION FlElrD WORK. 47

tions in regard to setting tablets.) When practicable, bottles or
other imperishable material should be left as subsurface marks.

Two or more permanent reference marks should be established
about each station mark. These may consist of holes drilled in rock
in place, spikes in roots of trees, or large stones set solidly in the
grotmd. The azimuth and the distance to each reference mark
must be duly entered in the field record.

When old stations are revisited and anv of the marks are found to
be defective or to have been destroyed, new marks must be estab-
lished in their place.

' Signals. — Triangulation signals must be built with a view to their
permanence as well as to their visibility. They may be of various
forms, the form selected depending on the locality and the materials
at hand. Thus, a signal on a bare mountain peak may be a rock
cairn; one on a partly wooded summit may be a straight tree, the
surrounding timber being cleared away; one on cleared land may be
a tripod or quadripod.

Rock cairns should be not less than 8 feet high and should be well
put together, so that they will withstand strong winds and heavy
snows. A pole or a small green tree placed in the top is of advantage
in sighting.

Signal trees are most satisfactory if stripped of their branches,
except a tuft at the top. They form the best of targets when sighted
against the sky, but if they are to be sighted against a dark back-
ground they should carry two triangular targets 3 to 6 feet on a side,
placed at right angles to each other and covered with white cloth.
Tripods or quadripods should be built of sawed lumber if such mate-
rial is available. For the legs and center pole 2-inch by 4-inch
scantlings may be used, for the cross braces i-inch by 6-inch boards.
The base of the pyramid should be large enough to permit a the-
odolite to be set up under the center pole. In order to increase its
visibility, boards may be nailed across the sides about a foot apart
and covered with signal cloth, and cross targets may be attached to
the center pole above the apex of the pyramid. The best colors for
this cloth are white and black or white and red.

Most signals stand in exposed places and should be securely
anchored to prevent their being blown over. Ths, Xs?;^ ^^ \xs:^R»ft>s.

4$ INSTRUCTIONS TO TOPOGRAPHERS.

91^4 qua4ripods ahoijild he planted ip the fgfqva^i at least 2 feet;
each slioiild be fastened to ^ "desman " and the holes filled wkjb
t^ioipu^y tamped eafth or xocks, or else a stake 4 fjset long should
he driven iiM^ th^ gpu|id at an angle wit)i each leg and $nn)y
spike4 to it. If the giotm4 is too rocky to perpiit the digging ol
hQJies, a 4-foot prosspi^ce should he nailed to each leg at nght angl^
flat on the grotind and weighted doyrp wit)i rocjcs.

^^ffolds. — If it becomes necessa^ to elev^t^ t)ie instrupiesit a
8pa%)d ipv^t he erected in the form of a tripQ4> ca|^)ed mth a tt^io]^
board 12 inches square to support the instrument. Around thi^
sc^lEoId, but entirely independent of it, should be built another, in
qti^adripod form, supporting a platform on which the observer is tQ
st^nd. If very high, S3^ a scaffold sjipuld be poqapo^ed of sui^c^
sfye be;^ts, each 8 or 12 fee^, with diagoi]Lal bracing. Thje o\ft%f
sca|tol4, fujrther, is to serve as a signal, and for that pi^rpose sh^juld
ext^d at least 6 feet ^hove the observing platform an4 he suf-
moimted by a mast bearing cross targets. Before fixing signals in
potion the direction in yrhich sights are to be t^en should be
cariefiully ascertained, so that no woodwork will interfere with thie
observations.

The size of the timbers to be used necessarily depends on tl^e
hjdgljLt of the structure. The amount of Itunber required may be
determined by means of a rou^ drawing of the structtpre to scale.

Centering of signals. — Great care must be taken to insure perfect
c^s^ring of signal and scaffold over the station mark, tljie phfop^
hfih being used for this purpose. Signals s)iould stand over statioii
marks wherever possiblci so as to avoid the necessity of oonipnti^g
syidngs for the angles, but i| this is impracticable, as it is with a tiref^
signal, then the distance and bearing of the signal to the st9$30^.
mark must be carefully meastu'ed and recorded.

The permanent mark, tablet, or post must always be con^der^
^s the station for which the geodetic position will later be compnjted*
and when observations are made for angles the theodolite $hoi])4
be set up over its center if possible. If it is impracticable to center
the instrument over the station mark the distance between t)i^
point occupied and the station mark must be carefully measured
^nd recor<^ed. Also one or more sets of angles must be read between

TRIANGULATION FIELD WORK. 49

the station mark and the other stations, in order of azimuth, pref-
erably with the o° ct for the pointing to the station mark.

Heliotroping. — ^The heliotrope outfit commonly used by the Survey
is either the Steinheil or a plane mirror with a screw hinged to the
back to give it tmiversal motion and improvised diaphragms of tin
or wood with round apertures. The plane mirror is generally pre-
ferred to a heliotrope of the more elaborate form.

A heliotrope is usually set up by mounting the mirror on a stake
or board immediately over the center of the station and the dia-
phiagm on another stake, lo or 20 feet away, carefully lined in with
the distant station. The operator must constantly watch the
reflected image of the mirror and keep it symmetrically over the
aperttire. If the sun is back of the observer a second mirror a foot
or two from the first may be used to reflect the light into the first.

To the observer the flash should appear as a clearly defined point
of light; if of appreciable size it will be necessary to bisect it, and an
error is thus likely to be introduced. A good rule to follow is to
make the diameter of the opening in inches equal to one-fiftieth of
the distance in miles for wcwk in the West, and twice this size for
work in the East, with a minimum opening of one-quarter itu:h.

OBSERVING AND RECORDING.

Time of observing. — As a rule the best time for observing is the
three hours before sunset; the atmosphere is then steadiest and
diows no "boiling." The early morning hours are occasionally
good but are likely to be less satisfactory. Many cloudy or over-
cast days are favorable. As a last resort observations at night may
sometimes be necessary, but these require special night signals
and asnstants to operate them, and because of the additional, cost
involyed are seldom warranted.

Preparation for observing. — ^Whenever practicable the theodolite
must be set over the station mark for reading angles, to obviate
reduction to center. In setting up the tripod the head bolt thumb-
screws must be left loose until the legs are firmly placed and then
tightened.

66512—13 — 4

50 INSTRUCTIONS TO TOPOGRAPHERS.

The instrument must be sheltered from both wind and sun. If
the region affords no material readily available for constructing
wind screens and sun shelters, a folding wind screen and a sun
umbrella must be carried as a part of the regular outfit.

Before observations are begun at a station all adjustments of the
theodolite must be tested and such as are found in error must be
corrected, special attention being paid to the micrometers to elimi-
nate errors of run. The stations to be sighted must next be carefully
identified by means of the directions shown on the plat or by means
of angles previously taken with a prismatic compass. If any of the
distant stations can not be seen with the unaided eye some object
in line with each which can be foimd quickly must be selected, or,
if necessary, the direction to each may be marked by some object
near by, so no time shall be lost in making the pointings when the
angles are being read.

Method of observing. — ^With micrometer theodolites either single
angles may be measured or circle readings (directions) may be
made. In using the latter method select for the initial point some
station that is especially distinct and easily sighted and use it as
the initial point for all sets of readings. The telescope being set
on the initial point, read both micrometers, then sight the other
stations in succession in the order of their azimuths (clockwise rota-
tions), closing on the initial point. Then reverse telescope, set on
initial point, and sight the stations in reverse order. This com-
pletes one set of readings with telescope direct and reversed. Now
shift the circle about 36° (examine the plate bubbles after this shift and
relevel if necessary) and commence another set. When pressed for
time, it is advisable to shift the circle when telescope is reversed.
No angle should be considered as well determined that has not been
measured on at least 5 different parts of the circle or 10 times in all,
5 with telescope direct and 5 with telescope reversed. When the
telescope is reversed each end of its axis will rest in the same Y as
before. Reversals are of especial importance when there is appreci-
able difference in the elevations of the points sighted.

If the observations are made in the afternoon it is advisable to
take all secondary pointings before commencing the observations
to stations, and there should be at least two sets of such pointings;

TRIANGULATION FIELD WORK. 5 1

the remaining time for observing can then be devoted to the accu-
rate measurement of the important angles while conditions are
the most favorable.

The graduated circle should never be placed so that when pointing
at any particular station the micrometers will be set to even degrees
except, as before noted, while data are being obtained for "reduction
to center."

Field record. — The field record is to be kept in book 9-912. It
must be written in a plain, neat hand, with a No. 4 pencil, or with ink,
and no part of it must on any account ever be erased. A single line
should be drawn through erroneous records, the corrected figures
being written above. If deemed necessary, an explanation should
be written in the column for remarks. The memory should not be
trusted for data of any kind ; the record must be faithfully kept in
all particulars and be made so complete that it can be understood
by another person at any time.

On the flyleaf of each field notebook is a blank in which all infor-
mation necessary to identify the book must be recorded. This blank
should be filled so far as practicable on or before the first date of entry
of field notes, and it must be completely filled before the book is
forwarded to the Washington office. Any failure to fill in completely
the blank on the flyleaf of a field notebook should be reported by
the computer to the geographer in charge of the division. One of
the blank flyleaves must contain an index of the contents.

The date, name of station, time of observing, and names of observer
and recorder should be systematically entered at the head of each
page.

The position of the instrument with respect to the center of the
station must be clearly defined, and if it is set up off the center a
full statement must be given of the distance and the angles measiu-ed.

On the page immediately preceding the record of angles should be
written a minute and complete description of the station occupied,
the station marks, character of signal, nearest camping or other stop-
ping places, roads, and trails, also a statement regarding the own-
ership of the land and such other information as will be helpful
to the topographer. The description must be written before the
recorder leaves the station and should be accompanied by a ro\s5^

52 INSTRUCncmS TO TOPOGRAPHERS.

diagram showing directioiis to other statioos and plan indicating
location ai instrument or signal if it was not centered on the ctatioa.

Reading and recording of angles. — ^When the micfometer wires are
set for a reading with the Geological Surrey theodc^tes it is rery
important that the last movement of the wires be toward the right.
The readings on the graduated head are then decreasing and the
spring attached to the slide which holds the wires is being com-
pressed. If the CTDSS wires are moved the least bit too far to the
right they must not be turned t>ackward merely to the setting, but
mnst be turned backward at least a half turn of the screw, then
brought forward slowly to correct setting. When the setting is
properly made a divisiosi on. the graduated plate will appear exactly
midway between the two movable cross wires and an equal amount
of white space will show on each side of it. A part at least of the
micrometer adjustment errors can be eliminated by making the
settings with less than five turns of the screw; this can alwa3rs be
done if the right-hand part of the comb scale is sometimes used for
comb scale and micrometer head readings, the lo-minute q>aoe being
taken from the left.

For all precision instruments where a tangent screw and ^>ring
are used together, the setting should be made while the ^ring is
being compressed, otherwise the "slack'' of the screw may cause
an error.

The recorder should not only take down the readings called off
by the observer but should without delay compute the angles be-
tween successive stations and also the mean readings. The following
form is to be used for recording angles by the method of directions:

TRIANGULATION FIELD WORK.

33

IS

Hi

Ota

3S

'I

^ I

^1

o d «^i "i «^ "^

J^S^v^'^S^S*

s:

2;

DC

,<fe-

<i^

i

■>• ^ »n "^ ^ H ^^•^•'v'^N

IV > «v^ O > Q

o >»• o>.5i^ 5^

>0 «»^oo

* O ^ N O 5^ •>» "^

3«^

a

§

Oi

5s

1

•«« N* N

Six *^s

HSl^ ^l^^i^^ll

as

«1
11*^*1 III -i**

o

•5 s
"2-2

^ 3

^!

1.2

s|

la
%

el

54 INSTRUCTIONS TO TOPOGRAPHERS.

Opposite each angle record any necessary information as to visi-
bility of signals or atmospheric conditions.

Field computations. — Angles at each station should be reduced to
center in the field in order to test the triangle closures, which for a
primary scheme should not exceed 5''''.

Arbitrary adjustments and preliminary computations of positions
should also be made in the field. Book 9-889 should be used for
summary of angles and for miscellaneous computations. Compu-
tations for distances should be entered in book 9-901 and for coor-
dinates in book 9-902. For field computations of coordinates where
the lines are short five or six place logarithms will give sufficient
acctu^acy and the computations may be shortened by omitting some
of the minor corrections, carrying results to tenths of seconds of lati-
tude and longitude only.

As soon as the preliminary computations are made the record
books should be sent to the Siu^vey office by registered mail. The
computation books should also be sent by registered mail, but on
another day.

Triangnlaiion plot. — A careful plot of the work should be kept on
the scale of 10 miles to an inch, and each month a reduced copy, on
which angles measured are indicated by the usual sign, should be
sent in on the monthly report blank. The plot, if carefully made,
will prove invaluable for finding directions to distant stations.
Place the protractor on the plot with 0° in line with a station that
can be seen clearly, then read in turn the angle to each other station,
thus obtaining an observing list.

Azimuth observations. — There must be not less than two azimuth
stations in each triangulation scheme, but if the azimuth of any line
in a scheme can be computed from former observations then only
one azimuth station need be established for each square degree
controlled.

The azimuth mark should be placed at least half a mile from the
station. It should consist of a vertical slit one-fourth to one-half
inch wide and 6 inches long, cut in a small box containing a candle
or lantern. To illuminate the cross wires of the instrument and to
read the angles, an electric hand lamp is to be preferred.

^e observations should consist of not fewer than five direct and
reversed measurements between the slat and mack. As the

TRIANGULATION FIKI^D WORK.

55

star is at a much higher angle of elevation than the mark it is impor-
tant that the horizontal axis of the theodolite be adjusted with care
and leveled. The ends of the striding level bubble must be read at
each setting on the star and a level correction computed if there i^
an appreciable difference between them, as shown in the example
attached.

Observations on Polaris should be made immediately preceding
and following elongation, as any error in the time of observation has
then the least effect on the resulting azimuth. The time of setting
the cross wires on the star must be recorded to the nearest second.
The watch error must be known and to this end the observer should
compare his watch frequently with telegraphic time, which is sent
over Western Union lines once a day, usually at noon, Washington

time.

Exatnple of record of azimuth observations.

Station: Canada, Ky. 8-inch theodolite No. 434. One division of micrometer— 3".

One division of level =-3" of arc. June 11, 1910. Watch o™ 33"«« slow, 90th meridian

standard time.

Telescope direct.

Object.

Time a. m.

1
Level.

Micrometer.

A. B.

• ' div. ' • ' div.
352 54 09 172 53 21
288 35 24 108 35 OS

Mean. , Angle.

1

West. East.

Mark(i)....

//. m. s.

1

Div. Div.

1

f It Q t ft

173 ^4 00 :

Polaris (2)..

2 30 50

II. 10. 1
9. 12.

108 35 39 '

20. 33.
—3.

1

Tele

64 18 31

—

1

Bcope reversed.

Mark (4)....

1

172 Si 04 i 353 52 13

108 34 10 \ 2«8 33 37

352 52 47
388 34 07

Polaris (3)..

2 3648

, II. 10.0

' 9.0 13.

1 30. 33.
1 —2.0
10.0 II.

lao XI.

64 18 40

Mark (0 . . .

a02 41 13 : 23 40 23
138 22 24 318 33 06

32 41 05
318 22 30

Polaris (6)..

2 40 26

20. ' 22.
—2.0

1

»

64 18 35

•

\

\

56

INSTRUCTIONS TO TOPOGRAPHERS.

Example of record of azimuth observations — Continued.

Telescope direct.

Object.

Time a.m.

Level. 1

1

Micrometer.

Mean.

Angle.

West. Bast.

A.

B.

Mark

H. m. s.

1 '
Div. i Div. i

*• ' div.

33 41 07

318 33 30

• ' div.
207 40 17
138 33 13

//

303 40 S4
138 33 ^^

• in

Polaris

3 46 sa

10.0 : II. 1

11. , lOwO

31. 1 31. '
0.0

64 18 ax

N0T8.— Four other sets shMild be taken.

TRIANGULATION COMPUTATIONS.
Preliminary computations of distances from unadjusted angles
should be made in the field , as required by the rule on page 54.
The steps in the final adjustment and computation are as follows:

Closing the horizon.
Tabulation of angles.
Reduction to center.
Computation of azimuth.
Tabulation of triangles.
Computation of spherical excess.
Least-square adjustment:

Angle equations.

Side or sine equations.

Equations of condition.

Table ci correlates.

Normal equations.

Solution o# normal equations.
Computation of distances.
Computation of geodetic coordinates.
Tabulation of results.

Operations are completed in books 9-913, 9-889, 9-901, and 9-902.
The results are tabulated on printed blanks 8 by io>^ inches in
size, one blank for each station.

Closing the horizon. — In careful work closing errors will always be-

small and may be distributed among the various angles in propor

tion to their number. If any of the angles measured should equal

the sums of smaller angles, proper adjustments must be made before

the horizon is closed.

Tahulaiion of angles. — For convenience of reference a rough plot
he made for each station on part oi a pa^^t in book 9-839,

TRIANGUI.ATION COMPUTATIONS.

57

showing the relative size and position of the various angles with
names of stations sighted, and on the same or the following page
should be given a summary of all the angles at the station, in order
oi azimuth, with the angles and distances to signals for eccentric
stations.

Reduction to center. — For eccentric stations the data for reduction
to center should be indicated on the plat and figures given for them
in the summary. An illustration of the method of prociu-ing these
data is given below. (See also fig. i, p. 60.) Two sets of angles
were read at Elk station (where an eccentric point was occupied),
with one of the micrometers set very nearly on 0°, when the tele-
scope was pointing directly toward the center of the signal. The
angle to each point in turn is given below. By measuring the angle
with this setting the computer is saved considerable trouble, and
the possibility of error is lessened. The measured distance between
the center of the instrument and the center of the station was 4.7
feet (1.43 meters).

The formula for computing the swing in seconds for any line is —

Distance to signal Sine of angle between signal and far station
Sine i^^ ^ Distance to far station

The distance to signal will be a constant for each set up, hence its
logarithm may be combined with the sine of i second and this con-
stant used throughout the computation. The distances to the
distant stations in logarithms of meters are derived from a preliminary
computation.

log 1.43
log sin 1"

■o. IS534
■4-68557

log constant =■ 5. 46977

ELK STATION.

SUtion

Angle

I«og constant

I«og sin angle

A. C. log distance

I«og correction

Correction in seconds

Dick.

23" 07' 10"

5-46977
9. 59400

5- 70154

o- 76531
+5-83

Taylor.

68* 43' 40'

s- 46977

9-96935
5' 59«9*

1. 03108
+ 10.U

Browning.

109* 16' 54"

5-46977
9- 97493
5- 56734

\

X. oiao4

Tweedy.

206* 2^' 10"

5- 46977
9.6488X

5* 63*75

o. 75133

\ — v^*v

58 INSTRUCTIONS TO TOPOGRAPHERS.

The aign for any correction is the same as that for the sine of the
angle, therefore for an angle over i8o° it will be negative.

The correction for any angle will be the difference between the cor-
rections for the two lines bounding it, alwa^-s taking the lines in
order of azimuth. Thus, for Dick-Blk-Taylor it will be —

+10.74

— 5-83

For Browning-Elk-Tweedy it will be — ,

— 5-64

— io.a8

— 15.92"

The general rule is, change the sign of first correction (in order of
azimuth) and add algebraically to the second correction. The sum
will be the correction to the angle. The angles listed on pages
62-^3 have all been corrected.

The foregoing formula may be used also ^yhen it is desired to com-
pute the "swing" for a line, which is to be applied at a distant sta-
tion to change the pointing to the marked point — ^that is, the station
center — from that taken to the signal. Whether the computed swing
is to be added to or subtracted from a given angle may easily be
found by an inspection of the diagram.

Computation of azimuth. — The daily change in Polaris is so slight
that for the following computation no account need be taken of a
fraction of a day in computing its position.

Com,putation of azimuth observations,

Canada. Ky., triansulation station. June 11. 2.30 a. m., 19x0 (dvil date).

Latitude: 37* 35' 46". Longitude: 82 • 21' 39".

Watch time of observation 2*» 30"* so* a. m.— 14»» 30™ 50* of the astronomic H. m. s.

day which commenced at noon June 10 14 30 50

Correction from seventy-fifth meridian time to 82* 21' 39" correction

for 7" 21' 39" (p. Ill, " Geographic tables and formulas") —29 27

Watch slow by telegraphic time + 93

Local mean time (astronomic day) X4 oz 46

Correction, mean to sidereal time (p. 1x3, "Geographic tables and formu-
las." or Table III." "Nautical almanac") -fa z8

TRIANGULATION COMPUTATIONS. 59

Right asceiision oi mean sun at Greenwich noon, June lo, corrected for H. m. s.
jh 29m 27" to change to noon at 82* ai' 39" west longitude ("Nautical
almanac," June, Table II; change for longitude made by Table III,
last part of almanac) 5 xa 45

Sidereal time of observation 19 16 49

Right ascension of Polaris for nearest Washington transit — ^June 10.8
(" Nautical almanac, " circumpolar stars for June) i a6 xa

Hour angle of Polaris at time of observation 17 50 37

Hour angle of Polaris in arc^t (p. 1x2, "Geographic tables and formu-
las") 267'39'xs"

The following are the formulas for azimuth and level correction:

tan A = r r a— sec cot J 6=tan^cot^

1—6 cos t. ^

Level correction = [('w+w')~(e+e')] tan A;

4

in which —

^"-latitude of station (37* 35' 46").
A -"azimuth of Polaris at time of observation.
d<* declination of Polaris at time of observation (88* 49' 21").
/•=hour angle of Polaris at time of observation (267* 39' 15") (both the sine

and cosine of this angle are negative for this example).
rf«=value of one division of level (2.0").
w, itf'—readings of west end of level bubble, direct and reversed.
«, e'= readings of east end of level bubble, direct and reversed.

ABangular elevation of star (at elongation this is equal to the latitude, nearly).

The following is the computation of the first of the preceding
observations (p. 55):

a
Level correction— —(2 X o.77)=o.77"

4

Log tan ^ 9. 88649

Log cot 9 8. 31290

Log cos t 8. 61205 (negative).

Log b cos t 6. 81144 (negative).

b cos t — o- 000648

I

1—6 cos / 1.000648

Log sec o. 10109

Log cot (? 8.31290

Log sin / 9. 99964 (negative).

Log a sin < 8. 41363 (negative).

Log i—b cos i o. 00028

Loir tMn A — %. a.t.'j,^^*

6o

INSTRUCTIONS TO TOPOGRAPHERS.

Level correctioa .

01.7
+ 0.8

//

Add i8o' to refer to the south — 180

Angle star to mark 64

29

02.5

x8 3a

34".S

Azimuth of mark 245* 47'

Bach azimuth computation should be made in a single column
and for convenience the columns should be placed side by side in
tabtilar{f6rm.

Tobulation of triangles. — By an inspection of the field plat of the
triangulation determine what groups of triangles are so interrela ed

Taylorix^

Dick

Browning

Elk

PiOURS I.— Diagram showing quadrilateral for adjustment by least-square

methods.

that a change in one will afifect the others and what groups of tri-
angles should be adjusted as a unit. For the triangulation by the
Geological Survey, which is not executed for geodetic purposes, it
is not advisable ever to include more than 15 or 20 triangles in such
a group, because the labor of solving equations for the adjustment
of any group increases rapidly with its size.

Four overlapping triangles form the simplest group that may be
adjusted by the usual least-square methods.

Assume the group shown in figure i for adjustment. Tabulate

the angles for each triangle, as shown at (a), (b), (c), and (d) (pp.

^-^j)' Any angle in any of these triangles may be considered as the

fiilFerence between the azimuths (direcUons") of its two sides. For

TRIAKGULATION COMPUTATIONS.

6i

example, angle Dick-Elk-Taylor, or 3.0.2, using for convenienee the
figures asBtgned to each angle vertex, would be the azimuth or dimc-
tion of the line 3-0 subtracted from the azimuth or direction <if the
line 2-0. Azimuths are always measured in a clockwise directkMi.
Therefofe this angle may be indicated as —3.04-2.0 or — j/o-fa/o.
In the latter form the denominator is always the figure at the vertex
of the angle and with the vertex pointing toward the observer the
left-hand direction is always given the minus sign. (Directioas
will hereafter be referred to as sides.)

Computation of spherical excess. — For any triangle on the earth's
surface the sum of the three angles, if correctly measured, will
exceed 180^ by an amount varying with the area. For use in oom-
puting distances the observed angles must be reduced to their plane
values by deducting one-third the* spherical excess from each.
The spherical excess for any triangle between latitude 25® and
45° is approximately i second for each 75.5 square miles of area,
or exactly equals in seconds abm sin C, in which a, b, and C are,
respectively, the lengths of the two sides in meters and the in-
cluded angle of any triangle, and m is a constant depending on the
latitude.* In computing spherical excesses for any figure (as fig. i,
for example) arrange the work systematically, the logarithms of each
of two sides in meters from a preliminary computation, the loga-
rithm of the sine of their included angle, and the logarithm of m for
the mean latitude for each triangle; place in a column. Give the
figures for the triangle at the head of the column, as 3.0.2, using the
angle 3.0.2 and the sides 3-0 and 2-0 in the computation.

Computation for spherical excess.

Triangles.

Log side a

I/^side b

Log sin C

Logm

Log spherical excess

Spherical excess in seconds

3.0.2

a.o.z

4. 29846
4.40804
9. 85406
1.4047s

4.40804
4. 252x9
9. 8x304
1. 4047s

9-96531
0.93

9. 8780a
0.76

Mean latitude, 37* 35'.

> Logarithms of m are given in Geographic ta.b\^ %xvd V«rTDNi2«.v v- "ar^N "«»^^^=^
Bull. U. S. Gedi. Survey No. 234, 1904, p. a66.

62

INSTRUCTIONS TO TOPOGRAPHERS.

In the same manner compute the spherical excess for each of the
remaining triangles. Many such computations can be conveniently
made in the book (9-901) used for preliminary distances, in the left-
hand column adjacent to each triangle.

As the spherical excess for a given area is constant, the sum of the
spherical excesses for the triangles 2.0.1 and 3.0.2 must equal the
spherical excesses for the other two. This check should always be
applied to the results.

Least-square adrjustment. — ^After deducting the spherical excesses
from the sums of angles for each triangle (a), (b), (c), (d) (see below)
the differences between the remainders and 180® will be the errors,
plus for remainders over 180° and minus for those less than 180°.

The rules for determining the number of angle equations a nd the
number of sine or side equations required for the proper adjustment
of any figure are these:

L- S+i=
L-2S+3=

> angle equatioas
* sine equations

where L equals number of lines in the figure and S the number of

stations. A solution of these equations for a quadrilateral shows

that three angle equations and one side equation are required. In

the present example it is immaterial which three triangles are used

for the adjustment.

Angle equations.

Stations.

(Elk

(a)<{ Browning
[Taylor. . . .

—2/0+1/0
— 0/1+2/1
—1/3+0/2

//

40 33 19-17
95 23 07.62
44 03 30. 52

179 59 57-31
■76

Error —3. 45

//

+ 2. 13
+ 0.71
+ 0.62

Corrected

spherical

angle.

ff

40 33 ax. 39

95 23 08.33
44 03 31. X4

z8o 00 00. 76
Spherical
excess.. 0.76

TRIANGULATION COMPUTATIONS.

63

Angle equations — Continued;

Stations.

[Elk...
(b)^ Taylor.
[Dick..

|Elk

(c)< Browning,
pick

Observed,
angle.

//

—3/0+2/0! 45 36 34-90
—0/2+3/2 i 50 34 37-57
-2/3+0/3 ' 83 48 53.15

180 00 05.62
.92

—3/0+1/0
-0/1+3/ 1
-1/3+0/3

Error +4. 70

86 09 54-07
SO 10 30. 58
43 39 38.99

180 00 03.64
.90

Correc-
tion.

-2.97
-0.40
■1-33

■0.84
-1.47

■0.43

{Dick —2/3+1/3
Browning '— 3/1+2/1
Taylor -1/2+3/2

Error +2. 74

40 09 14. 16
45 12 37.04
94 38 08.09

—0.90
+ 2.18
+0. 21

Corrected

spherical

angle.

45 36 31-93
SO 34 37-17
83 48 51-82

180 00 00.9a
Spherical
excess.. 0.9a

86 09 53- 23
50 10 29. II
43 39 38. 56

180 00 00. 90
Spherical
excess. . o. 90

40 09 13. 26
45 12 39.22
94 38 08.30

179 59 59-29
.78 I

I

Error —1.49

180 00 00. 78
Spherical
excess. . o. 78

To select the sines for the side equation: Consider the figure
as a pyramid with vertex at 2; by redrawing the figure with the
line 3-1 dotted and the triangle 2-3-0 shaded, it will appear to
the eye as such a pyramid. Select for the first set of angles for the
sine equations those opening to the front in going around the base
of the pyramid from 3 to o to i to 3 ; for future reference mark them
with solid arcs of circles; the remaining angles around the base make
up the other set and are marked with dotted arcs. In selecting the
point for the vertex of the pyramid, as a general rule choose the one
which includes the smallest angles, but if all the angles are greater
than 30° either station may be chosen. Find the sines for each set of
angles, recording also the differences for 1^^ for each; call the first

64

INSTRUCTIONS TO TOPOGRAPHERS.

set of sines plus and the second set minus, find the difference between
them, and give it the sign of the greater.

Sine eqiuition.

Sides.

Angle.

Sine.

Differ-
ence for
i".

Correc-
tion in
seconds.

Cor-
rection
to sine.

Corrected
sine.

' -2/3+0/3
-*-< — 2/o4-i/o

1-3/X+2/1
(-8/3+1/3

— —3/0+2/0

I 1-0/I+2/I

/ //

83 48 53- 15
40 33 19- 17
4S 12 37.04

40 09 14. x6
45 36 34- 90
95 23 07. 62

9. 9974645
9. 8130350
9. 851073 1

-f-02. 2
+24-6
+2a9

-1-33

+2. 12
+20.9

— 3

+52
+46

9* 997464a
9- 813040a
9. 8510777

(e)

9. 6615726

9-8094543
9. 8540576
9. 9980787

9. 66x5831

+24-9
+20.6
— 2.0

—0.91

—2.97
+0. 71

-23

-61

— z

9-8o945«o
9. 85405x5
9. 9980786

9. 6615906
Error —180

9. 661 5821

Equations of conditions are now made up as follows: For triangle (a),
equation (f), error equals — 3.45^''; this is made up of the errors in the
azimuth or pointing of the sides —2/0+1/0— 0/1+2/1 — 1/2+0.2, six in
all. In like manner form equations (g) and (h). The sine equation
(i) is made up as follows: The error of the sines, being the difference
between the two sets, is —180. To correct the sines, changes in
seconds to be fotmd for the angles must be multiplied by the differ-
ences for 1^^ in column 4 of (e) for the given angle; hence for the first
sine this will be +2.2 multiplied by the corrections to be given the
directions —2/3 and +0/3, or if expressed in a simple form it will
be —2.2 2/3+2.2 0/3. Treat each side and difference for i^' in like
manner, noting, however, that for the second set of sines, which is
considered negative, each sign given for the side will be reversed;
for example, the first one is written +24.9 2/3—24.9 1/3. It will be
noticed that in the first form of (i) as written, 2/z appears twice with
like signs, 2/3 appears twice with unlike signs; combine like terms
algebraically, thus reducing the equations to the second form of (i).
For the convenience of the computer and in order to avoid the
handling of large numbers, equation (i) has been divided through
by-iToo; this, of course, does not alter its value.

TRIANGULATION COMPUTATIONS.

65

Equations of condition,

(f) o^ —3.4s"— 2/0+1/0— 0/1+2/1— 1/2+0/2

(g) o— +4.70"— 3/0+2/0— 0.2+3.2— 2/3+0/3
(h) o- +2.74"— 3/0+1/0— o/i +3/1— 1/3— 0/3

«— X.80"— .022 2/3+.022 0/3— .246 2/0+.246 1/0-.209 3/1+.209 2/1+.249 2/3
—.249 1/3— .206 3/0— .206 2/0— .020 0/1+.020 2/1

«— i.8o"+.227 2/3+.022 0/3— .452 2/0+.246 1/0— .209 3/1+. 229 2/1
—.249 1/3— .206 3/0— .020 o/i

(i)

There are now four equations to be solved and twelve unknown
quantities; the latter are combined and reduced to four in the table
of correlates. Column (j) contains the marks for the sides or direc-
tions for which corrections are required. Column (k) contains on
the proper lines the algebraic coefficients for the various sides from
equation (f); for example, —2/0, considered as a quantity, might be
written — i (2/0), and +1/0 in like manner written +1(1/0); — i and
+ 1 are therefore the entries for column (k), lines 2/0 and i/o.

Table of correlates.

(j)

I
+1

-X

• • • • •

— I

+1

0)
'+i'

(m)

3
+ 1

• • • •

— I

— 1

(n)

1

4

1

+0. 246
-0. 452
+0. 206
—0. 020
+0. 229 j
— 0. 209

Cdrrelates after substituting computed values.

Sides.

i

I
+0.275

« i 3 i 4

— 0.063 i •"0.589 +3.007

1

Correc-
tions.

+a426

-1.697
+1. 271
+0.254
+0.964
—1.2x7
+0.338

-0.275
—0.063
-0.586
0. 160
+0.746

Sides.

I/O

2/0
3/0
o/i

2/1
3/1

0/2

1/2

3/2

0/3
'^

2/3

i/o
2/0
3/0

O/I

2/1

0/2

j/2
3/2

oh

2/3

+0. 275
-0. 27s

1

— 0. 275

+ 0. 27<

1

-a 589

—0.063

+0.063 i+o. 589

,+0.589

'

+0.740

-I- 359
+0. 619
—0.060
+0.689

+ 1

1 — 0. c8o

-a 628

+1

— I

— I

i+o. 27s

+0. 063

' * t

, , . . , ;

(-0. 27s

* . . '

+1
+1

::::. .::::::!

— 0. 063 1

+1
—I

• • • •

+0. 022
— 0. 249
+0. 227

1

1

—0.063 i— o« 589
+0. s8o

+ao66
— 0. 749
+0.683

~^

1

1

+0-063

The formation of normal equations from the table of correlates is
as follows: Column i, line i, of (o) (p. 66) contains the sum of the
squares of each quantity in column (k). Column 2, lines i and 2, con-
tains, first, the sum of the products of each quantity in column (k) by
corresponding quantities in column (1); second, the sum of the
squares of each quantity in column (1). Column 3, lines i, 2, and 3,

66512 — X3 — 5

66

INSTRUCTIONS TO TOPOGRAPHERS.

contains the sum of the products of (k) by (m), (1) by (m), and (m) by
(m) (the squares). Column 4 is made up in the same manner, using
the quantities and signs as given. If columns 1,2, and 3 are com-
pletely filled out by products found as indicated above, it will be
fotmd that the quantities from +6.000 down the column are the same
as those from +6.000 along the lines to the right to column 4. But as
the former are not needed in the solution they may be omitted ; when
retained the equations in full will be as follows, the second member
of each equation being zero:

(0) Normal equations.

I

2

3

4

+ 0.947
-0.863
+0. 122
+0. SI779

Absolute
term.

—3- 450
+4.700
+ 2. 740
— 1.800

1

1

+6.000 !

2.000
+6.000

+ 2.000
+ 2.000
+6.000

—2.000 ,

1-

1 +2.000 !

+0.947 I

1

+ 2.000
-0.863

+0. 122

These are ordinary algebraic equations which may be solved by
the usual rules of algebra, but as the solution of 5, 10, 15, or more
equations is often required in Geological Survey work the process
should be conducted systematically as shown.

Solution of normal equations.

(P)

z

2

I
1

3

4

1

1

+0.947

! -0.1578

Absolute
tenn.

isi

+6.000
(0. 1667)

2.000
+o- 333

+ 2.000
—0. 333

-3- 4SO

+0. 575

\^i

' +5- 333
(0. 1875)

+ 2.667
1 0.500

; -0. 5473
. +a 1026

+3- SSO
-0.666

H

1

1 4.000

' +0.0800

+ 2. IIS

(pt)

(0.

250)

1 —0. 02D0

—0. 529

j (pt)

^ /

(3.

+ 0.31060
2196)

—0.934
+3- 007

TRIANGULATION COMPUTATIONS.

67

Solution of normal equations — Continued.

(q)

(0

(ri)
(rs)

(n)

(ft)

+0. SIS
-o. 475
+0. 196
—0.021

+0. 27s

-0.666
+ 0.309
+0. 294

— o. 063

'O. 529 +3. 007
-0.060

-0.589

2

3

4

Absolute

term.

1

!

(qO
(qs)

+6.000
—0.667

+ 2.000
+ 0.667

-a 863
+0.3157

+4. 700
— I. 150

(qs)

(qO

1 (qs)

+ 6.000
-0.667
— 1.333

+0. 1220

—0.3157
+0. 2737

1

+2. 740 ;
+1.150

-1-775

i (q«)

+0. 51779

— 1.800

(q»)

i

—0. 14944
—0. 05615
—0. 00160

+0.544
+0. 364
—0.042

The first normal equation is written in full on line (pi); parts of
the other equations are written on lines (q,), (qa), and (q^). The
reciprocal from Barlow's tables of the first quantity (+6.000, line
(pi), column i), is placed at the left. The product of this reciprocal
(0.1667) by the quantities on line (pj), columns 2, 3, and 4, and
absolute are written immediately under each in turn; the quantity
-fo.333 (line (pa), column 2) is now used as a multiplier for line (p,)
(omitting column i), and the products are placed in columns 2,3,4,
and absolute, line (qg): in like manner the quantities —0.333 (1^*^® (p2)»
column 3) and —0.1578 (column 4) are used as multipliers and the
products written on lines (q4) and (q;). The algebraic sums of lines
(qi) and (qg) are now written on line (pa), which is then used as if
it were an original equation. The reciprocal of +5. 333 is found and
used as a multiplier as before and the products voyXX^tl ^tcX«\r. V:s^K^

68 INSTRUCTIONS TO TOPOGRAPHERS.

The next products are written on lines (qj) and (qg). The sum of
each column of lines (qs), (q4), and (qg) is carried over to (ps). The
process is repeated for each equation tmtil finally the product
+3.007 is found, which is the value for unknown quantity numbered
4. This value and also the quantities in the column of absolute
terms, lines (po), (P4), and (pj), are copied in table (r), line (ri).
With -{-3.007 as a multiplier products of each quantity in column 4,
lines (pj), (P4), and (P2), are found and written on line (rj), columns
3,2, and I. Column 3 of (r) is then summed and the result (—0.589)
is the value of unknown quantity numbered 3. This is used as a
multiplier and products found with quantities from columns 3 and
2, lines (P4) and (pj), and in like manner values for unknown quan-
tities numbered 2 and i are found.

The solution of the normal equations and the values found for the
unknown quantities may be checked, if desired, by substituting in
the full equations (p. 66), but usually an experienced computer
will not need to undertake this extra work, depending rather on the
accuracy of his results until checked by use as correction in the
original triangles, (a), (b), (c), and (d), and in the sine equation (e).

The next step in the adjustment is to substitute the values for the
foiu: unknown quantities in the tables of correlates (p. 65) and to find
the correction for each side. The method of doing this can'be easily
seen by following the process through the right-hand half of that
table. For convenience, the value found for each unknown quan-
tity is written at the head of columns 1,2,3, ^^^ 4- Bach of these in
turn is multiplied by quantities in columns i, 2, 3, and 4 of the left-
hand part of the table and the products are placed in the right-hand
part on the same line with the multiplicand. The final correction for
any side is then the algebraic sum of the quantities, which are on line
with the side number in columns 1,2,3, ^^^ 4 (^^ ^^^ nglit side of the
table). Thus the correction i/o is made up of -I-0.275, —0.589,
-f 0.740=4-0.426; this is the correction in seconds to the side. The
correction for any angle, then, is the difference between the correc-
tions for the two sides bounding it. For example: Angle at Elk, tri-
angle (a), is:

— correction 2/0 ■- + i. 697
+ correction i/o ■- + . 426

TRIANGULATION COMPUTATIONS. 69

The correction for any sine is the correction for the corresponding
angle multiplied by the difference for i^' in the sine.

It is desirable to have triangles close without errors greater than
a hundredth of a second and sine equations close to the seventh
place o>f logarithm, but unless the normal equations are carried to
three or foiu: decimal places, there will possibly be residual errors
of two or three hundredths in some triangle closures. It is, however,
considered allowable to make arbitrary changes of not over ±0.03^''
in angles in order to procure consistent results.

The figures for adjustment will generally be larger than quadrilat-
erals, though they may be made up of quadrilaterals or triangles
which do not overlap and are therefore independent each of the other.
When they do overlap select for the first pyramid group (p. 63) the
one which takes in the largest number of triangles and set down (ac-
cording to the formula on p. 62) the number of triangle equations re-
quired to completely adjust it, remembering that the triangles used
must always cover the whole area once, but not twice. For the sec-
ond group set down the number of triangle equations required by the
rule, as though they were from an independent pyramid group, but
omit from those selected all which would be adjusted in or by the first
group, the vertex of the pyramid being so situated that a base triangle
will not be included in a former group. In other words, as group by
group is added to the first, find for each a single sine equation and as
many additional angle equations as are required, including in the
number all triangles adjusted by a previous group, excluding those
which appear in each or which would appear in each if the vertex of
the pyramid were taken in a different place.

In order to adjust an extensive triangulation scheme, the
strongest groups are adjusted first; then if lines or triangles in
them form parts of other groups, their first adjusted values are given
infinite weights and thus left unchanged. Weights if used in an ad-
justment appear in the table of correlates only. For any side they
are used by inserting them in an extra column in the table (this would
be placed between (j) and (k) if used in the present example). The
weight for a side taken as a whole number 1,2,3, etc. , or 00 , is written
on the line with the side number. Any product with quantities on
that line in either the right or the left side of ttv^\afc\fc.\% ^iwrv^^V'a^

70

INSTRUCTIONS TO TOPOGRAPHERS.

the corresponding weight before it is used in any way; where c» is
used this results in canceling all of the corresponding products-^in
other words, the side may be omitted from the table of correlates.

Computations of distances. — These are to be made in book 9-901.
The triangles are arranged in order from a given base or known side ,
one page or part of a page being taken for each new station. For each
triangle the adjusted spherical angles and the spherical excess are
given to hundredths of seconds.

Example of computation of distances.

Station.

Spherical | Spherical
angle. excess.

Browning 50 10 29. 11

Elk 86 09 S3. 23

Dick 43 39 38. s6

0.30
•30
•30

Plane angle.
9.8853615

//

50 10 28. 8z
86 09 52.93
43 39 38. 26

180 00 00. 90 180 00 00. 00

Miles, i6. 827 Browning to Elk.

Miles. 24.319 Browning to Dick.

Log sines
and dis-
tances.

4. 4789254
0.1 146385
9.9990263
9.8390917

4« 4326556
4- 5925902

After the adjustment of several overlapping figures has been com-
pleted, it is occasionally necessary to find the length of some line
joining two points which has not been included in the adjustment.
Such lines may usually be computed by the formula for "two sides
and the included angle. " ^

The rule for the solution of plane triangles for which the three
angles and one side are given is that the sides are proportional to the
sines of the opposite angles. By always arranging the angles in the
above form with the new station first, the solution is made somewhat
mechanical. The logarithms of the sines of plane angles are, of
course, used; that for the angle at the new station from which dis-
tances are required to the other two stations is written immediately
above the angle; its arithmetical complement (10 minus the sine)

» Geoirraphic tables and formulas, p. 8; Bull. U. S. Geol. Survey No. 234, 1904. p. 8.

TRIANGULATION COMPUTATIONS.

71

is written to the right and on line with the angle. Each of the other
sines is placed on line with the angle to which it relates. Imme-
diately above the sines is written the logarithm of the distance in
meters between the second and third stations in the triangle; in the
example this is 4.4789254 for the line Elk to Dick.

To get the logarithm of the distance from the new station (Brown-
ing in the example) to one of the other stations, omit the sine opposite
the latter and add together the remaining logarithms in the right-
hand column. The distance to thousandths of a mile for each com-
puted line must be found and placed to the left of the names of the
terminal stations. The work should be verified by comparing dis-
tances for each line that has been computed from two or more
triangles:

Computation of geodetic coordinates. — For this work use book 9-902
and check results by computing each position from two stations
which form a triangle with the new station. For convenience, only
one of the computations is here given:

//

Azimuth a: Elk-Dick q6 56 01.12

Spherical angle at Elk 86 oq 53. 23+

Azimuth a': Elk-Browning 183 05 S4- 35

Aa+i8o* 180 00 36.47

Azimuth (a): Browning-Elk 3 06 30.82

Geodetic Coordinates.

LATITUDE-

e / n

<f> 37 2S 47-32

A<f> J4 37'Zoi-i-)

LONGITUDB.

o /

//

^' 37 43 2442

Computation for latitude:

logs 4.4326556

log B 8. 5110415

log cos a' — 9- 99Q3(i47(.—)

Elk.
Browning.

X 82 00 16.16

A A 59.77^

A arc and sine
{log s)... —13
{logY).. +00

X' 81 59 16.39

Computation for longitude:

log s 4. 4326556

log sin a' 8.7328074^—)

log A' 8. 5091756

log sec ^' 0. 1018382

log (I) 2.943o6i8{-)

log s* 8.86531

logC 1.28943

log sin' a'... 7-46561

•13

A a and s .

(-/J)

log (V) 1. 7764755^")

59' 769-
AX 59-77—

log (II) 7' 62035

72

INSTRUCTIONS TO TOPOGRAPHERS.

logD 2.y77i

logll+IiP.. S'8Ui

Computation for azimuth:
log(V) t'776476{'-)

log (III) 8.Z632

'og E.

6. 0528

logs* sin* a\ 6.330Q

log (I) 2.Q43li—)

-log (IV)... 5'3268i+)
Computation for latitude:

(I) 877'i26{-)

(II) 004 +

(III) 018 -¥

(IV) ooo{+)

-A<^ 877'I04{-)

I II

• 1

4137-28-

4^*37 43

II

-47-3
24.4

log sin (^i^'^ Q. 785450
log sec ( — — ) 0.000000

72

11.7
II

37 36

06

log (VI).. i.56i926i-)

-Aa 36".47i-)

Aa 36".47i+)

Azimuth check.

[i+m 877.122

log [I +11] 2.94306
logH+IiP 5'886i2

Spherical angle
at Browning

• I II

S3 16 59.94
3 06 30.82

50 10 29.12
50 10 29.11

A^ 14 37.ioi+)

Computation of Azimuth a, in Book 2752, page 21.
Spherical angle and distances — s, in Book 2751, page 9.

Computed by D. M. E.

[Note. — The signs (+) or (— ) placed after logarithms are the signs of the cosines or
sines of the azimuth used in the computations.]

In this example the azimuth, 96° 56'' 01''^. 12, is derived from a
previous computation. The spherical angle is that at Elk from the
adjusted figure. Whether to add or subtract this can be determined
very easily by inspecting a plat of the stations, but when for one of
the pair of computations the spherical angle is added, the other is
always subtracted. The latitude and longitude at Elk are also
derived from a previous computation. Logarithm s is the logarithm
of the distance in meters between Elk and Browning. The constants
B, C, D, and E are from "Geographic tables and formulas"^ for the
known latitude at Elk. (Cosine 2/ and sine 2/ are fimctions of the
azimuth Elk to Browning. The algebraic sign of each of these as
fixed by trigonometric rules determines the sign of the resulting
quantity. The signs of (II) and (III) are always positive; that for
(IV) is always opposite to that of (I). The constant A'' and secant ^^

1 See also Special publication No. 8, Coast and Geodetic Survey, 191 1.

TRIANGULATION COMPUTATIONS. 73

in the longitude computation are for the new latitude, which requires
that the latitude computation be made first. These two factors will
be the same for each of the pair of computations for the new position.
For short lines, corrections (III) and (IV) will usually be less than
o.oi^^ and may be neglected.

When the logarithm of distance s in meters exceeds 4.0000000, a
correction will usually be required for logarithm (V) for the differ-
ence between the arc and sine. The constants for computing this
are given on page 269 of *' Geographic tables and formulas, "^ the argu-
ments being log distance s and log (V). The difference between
the values found is to be applied, according to the sign of the greater,
to log (V) before finding the value of the latter in seconds.

Six places of decimals will usually give sufficient accuracy for

log (VI). The logarithm of secant (^^ ) may be taken from page

268 of the tables. When log (V) is large, say over 3.5000000, a cor-
rection in seconds will be needed for Aa expressed by the factor
^X^ F. The logarithm of (V) is multiplied by 3 and added to the
logarithm of F, which is given in the tables; the value in seconds
for the resulting logarithm is always to be added to the previously
found value in seconds for (VI).

The latitudes and longitudes for each point thus computed in
pairs should agree within one or two hundredths of a second. The
difference between the two reverse azimuths should also agree
with the corresponding adjusted spherical angle within one or two
hundredths of a second.

The formulas for finding azimuth and distance between points
whose latitude and longitude are known and the form for 3-point
computations are given in "Geographic tables and formulas."'
Special blanks for 3-point work may be secured by application to
the Washington office.

Tabulation of results. — ^The final step in the computation of trian-
gulation is the tabulation of the results. A printed blank is used;
on it is written the name of the station, the State and county in which

1 See ako Bull. U. S. Geol. Survey No. 234, 1904, p. 264.
' Idem, pp. 14 and 365.

74 INSTRUCTIONS TO TOPOGRAPHERS.

situated, the kind of signal and the center mark tised, a full descrip-
tion of the station (see p. 51), the latitude and longitude, the azimuth
back azimuth, and logarithms of distances in meters to all other
stations from which it is visible; also for each logarithm of distance
the corresponding distance in miles and thousandths.

PRIMARY TRAVERSE.

FIELD WORK.
PERSONNEL AND OUTFIT OF PARTY.

In primary traverse the party consists of an instrument man in
charge, a recorder, two chainmen, and two rodmen; also a cook and
a teamster when camping is necessary.

The following supplies can be obtained on requisition;

One transit, graduated to 30 seconds, and furnished with stadia wires.

Two 300-loot steel tapes, graduated to feet throughout.

One 100-foot steel tape.

Two red and white transit rods.

Two plumb bobs.

Eleven tally pins.

Four hand recorders.

Two electric hand lamps.

One tape repair outfit, punch, and rivets.

Three tape clips, temporary repairs.

Two tape holders.

One set steel dies, figiu^es.

One set steel dies, letters.

Three large book bags.

Standard bench-mark tablets or posts (according to the requirements of the

country).
Canteens.
Cement (in cans).

Drills, hatchet, hammer, post-hole digger.
Primary traverse field notebooks gr92S.
Chainmen's notebooks 9~939-

Blank notebooks 9-896, or 3 by s inch pieces of nianila paper.
Book of instructions.

The instrument man must carry a reliable watch.

PRIMARY TRAVERSE FIELD WORK. 75

PREPARATORY WORK.

Location of litie. — Primary traverses should always be run in cir-
cuits or ,tied to points previously located. In 15-minute quad-
rangles, in country where routes can be readily planned, traverse
lines should follow as closely as possible the borders of the quad-
rangles to be controlled, not departing from them more than is abso-
lutely necessary to keep on roads. If there is a choice of roads, select
the one in unmapped areas. An additional line should be run to
bisect the quadrangle.

In areas where the country will not permit this plan to be followed
economically and where the selection of routes for the lines must be
influenced by the location of highway's, it will be necessary to plan
the routes to meet the specific requirements.

Permanent marks. — In regions where topographic conditions per-
mit, tablets or iron posts (see C and F, PI. I, p. 46) must be set as near
as possible to each corner of each 15-minute quadrangle, one on each
side halfway between the comers and one in the center of the quad-
rangle, making nine in all. All such marks must be stations on
the line and should be stamped '*Prim. Trav. Sta. No. — " (num-
bered consecutively) and also with the year of survey. In areas
which can not be traversed according to the regular plan, permanent
marks must be established at intervals not greater than 6 miles.

In cooperating States use the appropriate State post or tablet {A ,
PI. I, p. 46).

Where level bench marks have been established along the route of
survey, they should be tied to and stamped as above and thus made
to serve as permanent marks on the traverse line.

It is desirable that every permanent point be tied to two or more
witness or reference points, the bearings, distances, and descriptions
being duly recorded in the notebook.

Secondary points. — Besides the permanently marked points, a
number of other points should be carefully located along the traverse,
and these points should be specifically designated in the field notes.
Of special importance are the crossings of boundaries of States,
counties, and civil townships, and the location^ of the principal
cross roads, of railroad stations when the line follows a railroad, and

76 INSTRUCTIONS TO TOPOGRAPHERS.

of township and section corners if the region is subdivided by public-
land surveys. Note should also be made of less important land-
marks, such as road forks, mileposts, railroad switches, road and
stream crossings. These points should be so completely described
in the notebook as to be readily identified.

TAPING.

Duties of chainmen. — The front chainman carefully marks off each
tape length; if on a wagon road, with tally pins; if on a railroad, with
keel on the rail. Each time he marks off a tape length he registers
it on his hand recorder; each time the rear chainman reaches the
mark left by the front chainman he does likewise. When a transit
station is established the two chainmen compare their hand recorders
for check on the measurement. Should they differ, the course must
be remeasured.

Transit stations should be made at even tape lengths or even
lo-foot marks, wherever possible, in order to simplify the work of
the computer. They should be selected at points affording not
only an imobstructed view back to the transit but also a clear view
forward. Each station is to be marked, if on a wagon road, by a
ID-penny nail driven into the ground through a piece of paper on
which the front chainman has written the number of station and
distances; if on a railroad, by a keel cross on rail, with number and
distance on nearest tie.

Stations on main lines are to be numbered consecutively, begin-
ning with zero; those on short spur lines to section comers or other
points to be computed are to be lettered instead of numbered. Sta-
tion numbers should never be duplicated in a single locality.

The two chainmen must keep in book 9-929 separate records of the
number of stations and distances between them. At noon and at
night these records must be compared with the recorder's notes, and
should there be a difference, it must be corrected before the line is
carried forward, the line being retraversed if necessary.

In locating transit stations the front chainman should bear in mind

that it is desirable for the instrument man to be able to sight the

bottom of the rod in each direction. This is especially important

OJ7 short sights, for errors due to sighting the upper part of a rod which

be out of plumb may appreciably affect t\vct aiccMracy of the line.

PRIMARY TRAVERSE FIELD WORK. 'JJ

Method of measuring, — ^When measuring along a wagon road the
tape must be kept horizontal unless the grade is very slight; on
steep slopes a plumb bob must be used either to bring the tape end
vertically over an established point or to establish a new one, as the
case may be. Judgment should be used in selecting the proper
length of tape on slopes; no attempt should be made to use the
full 300-foot length; about 150 feet is ordinarily all that a chainman
can hold horizontal with the proper tension and plumb at the same
time. On slopes that require "breaking" the tape into short sec-
tions, the entire tape should first be drawn forward its full length
by the front rodman if convenient, or by the front chainman, who
then returns to help "break** the tape at the proper places, until
the end of the tape is reached. In this manner the distance is meas-
ured on the whole tape and does not depend on the sum of the
separate horizontal measurements.

Some tension must be put on the tape, but the use of a spring
balance has been found by experience to be unnecessary.

Errors in taping. — The errors that most seriously affect the accu-
racy of taped lines may be classed under two heads.

The errors of one class are due to failure to keep the tape horizontal
and to careless plumbing. The instrument man should impress
chainmen with the fact that the accuracy of traverses depends on
their work more than on the instrumental work, for the latter is
checked at every azimuth observation, whereas there is no check on
the taping until the circuit is closed.

The errors of the second class are gross mistakes arising generally
from carelessness in counting tape lengths. They may be eliminated
by checking the count of tape lengths by independent measurements.
To do this, the instrument man should read each distance by stadia
on the red and white transit rod or on a special stadia rod carried
for this purpose. In case the distance is too great to be read by a
single sight, he should set up the transit between stations and read
both front and rear rods. Stations should in no case be more than
2,600 feet apart, which is about the limit of visibility of the rod.
On railroads an additional check on the taping may be had by coimt-
ing rail lengths. This should be done by both rodmen and by the
recorder, or by the instrument man while moving from one ^ta.<kscL
to the next. In other places a check ma.7 \i^\v8AVj -^^^va?^.

78 INSTRUCTIONS TO TOPOGRAPHERS.

OBSERVING AND RECORDING.

Deflection angles. — At each station, in reading deflection angles, the
instrument man should proceed as follows : Sight rear rod with transit
circle set at last reading at previous station, transit telescope, sight
front rod, and read both verniers. Turn instrument with the two
plates clamped, the vernier remaining undisturbed; sight rear rod
again and remeasure the angle. If the two results thus obtained
differ more than tof\ repeat the operation.

When the transit is carried from ore station to the next, keep the
upper plates clamped so as to retain the last vernier reading; after
setting up the instrument verify the reading and use it as the first
back sight reading at the new station. It may at times be necessary,
in order to get the best pointing on the rod, to change the reading a
minute or two, but by following this general plan a useful check on
the readings is secured without trouble.

Azimuth observations. — Observations on Polaris for azimuth must
be made at the close of each day's work, if the weather permits. On
a crooked line with many short cotu^es azimuth stations should be
not more than loo stations apart; on a traverse with long tangents
they should fall not more than 15 miles apart. These requirements
may necessitate going back over the line in order to make the neces-
sary observations, but if conditions are favorable it is possible to make
azimuth observations in broad daylight.

Both the transit and the azimuth mark must be at stations in the
traverse not less than 500 nor more than 1,500 feet apart. Each
point should be marked by a stake with a tack, or, if on a railroad,
by a nail in a tie. The azimuth mark may consist of a vertical slit
one-eighth inch wide and 6 inches long cut in the side of a box or tin
can containing a candle or lantern, which should be carefully cen-
tered over the tack in the stake. In pointing the telescope tise the
electric hand lamp to illuminate the cross wires, holding it nearly
in front of the object glass, or allow it to shine on a piece of paper
fastened in front of the object glass with a rubber band and haying
in it a half -inch hole.

Angles should be read as follows: Set on azimuth mark, then on
star; reverse telescope, set on star again, and then on azimuth mark.

PRIMARY TRAVERSE FIEI.D WORK.

79

Each observation should consist of not less than three direct and
three reversed measurements, the circle being shifted for each set
by about 60° . (See sample page of record below. ) Observations may
be made at any time the star is visible, but preferably when at or
near elongation. The time of setting the cross wires on the star must
be recorded to the nearest second. Observations should be made
rapidly; not more than 15 minutes need be taken to complete a set,
The notes must be kept in the following form :

Date, Sept. 10, 1912. Line from Pikeville west to Dayton, Mo-
Azimuth observation 2.5 miles southeast of Dayton, Mo.. Sept. 10, 1912. Mag.

bearing sta. 327-328 N. 59" 30' W. Lat. 39° 00'. Long. 92" 15'.
Instrument at station 327- Mark at station 328. Watch 35 seconds fast, 90th

meridian time.

Point.

Mark.
Ster»
Star..
Mark.

Mark.
Starff
Star..
Mark.

Mark.
Star*
Star..
Mark.

Vernier A. Vernier B.

2 30 54
274 48

94 50
40 56

352 02

45 57

22s 57

172 02

n

00

00 <

30 i

00 ■

I
I

30 ;
00 I
00 I
00 i

99 OS C30
153 01 30
333 02 30
279 06 30

40 54 00
94 48 00

274 SO 30
220 56 00

172 02 00

225 56 30

45 57 00
352 02 30

279 06 00

333 01 00

153 03 00

99 06 00

Mean.

Deflection
angle.

o / // o / //

Azi-
muth.

40 54 00
94 48 00
94 50 30
40 56 00

t>l 54 00
53 54 30

172 02 15

225 56 45

53 54 30

225 57 00

53 54 45

172 02 15

99 05 30

153 01 15

53 55 45

153 02 45

53 56 30

99 06 15

53 55 00
Watch fast

Corrected t

o Reverse telescope between each two readings on star.

Time.

H. m. s.

8 31 33
834 48

8 40 28
8 41 50

8 43 55
8 44 S6

8 39 35
35

8 39 00

The latitude and longitude of each azimuth station, scaled from
the best map available to the nearest minute, should be given,
together with the date of observation, on the page with the other
records, in order to enable the computer readily to convert standard
to local mean time.

8o INSTRUCTIONS TO TOPOGRAPHERS.

In case unfavorable weather prevents the taking of the azimuth,
leave adequate marks at a point selected, before proceeding with
the line, and return to them later to make the observations.

Waich error. — The instrument man must carry a reliable watch and
keep it in good condition. He should ascertain its error daily by
comparison with telegraphic time, which is sent over Western Union
lines once a day. In case he has no opportunity to make this com-
parison while running the line, he should do so as often as possible,
figure the rate of error per day, and record the proper correction for
each azimuth observation made. A watch error of 20 seconds or less
will not appreciably affect the accuracy of the determination. At
least once in each notebook he should state whether he uses standai-d
time; if so, for what meridian.

Magnetic declination. — A careful reading of the needle for magnetic
declination should be made at frequent intervals and recorded
opposite the proper station number in the notebook. Such deter-
minations should be made at each azimuth station and at favorable
points along the line where the needle is not likely to be affected by
rails, electric wires, or similar disturbing elements. At azimuth
stations determine the magnetic bearing of the azimuth mark at the
time it is established. If the line follows a railroad, magnetic
determinations should be obtained from a parallel line at a distance
of 25 yards from the rails or wires.

Field record. — Complete notes must be kept by the recorder in
book 9-928, to be written in a plain, neat hand with a No. 4 pencil.
The blanks in the title-page should be filled in the first day the book
is used. A single line should be drawn through erroneous records,
which must never be erased.

The recorder must take down the vernier readings, as they are
called off by the transit man, and compute the mean pointings and
deflection angles, giving proper signs to the latter. He must keep
up vnth the instrument man in these computations, as they enable
him to note by inspection whether the instrument man has made
errors in his readings and to call attention to them before the instru-
ment is removed from the station. He should take special p^ns to
see that the degree and minute numbers for the two verniers are
consistent and are recorded in the proper column.

PRIMARY TRAVERSE FIEI<D WORK.

8£

The notes are to be kept in the following form:

Date, Sept. 9, 1912. I«ine from PikeviUe to Dayton, Mo.

Stations, dis-
tance between.

Vernier
A.

Vernier
B.

Mean.

Sta.326:3tapes

Sta.3a7: 4 tapes

H-I20=»

i

//

//

//

316 51 30
275 06 00
233 21 00

[233 21 30

53 32 00

279 04 30
324 48 30

99 OS 30
144 49 30

136 52 30 I3I6 52 00
95 07 30 '375 06 45
S3 22 00 333 31 30

233 ax 45

379 OS 00

324 49 00

Sta. 337+90 feet, stream crossing

Sta. 327+430 feet, crossroad at Tanbark P. O

Sta. 328-

<o°

324 48 30

343 08 00

144 49 30 324 49 00
163 09 00 343 08 30

359 27 00 1179 28 00 359 27 30

Deflec-
tion
angle.

/ //

41 45 15
41 45 15

-41 45 IS
45 43 XS
45 44 00

+45 43 37

17 19 30
X7 19 00

+17 19 XS

Azimutb. 1 Remarks.

O / // I

'^123 35 00

I

b 81 49 45
C81 49 47

Stadia 905.

Sta. 327-328
N.59°3o'W.
Stadia 1,330.

6127 33 23 j
C127 33 26 I

*I44 52 37
Cx44 52 43

Stadia 360.

a Written in red ink. & Written with black pencil. c Written with black ink.
NoTB. — The entries in the azimuth column are a part of the office computation.

The record must contain also a description of the starting and
ending points of the line, of each permanent mark established along
the line, of each point which is to be computed for the use of the
topographer, and of all crossings and other landmarks that may be
of value to him. Such descriptions should be concise, yet full
enough to leave no possible doubt as to the identity of the points
described. Each should be supplemented by an explanatory sketch
if necessary.

Example of description of permanent mark:

Station 1025, bench-mark tablet stamped " Prim. Trav. Sta. No. 4, 1912," set in
sandstone ledge, top of Walden Ridge, 3 miles northwest of Dayton, Mo., at junc-
tion of Dayton, Pikeville, and Morgan Springs roads, 335 feet west of residence of
John Neilson. Reference marks: Cross cut in ledge 60.25 feet N. 25" 30' E.; spike in
root of white oak tree 14 inches in diameter, 75.60 feet N. 45** 15' W.

66512 — 13— —6

82 INSTRUCTIONS TO TOPOGRAPHERS.

Examples of description of points to be computed and other

landmarks:

«

. Station 625+730 feet [center of crossroads at Antioch Church].
Station 7^0+330 feet, cast abutment of bridge over Glade Creek.
Staticm 73a is road fork at Johnson blacksmith shop.
Station 936+aio feet [center of track opposite semaphore, Lee station].
Station 936+300 feet, road crossing one-half mile east of Sequatchie railroad bridge.

Each point to be computed should be marked with brackets in
ink immediately upon its selection by the instrument man.

As soon as the records in a field book are completed 1 it should, if
not needed for reference, be sent at once to the Survey office in Wash-
ington by registered mail. Chainman's books should be sent sep-
arate from other notes and on another day.

PRIMARY TRAVERSE COMPUTATIONS.

The steps in primary traverse computations are as follows:

Computation of azimuths.

Computation of observations on Polaris.

Computation of the deflection angles.

Adjustment of closing errors.

Computation and tabulation of latitudes and departures, which are the north and

south distances and the east and west distances, by two computers working

independently.
Computation of latitudes and longitudes.
Adjustment of closures in position.
Computation of diagonals.
Tabulation of results by atlas sheets.

The computations are made in books 9-938 and 9-931. The
abstracts of results (7) are placed on long sheets of blank paper.

Computation of azimuths from observations on Polaris. — First find
the mean of time of observations and corresponding mean of angles
meastu'ed between mark and star (p. 79). Having given the ap-
proximate latitude and longitude of the azimuth station, compute
the true azimuth of star by the tables published annually by the
General Land Office.

PRIMARY TRAVERSE COMPUTATIONS. 83

Example of computation: The station (see p. 79) is in latitude

39° 00^ N., longitude 92° 15^ W.

//. m. s.

Sept. zo, 1912, 90th meridian standard time of observation, p. m. (correc<

tion having been made for watch error) 8 39 00

Correction for a* 15' longitude west of 90" — 9 00

Local mean time of observation 8 30 00

The nearest upper cuhnination <^ Polaris as given in the tables is that for
September 11 at a'* 9.6™ a. m., Greenwich mean time, civil date. The
correction, always negative, to reduce this to local meridian is:

?-^ of the daily change (3.9™)= — !" o«.
360

H. w.

Local mean time of upper culmination (Sept. xi , a. m.) a 08. 6

Hour angle, being the interval between time of observation and

time of culmination ^ 5 38. 6

With this hour angle as an argtunent and the declination for the given date
(88* so' is"), find by double interpolation from the table of "Azimuths of
Polaris" in the Land Office tables the azimuth angle for the latitude • r

and time x 29. s

Since the star had not reached upper culmination, it is east of north, or, 180**

being added, has an azimuth of xSi a9. s

Angle between mark and star (p. 79) (star east of mark) $3 55.0

Azimuth at station 327 to 328 127 34. s

A rough check on this azimuth may be found by comparing it
with the observed magnetic bearing, allowance being made for dec-
lination. To interpolate for hour angles near elongation, use for
the latter 5^ 55™.

Each azimuth computation is to be made in the field notebook
on the same page with the observations and the results written in
red ink in the azimuth column of notebook (see p. 81) on the line
with the station occupied.

Computation of deflection angles. — The deflection angle is added
or subtracted according to its sign, and the sum or remainder is
written in pencil on the line with the mean deflection angle. The
next deflection angle is combined according to its sign with this

^ The hour angle will always be less than 12 hours and must be fotmd from the
nearest upper culmination; when, as in this case, the nearest upper culmination is
in the following day, add 12 hours to its time before subtracting the time of observa-
tion.

84

INSTRUCTIONS TO TOPOGRAPHBRS.

azimuth and the resott placed in pencil opposite the deflection
angle used. This process is repeated until the next compated
azimuth, written in red ink, is reached.

The last azimuth in pencil will pcobably not agree with the ob-
serred azimuth. For any line not running due north or south
there will be a discrepancy between observed and computed
azimuths, due solely to convergence of meridians, which for lati-
tude 30^ will be 0.5^ for each mile run east or west. For latitude
49^ the amount will be zf. For any latitude the convergence in
minutes d arc will be the difference in minutes of longitude between
ends of line, multiplied by the sine ci the middle latitude. For
lines running east the computed azimuth should be less than the
observed. For lines running west it should be greater.

Adjustment of closing errors. — If no large errors appear in the results,
the discrepancy between computed and observed azimuths at the
second station is to be divided by the number of stations and a
proportional correction applied to each penciled azimuth, the
corrected figures being written in black ink.

Computation of latitudes and departures. — Latitudes and depar-
tures are to be computed in book 9-931, as shown below:

Line from Pikeville to Dayton, Mo.

SUtion.

Azxxnntli. *a^nf^ sine

Cosine.

0. 143
.6x0

Nofth.

South.

East.

West.

32610337

337 + 430

8x 49 47 900 a 990
X27 34 30 430 . 793

362

138

891
341

i

1

1

"7 34 30 890 1 . 793

.6x0

363

128

X38 I

1

1.233

337+430 to 338

134

543

706

Natural sines and cosines for the azimuth given are written in

the appropriate coltmms. By means of Crelle's tables the products

of these by distances are found and placed in the proper columns.

The nnes multiplied by the distance give departures east or west.

*&e sine is positive, the new point is west; when negative it

PRIMARY TRAVERSE COMPUTATIONS. 85

is east. Cosines multiplied by distances give latitudes north or
south. When the cosine is negative, the new point is north; when
positive it is south. The direction of the new point can readily be
determined by noting the azimuth, remembering that 0° azimuth
is for a line nmning due south, 90° for a line due west, 180° for a line
north, and 270° for a line east. In the example 81° 49^ 47''^, being
for an azimuth between due south and due west, will be to a point
southwest. Four decimal places in sines and cosines should be
used when distances are greater than 1,000 feet.

When traverse tables for distances i to 100 for single minutes of
arc are available, the latitudes and departures may be written in
the north, south, east, and west columns direct for each azimuth
and distance.

Whenever a point is reached for which the latitude and longitude
are desired, as at 327+430 in the example, leave six blank spaces
for the computation. The data for the computation for such a
point are foimd from the record on page 81, as follows: For the
crossroad at Tanbark post office, which is on line between stations
327 and 328, the azimuth is the same as to station 328. The distance
by measurement is that given, 430 feet from station 327. In order
to make the computations continuous, station 328 is taken as
1,320— 430=890 feet from the intermediate point used, the azimuth
being the same for both points.

Computation of latitudes and longitudes. — The next step in this work
is the computation of latitudes and longitudes. These should be
determined for important points a mile or less apart. Assume, for
illustration, that for station 326 (p. 81) the coordinates have been
computed, and that 327+430 is the next location desired. Each of
the four columns — ^north, south, east, and west — is summed, and the
difference between the sums of the north and south columns is
placed in the column of the greater. Likewise, the difference
between the east and west columns is placed in the column of the
greater. The computations of latitude and longitude and the
descriptions of the points are placed on the right-hand page of the
book opposite the group of stations.

The logarithms of the geodetic constants for metric measiu^es,
called "the A, B, C factors,*' are on pages 196 to 267, incluslv^^^^

86 INSTRUCTIONS TO TOPOGRAPHERS.

Geographic tables and formulas.* Factors A and B are used to five
decimal places only. These will be practically constant for a
distance of lo or 15 miles north and south, the value for the middle
latitude being used.
For the example on page 84:

Ix)g distance 134 (north) a. 12710

"Log to reduce feet to meters 9. 48402

Log B for latitude 39* 00' 00" 8. 51093

Ob 12205

The sum, 0.12205, is the logarithm of change in latitude in sec-
onds between station 326 and 326+430=* 1.32^' (north).^
For change in longitude:

Log distance 1,232 (west) 3. 09061

Log to reduce feet to meters 9. 48402

Log A for latitude 39* 00' 8. 509x4

Log secant of middle latitude 10950

Log of change in longitude in seconds' x. X9337

New point west 15. 61"

These differences are to be added to the latitude and longitude
of station 326.

To check the plotting, the distance between successive positions
must be computed. As the lines are seldom as much as a mile in
length and never over 2 miles, the latitude and departure can with
sufficient accuracy be taken as the base and perpendicular of a
plane triangle. The distance sought will then be the hypothe-
nuse and its square will be equal to the sum of the squares of the base
and altitude. For distances less than 10,000 feet Barlow's tables
should be used in finding squares or square roots. The distance
should be written in red ink, inclosed in a circle, on the right-hand
page of the computation book in the blank space between the two
stations referred to. After the record is complete its accuracy should
be tested by computing a side from the given distance (hypothenuse)
and the other side.

^ See also Bull. U. S. Geol. Survey No. 234, X904. pp. 191-362.
* Tabks have been published by the Survey for finding the logarithms of seconds of
iUitit^ • f^mgitude direct from the logarithms of latitudes and departures in feet.

LEVELING. 87

Adjustment of closures. — These operations are repeated for each
selected point until the traverse line closes back on itself or ties to
another point previously determined. The errors of closure for a
1$^ quadrangle, if not in excess of 1^^ in latitude or 1}^^^ in longi-
tude, may be distributed proportionately between initial and clos-
ing points.

Where so many operations are involved, errors are very likely to
creep into the computations. Therefore each step of the work
should be checked as well as possible. The azimuth computation
should be compared with the observed magnetic bearings; but
because of the possibility of local variation little dependence can
be placed on this comparison as a check. If the computed and
observed azimuths for a line differ about 10^, look for an error of
that amount in the deflection angle or in the adding and subtract-
ing of deflection angles to azimuths. If the difference is larger, it
is very likely that a wrong sign has been used for a deflection angle.
To find the error, divide the difference by 2 and look for a deflec-
tion angle with an incorrect sign equal to the quotient. Errors of
about 180** occasionally result from the recorder placing the vernier
readings in the wrong columns. By a careful inspection of the rec-
ords it is sometimes possible to detect such an error. The latitudes
and departures, as well as the other steps in the work, should be
computed by two persons working independently of each other;
after each has completed his work the results should be compared
and differences corrected and verified. Errors are often due to
incorrect multiplication by the distance, to the decimal point being
in the wrong place, or to the product being written in the wrong
column — in the north column when it should be in the south col-
umn, etc.

PRIMARY AND PRECISE LEVELING.

DISTRIBUTION OF PRIMARY-LEVEL CONTROL.

A sufficient amount of accurate spirit leveling should be done to
insure the placing of at least two standard bench marks in each
township or equivalent area 'surveyed, except in forest-clad or
mountain areas, where at least one such mark should be placed in
each township.

88 INSTRUCTIONS TO TOPOGRAPHERS.

Permanent bench marks should be established along level lines
at intervals of approximately 3 miles, unless otherwise instructed,
and in no case should the distance between bench marks exceed
6 miles.

BENCH MARKS.

Permanent bench marks. — Bench marks should be established, if
practicable, at the township comers of the public-land surveys,
near all important lakes and reservoirs, at the crossings of impor-
tant streams and divides, in every city or town passed through,
and in the vicinity of important mines. They should be so located
as not to be liable to injtuy or disturbance, yet should be so promi-
nently situated as to be easily found. Along a railroad or highway
bench-mark posts, if used, should be placed either outside of and
close to the right of way or on the right-of-way line. They must
not be set close to trees, telegraph poles, or fence posts.

Standard bench marks consist eitiier (i) of tablets fastened with
cement into solid rock in place or into masonry structures, such as
the foundations of buildings or bridge piers, or (2) of iron posts set
in the ground so as to project not more than z foot from the top of
a conical mound of earth about 3 feet in diameter and 6 or 8 inches
in height. (See PI. I, p. 46.)

Portland cement in air-tight cans is furnished from the Washing-
ton office for use in setting tablets. If good clean sand is available,
it can be mixed with the dry cement in equal parts. The drill hole
for the tablet must be well cleaned and wet. The cement and
sand, or cement alone, if pure sand can not be conveniently pro-
cured, should then be thoroughly mixed with water to a thick paste
and the drill hole iilled with it. Into this the tablet should be
pressed, the excess cement being forced out, so as to completely
fill the space under the tablet face. In order that the cement may
set well, it should be kept damp and protected from the sun for at
least a day, and it must not be allowed to freeze for 12 hours. Dry
earth or a piece of sacking will probably be sufficient protection.
When a tablet is set in a vertical wall, it may be necessary to hold
it in place by a prop of some kind fdr a few hotu's.

The intersection of the cross lines on either style of mark is the
/e^™"''' oolnt Beiore a tablet is set the figures indicating the

IrEVEUNG. 89

elevation (to the nearest foot only) are to be stamped into the metal
before the word "feet." Posts should be stamped after they are in
place. If a post or tablet is wrongly stamped, the levelman or
topographer who discovers the error should immediately correct it
by cutting out the erroneous figtu'es with a chisel and stamping in
their place the correct ones. The facts should be promptly re-
ported to the chief geographer.

In cooperating States the name of the State must be stamped or
cast on standard bench marks.

If a tablet is inconspicuously situated, a mound of rock should
be erected near it, the rock about it marked with paint, or a near-by
tree blazed as a witness tree.

The steel tape instead of the leveling rod can often be used to
advantage for determining the elevation of a tablet set in a vertical
wall.

All standard bench marks should be used as turning points in
the line, but where this can not be done their elevation must be deter-
mined by two readings from different set-ups or from separate tempo-
rary bench marks.

Temporary bench marks. — Temporary bench marks must always be
turning points in the main line and should be set at intervals ranging
from half a mile to iX miles. They may consist ( i) of chiseled marks
on solid rock or masonry, or (2) of copper nails (with washers) or spikes
driven in telegaph poles, mileposts, fence posts, or trees. The copper
nails with lettered washers must be used when practicable. Where
there are no natural objects for temporary bench marks, pieces of iron
pipe, about 20 inches long, may be used. Select a place where the
mark mil not be likely to be disttu'bed and yet can be readily found ,
preferably near a road jimction, so that it may afford a convenient tie
point for other levels or traverses. The location should be con-
spicuously indicated by large figures in white or red paint, thus:

US

[elevation]

BM

Useful elevations. — Besides the bench marks a number of inter-
mediate elevations are required for the use of the topographer, and
these also should be selected with a special view to thfevt -^a.^^xJcast^*

90 JNSTRUCTIONS TO TOPOGRAPHERS.

in topographic mapping. The levelman should bear in mind that
his work is not an end in itself but a preparation for the work of others,
and that the accuracy with which his circuits check, though of para-
mount importance, is not the only thing that determines its utility.

Ground elevations should be painted conspicuously along the side of
the road, on fenc.es, telephone poles, trees, or rocks. If practicable,
they should all be marked on the same side of the road, preferably on
the north or east side.

The points at which elevations are particularly desired are the top
of the rail at railroad stations, junctions, sidings, and crossings, the
ground at crossroads, road forks, and bends; on summits and ridges;
near schoolhouses and other public buildings, lone houses, and im-
portant mines, quarries, and oil, gas, and artesian wells; on some
permanent part of a bridge other than a wooden floor; the water sur-
face of streams under bridges, at stream crossings, and above and
below dams; and water surfaces on lakes and reservoirs. Where
water-surface elevations are recorded, always give the date.

The number of these elevations should be varied with the nature
of the country and the contour interval; thus in rugged regions
mapped with 50-foot or 100-foot intervals relatively few elevations
are required (mostly on summits and in hollows); but in areas of
gently rolling relief they should be more numerous. In flat areas
where 5 or 10 foot contoiu^ are used, each contour crossing should be
marked with a stake or otherwise. This is important, as in such
areas a difference in elevation of a few tenths of a foot may mean a
difference of several hundred feet in the location of a contour.

Descriptions of bench marks and useful elevations. — Complete descrip-
tions of all bench marks and useful elevations must be made in the
notebook and copied in the description book (9-916) at the close of
each day's work. A sketch must accompany the description of each
standard bench mark, showing directions and distances to near-by
objects.

Descriptions should be written with items in the following order:

I. Name of the nearest post office, town, village, or other well-
known locality, with direction and distance from it to the bench
mark in miles and tenths; or township, range, and section in which
bench mark stands, with direction and distance from nearest comer.

PRIMARY LEVEUNG. 9 1

2. Position with reference to buildings, bridges, mileposts, street
or road comers.

(Items 2 and 3 should be written in direct form of speech.)

3. Description of object on which the bench mark is placed — tree,
bowlder, bridge, etc.

(The above three items answer the question where and should be
followed by a semicolon (;) and by item 4. which answers the ques-
tion what.)

4. Natiu*e of the bench mark — copper nail with washer, bolt, mark
on rock, tablet, post, etc. — and how marked or stamped. Old bench
marks must be fully described.

Descriptions should be kept in the order in which the bench marks
occur. If standard bench marks are not established when the line
is first rtm, spaces should be reserved in description books for them
in their proper order. A brief description of the line should be given
at short intervals, especially when changing direction. When cir-
cuits are closed, complete descriptions of closing points, closure error,
old and new elevations, and page reference to connecting points
should be given. A plot of all lines or circuits must be made on a
page near the back of the description book for each group of circuits
and the names of enough places to identify the line readily should
be added. Boundaries of quadrangles should be shown, and also,
if the area is covered by public-land surveys, the position of the line
"with reference to township and section lines. Alongside of each line
reference to the page of the description book where the record is made
should be entered. The records in this book are incomplete without
this diagram.

PRIMARY LEVELING WITH Y LEVEL.

Personnel atid outfit. — A primary-level party consists of a levelman,
one or two rodmen, and in some cases a bubble tender.
The instruments required are as follows:

One ao-inch Y level.

One or two New York rods.

One or two plumbing levels.

Two steel turning pins.

One set dies (figures and letters).

One 25-foot steel tape.

92 INSTRUCTIONS TO TOPOGRAPHERS.

Bendi-mark tablets or posts.

Copper naib and washers for temporary bench marks.

Cement in cans.

Level notdxwks 9-903 (those in black covers to be used by levelmen; those in

yellow covers by rodmen).
Bench-mark description book 9-^x6.
Two book bags.

Other accessories to be purchased in the field:

One or two hatchets.
One drill hammer.
One posthole digger.
Stone drills (x|-inch bit).

Character of lines. — Primary levels should be run as single lines in
circuits wherever practicable, otherwise checked by rerunning,
preferably in the opposite direction. No work is completed until
it is checked in some way. Lines should be connected with near-by
bench marks of railroads, cities, and other organizations.

Accuracy. — The closure error of a circuit in feet should not exceed

0-05 VlcJig^ oi circuit in miles.

If it is greater than this, the facts must be reported to the geographer
in charge immediately.

Adjustment of instruments. — ^The adjustment of the level must be
tested daily and corrected whenever it is found in error; the adjust-
ments of the line of coUimation and of the level tube are especially
important.

The tripod clamping screws must be loosened before the instru-
ment is set and tightened after the legs are firmly placed. After
setting the target and before the **all right'* signal is given the level
bubble should be examined, and if found to be away from center
it must be corrected and the target reset.

Equalization of fore and back sights. — In order to eliminate instru-
mental errors and errors caused by curvature and refraction, it is
very important that the length of fore and back sights be equalized,
but when this is impracticable because of some obstacle, enough
unequal sights to balance should be taken as soon as the obstacle is
passed, provided this can be done before a readjustment of the level

PRIMARY LrEVKUNG. 93

is made. When the adjustment of the level is changed, further
attempts to eliminate instrumental errors by the balancing of previ-
ous sights are useless. The failure to balance sights is one of the
principal sources of error.

Maximum length of sight. — ^The maximum length of sight permissi-
ble tmder the most favorable conditions is 300 feet, except when
crossing rivers or deep ravines. In such places proceed as follows:
Establish a turning point on each side; set up the level about 20 feet
from each point in turn, taking in the first position a back sight to
the near point and a fore sight to the distant point; then cross the
stream or valley and take a back sight to the distant point and a fore
sight to the near point. For very long sights several readings should
be made on the distant rod; the mean of these determinations of
elevation may be accepted as correct.

Measuring of distances, — Distances may be measured by stadia
readings on the rod, by cotmting rails if along a railroad, or by pacing.
The distances in miles or feet of both fore and back sights must be
recorded in notebooks in the proper columns.

Unfavorable conditions, — ^Work on primary lines should not be
carried on during high winds or when the air is boiling badly. Dur-
ing very hot weather an effort should be made to go to work early and
remain out late, rather than to work during midday.

Inspection of rod. — ^When the rod is lengthened beyond 6.5 feet,
both the rodman and the levelman must examine the setting of the
target as well as the reading of the rod vernier. When the rod is
closed they should see that the rod vernier indicates 6.5 feet, not
depending on the abutting ends to bring it back to place. The lower
end of the rod and the top of the tiuning point must be kept free
from mud and dirt.

Plumbing levels must be tested at intervals and kept in adjust-
ment.

Turning points. — The regular steel turning-point pin should be
used wherever no rock or other suitable points are available. A
marked point on the top of the rail may be used when running along
railroads.

Reading of target. — Both the levelman and the rodman must read
each target setting independently and keep separate records. TVvjei

94 INSTRUCTIONS TO TOPOGRAPHERS.

mtist not compare figures until their respective records for a given
sight are completed. If the difference exceeds o.ooi foot, each
must read the rod again before comparing anything but results.

Records, — ^All level notes must be recorded directly in book 9-903.
Under no circumstances should separate pieces of paper be used for
figuring or for temporary records. Use ink or No. 4 pencil, make all
figures distinct, and do not crowd them. When two important
bench marks come close together provide ample room for placing
their written descriptions opposite the appropriate figtues by drop-
ping the figures for the record one or more lines down the page.
For a given H. I. (height of instrument) the rodman's notes must be
at least two lines lower down the page than the levelman's and they
must not ttun over a leaf at the same time. Erasures with rubber or
knife are not permissible imder any circumstances; a single line
should be drawn through an erroneous record and the corrected
figures written above it. The flyleaf of each notebook must be
properly filled in when the book is first used.

Both the levelman's and the rodman's books must be balanced
daily. At the bottom of each page, and at the end of the day 's work,
each column of fore and back sight distances and readings should
be shown to agree with the difference of elevation previously com-
puted. This check must never be omitted and the computation
mu^ appear on the page opposite the notes. Side sights which are
not a part of the continuous line should be recorded in an extra
column or within brackets.

>^Tien field work is completed notebooks should be forwarded
promptly to the Washington office of the Survey by registered mail,
the levelman's books in one package and the bench-mark book and
rod man books in a separate package and on another day.

PRIMilRT LBVSLINO WITH YARD ROD AND PRISM LEVEL.

Personnel and outfit. — A prism-level party consists of one levelman,

two rodmen, a recorder, and an umbrella man.

The instruments and outfit consist of the following:

One prism kveL

Two yard rods, cadi to have plumbing level and thermometer attadied.
Oae steel tape (95 feet).
TWo steej tuming'point pins, hollow head.

PRIMARY IrEVEUNG. 95

One Irocke level.

One umbrella with staff.

One set dies (figures and letters) .

Bench>mark tablets or posts.

Cqpper nails and wt&hers for temporary bench marks.

Cement, paint can, keel, and other accessories.

Two book bags.

Prism level notebook 9-940.

Bench-mark description book 9-916.

Character of lines. — Priinar>' levels executed with a prism level
need be run in one direction only, but must be in circuits or other-
wise checked.

Accuracy. — Circuits must close with an error in feet not exceeding

0.04 ^length of circuit in miles,
which is equivalent to

0.056 .^distance between bench marks in miles

for forward and backward lines.

Graduation of rod. — The rod used is graduated to yards, tenths,
and hundredths, and is read by estimation to thousandths. Each
yard has a diiferent and distinctive color, which must be recorded
for each reading. One edge of the rod has also graduations in feet
and tenths for use as a check on yard readings.

Locke levels. — In a hilly country time can often be saved by supply-
ing each rodman with a Locke level, by means of which the rodman
can select the places for setting up the level and for turning points.

Ratio of wire intervals. — The rod is read with each of the three
horizontal wires in the instrument. The mean of the two wire
intervals in thousandths of a yard as read upon the rod should equal
the distance to the rod in feet, but this should be tested. As the
upper and lower wires are not always equidistant from the middle
wire, the ratio of the wire intervals must be determined from the
first day's level notes for use as specified in the next paragraph.

Methods of reading. — The program at each set-up is as follows:
After the tripod is firmly set and the clamp screws tightened, level
approximately by the circular level, which has been adjusted by
comparison with the long level. Point the instnwasft.'ivl^jcr^'^^*'^^

96 INSTRUCTIONS TO TOPOGRAPHERS.

rod and clamp; bring the level bubble to the center of the tube by-
means of the micrometer screw. Read on the rod, and first call off
the color initials for the lesser and greater extreme readings; second,
call yards and tenths for each wire, taking the smallest reading first;
third, repeat and read yards, tenths, hundredths, and estimated
thousandths; fourth, for additional check on the yard ntunber,
read the middle wire on the tenths of feet scale on the back of the
rod. Before the level is moved the recorder should first see that
the color agrees with the yard readings; second, he must compute
the two wire intervals and if their ratio one to the other differs more
than I per cent from the true ratio (see preceding paragraph), the
levelman must repeat the readings; third, he must compute the
mean reading in feet by summation, and test units and tenths by
mentally multiplying the middle reading by 3, also by comparing
with the reading on the scale on the back of the rod. An agreement
must be reached before the next sight is taken. The temperature
must be recorded for each hour.

Level adjustment. — ^When the work is commenced, and at least once
each day thereafter, the adjustment of the level must be tested by
the "peg method" as follows:

At some convenient set-up, after the usual back-sight and fore-
sight readings have been recorded, copy the fore sight on a separate
line as a new fore sight apart from the leveling record, leave the
fore-sight pin in place, and set a second ttuning pin about 30 feet
back of the instrument; read rod on it for a new back sight; find
from these the mean readings in feet as usual. Move the level for-
ward to a set-up about 30 feet back of the fore-sight pin and take
readings on the fore-sight pin and then on the back-sight pin. The
constant "C," which is a factor of the adjustment correction, must
then be determined thus: Sum of readings on near rods minus
that on far rods, corrected for curvature and refraction in feet,
divided by three times the difference between the simi of the greater
and that of the lesser rod intervals in yards.

The rod interval for any sight is the difference of extreme wire
readings.

PRIMARY LEVELING.

97

Example of computation of C,
[To be made in the field,]

Determination of C, S.so a. m. August 28, 1910.

Thread
reading.

Thread
interval.

Sum of

thread

reading.

1.5x5 j 0-013
X. 528 I . 014

1-543

2. 252
2.357

2.462

027

.105
105

4-585

210
209

7-071
1-385

419
052

8.456
—0.0005

• 367 yds.
3

8-4555

I

I. zoi ft.

419

The fraction —210 feet=sum for far-rod distances.

. 002

/Si. ' Sum of thread Thr««i
ment.

I reading.

I

1.386

' 3-865
4-585

' S. 450

! 8.4555

1. loi)— . oo55(— o. 005

Thread

Thread

interval.

reading.

0. los

0-357

.104

.46a
.566

.309

.012

1.276

.013

x.aSS

I- 301

.025

• 025

.027

.052

For correction to be applied to the sum of readings on distant rods
for curvature and refraction, see table in back of field book 9-940.

When the sum of the readings on the near rods is the greater, the
sign of C will be plus, and vice versa. Great care must be taken in
pointing off decimals and in giving proper signs.

Adjustment of bubble. — If the resulting value for C numerically
exceeds 0.005, ^^ adjustment should be made by changing the po-
sition of the level bubble only, as follows:

Point to a distant rod with the bubble in the middle of the tube
and read; move the telescope (by micrometer screws) so as to
raise the middle cross wire by an amoimt which in yards is equal
to C times the extreme wire interval. While holding the telescope
in this position, bring the bubble to the middle of the tube by
66512 — 13 — 7

98 INSTRUCTIONS TO TOPOGRAPHERS.

raising (or lowering) one end of the level vial with the adjustment
wrench; if C is negative, the middle wire must of course be lowered
on the rod. After the adjustment has been made* its accuracy
should be tested by redetermining the value of C.

In case the cross wires break and the level-tube adjustment has
not been disturbed, insert new spider threads and determine a
value of C, as above directed. Compare with the last determination
of C, and adjust for the difference by changing the position of the
cross- wire ring only — ^not the level bubble.

When both level and cross wires have been disturbed the latter
can be put in proper position by means of improvised wooden wyes
in which the telescope is turned while watching a clearly defined
point through it, the operation being the same as for the coUima-
tion adjustment for a Y level.

Care of instrument. — When the level is on the tripod, be sure that
the central tripod clamp screw is tight. Keep the telescope off the
micrometer-screw bearing while carrying it between stations. Leave
the three tripod wing nuts loose when carrying; clamp tight when
tripod is in place for work.

The level must be shaded by an umbrella when in use and by a
cloth hood when carried between stations. In rough country the
place to set up the rod or level can be quickly found by means of a
hand level.

Care of rods, — ^The rods must always be kept covered when not in
use. The painted sides must never touch the groimd. Should
difficulty be fotmd in holding a rod steady because of wind, two
pieces of bamboo or other light poles, 8 feet long, may be held by
the rodman against the rod, so as to make a triangular brace against
the wind. Plumbing levels must frequently be tested and kept in
adjustment.

Testing of rods, — At the beginning and end of the season and at
least twice each month during the progress of the leveling the
intervals between the metallic plugs on the face of each level rod
must be measured carefully in feet to the nearest thousandth,
always with the same steel tape, kept for that purpose. The tem-
perature must also be recorded and the number bf the tape.

PRIMARY LEVELING. 99

Length of sights. — The length of fore and back sights must be
equalized with the prism level as with the Y level. The maximum
letigth oi sight with the prism level is 360 feet except at river cross-
ings. Sights across broad river crossings should be taken in the
folk>wing manner:

Mount the instrument and place stakes so that the center wire
ynli fall near the middle of each rod; if the distance is too great to
read the three wires, use improvised targets of cardboard held in
place by rubber bands or other simple device, and make several
settings by raising and lowering them an equal number of times.
Rodmen should be provided with field glasses if necessary to read
signals. Prom bench marks on each bank the elevation of the
adjacent water surface should be determined as an additional
check.

Record. — ^The notes are to be kept in ink in book 9-940, as for
precise leveling (p. loi), except that each H. I. (height of instru-
ment) and level should be computed. No erasures are permitted,
either with rubber or knife; a single line should be drawn through
erroneous records. Extra fore sights when made should be recorded
in the special column on the right-hand page, opposite the H. I.,
and recorded with "backward," "forward," "right," or "left"
added to show the direction to the rod from the instrument.

Check computations. — The check of the means of columns 3 and 5
and of their sums for each page of notes must be made each night,
or oftener if convenient, by both levelman and recorder independ-
ently. At the bottom of columns 2, 3, 5, and 6 the total sums for
the page are required, but for columns i and 7 find the sums of the
center- wire readings only. At the bottom of column i it must be
shown that three times the sum of the center-wire readings plus
the algebraic sum of the excesses of the lower over the upper thread
intervals in column 2 is equal to the sum of the mean feet readings
in column 3. A similar computation must be shown at the bottom
of column 7 with respect to columns 6 and 5. No other computa-
tkm than these need be made in the field except those required to
carry forward the elevations of temporary and standard bench
marks. /" ; ' ' " '.■*

lOO INSTRUCTIONS TO TOPOGRAPHERS.

The difference (column 3 minus column 5) should be written at
the bottom of column 4 and should equal the difference obtained
by subtracting the first from the last elevation, which should be
written in the upper space at the bottom of column 4.

C is the constant which results from the "peg-method" test of
adjustment. The formula 3 C (column 2 —column 6), etc., at the
bottom of the right-hand page is for computing the correction to
the elevations for combined errors of level and coUimation. This
computation need not be made in the field. By "(column 2 —
column 6)*' is meant the difference of the continuous sums of the
rod intervals of columns 2 and 6.

On primary work the algebraic simi of the page excesses of back
sights or fore sights for each day should be written in the lower
right-hand comer of the right-hand page.

PRECISE LEVELING.

Observations. — For precise leveling the instrumental outfit and
the number of men in the party are the same as for primary leveling
with prism level, but the following modifications of methods must
be made.

Lines must be run independently in both the forward and the
backward direction. The allowable error in feet is

0.017 ^ distance between bench marks in miles,

and when this limit is exceeded on any section the forward or
backward measure is to be repeated tmtil a pair run in opposite
directions is obtained between which the divergence falls within
the limit. It is especially desirable to make the backward measure-
ment in an afternoon if the forward measurement was made in the
forenoon, and vice versa. The observer should make the two
measurements under atmospheric conditions as different as possible
without materially delaying the work for that purpose. At alter-
nate stations the fore sight is to be taken before the back sight —
that is, always take readings on the same rodman first.

The maximum allowable difference between a back-sight and
the corresponding fore-sight mean thread interval is 0.033 yard
(33 feet distance). The continuous sums of rod intervals for the
section between bench marks must not be allowed to differ more

PRECISE LEVELING. lOI

than 0.132 yard (66 feet distance), and they should be kept as nearly
equal as possible.

The last set-up of one running must not be copied nor used as the
first set-up of a return running — that is, the instrument must be
moved so that an independent reading can be obtained.

If any measure over a section differs more than 0.02 foot from the
mean, that measiu'e must be rejected. No rejection shall be made
on account of a residual smaller than 0.02 foot

Whenever a blunder, such as a misreading of i yard or one-tenth
or an interchange of sights, is discovered and the necessary correc-
tion is applied, such measure may be retained, provided there are
at least two other measures over the same section which are not
subject to any uncertainty.

When commencing work for the day and at the beginning and
ending of each section record the time. Record the temperature
for each set-up, using thermometer readings alternately for each rod.

It is not necessary to complete the H. I. and elevation column,
but the difference of elevation for each section should be computed.

The field abstracts for precise leveling must be made as the work
progresses, on form 9-937, provided for this purpose. When original
records are completed in the field send the books immediately to
the chief geographer, Washington, D. C, by registered mail, retain-
ing the corresponding forms until notice is received of the receipt
of the original records.

Records. — ^The following special instructions are necessary in
regard to the use of prism-level notebook 9-940 when used for
primary'' or precise leveling record:

The blanks on the flyleaf must be filled in the first day the book
is used.

The blanks at the head of each page must be filled in each day.
Bench marks run between must be indicated by their letters or
numbers.

Each horizontal space between two red lines is for a single set-up
of the level.

The notes for each section of line on precise work must be com-
plete in themselves and commence on a new page. Every primary

I02 INSTRUCTIONS TO TOPOGRAPHERS.

line record must begin on a new page, and the initial bench mark
must be fully described.

The columns being counted from the left, each is used as follows:

Column I is for the readings on the rod in yards for the three
threads, each set of readings to occupy a separate space between red
lines, the first recorded reading being for the wire giving the smallest
value. The color letter is to be placed beside the first and last
readings. The recorder should notice whether the color as recorded
corresponds with the unit called out by the levelman. Each day
the levelman should verify the comparison and, if a discrepancy
exists, renm the section.

Column 2 is for the thread intervals for the thread readings in
column I, the upper ones being the difference between the lowest
readings and the middle ones, the lower being the difference between
the middle and the greatest readings of each set. (See also next
paragr£4>h.)

Column 3 is for the sums of the three-wire readings of each space
in column i, between the horizontally ruled red lines, these sums
being equal to the mean in feet of the three readings on rod.

Column 4, with the exception of the last line, is not intended for
use in precise leveling, but can be used to compute approximate
elevations, being filled out only at bench marks. On primary work
the first entry on the page at the left of the words " Elevation brought
forward from page — " should be the elevation from a previous page»
or from another book. In the latter case, give book number and
page, and always carefully verify the copying. The second entry,
below the red line and above the short black line, is the height of
the instrument as found by adding the first entry in column 3 to the
first elevation in column 4. The third entry in column 4 is the ele-
vation computed by subtracting the first fore sight from the H. I.
In each case the H. I. will always be above a short black line and the
elevation always just above a red line.

The records in columns 3 and 5 should be placed on line witli the
H. I.

Columns 5, 6, and 7 are for fore-sight readings, corresponding with
3, 2, and I for back-sight readings.

Column 8 is for the record of temperature and time.

PRECISE LEVELING. 103

Column 9 is for the correction of curvature and refraction for un-
equal sights and need not be filled out in the field.

Column 10 is for extra fore sight at points which are not turning
points, also for their sum.

Column II is for description of bench marks, for elevations from
extra fore sights, for transcripts of bench-mark elevations, and for
general remarks or explanation.

In columns 2 and 6 write next above the red lines the continuous
sums of the rod intervals for the section. The mean of the last pair
of oontinuous sums in coltimns 2 and 6, multiplied by 1,000, will be
equal to the distance in feet for the page; its equivalent in miles
and tenths can be obtained from the table in the back of the book.
The total mileage from the beginning of the section on precise work
and of the line on primary work must be given at the bottom of each
right-hand page.

A sample page from a field book follows.

I04

INSTRUCTIONS TO TOPOGRAPHERS.

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Io6 INSTRUCTIONS TO TOPOGRAPHERS.

COMPUTATION AND ADJUSTMENT OF LEVEL CIRCUITS.

General corrections. — In the computation and adjustment of level
circuits the notes are first examined for errors in field computations
or records. Corrections are next made for rod errors, including those
due to changes in temperature, these being products for each differ-
ence of elevation by the rod error. Corrections are applied if
required for curvature and refraction for unbalanced sights; also for
systematic errors for which the law is known.

Orthometric correction. — On long lines at high elevations a correc-
tion is required to take account of the fact that level surfaces along
meridians at different altitudes are not parallel curves except at the
equator and at the poles. This correction, which depends on
meridional distance, latitude, and altitude, may be found from the
following formula* :

^^ ^m(^n— ^b) sin (^n+^ g)
659,000

in which

C= correction in feet.
/(m=niean height of line in feet.
<i>% and ^n=the latitudes of the south and north ends of section, respectively,
(^n—^a)^ difference of latitude in minutes of arc.

In applying the formula the lines must be divided into sections
of not over 100 miles each, and a division should be made where the
general direction changes materially. The corrections thus found
are applied to the several sections so as to lower the elevations at
successive division points going northward. Although orthometric
corrections may at times lead to apparently absurd results, such as
giving a lower elevation for the north end than for the south end of a
large lake having no outlet, yet in order to insure agreement between
different lines and to obtain results of the greatest theoretical accu-
racy, they must be applied when appreciable.

After all the foregoing corrections are made to the original results,
the remaining closure errors are those which are to be removed by
adjustment.

Adjustment of precise leveling. — Weights are first assigned for each
class of levels, and observation equations are formed and solved by

1 Rept, Coast and Geodetic Survey for 1899, 1900, p. 875.

COMPUTATION AND ADJUSTMENT OF LEVEL CIRCUITS. IO7

"least squares." In this manner every line helps to establish the
elevation for each junction point. When all the junction points are
fixed the corrections are distributed over the lines in proportion to
distance.

Adjustment of primary leveling. — The Geological Survey in adjust-
ing primary levels has adopted a method which may be described
as follows:

All adjustments are to be made in the bench-mark description
book 9-916, in which abstracts from the field books, which include
the description and elevation of each point as determined by the
levelman, are written by him in regular order for each line as run.

All the level lines associated with one another should be con-
sidered at one time, and in order to better comprehend their arrange-
ment they should first be platted on the office progress maps as
accurately as possible and from these tracings should be made on
paper, to be used in the adjustment and later filed with the descrip-
tion book as part of the record. The plat should show the approxi-
mate relation of all the lines, including the precise or previously
adjusted lines forming the base of the system, and the work of differ-
ent grades or different men should be represented by differently
colored inks or pencils or in some other manner, a suitable explana-
tory legend being attached. The names of a sufficient number of
towns should be given to identify the location readily, and beside
each line reference should be made to the page in the description
book where the bench-mark elevations for that line are given. On
each line a > is to be placed to show the direction in which it was
run. For small areas the diagram of routes prepared by the levelman
in the description book will probably answer in place of the tracing.

The field notes should be examined to see whether the work was in
accordance with the instructions; whether fore and back sights were
equalized, rod readings properly summed, balances checked, and
elevations properly copied from page to page. The entries in the
description book should be systematically checked to see that all
elevations, including those at starting, jtmction, and closing points,
and all breaks and second runnings are properly copied. Where
two runnings of equal weight are made over one course the mean
result should be accepted for adjustment and written in red ItOtL

Io8 INSTRUCTIONS TO TOPOGRAPHERS.

with the appropriate statement in the "unadjusted elevation"
column, the divergence being given in the margin.

At each junction point on the diagram should be ^vritten the
difference between the recorded elevation by some one of the lines
and those recorded in the description book for each of the other lines
for the same bench mark, with an arrow alongside and plus or minus
signs added to indicate that the elevations as brought by these lines
are greater or less than the assumed one. Also, as an additional aid
in the adjustment, the closure error for each circuit should be written
in the center of its plat on the diagram, each amount and sign being
computed in counter-clockwise order. Next ascertain by inspection
of the diagram which of the unknown junction points may be deter-
mined with the greatest apparent accuracy or by the greatest num-
ber of independent lines. From two or more lines connecting this
point with the points of known elevation obtain two" or more possible
corrections to the assumed elevation. Estimate and record relative
weights for these corrections, the weights to be based on length of
lines (usually in inverse proportion to their length), class of leveling
instrument used, number of times leveled, and in rare cases on rela-
tive standing of observers if two are involved. Weights should not
be influenced greatly by closure errors. Where corrections from
different soiu*ces have a line in common, the length of this line
should be doubled in fixing the weights of each.

From the weights adopted compute the weighted mean correction
to the assumed elevation of the new point as follows: Multiply the
correction computed for it through each of the independent lines
from known points in turn by the weight of the line; divide
the algebraic sum of these products by the sum of the weights.
The quotient is the correction to apply algebraically to the as-
sumed elevation; it should be written in the diagram at the
proper junction point in a small loop or rectangle with the letters
"Cor." and the plus or minus sign. In complicated nets it may be
necessary to assign a preliminary correction to a junction point in
order to carry a correction from it to some other point; after fixing
the correction for the second point from its various lines a final
correction is determined and substituted for the preliminary value
ol the ^rei- noint.

COMPUTATION AND ADJUSTMENT OF hUVHh CIRCUITS. IO9

In this manner weighted values are found for each junction point
in turn, and between the points thus fixed corrections are distributed
in proportion to the distance. A line or point once thus adjusted
should not be readjusted unless readjustment is required by new
field data.

Figure 2 is given as an illustration of the method of adjusting a
level net. By inspection of the diagram, junction point E appears

A

Mean v^ B >Vr-'-^.32 5 ,

FiGURB 2. — Diagram showing method of adjusting a level net.

to be the most favorably situated for adjustment first. The line run
from A via B and E to D closed at D 0.250 foot low; from H via I to E
0.500 foot low. The correction to the recorded elevation for E on
the line from A is 0.00 by that line itself, +0.250 computed from D
by reversing the closure, and —0.500 from H. The distances to be

used in assigning weights are taken as A via B to E=— +8=13

2

miles (A to B, being a double-run line, must be given double

weight, which is done by dividing the length of the line by 2); D

to El 5 miles; H via I to E, 10 miles. The weights to be assigned

should be in inverse proportions to the length of the lines, or nearly

so. To determine the weights, divide a convenient number — a&vv^

no

INSTRUCTIONS TO TOPOGRAPHERS.

in this example — by the computation distances 13, 5, and 10 each
in turn, obtaining i, 2.6, and 1.3 for the weights of the respective
lines. These weights are each to be multiplied by the corre-
sponding assumed corrections o, +0.25, and —0.50, giving prod-
ucts of o, +0.65, and —0.65. Divide the algebraic sum of tliese
products by the sum of the weights (4.9); the quotient will be the
weighted correction; this is o for the point in question, but as
there is another line to this point which has not been conddered
this correction must be accepted as preliminary only. The fore-
going data may, if desired, be assembled in tabular form, thus:

From
point—

MUes.

Weight.

Correc-
tion.

Weight
X cor-
rection.

A....

D

H....

Sum .

13

S

10

I.O

2.6
1-3

0.000

+ .250

• soo

0.00
+ .65
- .6s

4.9

.00

Jtmction point B may be considered next. The preliminary cor-
rection for this point is taken as o, as found from three lines, two lines
from A and one from E. A preliminary correction of -fo-i foot for
I can be obtained by taking a proportionate part of the closure error
at E (one-fifth). Junction point F depends for its elevation on
values from several lines. The corrections from E, B, and I are, re-
spectively, o, —0.32, and —0.18; the corresponding distances aie la,
10, and 26; the weights 2.2, 2.6, and i.o; the resulting preliminary cor-
rection for P is —0.18. A final value for E may now be found botn
B, D, I, and F; this is necessary to include the effect of P, and by the
foregoing method it is found to be — o. 03 . G is found from Unes from
B via C, P, F via C, F via J, and I, with the computation distances ^,
7, 44, 28, and 38, respectively; in this case the distances C to G and J to
G, which are common to two lines, should be doubled in order not to
give them undue weight. The final corrections to the assumed ele-
vations are now fotmd in a similar manner, the computatioBS for B,
I, and F being repeated to secure the effect of the additional Unes,

COMPUTATION AND ADJUSTMENT OF LEVEL CIRCUITS. Ill

and are as follows: B, coo; C, —0.30; E, —0.03; F, —0.18; G, —0.38;
I, +0.09; and J, —0.18, two places of decimals only being used for
junction points. Each of these corrections is placed in a rectangle
on the diagram near the point to which it belongs.

After the corrections for the junction points are fixed, corrections
proportioned to the distance are found for intermediate points along
the several lines.

Lines on which the closure error is much over the permissible limit
must be omitted in adjustment; they may be tied in afterwards, but
in publishing the results a statement must be made cautioning
engineers against dependence on them. If gross errors are evident,
the results must not be published until the lines are renm.

For high altitudes the orthgmetric correction should be applied
(p. 106).

The computer should report to the division geographer in writing
any failure on the part of the levelman to comply with instructions;
he should also report all circuit-closure errors in excess of the allow-
able limit (pp. 92, 95, and 100). These data should also be written
on the last inside page of the bench-mark book.

SECONDARY CONTROL.
PLAlf£-TABLE TRIANGULATION.

GENERAL INSTRUCTIONS.

The projection of the sheet under consideration should be made
with the utmost care and the points plotted thereon tested in every way
possible. Both the projection and the plotting of the triangulation
points should be carefully checked by another topographer.

Before the projection is made a thorough study of all the positions
available for the control of the area should be made and the podtion
of the projection on the paper arranged so as to include the greatest
number of desirable points.

In the field it is often necessary to construct a projection without
the use of a beam compass. A substitute for this is readily made
with a wooden strip, into which is inserted a needle large enou^
to be rigid and a section of pencil.

Seasoned double-moimted paper, attached to the board by brass
thumb screws or tacks, should be used to reduce to a minimum the
unavoidable expansion or contraction caused by climatic condi-
tions, and while in use all sheets should be protected with cover
paper.

When practicable, the projection lines and as many located points
as possible should be plotted on the traverse sheet before the work
is begun, thus enabling the traverseman to check his work by three-
point location or otherwise.

Before commencmg work the adjustment of the alidade for colli-
mation and parallax should be carefully inspected. If the hill is
high and the weather is at all windy a weight should be suspended
from the head of the tripod to steady the plane-table and to prevent
accidents. The use of a large umbrella if the sun is bright greatly
facilitates the work and protects the eyes and paper. The instru-
ments and the paper should be clean from sand and grit.

112

PLANE-TABLE TRIANGULATION. II3

Substantial signals, of whatever material is in the vicinity of the
stations, should be erected on the main triangulation points and on
other prominent hilltops. Unbleached red and white cotton makes
the best all-around flagging. While placing the signals every oppor*
tunity should be utilized to learn the topography of the country, to
pick out the best subsidiary stations and to locate them on the guide
map, and to fix in one's mind the peculiarities of objects most likely
to be seen from the stations thereafter occupied.

CHOICE OF STATION.

In choosing the first station to be occupied it is best to select one of
the most prominent triangulation stations, located preferably in the
southern part of the sheet, so that w^hen the majority of the sights are
taken the topographer will be looking away from the sun. In this
way objects may be more clearly seen and peculiarities noted.
Clear atmosphere is essential when the first stations on the sheet are
occupied.

Where topographic mapping is carried on simultaneously with
plane-table triangulation, the availability of vertical control should
be considered in the selection of the initial station. In the prose-
cution of such work the topographer must necessarily locate a suf-
ficient number of points for the control of the contours. The char-
acter of the country, the amount of supplementary plane-table
traverse, and the scale of the work must be considered in deter-
mining the number of points to be located .

OBSERVING AND RECORDING.

After leveling the table place the alidade on a line connecting
the station occupied with one of the triangulation points farthest
away (the other end of the base) and revolve the table until the
farther signal is bisected by the vertical wire of the alidade and
clamp table. Verify the orientation by sights to additional visible
triangulation stations. Now make the circuit of the horizon syste-
matically and take fore sights to a definite point on prominent
objects, such as signals, cupolas, towers, chimneys, flagpoles,
monuments, church steeples, schoolhouses, dwelling houses, bams,
windmills, trees, hilltops, sptu^, etc. These sights and desccv^tks^a-

66513 — 13 — 8

114 INSTRUCTIONS TO TOPOGRAPHERS.

may be entered in notebook, and brief descriptions should be noted
on the sheet itself, along the lines of sight. Draw the lines of sight
with a chiseled edge of 9-H pencil at considerable length along the
square edge of the alidade, being careful always to hold the pencil
at the same angle and see that the contact of the rule and paper is
perfect. Get azimuths of long, straight stretches of road and rail-
road wherever possible.

After all the sights have been made adjust the striding level and
read the vertical angles to objects whose elevations are desirable
and necessary for vertical control. The stadia rod may be used for
obtaining distances and elevations in the immediate vicinity of the
station. From time to time, while making observations and upon
completion of the work of each station, ^heck original orientation
to see if any movement of the table has occurred. In mountainous
or hilly sections the topography of the top of the hill should be
sketched on the plane-table sheet for identification. After the work
on this initial station is completed repeat the operation on the sta-
tion at the other end of the base.

All triangulation stations should be occupied. Other stations
may be made by setting up the table on a fore sight, getting orienta-
tion by sighting back to the station from which the fore sight was
taken, and resecting from another station or located point. This
location is checked by sighting to some third located point. All
identifiable objects to which lines were drawn from the first station
are sighted and intersected. All intersections should be verified by
a direction from a third point. A signal should be erected when
necessary to mark place of station for future referenced Extreme
care should be used in prolonging a short line for orientation.

In areas of great relief and of difficult access advantage should be
taken of every opportunity to contour, even approximately, topo-
graphic features, such as bottoms of canyons, rock exposures along
canyon walls, ground siu^aces in heavily timbered, inaccessible
mountain gaps, and indefinite slopes of mountain masses which
practically can not be occupied.

The stations should be designated by roman numerals I, II, III,
*»tc. Each sight should have a number. All the sights to the same

^ct from other stations should retain the number, and the object

Id be A'noHTi by this number during l\ve v^^^Si^ ol >iJjv^'WQclc^

PLANE-TABLE TRI ANGULATION. II5

After completing the first station the numbers of the sights taken
from the second station should follow consecutively and not dupli-
cate those taken for the first station.

After an intersection has been made a cross ( X ) should be placed
opposite its number in the book and its elevation computed. Verti-
cal angles should thereafter be measured to this located point at
every station from which it can be seen until its elevation has been
satisfactorily determined. It should be remembered that vertical-
angle elevations have relative values dependent on the size of the
angle measured and the distance between the points.

In areas where the plane-table tri angulation is independent of
and precedes the mapping the system of symbols provided for
plane-table traverse should be used.

THREE-POINT METHOD.i

A plan frequently adopted for the location of plane-table stations
is that known as the "three-point method," which can be advan-
tageously followed when three or more previously located points
properly distributed are visible. When making three-point stations
a compass should be used for approximate orientation.

In figure 3 (p. 116) the triangle formed by the three fixed points
is called the great triangle and the circle passing through them the
great circle. When the table is imperfectly oriented, the lines
drawn from the projected points will not intersect at one point ex-
cept when the table is on or near the great circle but will form a
triangle of error.

When the new point is on or near the circle passing through the
other points, the location is uncertain. (See fig. 3, case 2.)

UTien the new point is within the triangle formed by the three
points, the point sought is within the triangle of error. (See fig. 3,
case I.)

When the new point is without the great circle, orient on the
most distant point, then the point sought is always on the same side
of the line from the most distant point as the point of intersection
of the other two lines. (See fig. 3, case 4.)

^ For mathematical solution of the three-point problem, see Rept. U. S. Coast and
Geodetic Survey for 1880, appendix 13. Idem (ot iR«iT-^%.,«>.v^wafiacK.^v ^^3wai^»:sS^2hS5.
tables and lormulas, pp 9-10, or Butt. "U . S. 0«A. S>ar5rc^ "^ti. a-^v -t^v.v^- ^"S"^'^'

Il6 INSTRUCTIONS TO TOPOGRAPHERS.

When the pcnnt sought falls within either of the three s^ments
of the great circle formed by the sides of the great triangle, the line
drawn from the middle point lies between the true point and the
intersection of the other two lines. (See fig. 3, case 3.)

The tme point is always distant from the three lines drawn from
the three fixed points in direct proporticm to the distance of the
thiee points from the point occupied.

The point sought is always to be fotmd on the same side of each
line drawn from the three fixed points; that is, if it is on the right
side of one line it is on the right side of each of the other two; if on
the left of one, it is on the left of the other two.

■/i^r^

PIOURS 3.— Diagram showing graphic solution of three-point problem.

When the true point has been estimated and marked on the
sheet, a new orientation is made. If the lines from the three fixed
points now intersect at that point, the position is determined. If a
new triangle of error is formed, the operation must be repeated.

PLANE-TABLE TRAVERSE.
METHODS.

Traversing consists of much more than getting direction and dis-
tance, though these are absolutely essential features. All the essen-
tia] topographic features on each side of the line are to be obtained
at the time the traverse is made.

PLANE-TABLE TRAVERSE. II7

Acctiracy of plane-table traverse depends on two factors, namely,
the obtaining and platting of distances and the orientation of the
plane-table.

Distances are obtained by stadia, wheel, tape, or pacing, and the
orientation is made by magnetic needle, by back and fore sights,
by the Baldwin solar chart, or by other approved solar apparatus.

When the needle is used, the accuracy of orientation is dependent
on the freedom from local attraction and the length of needle. For
these reasons it is well to avoid the use of the compass near rail-
roads, electric-transmission lines, large bodies of steel or iron, and
in volcanic regions. No plotted line should be greater than the
length of the needle.

The method employed in determining distances will be governed
by the character of the country and the scale of the work. Traverse
lines should be run along roads, ridges, streams, or at intervals in
timbered country when necessary; the method in general practice
when the needle is used is to set up at alternate stations, using
intermediate stations as turning points. Sights should be taken from
these stations to prominent hilltops, spurs, houses, windmills, lone
trees, and other conspicuous objects, and these should be intersected
at subsequent stations. Following this plan, the traverseman should
locate all railroads, roads, trails, houses, churches, schools, bench
marks, all State, county, township, and city boundaries, also all cul-
tural features as listed on page 135.

Streams should be mapped near the roads as accurately as the
skill and experience of the traverseman will permit. Especially
should streams crossing and recrossing roads traversed in ravines or
gulches be located and junctions shown with side streams.

In traversing railroads, frequent locations by three-point method
should be made if possible and the line extended by means of fore
and back sights. If this is not practicable, and it becomes necessary
to rely on the needle, it is important to set up the plane-table a
sufficient distance from the rails to prevent their influence on the
needle. The distances can be obtained advantageously by measur-
ing a rail and counting the number of rails between stations.

Where traverse is extended along roads over which levels have
been carried, note elevations marked on fences, at aRitw3xv\s»,V«:'A!i§A^>
cor ers, etc., and record same otv ttavetat ^^«X.. '^^tdr;^**^^'^^^^ '^

i

Il8 INSTRUCTIONS TO TOPOGRAPHERS.

Streams, hills, etc., sliotild be obtained in the field as far as possible —
especial care being taken to get correct ^)elling — and be written
plainly on the traverse.

Traverse should not be made to close, but should show the two
tie points by a double arrow between them; such junctions shoidd
never occur in towns or villages.

Traverses should extend a sufficient distance beyond the edge of
the sheet to overcome any possible error that may occur in the
adjustment.

Single-motmted paragon paper is ordinarily used, though celluloid
may be substituted to advantage in wet weather. Before using the
sheet the name of the State, quadrangle, date, name of the traverse-
man and that of the chief of party should be written in the lower
left-hand corner.

The proper method of plotting is to place the fractional scale divi-
sion on the old point and prick the new location with the needle at
the even division at end of the scale. This operation should be per-
formed with the greatest care, as more closure errors are to be attrib-
uted to careless plotting than to any other cause. When aneroids
are used the elevations should be recorded on the sheet at road
and stream crossings, divides, and traverse stations. To insure accu-
racy the aneroid should be compared and corrected with bench-
mark elevations whenever possible.

STADIA TRAVERSE.

In stadia traverse instrumental measurement of distances and ele-
vations gives sufficient control to permit considerable sketching to
be done on either side of the line.

Determination of elevations. — If the elevations are determined by
vertical angles, ground elevations may be carried by using a mean
height of instrument (4^ feet) as a turning point on the rod, or ordi-
nary level notes may be used with H. I. computations. Accurate
distance readings are essential, and sights for turning points should
not be over 1,000 feet, unless imder exceptional circumstances. In
large-scale detailed work 300 feet is a better limit. When the lower
hair comes near the groimd on long sights serious errors are liable
to occur at certain hours of the day through refraction. The Ander-

or Johnson stadia tables are proba\Ay l\v^ mo^X. %^\i"daLctory for

PLANE-TABLE TRAVERSE. II9

computing differences of elevation and horizontal correction. On
scales of 1:48,000, or larger, the horizontal correction can readily be
shown in plotting. On larger scales it becomes important. Angular
measurements exceeding 15° should be avoided.

Whenever possible, as in regions of low relief, elevations should be
determined by using the alidade as a level and the rod as a level rod.

Beamav stadia arc. — The use of vertical angles may be avoided by
the use of the Beaman attachment to the telescopic alidade. This
attachment consists of a stadia arc, which is screwed on the outer side
of the old arc and which carries two separate double scales having
coincident zero points marked 50 and o, respectively. Either scale
is read by reference to the common adjustable index, which, when
the telescope is level, must be set at zero point of scales before the
stadia arc is used. The two scales are:

To the right, next index, a multiple scale, with zero point marked
50, which indicates multiples for obtaining differences in elevation.
To get desired multiple, subtract 50 from scale reading and use alge-
braic remainder; for example, if scale reads 56, multiple is 56 — 50
= +6. If scale reads 47, multiple is 47— 50=— 3.

To the left a reduction scale, with zero point marked o, which
gives percentages of correction that may be used, if desired, to
reduce observed stadia distance to horizontal.

To determine differences in elevation read the distance subtended
on rod and express in feet (for example, 8.7=870 feet). Clamp tele-
scope and level. Set index exactly at 50, by means of the tangent
screw back of arc, and do not touch this tangent screw again.

Then, by means of the customary clamp and tangent movement,
raise or lower telescope until there is brought exactly opposite the
index such a graduation on the multiple scale as will throw the
middle stadia wire somewhere on the rod, it does not matter where.
The arc reading, minus 50, multiplied by the observed stadia dis-
tance gives the difference in elevation between the instrument and
a known point on the rod — that is, the height on rod indicated by
middle wire. Settings of both index and arc should be made care-
fully imder reading glass. ^^

Example: Suppose observed stadia distance is 6.3 (630 feetWulas,
that telescope is so inclined that multiple scale reads «^^, "ii^
exact setting the middle wire on rod reads "^ .1 Vl '^ ^^^'^ '^'^^

122 INSTRUCTIONS TO TOPOGRAPHERS.

number of turns of micrometer head on different bases to give dis-
tances in feet or himdredths of a mile. These tables and constants
should be tested on measured bases of different lengths at beginning
of season.

Base. — In establishing a base its bearing should be placed on the
sheet for future reference. At new station (fig. 4), if the line of
sight is not perpendicular to the established base, orient as closely
as possible, and draw a line to one of the signals. Plot the base as
long as paper will permit. Erect a perpendicular to the line of sight
at one end of base (a). Draw a line parallel to the first line of sight
through the other end of plotted base (b). Measure the distance
of the perpendicular from (a) to intersection with line through (b)
on the same scale as base was plotted. This distance (a b^) is the
corrected length of base to be used; then a b'=ab sin y. The solu-

"^^■^■^T*"

Figure 4. — Diagram illustxating correction of base line.

tion depends on the fact that the angle between the lines of sight
to opposite ends of the base is so small as to be disregarded, and
angles V and W are practically 90°. A protractor may be used to
make the angle y between the plotted base at (b) and the line (bb^)
the same as the supplement of the angle V-\-x between the plotted
base and the perpendicular erected at (a).

The same principle applies to a vertical base which may be above
or below the station occupied.

Instruments. — ^The instruments needed for stadia traverse consist
of a telescopic alidade, with compass attached, plane-table not
smaller than 15 by 15 inches, with Johnson tripod, and standard
stadia rod. Establish magnetic north line on the sheet at the
beginning of work for future orientation.

It is necessary that the stadia wires give the correct reading on

the rod. Therefore, before work is commenced they must be tested

on a measured base not less than 500 feet in length, and if an error is

PLANS-TABLS TRAVERSE. I23

found a correction must be applied to each distance measured. It
is not desirable to graduate rods to fit the peculiarities of individual
instruments.

Correct adjustment for coUimation and striding level must be
maintained. The eyepiece should give a clear-cut image, free from
parallax. To obtain this throw the object glass out of focus and
adjust the eyepiece so that cross wires are perfectly distinct and
stationary at every position of the observer's eye.

WHEEL TRAVERSE.

Revolutions of the wheel may be used for obtaining distances
along the traverse line. Tables are furnished to facilitate reduc-
tion. A hand recorder may be used as a check on long sights. A
record of distances should be kept until closures are made as a check
on plotting.

TAPE TRAVERSE.

In some parts of the country dense forest and undergrowth make
it impracticable to carry stadia or wheel traverse, and the lack of
open tops puts a narrow limit on triangulation methods. Under
these conditions, a form of tape traverse depending on aneroid ele-
vations has been devised for obtaining the topography. It is appli-
cable only to scales of i : 48,000 or smaller.

A plane-table 9 inches square, with compass attached, and Bum-
stead tripod, are best for the work. A sight alidade, 528 feet of
tailor's linen binding tape, and a pocket compass are the instruments
required. The tape should be marked at 100-foot intervals with
red ink in a manner to be clearly imderstood. It should then
be run through hot paraffin, and the rear end stiffened to avoid
catching and tangling in the brush. It will be necessary to paraffin
the tape frequently, especially the rear end, and it should be thor-
oughly dry to have the best effect. Knots and weak places should
be promptly mended with needle and thread.

The chainman should carry a pocket compass, light ax, and marking
crayon. He blazes one or more trees at the end of each tape length,
and the topographer occupies the point as his next station, thus set-
ting up at every station instead of alternate ones. The s.vsf^^ -^xs^

124 INSTRUCTIONS TO TOPOGRAPHERS.

taken in the direction shown by the tape and the signal of the ta{>e-
man. It is well to number the stations to avoid enor in makitig
closures. Lines should follow natural features, such as ridges, valleys ,
and spurs, rather than gridiron the territory. The greatest error of
the lines comes through the tapeman not keeping a straight course.
Adjustment of aneroid elevations should be made daily and the
contours altered to agree, care being taken to preserve topographic
shape and detail. Adjustment of horizontal errors should not be
made on traverse sheets.

FOOT TRAVERSE.

The method of obtaining distances by foot or animal paces is
resorted to in timbered countries and mountainous regions without
roads. Careful measurements of the average pace of an animal or a
traverseman on a level or a slight incline should be made, and a table
prepared in hundredths of miles.

USE OF ANEROID.

In certain classes of work in various parts of the country the aner-
oid, properly supported by level and vertical angle elevations, is
used to great advantage in the completion of topographic detail.

In order to obtain the best results from its use, however, the topog-
rapher should realize its limitations as a result of its delicate mech-
anism and its susceptibility to meteorologic influences.

Aneroid readings should be checked by previously determined
elevations whenever opporttmity is afforded, as well as at the begin-
ning and end of each day's work. Whenever a station is occupied
for a considerable length of time, the usual record should be supple-
mented by an additional reading made just before departure, for a
possible correction. The uncertainty of the aneroid is increased in
unsettled weather and it is practically useless immediately before
and after a thtmderstorm.

Because of its delicate mechanism the aneroid should be trans-
ported and handled with care and should be protected from all
sudden jars. It should be carried preferably in a closely fitting vest

USE OF BALDWIN SOLAR CHART. 125

or short pocket secured by string. The transportation or shipment
of aneroids across country, the elevation of which is beyond the
limits of the aneroid range, should be avoided whenever practicable.

USE OF BALDWIN SOLAR CHART.

BXPLANATION.

The chart (PI. II) consists of elliptical lines indicating the sun's
path for different latitudes from 30° to 90° N., intersected by straight
sun-time lines at 5-minute intervals; the hour lines are heavy and are
marked by their respective hoar figures. The intersection of these
time lines with latitude ellipses are called sun-time points. Fig-
ure I (PI. II) represents the portion of the chart not completely shown
in the sections between 5 and 7 o'clock. It is an auxiliary diagram
to aid in finding sun-time points between these hours. It is
divided into before and after 6 o 'clock segments, on each of which
the latitude is to be interpolated between the radial lines and the
sun time between the circular curves. A supplement to this chart
for use in latitudes below 30° is available.

Figure 2 (PI. II) is a diagram for finding daily the pivot points on
the arrow, the positions for which vary according to the sun's decli-
nation and the latitude. Figiu-e 3 (PI. II) is a diagram by means of
which local mean time may be converted into local apparent time.
Below it is the factor required to convert standard to local mean time.

To use the chart some form of stylus or gnomon that will cast a
good shadow must be provided on the alidade.

OBJECT OF THE CHART.

The chart is designed to supply a means of obtaining true north in
regions where the local conditions will not permit the usual deter-
mination by compass. When it is turned so that the proper pivot
point on the arrow and the sun-time point on the latitude arc are
on a line parallel to the shadow cast by a plumb line upon a level
table the arrow will point true north. The chart is intended to be
used with the plane-table, which may be oriented by its aid.

126 INSTRUCTIONS TO TOPOGRAPHERS.

PREPARATION OF CHART FOR USE.

Two methods may be used to adapt the chart to local use :

1. It will be found convenient in surveying an area of small
range in latitude to emphasize, by drawing in pencil or colored ink
on the main diagram (PI. II) the curve for the middle latitude of the
area under stirvey, producing the curve so as to complete the ellipse
to the 6 o'clock point. Draw the same latitude lines (radiating
from A and 6, respectively) on figures 2 and i. In Plate II such
lines are drawn for latitude 43° N.; new lines should be provided for
any material change in latitude.

2. Plate III, upper half, is a working chart constructed from the
main chart by drawing only the portions essential for Immediate
use. It consists of the ellipse for the latitude of the area, the. hour
lines, and the north-south arrow. As the chart is designed to be
used with local apparent time and to provide for daily change in
declination, figures 3 and 2 on the main chart (PI. II) will be used
for converting standard time to local apparent time and for fixing
from day to day the pivot points a and of.

Plate III, lower half, is a special chart constructed from the main
chart to illustrate the use of the figures. In figures 2 and 3 (PI. Ill)
the day lines intersect the month 's ctirve at date points correspond-
ing with noon values of declination and equation of time, respec-
tively, for the year 19 13 at Greenwich, England. For other years
and places a date correction must be made, as tabulated on the face
of the main chart (PI. II). Figure 2 (PI. Ill) is used to obtain pivot
points on the arrow, two being required for each day. The north
one is the a. m. pivot point and the south one the p.m. pivot point,
when the day is one included in the half year between March 22 aad
September 21, inclusive (that is, when the position of the sun is
north of the equator), the relative positions being reversed during
the other half of the year. The a. m. pivot point is always directed
toward and the p. m. pivot point away from the sun with respect to
the sun-time point.

Example: On July 28, 1913, find pivot point (a) and sun-time
point (b) at 10 a. m., latitude 43° N., longitude 97° W. At longitude

USE OF BALDWIN SOI^AR CHART. 12/

97® W. the local noon date point on July curve (fig. 2, PI. II) is about
a quarter day space from the 28th toward the 29th day line (97°
falling between longitudes 45° and 135° west of Greenwich). From
this point project a vertical line to intersect the diagonal latitude
line 43°. Draw a horizontal line from this intersection to the arrow.
The point of intersection of this line will be the a. m. pivot point
(a). The same distance below point C will be the p. m. pivot point
2! . Transfer these points to Plate III (upper half) if the work chart
is to be used. Note that if the date had been between September
21 and March 22 the first pivot located would have been the p. m.
pivot point. To find the sun-time point at 10 o'clock a. m., follow
the hour line 10 to its intersection with the latitude ellipse 43°,
as shown at b (PI. Ill i; this is the sun-time point.

To find the sun-time point at 6.30 o'clock a. m., same latitude,
use the auxiliary diagram (fig. i, PI. II). Follow the sun-time curve
for 6.30 o'clock to its intersection with latitude line 43°. Project
this point horizontally to the ellipse and its intersection is the sun-
time point for 6.30 o'clock at (e) on the diagram.

Figure 3 (PI. II) is used to obtain the correction necessary to con-
vert local mean time to local apparent time. This, combined with
the correction for longitude, gives the total correction to convert
standard to sun time. To convert standard time to local mean time
a correction of i minute must be made for each ^ degree of longi-
tude east or west of the center of the time belt in which work is
situated, to be added if east or subtracted if west.

Standard-time meridians ordinarily are multiples of 15° of longitude
east or west of Greenwich, England. Those crossing the United
States proper are at longitude 75°, 90°, 105°, and 120° W., and are
the central meridians of the eastern, central, mountain, and Pacific
standard time belts, respectively. Hawaiian standard time merid-
ian is 157° 30'' W., and there are some other exceptions.

To convert local mean time to local apparent time, locate on this
figure a date point by following the proper day line to its intersec-
tion with the proper month curve, and the corresponding time cor-
rection can then be read on the minute scale at the top.

Example i: Plate III (lower half), July 28, longitude 97°, find the
correction to convert standard time to sun time. Longitude 97° ia

128 INSTRUCTIONS TO TOPOGRAPHERS.

7° west of the center of the central time belt 90°, and this interval
equals a correction of 28 minutes to subtract. The July 28 date point
on the July curve is opposite 6>^ minutes to subtract. The combined
correction is therefore 34K minutes to subtract from standard time.

Example 2: On November 15, at longitude 106^ 1$^ W., the cor-
rection would be 5 minutes to subtract and 15 minutes to add, on
account of longitude and date, respectively, a combined correction
of 10 minutes to add.

Standard time can be obtained at most railroad stations or tele-
graph oflfices. The watch used should be set each day to apparent
sun time by applying the constant correction for longitude and the
daily correction for equation of time.

ORIENTATION OF PLANE-TABLE.

To orient the plane-table by use of the chart, attach the latter to
the plane-table sheet so that the arrow will be parallel to the line
on the sheet representing the local meridian. The plane-table be-
ing leveled at a station, select the sun-time point for the instant of
observation, place the edge of an open-sight alidade at the sun-time
point and the pivot point, and revolve the plane-table until the
edge of the alidade lies parallel to the shadow of a plumb line, or the
shadow of some other gnomon placed on the alidade. The gnomon
must be perpendicular to a level line transverse to the alidade edge.

Example: Plate III (upper half), at 10 o'clock, July 28, latitude
43°, longitude 97° W. Place the edge of a sight alidade at pivot
point (a) and at sun point (b), using the open sight as a gnomon to
cast a shadow on the ruler. Revolve the plane-table board until the
shadow of the sight is bisected by a line on the alidade parallel to
the edge; then clamp the board. The arrow is now in its true north-
south position.

To obtain best results it is necessary to use accurate time and to
carefully plumb the shadow plane.

In using a telescopic alidade with the solar chart it is essential
that the telescope sight line be parallel with the ruler edge; this
may be tested by means of a metal sight alidade or two pins placed
against the ruler of the telescopic alidade. The open sights (or pins)

USE OF BALDWIftJ SOLAR CHART. 129

are set on a point about 1,000 feet distant; if the cross wires in the
telescope also cut the point sighted t^ie line of cpUimation a|i4 the
edge of the rul^r ^re parallel. If ai; appreciable error \s foun4i in
order to correct it place the arrow lijie of the ch^ parallel tq the Ji^e
joining the pins, then shift ^lidadp over the chart till the telescope
cuts the point sighted ^nd draw ^ meridian line on thp chart ^Qi)g
the aliflade edge, whjch will in use be placed parallel to a inerid^a^
of the field sheet.

The length of sight on the field sheet should not exceed the dis-
tance on the chart between the sun-time point (b) and the pivot
point (a), or the length of the shadow of a vertical gnomon. This
will vary with the time of day and the season of the year.

ERRORS.

The error in azimuth caused by errors in latitude, time, and level
can be foimd graphically upon the chart for various conditions, but
it is important to observe that the error in azimuth due to error in
time is most apt to be serious. At the pole 4 minutes error in time
causes 1° azimuth error. Elsewhere, if the sun time used is not over
3 minutes in error, the error in azimuth will usually be less than i*'
before 10 a. m. and after 2 p. m.; the error at low latitude being
least, but near these homrs the error at low latitudes changes more
rapidly than at high latitudes and at and near noon is greatest. On
June 22, at latitude 30° north, 3 minutes error of time at noon will
cause about 6° error in azimuth, but at 10 a. m. and 2 p. m. it will
cause only 0.5°. At latitude 40° north the error at noon will be
less than 2.5°, whereas at 10 a. m. and 2 p. m. it will be about 1°.
To obtain good results with the chart in secondary traverse, time
error should not exceed 3 minutes in most cases, and near noon in
low latitudes it should not exceed i minute. Fast time increases
the measured azimuth of a course and since the error is greatest at
noon, a straight course run throughout one day would appear as a
slight reversed curve, the morning ctu've to the right and the after-
noon part to the left.
66512 — 13 — 9

130 INSTRUCTIONS TO TOPOGRAPHERS.

TIME CORRECTION.

Stin time can be found as described in the foregoing text. It can
also be found directly from watch time (whether tiiiat be fast or slow)
if the plane-table can be reliably oriented each morning by known
points by placing the alidade edge against the proper pivot point
and toward the sun. The edge of the alidade will then cut the true
latitude curve at sun time and by subtracting the watch time its
correction will be obtained.

MAP CONSTRUCTION.
FIELD WORK.

GENERAL CHARACTER OF ATLAS SHEETS.

Quadrangles, — ^The topographic maps of the United States Geologi-
cal Survey are designed to constitute a topographic atlas of the United
States for a geologic base. To that end they are issued in standard
sheets approximately uniform in size (lyi inches long and 12 to 15
inches wide according to the latitude), representing quadrangles,
each bounded by meridians and parallels.

Projection. — ^AU atlas sheets are based on the polyconic projection.
Each sheet is laid out independently with respect to its own medial
meridian.

S:a es. — Standard field scales are 1:192,000, 1:96,000, 1:48,000,
1:31,680, 1:24,000, and 1:12,000.

Contour interval. — The relief on all atlas sheets is expressed in con-
tours. The intervals adopted are 5, 10, 20, 25, 50, 100, 200, and 250
feet.

Contents of the map. — The data shown are essentially the same for
all maps of the topographic atlas and differ only with the limitations
of the different scales. They comprise all habitations, routes of
commimication, and other works of man that are permanent in char-
acter; the boimdaries of civil divisions, reservations, and grants, as
well as the lines of the public-land surveys, accurately determined
useful elevations; water features, swamp and marsh land; relief
features, and the names of all features, cultural and natural.

PRELIMINARY INSTRUCTIONS.
PREPARATORY WORE.

Preparation of field sheets. — Before starting for the field, the topog-
rapher should prepare his field sheets in the form best suited to the
conditions under which his work is to be carried on.

132 INSTRUCTIONS TO TOPOGRAPHERS.

Drafting of projections. — Coordinates for projections should be
taken from the poly conic projection tables.^ Whenever convenient
the plotting may be expedited by the use of the Bumstead projector
(i : 48,000 and i : 96,000). Whether this device be used or not, each
projection must be subjected to a thorough test by some person other
than he who did the plotting. It does not suffice that he merely
repeat the plottings of the first draftsman with the figures used by the
latter. A true check consists of independent computations and
measurements throughout. The verifier should therefore enter the
tables anew, replot the coordinates, and, as a final test, measure the
over-all dimensions of the projection and compare the length of its
diagonals.

The plotting of primary control points should, similarly, be checked
by independent measurements.

Data from other surveys. — Existing map material of Federal, State,
and municipal siu^eys and other authenticated organizations
should be diligently sought. Maps of the General Land Office, the
Coast and Geodetic Survey, the Hydrographic Office of the Navy,
the Corps of Engineers of the Army, the Mississippi River Commission,
the survey of the Great Lakes, the National boundary surveys. State
boundary surveys, boundaries of National parks, forests, monuments,
game and bird preserves, Indian and military reservations, land
grants, surveys made by the Reclamation Service, Forest Service,
and Bureau of Soils, should be examined and such of them as prove,
on field examination, to be adequate, should be incorporated in the
field sheets, with proper recognition.

All such material will, upon requisition, be reduced by photog-
raphy to the field scale.

Sheet borders. — It is of prime importance that contiguous atlas
sheets shall join perfectly, so that, when they are laid edge to edge,
the lines on them shall pass without break or offset from the one to
the other. In order to insure such perfect joining, compliance with
the following rules is necessary:

Before beginning field work on a new sheet, the topographer should
procure a border strip from each adjoining sheet already mapped,

■' Geographic tables and formulas, pp. 38-94; Bull. U. S. Geol. Survey No. 234, 1904,
/"" - - Also Coast and Geodetic Survey Special Publication No. 5, 1910.

MAP CONSTRUCTION. 1 33

such border strip to embrace a width of at least i mile and to be
photographed to the field scale.

Should it appear in the progress of field work that the older sheets
contain inaccuracies, or are not up to date as regards developments
in culture, the new work shall be considered as standard and the
older work be revised for such a distance over the border as may be
necessary to effect a good adjustment (geliefally not over a mile).

vShould the older sheets prove so deficient in quality, or so far out
of date as regards culture that faidical revision would be required to
make them join to the new work, the topographer must at once
report the matter to the division geographer.

Border corrections to be applied to sheets already published should
be submitted on tracings upon completion of the inking of the new
work.

Wherever the adjoining sheets have not been mapped, the field
work should be carried across the border of the new sheet for approxi-
mately one-half mile.

Identification of field sheets. — It is of the utmost importance that
every field sheet, whether plane-table or traverse, should be marked,
before work is begun on it, in a manner that will insure its ready
identification. Accordingly, each should bear on its margin in
indelible black ink the name of the State, the name of the quadrangle,
the scale and contour interval, the name of the person responsible
for the mapping, and the year in which the work was done. The
latitude and longitude must be clearly marked in pencil at each of
the four comers of the projection.

NAMES.

Nanics to be shown. — The rtlap should show the names of —

Cities, towns, villages, and other settlements, including all coun-
try* post offices and railroad stations. (Where the name of a rail-
road station differs from that of the corresponding post office, both
naitfes should be shown, the one most widely known being given the
greatef pltrminence and the other being followed by P O or Sta, as
the case itiay be.)

Country schoolhouses.

Country churches.

Isolated ranches constituting important landmarks in a^iax^ft-V^^
settled districts.

134 INSTRUCTIONS TO TOPOGRAPHERS.

Important public institutions, such as universities and colleges,
State hospitals, asylums, and penitentiaries.

Railroads (steam or electric). In addition to the name of the
system, it is desirable, as a rule, to give the name of the branch,
line, or division.

Highways, turnpikes, and boulevards.

Bridges, ferries, and fords.

Through trails.

Important steamboat routes on large lakes.

Important canals, ditches, aqueducts, etc.

Timnels, dams, lakes, reservoirs, and other public works.

Lighthouses, lightships, and life-saving stations.

Parks and cemeteries, if scale will allow.

Isolated mines, quarries, prospects, and oil wells.

Isolated furnaces and smelters.

Civil divisions.

Reservations.

Hydrographic features.

Springs, wells, and tanks, especially in arid regions where these
features are of vital importance.

All relief features.

Authority for names. — ^The topographer should utilize local oppor-
tunities for obtaining the correct names and spelling of all features
shown on the map and not resort to correspondence on this subject
after his return to the office. The general policy should be to con-
form to local usage.

New names. — In unsettled or sparsely settled regions it may often
be found desirable to give names to the more important land and
water features as a means of reference. Such names must be sub-
mitted through the geographer in charge to the chief geographer
with full particulars showing their appropriateness for final action.
The selection of new names should not be a mere matter of whim
but should be made with due consideration of their geographic
value and significance. Following are some of the principles
adopted by the United States Geographic Board:

{i>> ~~ « suggested by peculiarities of the topographic features

1 as their form, vegetation, or animal life, are gener*

but duplication oi ivamts, ^s^^casJCv^ within ooit

MAP CONSTRUCTION. 1 35

State, should be avoided. The names " Elk, " " Beaver, ** " Cotton-
wood/* and "Bald" are altogether too numerous.

(6) Names of living persons should be applied very rarely, and
only those of great eminence should be thus honored. No personal
names should be attached because of relationship, friendship, or
personal interest.

(c) Long and clumsily constructed names and names composed of
two or more words should be avoided.

(d) The possessive form of names should be avoided unless the
object is owned by the person whose name it bears.

(e) The multiplication of names for different parts of the same
featiu-e, such as a river or mountain range, should be avoided. Only
one name should be applied to a stream or mountain range through-
out its length.

Such names as "East Fork ** and "North Prong " for branches of
a river should be avoided unless there is a special reason for their
adoption. Independent names should commonly be selected.

MAPPING OF CULTURAL FEATURES.

Features to be mapped. — The following cultural features are to be
shown on all topographic atlas sheets by conventional signs, as shown
on pages 205-228.

Aqueducts, water and oil pipes. Locks.

Bench marks. nes and quarries.

Boundary lines (civil). Oil tanks.

Boundary monuments. 1 Oil wells.

Bridges. Power lines.

Buildings. Primary traverse stations.

Canals and ditches. • Prospects.

Cemeteries. Railroads.

Coke ovens. Reservoirs.

Dams. Roads.

Ferries. ' Steamboat routes.

Fords. i Trails.

Land corners. Tramways.

Land grants. Triangulation stations.

Land survey lines. Tunnels.

I,evees. cuts, and fills. ' United States location monuments.

Life-saving stations. United States mineral monuments.

Lighthouses. Wharves, docks, jetties, etc.

Lightships.

136 INSTRUCTIONS TO TOPOGRAPHERS.

Roads. — Under roads are included all streets and roads, public
and private. Distinction is to be made between first-class and
second-class roads, the former being shown by solid double parallel
llneS) the latter by broken double parallel lines. Metaled roads,
further, are to be distinguished on the engraved map by having
one of the two lines accentuated. On the field sheets it may be
convenient to represent roads by single lines, but it is nevertheless
important that the class of each mad shall be indicated on them in
S^Me Way. A isimple method of marking consists of placing a figure
or letter on each stretch of road, thus — i standing for first class, 2 for
seeotld class, M for metal. This should be done promptly, as fast
as the road traverses ore tun.

The classification of roads is governed by the following criteria:

First-class roads include all State, county, or other public roads
ih such condition as to be available for ttavel; all main or throflgh
fi^ads In ^arsely settled mountain or desert regions, regardless of
condition; all city streets and park and cemetery drives.

Second-class roads include all public roads which through disuse
or neglect have become impassable or can not be traveled without
risk (through roads in sparsely settled Regions excepted in accord-
^c^ with the fotegoing^ paragraph) ; all neighborhood roads in rul*al
districts (except those of sufficient importance to be regarded tts
through roads); all private roads, lanes, and stub roads to farms and
country houses.

Metaled roads include those first-class roads which are paved or
have a dressing of macadam, telford, gravel, or asphalt. Even a
thin layer of gravel or broken stone applied without specially pre-
pared subgrade and covering only a strip wide enough for one
vehicle is held to constitute "metal."

In areas where public highways generally follow the section lines
of the land suirvey the classification of roads is to be made with
reference to ownership and pei'manency of location, rather thati
condition or amount of travel. Roads which are considered per-
manently located include those along section lines and those which
leave the section lines for short distances to avoid natural obstacles.
Roads thus permanently located, when following a section liae fbf

MAP CONSTRUCTION. 1 37

one-fourth mile or more, are to be classed as first-class roads. Diag-
onal roads following section lines here and there are to be classed as
private, unless they constitute the main through routes of travel.

Lumber or wood roads generally are to be omitted, but any prin-
cipal through lumber roads which may be properly considered
permanent cultural features are to be shown by the second-class
symbol.

On the 1:192,000 scale no distinctions are to be made between
roads of different classes. They are all double parallel lines.

Buildings. — The map must show all buildings of a permanent
character, such as dwellings, public buildings, shops, factories, and
other industrial establishments; it should be reliable not only as
regards their location . but also as regards their orientation — ^that is,
the way each building is set with respect to the points of the compass.

Uninhabitable dwellings, whether farmhouses or miner's or lum-
berman's cabins, are to be shown only when they constitute impor-
tant landmarks in regions of sparse culttu-e.

The conventional black square is to be used for all buildings
except those of larger structures whose dimensions plotted to scale
actually exceed the size of the symbol. These should be shown
with their individual plan outlines. On large-scale maps all houses
may have to be thus shown.

On the i: 192,000 scale only isolated houses in the country should
be shown; those in towns and cities should be shown by a conven-
tional symbol giving the outline.

Houses should not be shown conventionally contiguous to the
roads, imlcss the actual distance that separates them from the edge
of the right of way can not be plotted on the scale of publication.

Detached houses in residence portions of cities, suburbs, and
villages are to be shown separate wherever possible. When the
scale does not permit individual houses to be shown, indicate the
group by a solid block.

Churches and school ho uses. — Churches are to be distinguished by
a cross and schoolhouses by a pennant; such cross or pentiant should
be attached to the house symbol, so as to point at right angles to the
roadway and not necessarily to the north. In centers of dense
culture these distinctive symbols should be omitted. Buildings

138 INSTRUCTIONS TO TOPOGRAPHERS.

used both for schools and for religious services should bear the
school symbol.

Railroads. — ^Under railroads should be included all steam and
electric railroads. Steam railroad lines are to be shown by the
regular railroad symbol; electric lu-ban, subiuban, or interurban
lines, lumber and mining roads, and tramways by a symbol on
which the crossties are placed closer together; and aerial tram-
ways by a broken black line with name.

Double tracks, railroad yards, spur tracks, and switches should
be shown so far as the scale will permit. Separate railroad lines in
juxtaposition and parallel tracks belonging to the same road should
be differentiated by placing the crossties as shown on the symbol
chart.

Railroads within a roadway should be shown by fine cross lines
not extending beyond the road lines; suburban electric lines, tram-
ways, etc., should be differentiated from long-distance lines by
closer spacing of the symbol.

A railroad-station building should be represented conventionally
by a large or elongated house symbol placed across the tracks. A
station without building should be indicated by name only.

Bridges. — The following classes of bridges should be shown by
symbols: All road bridges across double-lined streams; all road
bridges across single-line streams in sparsely settled regions or
wherever the existence of the bridge is vital to the use of the road;
all road bridges over canals and ditches not crossableotlierwise; all
important viaducts over railroads, railroad yards, roads, or streams.

Drawbridges on roads and railroads should be shown by a separate
symbol . Ordinary bridges and trestles on railroads are to be omitted.

The bridge symbol should further be omitted wherever in centers
of dense culture its presence would tend to confusion or impair the
legibility of the map; also on reconnaissance maps except where
it indicates important structures over streams othenvise difficult
to cross.

Ferries. — Ferries are to be shown by symbol wherever the stream
is wide enough to permit; where it is too narrow (this applies espe-
cially to the smaller scales), the ferry is to be indicated by the
wr ' " mes of ferries must be put on the map.

MAP CONSTRUCTION. 1 39

Fords. — The symbol for fords is similar to that for second-class
roads. On large-scale special maps the route of the ford, if diffictilt
to follow, should be shown, with its characteristic windings.

Trails. — In mapping trails the topographer should consider their
relative importance as a means of communication. Thus, in moim-
tain and desert regions, especially in the far West, where travel is
largely by trail, he should take pains to map every trail in use,
giving its name, if known; in the more densely populated districts,
where railroads and wagon roads are plentiful, he should show only
such trails as lead up mountains or through unimproved areas not
readily accessible otherwise. A mere "way through'* not regu-
larly traveled does not constitute a trail.

Steamboat routes. — Only those steamboat routes on lakes and
rivers are to be indicated over which a regular public service is
maintained by ferries or passenger boats.

Canals and ditches. — Canals, whether for navigation, irrigation, or
drainage, should be shown by double-line symbol only when their
actual width can thus be indicated on the scale of publication;
otherwise, by a single blue line.

The mapping of irrigating ditches is to be restricted to the main
feeders; laterals are not to be shown except on large-scale special
maps. On smaller scales only those ditches which constitute im-
portant landmarks in regions of sparse culture are to be indicated.

Canal locks. — ^The lock symbol should point upcurrent.

Aquedticts; water and oil pipes. — Only the more important aque-
ducts and pipe lines should be mapped.

Tunnels. — ^Tunnels of all kinds, whether on railroads, roads, or
canals, should be shown by the tunnel symbol; the route of the
tunnel should be indicated by double broken lines (black for rail-
roads and roads, blue for canals).

Dams. — Permanent dams on streams, lakes, or reservoirs should
be indicated by a heavy black line. Where a wagon road follows
the top of the dam, the road is to be shown in its correct place, the
road line on the upstream side being thickened to represent the dam.

Reservoirs. — ^Artificial reservoirs surrotmded by dams on all sides
should not be inclosed by the dam symbol, but should be outlined
in blue, like lakes or ponds.

I40 IN^TRl'CTIOXS TO TOPOGRAPHERS.

Levees. — Levees and cuts and fills should be represented by the
hachure symbol only if they are too small to be shown by cantotUB.

Cuts and fills. — ^The rule as to hachure symbols for levees applies
also to cuts and fills.

Mine dumps. — All mine dumps of sufficient size to deserve mapping
Should be hachured. Larger ones should be contoured, but fliiould
also be hachured, so they may not be mistaken for natural hilto.

Wharvesj etc. — ^Wharves, docks, jetties, breakwaters, and similar
stftlctures should be indicated by heavy black lines with such detail
as the scale of the mappiug permits.

Lighthouses, etc. — Lighthouses, lightships, and life-saving stoticMis
are to be shown by their respective symbols on all maps, whatever
the s<iale.

Cemeteries. — If of sufficient size, cemeteries should be shown with
their actual outlines; if too small for this, by a square outline in-
dosing a cross. Small private cemeteries should be omitted.

Mines, quarries, and wells. — Maps should show the location <tnd,
wherever practicable, the elevation of all mines, quarries, open pits
of clay, marl, or other material of commercial importance; all min-
eral prospects exceeding lo feet in depth, and all coMnXty c^al banks;
and all deep wells, whether drilled for oil, gas, or water, except
where such wells are so abundant as practically to be indistinguish-
able, in which case only the approximate outline of the podl is to
be shown.

These are to be recorded in red on the original sheets, but are not
to be engraved on the topographic maps, unless they refer to Odm-
mcrcial mines of coal, iron, clay, manganese, or bskUxite, or to tfldne
qttarries, or to exceptionally important and permanent metallif<£tmis
mined. Their commercial character may usually, though not inva-
riably, be judged by their possession of railway s\^'it<iheS Of ddeks,
to facilitate transportation, or of equipment perffldnent in charaiCifer.
Lack of these would exclude from the engraved maps prospect pits,
j^afts, or drifts and coal mines or clay pits worked only to M&pply
neighborhood demands.

In sparsely settled regions, where there is little culture to be rep-
r&Mtiited, isolated mines, quarries, and even prospects which ooniti'
tute important iandmarks and are widely kno\m, should be fihowli
black with their names and s\vou\d\^e etv^x^xt^.

MAP CONSTRUCTION. 141

The above rules apply only to standard-scale maps. On special-
scale mining map>s all mining features may have to be engraved,
even prospects and oil wells. It is for this purpose that the special
mine symbols, such as shafts, tunnels, drifts, etc., are provided.
On the standard atlas sheets only the crossed pick-and-hammer
symbol for mines and quarries and the sawbuck cross for prospects
should be used.

Furnaces and smelters. — No additional conventional sign is con-
sidered desirable to represent furnaces, and in many cases it will not
be practicable or desirable to name them. In sparsely settled
regions, however, the furnaces are frequently the most important
and persistent landmarks . They have well-recognized names , which
cling to the localities even after the practical disappearance of the
furnace itself. In such cases, therefore, it is desirable that the names
be given, even if nothing remains but a ruined stack. The same
rule applies to smelters, except that those located may be restricted
to smelters in active or prospective operation.

Coke ovens. — Only coke ovens connected with mines in operation
are to be shown on the engraved maps. Those attached to perma-
nently closed or abandoned mines are to be omitted.

Civil boundaries and boundary monuments. — All civil botmdaries,
whether National, State, county, district, civil township, reservation
(National or State parks, forests, game preserves, Indian, military,
or lighthouse), land grants, corporations (city, town, or borough),
parks, and cemeteries, are to be shown on the map by their respective
symbols. Special effort should be made by field parties to locate
such boundaries with acciuracy and directly from triangulation or
primary traverse stations if practicable.

Necessary descriptions, survey notes, and plats should be con-
sulted or secured of all lines of importance. Data on National or
State reservation boundaries should be obtained at or through the
Washington office prior to the beginning of the field work. Data on
minor civil subdivisions can best be procured locally, while the
survey is in progress. Many boimdaries are obscured or obliterated
by natural causes or artificial works; some are indifferently marked
to begin with; others have lost some or all of their marks. Infor-
mation frjm local settlers may often prove of value and save tvtsss:.

142 INSTRUCTIONS TO TOPOGRAPHERS.

and eflfort in the search for such obliterated lines. The tof)ographer
will do well to avail himself of it; at the same time he should bear
in mind that the word of a resident is not to be taken as authoritative,
but merely as an aid supplementing information from official sources.

All monuments on national and State boundaries must be located
in the field and represented on the map with the appropriate symbol.
On other boundaries it is desirable that monuments occupying con-
trolling positions, such as comers or important crossings, be located.

Where lines are found incorrect in azimuth and distance as the
result of field errors, it is a fundamental principle that the line
marked on the ground is the de facto boundary, and is to be shown
on the map in its actual position, regardless of what the statute calls
for. This may necessitate in some cases the accurate locating of a
number of monuments so each error in the alignment may be desig-
nated at the particular spot at which it exists.

Some civil boundaries are defined by statute to follow natural
boundaries, such as streams or divides between watersheds. Those
following large rivers should be given special attention, as they may
be variously defined as following the "middle" of the stream, its
main ciurent, or one of the banks.

Public-land surveys. — All public-land survey lines must be shown
on the topographic atlas sheets, and to this end it is necessary that a
number of "comers" on them be accurately located in the field and
shown on the engraved maps by a black-cross symbol.

In order to expedite the work of locating comers, party chiefs
must provide themselves, before taking the field, with copies of
plats of the land surveys of the assigned areas. These plats should
be assembled in the form of a combined plat, reduced to the scale
of mapping, on tracing paper or linen. A detailed description of
important comers may prove valuable in recovering them.

The topographer should be familiar with the system of rectangular
land surveys and the various intricacies peculiar to it. The more
conversant he is in these matters the more intelligentiy will he be
able to make use of land-office data. Acquaintance, further, witji the
standard monuments used for the various classes of land comeiSi
their marks, and their bearing trees, as well as with the ma^n n^r in

MAP CONSTRUCTION. 1 43

which blazes on trees become overgrown with bark, will prove most
useful both in searching for comers and in determining their authen- *
ticity where this is in doubt. (For a discussion of the public-land
survey system see pp. 183-192.)

United States mineral locating monuments, — ^Monuments erected as
permanent reference marks for the location of mineral and other
claims (often designated as USLM's) are important and should be
located with the same accuracy as land-siurvey comers and be shown
on engraved maps.

Triangulation and monumented primary-traverse stations. — Triangu-
lation and primary- traverse stations should be indicated on the topo-
graphic maps with the open triangle symbol only (without name).
Wherever practicable, the elevations of these stations should be
determined, either by levels, stadia, or vertical angles, and be
stamped on the tablet or post that constitutes the permanent mark.
If vertical angles have been used, the letters V. A. are to be stamped
below the elevation figures.

Bench marks. — All permanent bench marks must be accurately
located in the field and shown with their elevations on the engraved
maps. Topographic field parties should not rely upon finding bench
marks by search simply, but must locate them systematically with
the aid of the descriptions furnished by the level parties.

Temporary bench marks and other elevation marks. — ^AU temporary
bench marks (see p. 89) must be looked for in the field with a view
toward their inking in on the final office drawings. Temporary
bench marks will be inked with a large red location cross and with
black figures of elevation and will be engraved, but whenever inter-
fering with map legibility they may be shown with red figures of
elevation and not be engraved. Besides the permanent and tem-
porary bench marks it is desirable that the engraved maps should
carry a number of other reliable elevations distributed over the
entire area mapped. They should be spaced at intervals of about i
mile on the 1 162,500 scale and about 2 miles on the i : 125,000 scale.

In selecting elevations for publication on the maps, the topographer
should bear in mind that it is the policy of this Survey to publish
only such elevations as have a definite working value (p. 89).

144 INSTRUCTIONS TO TOPOGRAPHERS.

All elevation data must be assembled on an oversheet tracing in
the field, as the small elevation figures which have been placed on
the field sheets themselves are ever in danger of being erased or sc
obscured as to be illegible. On such an oversheet distinction be-
tween the different classes of elevations may readily be made bj
using different inks.

MAPPING OF HYDROGRAPHIC FEATURES.

Features to he shown. — The hydrographic features to be shown oi
all topographic maps are —

Shore lines. • Lakes, ponds, and sinks.
Tidal flats. Intermittent lakes.

Tidal (salt) marsh. > Dry salt lakes.

J, (Perennial. ; Fresh n^arsh.

^Intermittent. ' Submerged marsh .

Dry stream courses.

Springs.

Wells, tanks, and reservoirs.

Wooded marsh.
Glaciers.

Shore line. — On all topographic maps of the Geological Survey th«
line of mean high tide is considered to be the shore line.

Changes in shore lines. — Reported changes in shore lines should be
verified by independent field measurements before being adopted.

Tidal (salt) marsh. — Tidal marshes on low coasts are as a mk
traversed by a network of tidal channels. Unlike the rills in mud
flats these channels are fairly permanent in location and should be
mapped individually S3 far as the scale permits.

Large rivers. — Broad rivers which are to be water-lined on the
engraved map offer a perplexing problem to the topographer, as,
owing to their periodic fluctuations, their width often varies signifi-
cantly with their stage. The general rule is that the width shown
should correspond to the normal stage.

Bars should be "sanded" on the final map, and the limits of the
sand area indicated in pencil on the field sheets.

In areas where the flow of streams, though active for brief periDds.

dwindles or ceases altogether for many months, the normal or pie*

vailing stage is very low. Thus, rivers like the Platte are normallf

hraJded streams, and should be represented as such on the nuf

Many rivers in the desert regiotvs present nothing more than had

sandy washes and should be shovjtv \sy ^tKv^ ol ^asv.^\sM|^,

MAP CONSTRUCTION. I45

Mapping of river bank?. — If the contour interval is too large to
permit the delineation of river banks by contour lines, hachures
should be used, a single row being sufficient.

Double-lined streams. — No stream should be double-lined unless its
actual width can thus be shown on the scale of publication without
need of exaggeration.

Perennial streams. — The topographer will show on his field sheets
all perennially flowing streams that the scale of publication will
permit; to prevent confusion in inking, his field drafting should
clearly distinguish between perennial and intermittent streams.

Intermittent streams. — Intermittent streams are those having alter-
nating pools and dry stretches, or those flowing for only part of the
year.

On his penciled field sheets the topographer can not show too much
of the intermittent drainage. For the engraving, to be sure, only the
more important drainage courses are to be inked, but for the construc-
tion of the map all drainage lines are of value. They constitute a
controlling element of all normal-erosion topography, and serve as a
natural skeleton for the construction of the contours. Indeed, the
systematic tracing out of the drainage net can not be too strongly
recommended; the earlier the topographer begins to cultivate the
habit the more successful he is likely to be in his work. Even in
volcanic, sand-dune, or glaciated areas, where the topographic fea-
tures have been shaped by agents other than running water, the
drainage lines will often be invaluable to the topographer in making
clear the real nature of slopes and irregular surfaces that are in them-
selves deceptive to the eye.

Disappearing streams. — Many streams in limestone regions abruptly
sink into caverns and continue their courses for long distances
through subterranean channels. Special care should be given to the
mapping of this type of drainage; the points of disappearance and
reappearance should be accurately located.

Springs. — ^The importance of springs is dependent on their relative

usefulness as a part of the water resources of the region in which they

occur; and that is the criterion that should govern their mapping.

Thus, although it would be entirely proper to omit springs in large

66512 — 13 10

146 INSTRUCTIONS TO TOPOGRAPHERS.

numbers from maps of well-watered regions, it would be manifestly-
improper to leave them oflf from any map, even the merest recon-
naissance, of desert regions. There, springs are literally of vital
importance, and their omission or erroneous location may have the
gravest consequences to those dependent on the map. In such
regions it is further desirable to indicate the name by which each
spring is known. Intermittent, alkali , or undrinkable springs should
be so designated on the map.

Wells and tanks. — ^The importance of wells and tanks, like that of
springs, depends entirely on their relative usefulness as a part of the
water resources of the region. In semiarid regions both wells and
tanks must be shown. Wells, if artesian, should be so designated.

Lakes, ponds, and sinks. — Wherever doubts arise as to the limits of
lakes, ponds, or sinks, the line of the permanent land vegetation
should be mapped as the boundary.

Intermittent and dry salt lakes. — Shallow lakes and ponds which
are dry for many months each year and dry salt lakes are a physio-
graphic feature typical of some regions, and all those not too small
for the scale must be shown.

Fresh'Water marshes. — ^Fresh marsh and swamp land is defined as that
not suitable for cultivation without first being drained. All lands
of this class should be shown on the published map with fresh-marsh
symbol.

Submerged marsh. — ^Marsh lands that are partly submerged for
many months each year, are to be differentiated from ordinary marsh
and represented by a special symbol combining water and marsh
tufts.

Glaciers. — The area of each glacier is to be outlined by a dotted
(blue) line, and its surface is to be contoured (with blue lines on the
final map) with the same contour interval as that used for adjoining
land surface, and with the same degree of accuracy.

MAPPING OF TOPOGRAPHIC FEATURES.

CONTOURS.

For the cartographic representation of land forms several S3rstems
}Ie, but that which has proved most useful and has become

MAP CONSTRUCTION. 1 47

the standard in Geological Survey work is that of contour lines.
The superiority of this system lies in the fact that not only is the
vertical interval between the lines capable of being regulated to
suit the character of the relief, but each contour, being a line of con-
stant elevation lying wholly within a "level surface" parallel to
the spheroid of sea level, projects upon the plane of the map with a
minimum of distortion. It appears for all practical purposes with
its true length and true deflections, and consequently represents the
contour of the ground at a given level with exactness.

It requires more than one line to define a surface of any kind. At
least two lines are necessary to determine geometrically the position
of a simple plane, and many lines are needed for the adequate repre-
sentation of the cur\''ed or warped surfaces with which the topogra-
pher has to deal.

DELINEATION.

Uniformity in practice. — Uniformity in practice in the delineation
of topographic features is essential if harmonious results are to be
obtained, and although much of the divergence in style of contour-
ing arises from a deficiency in training of eye and hand in the artistic
phases of the work, some of it may be attributed to a lack of recogni-
tion of basic geometric and physiographic principles. The following
suggestions may assist in obtaining the required standard.

Methods of contouring. — In regions where the principal control is
obtained by different kinds of traverse generally extended along
])ublic highways, the usual procedure is to first contour the country
along the route of a given circuit; and then to complete the interior
of this particular circuit, subdivided by additional control which
will be a sufficient base for the accurate delineation of all essential
features required by the scale and contour interval. This subdi-
visional control may consist of one or more of the several kinds of
traverse, of intersections obtained from plane-table stations, or of
such a combination of methods as will in the judgment of the topogra-
pher secure the most accurate and economic results.

The method of contouring regions of bold relief, where all the
features are plainly visible, is that of delineating one feature at a
time; of drawing all the contours on one land form before commencltv.qf^

148 INSTRUCTIONS TO TOPOGRAPHERS.

on the next. To apply this method to best effect, the topographer
should learn, in the first place, to parcel the landscape into its con-
stituent masses or unit forms. The simpler and more easily con-
ceived their conformation the more readily and surely the delinea-
tion will proceed. He should, therefore, deal with each mountain,
hill, or spur, as a unit. He should, after sufficient control has been
established, segregate it from its neighbors by locating the drainage
lines that form its natural boundaries, and should, u^erever it is
practicable, trace out the crest lines and divides. These and the
drainage lines together constitute the natural skeleton upon which
to place the contours. This skeleton outline once prepared, it is
a relatively easy matter to locate the contours themselves. The
individuality of each unit should be kept in mind and all the lines
expressing its form should be drawn in succession in their correct
relations to one another. Each spur on a hill or mountain side
should thus be delineated with its own characteristic shape.

It is best, as a general rule, to use convex forms as units, the
intermediate drainage lines being used as boundaries.

Use of form lines. — It is realized that practical difficulties often
prevent the topographer from adhering rigidly to the method out-
lined. Incompleteness of control is a common interfering factor.
The upper parts of a hill or mountain may be ready for mapping,
while nothing is as yet available to determine the foot of the slopes.
In such cases it may be advisable to extend the sketch beyond the
control points and to indicate provisionally by "form lines" the
configuration of the lower slopes.

In regions of moderate relief, where each feature takes but a few
contours or where the mapping is done at short range, this mode of
provisional sketching by "form lines" is unnecessary, but when
dealing with intricately sculptured mountains it is often an absolute
necessity.

Topographic expression. — The topographer must possess, in addi-
tion to his qualifications as an engineer and surveyor, the ability to
delineate topographic features Avith such fidelity as to produce a
map which will clearly indicate the physiographic character of the
country.

MAP CONSTRUCTION. 1 49

It is most desirable, therefore, that the topographer should have a
thorough grasp of his subject. The features of the land must be
something more to him than a meaningless jumble of hills and
hollows. He must recognize the system that runs through them
and understand the significance of their individual shapes. The
smaller the scale he is working on the more important will such
physiographic knowledge be. Large-scale maps, on the other hand,
are less of a problem, as all features not insignificant in size can be
adequately shown on them. But in delineating even large-scale
maps with abundant control, physiographic knowledge is necessary.
Such maps are usually regarded as equivalent to engineering plats
in acciu'acy and are therefore bound to be correct. But, however
numerous the locations controlling a given contour, it is always pos-
sible, so long as they are an appreciable distance from each other
on the paper, to give the line different significant shades of mean-
ing, each equally justified by the control. That line is likely to be
nearest to the truth that is drawn most intelligently, with the fullest
comprehension of the character of the feature expressed. Geometric
knowledge, essential though it be, clearly is not alone sufficient;
the most accurate geometric concept of a land form is likely to
appear "wooden" or lifeless on a map, unless it is vitalized into its
real significance by an intelligent insight. It is, therefore, important
that the topographer have sufficient knowledge of physiographic
and geologic structure to understand the type of land form with
which he is dealing and to realize wherein its peculiar character
resides.

MAPPING OP LAND-CLASSIFICATION DATA.
GENERAL REQUIREMENTS.

Each member of the topographic branch when engaged in topo-
graphic mapping west of the looth meridian or in areas containing
public lands, national forests, or national parks east of that meridian,
must make the field observations and local inquiries necessary to
enable him to submit to the land-classification board a plat and
written report containing such land-classification data as will indi-
cate the possible uses of the lands which he maps.

150 INSTRUCTIONS TO TOPOGRAPHERS.

Such reports will be based only upon facts personally observed
by topographers or their assistants or obtained by them through
inquiry from known and reliable sources. Both graphic and written
reports must be signed and dated by the person or persons preparing
them, and must bear the names of the chief or chiefs of party, the
names of assistants engaged in collecting the material on which it
is based, and the date of the field work.

The general character of the information desired by the land-
classification board will appear from the following list of subjects on
which it is required to report to the Director for his submission to
the Secretar>^ of the Interior:

(a) Designations of (i) areas which are not susceptible of successful
irrigation at a reasonable cost from any known source of water supply
and which can, therefore, be entered under the general pro\dsions
of the enlarged homestead act (as suitable for dry farming); and (2)
lands in certain arid States which do not have an available supply
of water (either surface or ground) for domestic purposes such as to
make continuous residence on the land possible.

(b) Recommendations as to withdrawals of lands for water jxjwer,
reservoirs, and public watering places.

(c) Recommendations for the protection of mineral resoiu-ces and
for other public uses.

(J) Reports on the valuable power-site and reservoir possibilities
involved in (i) applications for rights of way for railroads or for
canals, ditches, reservoirs, etc., included in power and irrigation
projects; (2) proposals for alienation of tracts of land in Indian reser-
vations and in the public domain under any of the laws providing
for such alienation; and (3) designations by Congress for special
alienation or use of whole Indian reservations and other areas.

The board should be notified of the presence of any deposits of
coal, oil, gas, or phosphate, the topographer bearing in mind that it
is much better to report knowledge already possessed by the Siu*vey
than to fail to report facts not on file. The land-classification mate-
rial thus submitted will be filed with the other records for the area
covered and with them will become the basis for recommendations
to the department.

For the purposes of the land-classification board it is essential that
^*^ough land comers be identified on the ground and located on the

MAP CONSTRUCTION. 151

map to enable the best possible adjustment of the land-line net to
be made. The land must finally be classified by the smallest legal
subdivisions, and the immediate availability of the classification
data reported depends on its definite application in terms of the
land-office surveys to the land described.

AGRICULTURAl, DATA.

A sheet must be prepared which will show the classification of
the land in accordance with the general outline and symbols
described below. The base for

this sheet will be the topo- GREEN

graphic map of the area cov-
ered, but the classification will
be inked on tracing cloth, on
which allprojection lines should
be fully shown and numbered.
When transmitted to the board
it should be attached to an
undersheet, either a photolith-
ograph or a photograph of the
topographic map on the same

An accompanying written de-
scription should explain and
amplify.wherene cessary .the in-

, /. . ^, , ... FIOURB :.— Pattern and symbols for d«al|-

formation given on the classifi- nation d forest Isnd

cation sheet and should include

all facts which can not be clearly shown graphically, including the
characterof each examination. The descriptionshould, when practi-
cable, be arranged in the order followed in the list of symbols given be-
low and should be arranged in paragraphs, with headings correspond-
ing to those there given , including the index letters. This description
should include a discussion of the usual money value of the different
classes of land in the locality, so far as known. The description
should be appropriatclyheadcd and each page should be so designated
that if separated from the others it could be quicklyrestored to place.

The outline and sets of symbols (shown in figs. 5, 6, and 7 and
described below) should be used in preparing agricultural data for
submission to the land-classification board. The sTj-stt-Kv --jes-ntosi

152 INSTRfCTIOXS TO TOPOGRAPHERS.

the overlapping of diSercnt classes of lands to be sbotvn. For
exunple, land bearing mercbantable timber may be good summer
grating land, and these facts may be indicated by vertical lining
and the letters "F t" in green and by horizontal lining and the
letters "Gs" in yellow.

Hie boundaries between the four principal diiisions as listed
below should be inked in black. The boimdaries between the sub-

Ficmo a.— P»lt«n5 »Dd symbols l« rlrsinatiDn at IrahlF bnd.

divisiaDs of a principal division sbonld be inked in the colur of that

. F*t*tt luitJ(fig. 5; green ruling):
F t Merchantable limber.
F s Small or stunted timber ivhich may be used for pc

firewood, etc.
F b Burnt areas.

The kind of timber should alirays be described in the aco
panying text, and where possible its kind sbotild be ii
e^tedoa the clasificatioii sheet.

■prings. State
YELLOW

MAP CONSTRUCTION.

a. Arable land (fig. 6; red ruling):
C Cultivated land:

C i With irrigation.
Cd Without irrigation,
I Lands not irrigated but which may be irrigated;
I s Irrigable directly from stream^
unappropriated water
rights, it known; if un-
known, so state.
I r Irrigable from possible stor-
age reservairi.
1 K Irrigable from Tnells. Give
geologic source if known.
p Irrigable only by pumping
from any of the preceding
three (insert "p" to other

D Lands cultivable without irrigation

(dry farming).
S Sis-amps;

S e Easily or readily drainable.

S d Drainable with difficulty.

3. Groiinff and rial ural liay land {&g. 7; yellow

rulii^):
H Lands with sufficient natural grass

G Grazing lands not included under

"H," Indicate on classification " ' "

sheet where practicable the character of the vegeta-
tion and the duration of the range:

G y Year-long.

G s Summer.

G w Winter.

4. Barren or Ti-aste land (no pattern):

B a Alkali flats.

B r Rock wastes, escarpments.

B s Sand wastes.

B X Other barrens.

154 INSTRUCTIONS TO TOPOGRAPHERS.

Outlines and symbols for designation of agricultural water supply.

Wells: \

Character:

© Flowing.

O Nonflowing.
Description:

Dug or drilled.

Diameter and depth, indicated thus: ^^^ X i68^.

Yield, where well is pumped or where well flows.
Quality of water:

m Mineralized.

du Suitable for domestic use

St Stock use.

rr Railroad use.
Ownership.
Springs and watering places:
Location.
Description.

Quality of water (as for wells).
Uses (domestic, stock, etc.).
Ownership, public or private. If private, name of owner or

occupant.
Area of range controlled.

WATER-SUPPLY DATA.

River surveys in regular topographic mapping. — In connection with
or as a part of all regular topographic mapping on field scales of
96,000 or 48,000, river surveys of all important streams will be
made on a uniform scale, both in field and office, of 48,000. For
this piuT)ose important streams may, in general, be defined as those
adapted to the development of power by low or medium heads of
20 to 100 feet. It should be noted that when interpreted on a
48,000 scale the requirements as to showable or desirable detail
become automatically lessened.

The field traverse sheets when carefully inked should serve as
final copy for assembly on the plan sheets and for data from which
corresponding profiles may be made on separate sheets.

MAP CONSTRUCTION. 1 55

When regular field work is executed on 31,680 or 24,000 scale, the
river surveys and profiles should be made on 31,680 and 24,000 scale,
respectively.

In connection with field work executed on the 192,000 scale, only
written reports will be required as to water-supply data. Such re-
ports should be based on such general observations and local inquiries
as can be made without materially delaying the regular field work.

Written reports. — Signed written reports, accompanied by photo-
graphs when practicable, must be submitted in general conformity
with the following instructions, except that map references should
be made both to the plan sheets and to photolithographic copies of
the quadrangle sheet. Note, therefore, that many desirable facts
pertaining to small streams can receive all necessary attention in
the written reports.

Special river surveys. — Special river surveys involving the delinea-
tion of alignment, water-surface contours, and adjacent topography,
and the construction of a corresponding profile will be executed on
the scale of i to 31,680 (2 inches to the mile). The plane-table
method with stadia will be employed.

Topography in all river surveys. — The contour interval on water
surfaces will be 5 feet. In addition, the elevations at the head and
foot of all falls, rapids, and dams and at the mouths of all important
tributaries must be determined. When the stream slope increases so
that a 5-foot interval can not be readily sho\vn, the water-surface
contour intervals will be increased to 25 feet; beyond this the in-
terval may be increased to 100 feet, but only when demanded by
legibility.

The contour interval on land along river stretches will be 25 feet,
but wherever a 25-foot office interpolation can be accurately made
between the loo-foot contours the 25-foot contours will be omitted
and 100-foot (heavy) contours only will be drawn.

The land features, including all culture usually found along
streams but excluding large valleys or cities, must be accurately
and completely surveyed by additional set-ups, intersections, or
side traverses. The work must be executed in such a manner that
the data can be readily incorporated in topographic sheets when such
areas are regularly mapped.

In the absence of special definite instructions the topography as
outlined above should be mapped to an elevalvow q>1 v^^^ Vi5^ ^^ssrsvv^

156 INSTRUCTIONS TO TOPOGRAPHERS.

the stream and sketched for another 100 feet or more if such higher
sketching can be done without additional set-ups. Mapped topog-
raphy should be indicated by full lines and sketched topography by
dashed lines, thus enabling them to be clearly distinguished.

Exceptions to the above are: (i) Wide valleys with low flat floors,
in which the general height of the fk>or should be indicated cledriy
by auxiliary figures of elevation and the general relief feattdres
beyond sketched so far as possible without additional set-ups. (2)
Reservoir and dam sites. (See below.)

The more important tributaries ^ould be shown with top>ography
for about one-fourth mile and then be sketched as far beyond as
possible; for this one or more additional set-ups may be taken if
practicable.

Penciled figures of elevation must be placed on the field sheets
wherever they will be legible, and frequent contour numbers should
be placed on light as well as on emphasized contours.

All gaging stations must be located and the elevation of the zero
of the gage given. The ownership, whether United States Geological
Survey, Weather Bureau, Army Engineers, or private, must be stated.

Rapids should not be indicated by means of a conventional aign.

Long azimuth lines should be drawn on each separate traverse
sheet.

Reservoir and dam sites. — The relations between possible reservoir
sites and possible dam sites should be frequently observed £is the
Work progresses in order that these two counterparts when sufreyed
may serve to illustrate to the fullest the natural storage possibilities.
In considering the practicability of a reservoir site the character of
the improvements and industries and the amount, kind, and dis-
tribution of the timber should be noted and the land values
estimated.

The contours within reservoir sites must be accurately determined
on a 25-foot interval up to the height of the possible dam. t^ive-
foot intermediate contours must be surveyed (and drawn in close-
dotted lines and numbered) wherever an office interpolation would
otherwise seriously affect an estimate of storage; that is, wherever
an irregular spacing of 5-foot contours extends over a considerable
area.

MAP CONSTRUCTION. 1 57

Special surveys of dam sites favorably located in regard to reser
voir sites whose existence has been previously ascertained by survey
should be made on a scale of 1:31,680, with 5-foot contoiu-s up to the
height of practicable dam or storage. Depth of water at dam site
and character of bottom and abutments should be noted wherever
pos^ble.

Land lines. — In sectionized country it is imperative that the land
net be placed upon the sheets with an accuracy suitable for 40-acre
references. Therefore the best judgment must be used before giving
up the search for land comers. As aiding toward this accomplish-
ment:

Party chiefs must secure reproductions of land-oflfice plats, which
preferably will be photographs furnished on office requisition. They
must also secure a statement if any such plats are under suspension
by the General Land Office and must also make inquiry and secure
copies of the notes of all such retracements or exterior notes of town-
ships not sectionized as fall within the limits of the river survey.
General inquiry should also be made whenever practicable at the
local United States land offices.

Existing maps or plats showing comers previously found, such as
those of railroad, power, irrigation, and other companies, must be
systematically looked for and secured whenever possible.

Diligent inquiry must be made through deputy mineral surveyors,
county surveyors, and local engineers as to the existence and loca-
tion of known comers or ties, and diligent search must be made on
the groimd for all corners thus learned to exist near the line of survey.
Likewise a reasonable search must be made for such others as fall
near or within the work. The time warranted in search for obscure
comers will be generally determined by the probable regularity or
irregularity of the net and the proximity of comers already found.
If no local information is at hand, obviously the greater the necessity
for pioneer hunting for the needed land ties.

Stream flow. — An approximate estimate of stream flow should be
obtained a short distance below the mouths of all important tribu-
taries. The date of observation and the stage of the water should
be noted. Measurements should be made, if possible, at a straight
and uniform stretch of water about 200 feet long, free fcotn. 5:'aj;^vis^
and cross currents.

158 INSTRUCTIONS TO TOPOGRAPHERS.

The velocity of the current in linear feet per second should be
obtained by timing floats (chips) over a measured (stadia) couise
and using an average of two or more floatings made in or near mid-
stream and nearer shore.

The mean cross section in square feet may be assumed to be the
mean of the cross sections at the two ends of the stretch. The indi-
vidual cross sections are obtained separately by multiplying the
local width (stadia or intersect) by the corresponding average esti-
mated depth.

The desired stream flow (discharge) in second-feet is obtained by
multiplying the velocity in linear feet per second by the mean
cross section. Example: Course, 200 feet; floats average 100 seconds
in transit; upper and lower cross sections are 300 and 400 square feet,
respectively; 2 by 350=700 second-feet of stream flow.

Estimated flow of all important tributaries should be obtained
as above.

As the minimum low-water flow denotes the maximum availa-
bility of the stream without recourse to storage, and as the high-
water discharge in large measure gives its availability for storing,
all practicable and reliable information along these lines must be
sought, and all information regarding the range of water stages,
including data as to past floods, or extreme low water, with dates,
must be recorded.

Water power. — ^AU dams or other existing natural sites for water-
power development must be located and described. If any present
development exists, the ownership, character, abutments, possibility
of increasing height, and condition of stream bed must be recorded.

The plan and profile sheets of all dam and reservoir sites determined
by the river survey should be supplemented by all obtainable facts.

Any favorable stretches of stream which might be of value for
power purposes should be noted. The essentials are a diversion-
dam site (intake), a site for a waterway alongside (canal or conduit),
and a combined site for a relatively short pressure pipe line, and for
a power plant at shore.

Favorable sites for diversion of water for irrigation should be noted.

Information should be collected by observation and by local
inquiry as to (i) power development, noting location of existing or

MAP CONSTRUCTION. 1 59

proposed power plants, points of diversion, location and capacity of
conduit, amount of head available, location of power house, and
point of return of water to stream; installation of turbines and gen-
erators, including their rating; location and equipment of power
transmission lines, and ownership; (2) reservoirs, noting location,
height of dam, capacity, use, and ownership; (3) irrigation works«
noting canals and ditches, point of diversion, capacity, location,
and ownership; (4) municipal water-supply systems, noting loca-
tions of pipes, etc.

Character of adjacent land, — The belt of topography mapped should
be classified as to kind, amount, and distribution of timber; extent
of cultivated areas; existence of grazing or natural hay lands and
duration of range; and extent of barren or waste lands.

OFFICE WORK.

PREPARATION OF TOPOGRAPHIC FIELD SHEETS FOR ENGRAVING.

INKING.

Character. — In inking field sheets the topographer should bear in
mind that they are to serve as copy for the engraver. He should
therefore execute his inking with neatness and exactness, so there
may be no doubt as to the placing and meaning of the symbols and
lines; at the same time he should beware against wasting time and
effort on artistic effects or needless overrefinement. The aim should
be to give the drafting such quality and clearness as will enable the
engraver to work with rapidity and certainty, and an)rthing beyond
that is superfluous.

As most manuscript maps are to be reduced and transferred to the
copper by photographic processes, it is important that all lines,
whatever their color, shall be so inked as to photograph with dis-
tinctness.

Inks. — ^The inks to be used are Higgins's Waterproof Black, Win-
sor & Newton's Prussian Blue and Burnt Sienna, and a red ink pre-
pared by the Survey.

Sequence of inking. — Unless special reasons demand otherwise, the
features on the map shall be inked in the following order : ( i ) Culture,
(2) drainage, (3) elevations, (4) contoiuing, (5) lettervti^.

l6o INSTRUCTIONS TO TOPOGRAPHERS.

Symbols and conventions. — The symbols and styles of lettering
adopted for the topographic atlas sheets of the United States Geo-
logical Survey conform to the standards prescribed for all Govern-
ment maps. They are to be used in the inking of the manuscript
sheets, and all topographers are therefore expected to be familiar
with them. (See pp. 205-228.)

In addition to the features to be engraved, the manuscript sheets
carry many data for special uses. These are to be distinguished by
special colors or conventions, as specified in each case.

Timber and land-classification data are not to appear on the inked
manuscript sheets but are to. be assembled on a separate transparent
oversheet.

CULTURE.

Roads. — Roads should be inked with a uniform width which will
reduce correctly to the ^vidth used by the engraver on the scale of
publication. Pikes, drives, and boulevards of special width should
be shown to scale whenever they actually exceed the width of the
road symbol. On large special scales all roads should be shown with
their individual widths, wherever plattable. Metaled roads should
be inked like nonmetaled first-class roads, but with the addition of
a red overline.

Buildings. — The house symbol on the manuscript sheet should be
of such size as to reduce correctly to the size used by the engraver
on the scale of publication. Large structures which, platted to
scale, exceed the size of the ordinary symbol, should be shown with
their individual plan outlines.

Railroad crossings. — Wherever railroads and wagon roads cross one
another above or below grade — that is, not on the same level — the one
passing under the other is to be interrupted at the crossing.

Canals and ditches. — Canals and ditches should not be inked with
double lines unless their actual width can thus be shown without
exaggeration on the scale of publication.

Civil boundaries. — Where civil boundaries of different classes

coincide for a distance the symbol of the major subdivision should

take precedence, but in particularly complicated regions, e^)ecially

among minor subdivisions, it may sometimes be necessary for the

«^^e of clearness to depart from this rule.

MAP CONSTRUCTION. l6l

Where it is obvious that a civil boundary follows a stream or road
for a short distance, the boundary symbol may be omitted to avoid
confusion. In some places, however, clearness may be increased by
placing the boundar}'- symbol immediately alongside of the streamer
road, in red.

Public-land surveys. — All land survey lines should be inked in red
so they may not be mistaken for other cultural features; the thickness
of the ink line should be commensurate \nth the importance of the
survey line in the system.

Township and range numbers. — Township and range numbers
should be placed along the margin of the sheet opposite the middle
of each township; the township numbers along the right and left,
the range numbers along the upper and lower margins. The numbers
should be placed within the townships only where the numbering is
irregular.

Numbers and names of standard parallels and guide meridians are
to be shown.

Section numbers. — On the 1:62,500 scale and all larger scales, sec-
tions within townships should be numbered.

United States mineral monuments. — Mineral monuments must be
shown and accompanied by their numbers, the numbers being placed
before the symbol. .

BENCH MARKS AND ELEVATION FIGURES.

Permanent bench marks. — Symbols, letters, and figures pertaining
to bench marks should, wherever practicable, be arranged with the
letters BM above and to the left of the cross, and the elevation figures
below and to the right. Should they seriously interfere with other
features in these positions, this rule may be deviated from at the
discretion of the draftsman; in no case, however, should the letters
BM appear below or to the right of the figiwes . All shall be inked in
black and figures vertical.

Bench m^rks in cities. — In case a bench mark is situated in the mid-
dle of a city or other center of dense culture, the symbol should be
omitted and the letters BM followed by elevation figures placed im-
mediately under the name of the place.
66513 — 13 II

l62 INSTRUCTIONS TO TOPOGRAPHERS.

Bench marks on triangulation points, land-survey corners^ etc. —
Btiicii marics at tiiangtiiation and other marked points are «Bt to be
idBown by sjrtnbol, it being undesirable to superpose two tdiffeieitt
•yinbols oa each other. The letten BM and the eleTation tigores,
however, should appear in the usual place.

Temporary tench marks. — Temporary bench marks along foutes of
prinary lines diotild be shown by a bencfa-maric cross, inked in red
(to be engraved in brown), but should not be accompanied by letters.
The elevation figures should be black.

Elevation figures. — Elevation figures, if referring to points not
^lecially marked on the ground but readily identifiable, sach. as ctoas-
ttMids, road forks, road crossings, and railroad stations, should be inked
in bladi if to be engraved, in red if not to be engraved. Wherever the
location of the point referred to might remain in doubt, as on flat
motuitain or hill summits, use should be made of a small brown
cioss to iiKiicate the exact position.

Water elevations. — Elevations on water surfaces, as in lakes, above
and below dams, under bridges, or at fords, shall be in black if to
be engraved, in red if not to be engraved, preceded by a small W,
if necessary.

HYDROGRAPHY.

Water bodies. — Oceans, bays, lakes, ponds, and broad rivers
intended to be waterlined on the engraved maps are to be tinted blue
(blue tints will not photograph) on the manuscript sheets. As a
guide for the engraver, a deeper shade should fellow immediately
along the shores, islands, rocks, and other features at which the water-
lining begins. Bridges and other structures built over the water
■should not be thus outlined.

Dauble4ined streams. — Only those streams are to be double-lined
whose actual width can thus be shown without exaggeration on the
scale of publication.

Perennial streams. — Streams ^t. to be inked with a solid blue line,
increasing in strength with the importance of the stream, but nowheie
so broad as to be equivalent to double lines. Care should be taken
not to draw streams to the sheet edge with a width that can not
oroperly be continued on the next sheet. Stream lines should taper
toward the sources of the streams but should remain deep and

MAP CONSTRUCTION. 1 63

strong in color to the last. If allowed to become faint the blue will
not photograph well.

As a general rule, all perennially flowing streams are to be shown,
but the map ^Kmld not be overburdened with instgniticant rills
and forks, such as abound in well-watered countries.

Inkrmittenl streams, — The dash-and-three-dots symbol is used to
designate intermittent streams. On the penciled field sheets all
intermittent stream coutses are outlined down to their nriauter
ramifications, as an aid in contour sketching, but only the more im*
portant are to be inked and engraved. The general rule ^lould be to
ink no intermittent stream that will be less than three-fourths inch
long on the scale of publication . In the more arid districts less inter-
mittent drainage is to be inked, and the minimum length should be
increased up to two inches or more, according to scale, as may seem
apjwopriate to the degree of aridity. It does not follow, however,
that in regions of extreme aridity, such as the deserts of California
and Nevada, the map is to carry no intermittent drainage at all. It
is to be bcwne in mind that drainage lines are delineated, not merely
because they indicate water features, but because they constitute
an important element in the conformation of the land surface and
because, especially on contour maps on which lines of greatest de-
clivity are inherently absent, they afford supplementary informa-
tion of great value in the interpretation of the relief. Whatevw
the degree of aridity, therefore, a certain amount of intermittent
drainage is desirable on the face of the map for the sake of legibility.
More especially is this true in delineating intricately sculptured
areas, the topography of which in the absence of drainage lines ap-
pears chaotic and unintelligible at first glance, and featureless
surfaces on which the contours are far apart and the connection be-
tween the drains^ reentrants is not at once obvious. Aggraded
flats and valley floors devoid of well-defined stream channels or scars
are not properly shown with drainage lines rtmning through them.

Intermittent streams should not be inbed up to or close to the
divides. The contours along divides usually suffice to define the
location of stream heads, and the symbol should end between one-
e^th and one-fourth inch below these.

164 INSTRUCTIONS TO TOPOGRAPHERS.

TOPOGRAPHY.

Strength of contour lines. — Contoiirs should be inked with fine,
firm, smooth lines of even strength. Every fifth contour (in the case
of 25 and 250 foot intervals, every fourth) must be accentuated and
marked with its elevation for aid in reading. The accentuation is
to be gained by drawing the lines heavier, not by making them
broken or dotted. Their weight should make them stand out from
the intermediate contours, but should not be so excessive so as to
cause them to dominate the relief.

The extra weight of the accentuated lines must be considered in
the contour spacing, so that they may not cause an apparent in-
crease in declivity.

Uniform slopes. — On steep uniform slopes, on which the contours
are very closely spaced and no expression is lost, only the accen-
tuated contours should be inked; a much clearer working copy is
thus secured for the engraver, who can readily interpolate the inter-
mediate lines. The omission of the latter, however, is in order only
when their parallelism is manifest. Wherever any marked diver-
gence or discordance exists among them, they must all be inked for
the guidance of the engraver. As a general rule, the intermediate
contours should be indicated on every drainage line and every spur
crest.

Bluffs and cliffs. — Extreme care is urged in inking bluffs and
cliffs on which the contours can not all be shown. The lines should
be as sharp and smooth as they can be drafted, so as to lessen to a
minimum the chance of their blurring in transfer to the copper.
The general principle should be to ink no more lines than are abso-
lutely necessar)' for the guidance of the engraver, and to leave the
copy as open as the character of the topography permits.

Accentuated contours must not be dropped; they take precedence
over the intermediate lines and must be drawn first. The inter-
mediate lines should be inked only where needed to show detailed
expression; attempts to fill them in for the mere sake of enhancing
the appearance of the manuscript sheet are not permissible.

Depression contours. — Contours inclosing basin-like depressions are

to he accompanied by a row of hachtu'es (extending down slop>e)

ver failure to distinguish them mi^hl cause the map to be mis-

MAP CONSTRUCTION. 165

read. This applies equally to natural depressions, such as occur in
limestone regions, for instance, and artificial depressions, such as are
closed in by railroad or road embankments. If a depression takes
more than one contour, all should be hachiu*ed. In intricate areas
it is often desirable to indicate the bottom elevation of the basin
by figures, or, if size permits, to mark some or all of the contours with
their elevations.

Depressions of large extent covering a considerable area on the
map are often readily intelligible without the aid of hachures.
Such, however, should be liberally provided with contour figures.

Contour figures. — Elevation figures on accentuated contours should
be placed with a special view to their effectiveness as an aid to the
map reader. It is desirable, therefore, that they be placed in con-
spicuous positions; and that they be distributed with some system.

In general, contour figures are most effectively placed on or near
the end of spurs and other salients. Broad embankments, long val-
leys, and other hollow featiu*es of importance also require them, but
judgment should be used in placing them.

On features taking several tiers of accentuated contours the figures
should be placed in orderly series. Such series should follow the
features on which they are placed in easy, gentle curves. On very
steep slopes, where they would be too crowded, the figures should
be omitted on alternate accentuated contours. For most classes of
topography series should be about 2 or 3 inches apart on the scale
of publication. Each mountain group should have its own series,
so that there may be no need of referring to contour figures across
valleys or canyons.

In regions of moderate or low relief, where arrangement in series
is impracticable, tlie placing of the figures should be governed pri-
marily by the disposition of the larger topographic subdivision.
Each of these should have at least one complete set of figures. In
exceptionally intricate topography, as for instance in regions pitted
with solution sinks or traversed by high clifiFs, the figures on the
accentuated contours do not always suffice to make the delineation
intelligible. It is proper then to place figures on intermediate con-
tours wherever they will help to remove uncertainty. If need be,
elevation figures may be introduced to supplement the Q.cv»^ia*xix
figures.

l66 INSTRUCTIONS TO TOPOGRAPHERS.

Contour figures should not, as a rule, appear in dose proximity to
bench-mark and other elevation figures. The latter, on the other
hand, should not be considered as taking the place of the ooatDor
figures.

Finally, care should be taken to select such poation for oontoar

figures as will accommodate the engraving on the reduced aci^ of

publication.

LETTERIXG.

Position. — All names are to be so placed as to be readable from
the bottom of the map. Names parallel to a meridian are to read
from south to north.

Names of places, public institutions, ranches, mines, and other
lesser cultural features are to be placed horizontally and whenever
practicable to the right of the feature to which they refer.

Names of ponds, lakes, islands, swamps, and glaciers are to be
placed horizontally and to the right, unless the areas of such features
are large enough to accommodate the names within their limits.
Names of oceans, bays, coves, fords, and straits are to be placed
across these features in broad curves.

Names of railroads, highways, trails, canals, streams, narrow val-
leys, canyons, gorges, gulches, arroyos, and washes are to follow the
general trend of these features in easy curves. They are to be placed
on the upper side whenever practicable.

Names of broad, water-lined streams are to be placed within those
featiu-es.

Names of mountains, summits, peaks, hills, knobs, etc., are to be
placed horizontally and to the right; but if they refer to features of
considerable extent, as plateaus, motmtain groups, ranges, ridges,
basins, or valleys, they are to be spread over same either horizontally
or with the trend, as may be most appropriate.

Names of reservations, parks, and forests (national or State), civil
townships, and land grants are to be placed horizontally across the
areas to which they refer; but when such areas are narrow or winding
the names are to be placed lengthwise through them, in sweeping
curves, if appropriate.

State and county names are to be placed opposite each other on
f/ie boundaries. If a boundary falls on or close to the sheet edge,

MAP CONSTRUCTION. 167

both names may be placed on the ininde of the line, the one referring
to the area outside the sheet being given second place.

Punctuation. — Periods are to be consisteatly omitted on all letter-
ing within the margin of the map.

Style of lettering. — ^All place names and names of country post
offices, railroad stations, country schoolhouses, and chiuches are
to be lettered in roman. Where the name of a railroad station
differs from that of the corresponding post office, both names are to
be shown, the one most widely known being given the greater promi-
nence, the other being followed by *' PC* or "Sta,*' as the case may
be. The size of the letters is to be commensurate with the impor-
tance of the place. Large cities, State capitals, and county seats take
capitals.

Names of routes of communication, such as railroads, highways,
trails, canals; of public works, such as bridges, ferries, fords, locks,
tunnels, dams, and wharves; of public institutions, such as light-
houses, lightships, life-saving stations, universities, state hospitals,
and asylums; and of mining features, such as mines, quarries, pros-
pects, furnaces, and smelters, are to be lettered in small, slanting,
block capitals.

Names of civil divisions, such as States, counties, districts, civil
townships, and land grants; and of reservations, such as National
and State parks, forest and game preserves, Indian and military
reservations, are to be lettered in roman capitals.

In inking large roman capitals on manuscript sheets, the shaded
parts should be left open wherever there is danger of important
detail or dense contoiuing being obliterated or obscured.

Names of hydrographic features are to be lettered in map italic,
except oceans, large bays, straits, rivers, and lakes, which are to be
lettered in slanting roman capitals.

Names of topographic features and land features along coasts are
to be lettered in upright gothic. Only features of considerable
extent take capitals.

Marginal lettering.^ — All topographic atlas sheets should carry on
the margin —

The latitudes and longitudes of the projection lines.

At the top the word "Topography."

^ Sec p. ao6.

1 68 INSTRUCTIONS TO TOPOGRAPHERS.

Above thcv upper left-hand comer of projection the words —

U. S. GEOLOGICAL SURVEY.
Director.

Above the upper right-hand comer of projection the name of the
State or States within which the area mapped lies, and below this
the name of the quadrangle or sheet. If the entire area falls within
a single county, the name of that county should appear below the
name of the State and should be omitted from the face of the map.
In that case the heading at the upper left-hand comer will be
arranged in three lines to balance.

In cooperative surveys, the name of the cooperating State, to-
gether with the names and titles of the officials representing it,
should appear in the middle of the upper margin under "Topog-
raphy."

In the middle of the lower margin the scale in the form of a frac-
tion, a bar scale in miles, a bar scale in kilometers, the contour
interval and the datum of elevation should appear above each
other in the order named.

Under the lower left-hand comer of the projection should appear
the legend stating under whose direction the work was done, by
whom the primary control and by whom the topographic mapping
was executed, and the date of survey. In cooperative surveys,
further, the fact of such cooperation must be stated.

Supplementing this legend, and immediately to the right of it,
should be placed an "author diagram" showing the area for which
each contributor to the work is responsible, with his initials. A
diagram showing the mean magnetic declination for the quadrangle
should also be given. On maps of i: 125,000 and smaller scales not
carrying section numbers a small township diagram showing the
system of numbering sections should appear. Section and township
numbers should be given when required by the rule on page 161.

Besides these marginal features common to all atlas sheets, the
names of adjoining atlas sheets already published must be placed
along the proper sides or at the proper comers of the projection. If
the adjoining sheets are executed on scales differing from that of the
new sheet, their scale should be given. Lettering should be in map
Jtalic.

MAP CONSTRUCTION. 1 6

PREPARATION OF RIVER-SURVEY MAPS FOR PHOTOLITH-
OGRAPHY.

SIZE OP SHEETS.

Sheets showing river surveys are of uniform size (i8 by 22 inches)
with all plan or profile work kept within a 15 by 18 inch neat line,
which should be drawn with margins of i and 2 inches at top and
bottom, respectively. Marginal lettering should be kept within a
vertical space of 17X (preferably 17) inches.

PLAN.

Plans should be inked in standard colors; all the drainage and
culture should be inked, but only so much of the contouring as can
be clearly read on a reproduction by a single color photolithograph.

As it is the readability of the contours from the engineer's point
of view that is desirable rather than their graphic expressiveness of
relief, the penciling or inking of contours, wherever these closely
parallel any shown drainage or culture, should in general be avoided.

Water-surface crossings must be drawn heavy and solid from shore
to shore. Every fifth crossing (or intermediate crossings if spaced
far apart) must have its elevation placed at the outer end of a black
right line drawn out clear of all topography.

Distances along alignments will be indicated in black by figures
within small circles placed at the ends of right lines drawTi clear of
all topography from the center of the stream opposite each plotted
mile of channel flow. Preferably, they should be numbered
upstream.

The mileage must be plotted by pivoting and swinging a scale of
miles (drawn as a straight line on tracing paper) within the channel;
it must not be stepped off with dividers. The same tracing will
pick up the contoiu* crossings for subsequent plotting on the profile
sheets.

Ink in red for sheet record all water-surface elevations; accompany-
ing reference or direction lines should be inked in red but should be
kept clear of all topography. Such data are not for final printing and
will be brushed out on the negatives.

.170 INSTRUCTIONS TO TOPOGRAPHERS.

Numerous contotu* numbers and location crosses with j^gures of
elevations should be used for such exterior points as are instru-
mentally determined.

The plan should be assembled in as few and in as continuous
stretches on the same sheet as is practicable, and these stretcdbes
should be condensed within the sheet so far as the necessary allow-
ance for outlying section lines, lettering, and other markings will
warrant.

PROWtB.

Profiles should appear on separate sheets from the plans and should
be drawn directly across the sheet» with the separate rows condensed
as above. Their direction should be from left to right, irrespective
of easting or westing, and this direction of profile should be main-
tained for all sheets of the set.

For profiles tmiform vertical scales must be used so far as possible
and profile angles in excess of 45° must be avoided. The profile will
be constructed from the water-contoiu crossings, supplemented by
elevations determined at head and foot of falls, etc. (See p. 155.)
Profile lines should be drawn heavier than construction lines, and
sharp angles should be slightly smoothed.

DRAFTING.

Free-hand inking must be in sharp, fine dark lines, suitable for
clear reproduction by photolithography (see p. 169), and right lines
must be twice lined if fine or in color.

Land lines must be drawn solid and township lines emphasized.
Section numbers must be shown only where land has been sec«
tionized; they should be draA\-n preferably at the centers of sections
but should always be offset therefrom if necessar>^ to gain legibility.

Lettering in general should not be placed on or ^^'ithin the inked
topography but kept in open places.

MAP CONSTRUCTION. 17I

PROOF JISADXNG, INSPECTION, EDITINC, AND TRANSMISSION.

ORDER OF PROCEDURE.

Ob the oompletion of the inking, atlas sheets or other topographic-
map manuscript prepared either for engraving or for photolithography
will be transmitted by the topographer through the division chief in
accordance with the following routine :

Border corrections of adjoining sheets. — Whenever practicable,
border corrections will be made of previously engraved or transmitted
sheets that do not accurately join on to current work . If the previous
sheet is still in the editor's hands the original of that sheet should be
corrected ax&d the editor informed of the correction; if the previous
sheet has been transmitted for engraving, or is engraved, a more
elaborate procedure is necessary. If the correction is a small one,
it should be submitted in a distinctive color on an engraved or photo-
lithogr^hic copy, provided it can be legibly shown thereon; but if
it is extensive or involves close drafting, it should be submitted as
an oversheet tracing in standard colors, the scale being immaterial.
All corrections to engraved work should be inked in strong photo-
graphic colors and should be accompanied by a clear copy for the
corre^xmding take-out on the copper plates.

Lettering. — The final drawing, accompanied by a legible lettering
diagram on tracing paper or cloth, is transmitted to the drafting
room for lettering.

Land classification and woodland sheets. — Land classification and
woodland data are to be shown on oversheet tracings made to conform
to the usual requirements governing the joining of previous work.
(See p. 149.)

Proof reading. — Proof reading should be done by a topographer
who has not been engaged on the same piece of work. (See p. 172.)

Ta inspectors for examination. — The original drawing, the bcorder-
conectioaa material for adjoining sheets, and the land classification or
woodland sheets are all to be transmitted to the inspection room for
examination before being submitted for executive and administra-
tive approval.

Approval. — The sheet must be approved for photolithography, for
engraving, or for both, by the division geographer and later by the
chief geographer.

172 INSTRUCTIONS TO TOPOGRAPHERS.

Photolithography. — All sheets issued in photolithographic edition
should be marked "Advance sheet subject to correction."

Editing. — Sheets approved for engraving should, after the mailing
of photolithographic copies from the office, be released from the
fireproof safes and referred to the editor of topographic maps for
editorial review and examination.

Reference hack to the chief geographer. — On the completion of the
editing, the original drawing, accompanied by its edited photograph
and any other necessary sheets, will be referred back, in jacket, to
the chief geographer for reply to queries, approval, comment on
■editing, and retiu*n to the map editor.

Transmission for engraving. — On completion of the map editing
the sheet is formally transmitted by the chief geographer through the
Director (executive division) to the engraving division.

Engraved prqofs. — The first combined engraved proofs, after piDof
reading by the map editor, are referred to the chief geographer for
final approval before the printing of the map edition.

Transmission to land-classification hoard. — All land classification
and woodland sheets for public-land States and written reports
thereon are to be transmitted to the land-classification board.

Transmission of special reports. — ^AU special reports must be
referred to the division geographer for appropriate action.

Filing. — On approval of the final work on any sheet, all remaining
map material pertaining to it should be turned over to the custodian
of records for safe keeping or appropriate filing.

PROOF READING.

Before being transmitted to the inspectors for examination the
original drawing, together with all auxiliary map data (including
adjoining border corrections and land-classification sheets), must
be submitted, through the division geographer, to a disinterested
topographer for rigorous proof reading as to its completeness, accu-
racy, and general conformity with Survey instructions. For such
proof reading the form printed below (also issued sep rately) should
serve as a guide; it should, however, be regarded as suggestive
rath^" *^'^n ^s complete.

MAP CONSTRUCTION.

^7^

Record of proof reading Sheet.

Topographer

CHECK.

Subject of examination.

1. Houses, churches, schoolhouses, etc.

2. Roads, first and second class, trails, etc.

3. Railroads, trolley lines, switches, etc.

4. Civil boundaries, State, county, township, city.

5. B. M. symbols, triangulation stations, etc.

6. Public-land lines, township and range ntun-

bers, etc.

7. Dams, ferries, bridges, tunnels, etc.

8. Mines, quarries, etc. ■

9. Streams, double or single line, intermittent, etc..

10. Lakes, ponds, etc.

11. Swamps, marshes, flood plains, etc.

12. Contours, depressions, sand hills, etc.

X3. Elevations, contour numbers, B. M.'s, etc.

14. Names of post offices, villages, civil divisions.

streams, railroads, etc.

15. Borders and names of adjoining sheets.

x6. Marginal lettering, numbers of coordinates,
magnetic declination, scale, diagram of town-
ship, etc.

17. Forest reserves, Indian reservations.

Each pxofA reader check following numbers, corresponding to separate five-minute
blocks: also place check marks in coltunns above, opposite each subject, and sign
below:

321
456

987

19..

Topographer.

321
456

987

19.

Proof reader.

As it is a function of the inspectors to advise and instruct regard-
ing this proof reading and by examination to see that it is faithfully-
performed, not to do it themselves, such work by the proof-reading
topographer will be carried out so systematically and so thoroughly
as to preclude the necessity for any fiuther similar work by anyone
else. This will involve a minute and thoughtful checking up of
the entire map through all its features from every point of view
that can suggest itself to an experienced topographer.

In order that the proof reader mav know that his notations have '
been attended to, or can be satisfactorily explained by the autV

174 INSTRUCTIONS TO TOPOGRAPHERS.

or inking topographer, the latter, after due attention and correction,
will in all cases return such notations intact to the proof reader for
release or further action, pending wiricfa the proof reader will with-
hold his signature from the sheet margin.

In order that the general character and sufficiency of sucli proof
reading may be under the immediate supervision of the inspectors,
the division geographers should promptly advise the inspectors of
all proof-reading assignments.

EDITING TOfPCXJRAPHIC MAPS.

The editor of topographic maps examines and edits the manuscript
on a photograph made to scale of publication, and marks with red
ink all corrections, amendments, and changes for the information of
the engravers. The jacket, with manuscript and photograph, is then
returned to the topographer, that he may answer queries, supply
omissions, and review the corrections, interpretations, and rearrange-
ments made by the editor.

When the chief geographer is satisfied that the editing is com-
plete and in proper form he indorses the jacket "Approved for
engraving."

At the close of each month the editor of topographic maps adrases
the chief geographer of the sheets whose editing has been completed,
and such are then formally transmitted by the chief geographer to
the engraving division (through the Director).

When the engraving of a map shall have been completed and
combined proofs printed, the chief engraver refers the complete
manuscript, together with twelve engraved copies, to the chief
geographer. After further review by the editor, the chief gecigrapher
transmits the corrected proofs to the chief engraver, ai^ro^Rcd te
final printing.

In transmitting manuscript maps and pioofs irom one divtitoa to
another the officer in charge indorses on the ^ket tlie date of
transmittal and the purpose for which the map was referred.

After the completion of the engraving and ptrinting of may topo*

graphic sheet, the manuscript drawing will remain in tlie cxutady of

^he editor of topographic maps, and all other engraving material will

r^thP^ i^ ^^^ ^"g^'^^^ i^k^^ ^^ ^^ foreman of the pfate
ngra^'^ * -sion.

SUPPLEMENTARY DATA.

MEDICAL AND SURGICAL ATTENTION.
FIRST AID IN EMBROBNCT.

Sunstroke. — Get patient into the shade at once. Place on back,
loosen clothing, and apply cold water to head and neck. Do every-
thing practicable to reduce temperature of body and rapidity of
pulse. In ca^ of exhaustion and threatened collapse, with cold
skin and extremities, pale face, and weak pulse, alcoholic stimulants
and heat to the body become necessary.

Lightning. — Dash cold water over person struck.

Frostbite. — Carefully raise temperature of part frozen (which
looks white or bluish white and feels cold) by gentle rubbing, prefer-
ably with snow or a sponge or cloth dipped in ice water. Do not
expose to heat of fire. When congestion begins to subside incase in
flannel or cotton wool.

Burns and scalds. — Do not break the blisters nor prick them.
Cover at once with cooking soda and lay wet cloths over it; or use
olive oil and linseed oil mixed; or olive oil and limewater if
available. Put nothing on a bum that will be difficult to remove
afterward.

Drowning. — Remove clothing from upper part of body. Lay
patient face down and empty lungs of water by lifting the body by
the middle and jerking it a few times. Then place patient on his
back with a roll under his shoulders. Clean out mouth and nose
and pull tongue forward with a dry handkerchief. Start breathing
by alternately raising both arms above the head and then bringing
them down again, pressing them against sides and front of chest.
Repeat about fifteen times a minute and continue for at least one
hour. Occasionally hold ammonia to nose and slap chest with cold
wet cloth. Remove lower garments, rub skin dry, rubbing always
toward the heart. Help out breathing movements by blowing air
into mouth of patient at moment when arms are being raised (the
tongue must be pulled forward and the Adam's apple pressed down

176 INSTRUCTIONS TO TOPOGRAPHERS.

to make this efifective). Above all don't give up. Persons have been
brought to after hours of persevering, vigorous effort. As soon as
breathing begins give stimulants and warm drinks by teaspoonfuls,
and get patient to bed as soon as possible.

Mad dog or snake bites. — Tie cord above wound at once. Suck
woimd (but be siu-e you have no cuts or sores in your lips or mouth),
cauterize with corrosive sublimate or other caustic, or else with
white-hot iron; if none of these means are at hand cut out surround-
ing flesh with knife. The poison must be prevented from spreading
into the circulation.

The bites not only of venomous snakes and mad dogs but of prac-
tically all animals are dangerous and liable to produce blood poison-
ing, as their saliva is at all times charged with septic germs. Ever}-
bite, however insignificant, should, therefore, be very thoroughly dis-
infected, preferably with a solution of corrosive sublimate.

Venomous insects' stings. — Apply weak ammonia, oil, salt water,
or iodine.

Poisoning. — Ptomaines, that is, toxic substances developing in
spoiled or decaying food, are the most common soiu^ce of poisoning.
In all cases an effort must at once be made to empty the stomach by
vomiting. Tickling the throat with feather or finger or drinking
warm water with mustard are the best means to induce it. The
bowels should be cleaned out by the free use of Epsom or Rochelle
salts, castor oil, or some other laxative. After the poison has been
eliminated stimulants should be g^ven and heat and rubbing applied.

Poisoning by drugs or acids requires special antidotes.

For strychnine give mustard and water or sulphate of zinc in 10 to
15 grain doses. Keep the patient absolutely quiet. Plug his ears.

For opium, morphine, laudanum, and other opiates give strong
coffee and hot bath. Keep the patient awake and moving.

For any of the foregoing poisons a teaspoonful of tannic acid, fol-
lowed by an emetic in 15 minutes, is advised.

For arsenic, rat poison, or Paris green give milk, raw eggs, sweet
oil, limewater, or flour and water.

For lead, saltpeter, corrosive sublimate, sugar of lead, or blue
vitriol give whites of eggs, or milk in large doses.

Por chloroform, chloral, or ether dash cold water on head and
cliest Give artificial respiration. Put a. ipv^^it of ice in the rectum.

MEDICAL AND SURGICAL ATTENTION. 1 77

For mercury and mercury salts give whites of eggs, milk, and
mucilaginous drinks.

For carbolic acid give flour and water and mupilaginous drinks;
alcohol or whisky can be applied externally or internally with benefit.

For potash, lye, or ammonia give vinegar or lemon juice in water.

Tests of death, — ^Hold a mirror to mouth; if person is alive moisture
will gather. Press a pin head into flesh; in case of death the mark
will remain; if it closes life is not extinct.

SURGICAL ATTENTION.

Cuts and flesh wounds. — ^Reduce the flow of blood at once by apply-
ing cold water, snow, ice, or salt; also by elevating the limb or part
injured. If an artery is cut and the blood spurts in jets, try to stop
the flow by pressing the artery against a bone or muscle with the
thumb or forefinger. If the injury is to a limb tie a band tightly
around it above the wound — that is, between wound and heart. To
tighten, introduce a stick into the band and twist it. Stop turning
the moment the flow stops. Remember that too much force may
bruise flesh or muscles. Relax the bandage at the end of an hotir
any way, for keeping up the pressure too long may strangle the limb.
Keep bandage in place, however, ready to tighten again if necessary.

Remove all dirt from woimd and wash with antiseptic solution,
preferably corrosive sublimate (one tablet in one quart of water).
Avoid using carbolic acid, as it may produce gangrene. Attach a
long strip of sticking plaster to skin or on one side of cut, draw the
flesh together, and stick down the plaster on the other side.

Deep flesh woimds or holes such as one may get by falling on a
pointed stick or by stepping on a nail must be kept open; otherwise
they will grow over at the surface before they heal inside. Wash
out daily with corrosive sublimate and dust with aristol powder or
apply aristol and boric acid mixed half and half. Always leave a
strip of sterilized gauze in the woimd before dressing. It will auto-
matically drain the cavity by capillary action.

Bruises and contusions. — Use cold applications at once. Lead
water and laudanum on a piece of cloth frequently renewed will
help to allay inflammation. Then apply some soothing ointment or

66512 — 13 13

178 INSTRUCTIONS TO TOPOGRAPratKS.

lotion, like avka or witch hatel, and bwMt i ii inatj «i as to afford
moderate preaure.

Sprains mmd swollen joints. — Apply lead water umd Unsdamam on a
piece of dodi. Bandage tightly and ghF« wtSt, hut keep flMKks
from stiffenhig by occasional gentle massage and exercise. Paint
with ttnctnre d iodine, if available.

Rupture. — Place on back in reclining poiitkMi, head down and
abdomen and le§$ propped np, so bowels may retract with aid of
gravity. Redttee circulation of blood in parts affected by applying
cold wet cloths or ice if available. When bowels have ceased to
pfotrude, imprerrise trttss by bandaging tif^tly about abdomen and
thighs. Get patieilt to skilled surgeon without delay.

Fraciurss.'^Vo suit waste time making complicated dressings and
saints. Broken boaes recpiire the most ezpot sai)gical skill for
their proper acttfaig. Make up your miad that no time is to be lost
getting the ii^ured man to a surgeon, and confine yomr efforts t» pro-
vidiiig an iapcoviacd splint or supporting bandage that will enable
him to travel with tlie least possible suffering and diacomfart.

TtanspoftoHon. — Do not be afraid to traniqiort injured people to
camp <x town immediately after an accident. They can as a rule
stand more hardship and will suffer less in traveling the first few
hours after an accident than they will the next day.

M BIHCAL AND SURGICAL OUTRT.

Illness and injury have proved on the whole so infrequent. among
field men that few parties now carry medical or surgical outfits. It
is advisable, nevertheless, to keep a few simple remedies and sur-
gical articles on hand, especially when working in remote and rather
inaccessible areas. The following list may serve as a guide to those
most essential in making up a compact outfit:

Pocket cyclopedia of medicine and siu-gery, by Gould and Pylc.

Quinine, a-grain compressed tablets (or capsules, but not pills).
As a general tonic and preventive against malaria, take 2 grains
after each meal.

Quinine sulphate, 1% grains; arsenous acid, ^ grain; powdered
capsicum, }4 grain. One every three hours for malaria.

MEDICAL AND SURGICAL ATTENTION. 1 79

Compound cathartic, U. S. Pharmacopoeia. Extract colocynth, i}i
grains; calomel, i grain; resin jalap, y^ grain; gamboge powder, yi
grain. This is a standard cathartic. One or two at night.

Calomel, ^ grain. One every hour until cathartic action is
obtained; follow by dose of Epsom salts, castor oil, or sal hepatica.
For acute indigestion, biliousness, and torpid liver.

Epsom salts, sal hepatica, castor oil. For cleaning alimentary
tract in dysentery, ptomaine poisoning, fermentative diarrhea, etc.
Large doses of either salt are debilitating, and must be followed with
stimulating but light foods. Castor oil does not require this. Sal
hepatica in small doses is excellent for rheumatic troubles.

Sun cholera mixttu-e. Tincttu^ opium, 3 minims; tincture rhu-
barb, 5 minims; tincttu'e capsicum, 5 minims; spirit peppermint,
5 minims; spirit camphor, 5 minims. For diarrhea one to two every
three or four hours as needed. Do not take more than four or five
doses.

Limewater tablets. For acidity and nausea. Externally excel-
lent for bums and scalds when mixed with linseed oil. (These tab-
lets often require a long time to dissolve.)

Brown-mixture tablets. Standard remedy for coughs and colds.
Extract licorice, z/ao grain; camphor, 1/50 grain; acid benzoic, 1/50
grain; oil anise, 1/50 minim; opium powder, 1/50 grain; tartar emetic,
1/120 grain. Disiolve one on the tongue every hour until cough
becomes free. Do not take for a longer period than 36 hours, but
follow with an emulsion of cod-liver oil, teai^xx>nful three or four
times a day.

Boric-acid solution, diluted, for eye lotion.

Carbolized vaseline, for skin abranons aad wounds.

Blue ointment, for chnmxc ulceration and animal piuraaitic affec-
tions of the skin. Excellent for the preventioa of ntst on firearms.

Ichthyol ointment. Dilute 25 to 50 per cent with water for skin
diseases.

Glycerin. For skin a£teclk>ns, chapped hands, etc. Invaluable
for earaches pioduced by insects, foreign bodies in ears, etc.

Pond's extract ointment, camphor ice (Chesebrough's). For sore
lips, chapped hands, or sunburn.

l8o INSTRUCTIONS TO TOPOGRAPHERS.

Lead water and laudanum tablets. One tablet to 2 tablespoonfuls
of water. Invaluable for sprains, bruises, saddle chafes, etc.

Corrosive sublimate tablets. One tablet to i quart of water (or
about I to 2,000 solution) for washing open wounds. One tablet to
one-half pint for cauterizing snake or dog bites. Apply with cotton.

Aristol powder. For flesh wounds, ulcers, etc. Dust on wound
or apply with boric acid (equal parts).

Mustard leaves. For plasters, etc.

Arnica and witch hazel ointment. For bruises, contusions, etc.

Surgical sundries, such as bandages; absorbent cotton; antiseptic
gauze; adhesive plaster, in lo-yard spools, i-inch width; fever ther-
mometer; surgeon's assorted needles; surgeon's silk on cards; glass

dropper.

PACK TRANSPORTATION.

In many localities the topographer has to depend solely on pack
animals for transportation. Even where wagon roads exist pack
animals are often required for side trips or station work. As the
party chief frequently has to rely on his own knowledge and re-
soiu*ces in instructing assistants in these matters, he must be familiar
with details of packing and pack-train management.

PACK-TRAIN EQUIPMENT.

The following list may serve as a convenient guide in the equip-
ment of a pack outfit for a topographic party of six men (two instru-
ment men, two assistants, a cook, and a packer). Riding animals,
saddles, and the accessories that go with them are not included.

6 pack animals.

6 padcsaddles. with rigging and pads.
6 saddle blankets.
6 pairs pack bags or alforjas.
I pair small mess chests.
I stationery case, telescoping.
9 canvas pack covers.

9 lash cinches, each with a 40-{oot rope, K-inch.
6 halters, each with a 7-foot rope, H-inch.
6 sling ropes, 30-foot rope, ^inch or ^inch.
I stock bell with heavy leather strap and buckle.

Hobbles and 30-foot picket ropes with swivels, according to the nature of the
country and the disposition of the animals.

PACK TRANSPORTATION. l8l

Horseshoeing kit.

Extra shoes, one set especially fitted up for each animal, if work is to be distant

from a blacksmith's shop.
Hamessmaker's kit.
Extra harness leather, cinches, cinch hooks, lace leather, webbing, buddes,

rings, rope, etc.
Liniments, an.tiseptic washes, etc., for galls.

Experience has taught that the crosstree (sawbuck) saddle is best
adapted to the needs of the Survey for pack transportation, though
the Abercrombie, which is a combination pack or riding saddle, may
often be used to advantage. Either type should be rigged with
breast straps, breeching, and wide double hair cinches with the
large latigo rings protected with leather pads. If possible, the
saddle should be fitted to the animal's back and always used on the
same animal. Sweat pads, of 12-ounce canvas, renewed when neces-
sary, should be used between the blankets and the animal's back as
a protection to both.

ORGANIZATION OF PACK TRAIN.

In the pack train the natural leader should be the bell animal,
and only one bell animal should be in the train, unless there are
other leaders who tend to separate the pack train into small bunches,
in which event they should also have bells.

The bell animal should lead the pack train with one member of
the party riding him or the animal immediately following, and the
animals should be arranged in reference to their likes, dislikes, and
gaits. When practicable, distribute the men about four or five
animals apart, each man keeping the animals ahead of him in line
and preventing lagging. Until the animals are broken in, let each
man lead one, or if necessary a string of animals. Each man should
be instructed to watch the packs in front of him and should be held
responsible for them. No stops should be made to adjust a pack
without signaling those ahead to halt.

CARRYING CAPACITY OF PACK TRAIN.

It is safe to estimate that one pack load is sufficient for one man
for 22 days, the load to include portions of the ration, instruments,
outfit, camp equipage, and forage. When it is found necessax^ t$i

1 82 INSTRUCTIONS TO TOPOGRAPHERS.

transport forage for any length of time the size of the pack train
must necessarily be increased. Every attempt should be made to
make the loads as light as is consistent with the requirements; tents,
kitchen ware, stoves, or reflectors, foodstuffs, and other necessities
should be selected with special attention to this end.

Loads should average from 150 to 200 pounds, according to the
size and experience of the animal and the nature of the journey.
Heavier loads may be necessary, but loads within the limits given
will be found more expeditious, especially if the animals are just
from pasture, when heavy loads and long marches should be avoided
until they have had time to get hardened and packwise. Care must
be taken in balancing the heavy load in side packs, with the light
or bulky part on top, and in seeing that the pack is cinched tight.
Constant lookout must be kept to see that the load does not sliift or
turn; if it does it should be immediately straightened to avoid sore
backs or mishaps.

MARCHES.

The gait and distance when traveling depends entirely on the
character of the country. Over flat cotuitry , good roads, and smooth
trails* 30 to 30 miles is a good day 's joiuney . Across broken ooimtry,
over difficult moimtain trails, or through fallen timber, 10 miles or
less is all that can be made. If the train is to subsist on the country,
the different members of the party should be on the lookout for feed.

CARS OF PACK ANIMALS.

In rotigh country, where pack animals will have hard usage, they
should be given every possible consideration. If possible, camp
should be located convenient to feed and water. The saddle should
not be taken off at once; it should be loosened and allowed to stay
on the animal for half an hour if the back is wet. Immediately
thereafter, the pack animals should be allowed to roll and cool off
around camp, and if any of them have sore backs these should be
properly cleansed and treated. Their feet should also be inspected
frequently and shoes fitted and replaced when necessary. In regions
infested by mosquitoes a smudge should be built as a protection
f possible, shelter should be provided.

INSTRUCTIONS TO TOPOGRAPHERS. 183

UMITSD STAIBS SRTBlf OF PD9LIC-LAVP SOKVEYS.

The following discusskm, based on the " United States manual of
public-land surveys," to which the tofiQgrapher is referred for more
detailed information, is intended to give the topographer a feneral
outline of the plan and practices of the public-land •urve3rs.

TowvsHir innT&

The unit of the system is the town^p, a tract 6 miles square, or
nearly so, bounded on the east and west by true north-soutli lines,
and on the south and north by east-west lines, and subdivided into
36 sections, each a mile square, or nearly so.

As true north-south lines (that is, meridians) oonvefge nor&ward
to the pole, it is evident that the width of a towndiip decreases
slightly from south to north (41.9 links in latitude 30^ to 86.5 links
in latitude 5o^)S and that its shape is really trapezoidal and not
square. It is evident also that as the meridian lines are extetuled
northward town^ips wilt become pfogreanvety narrower and will
be reduced in area. These oomplesdties growing out of the tnhetent
convergence of meridians on a i^ilierical surfoce like that of the
earth were not taken into account in framing the original law, the
intent of which was, apparently, to pcovide for square URtti of uni-
form size ; nor was any pnmsfon made for a system of coRtpol Uoes
whereby the narrowing of the townships, on the one iamdt Ml ^^
inaccuracies in the surveying of the subordinate lines, on tjte odier
hand, might be kept within convenient limits. HoweTtr» tl|^ 4bst
public-land siu'veys to be executed, notably the gImIc '^Ikven
Ranges" in Ohio, demonstrated the need of remedying tfwie ^pfects,
and as a result there has been evolved by successiTe iMtl 9f^tf^ a
sy^em of rectangular surveying which ''harmoniret the HMMfMti-
bilities of the requirements of law and practice '* and hm taoome
the accepted standard for the entire country.

PRIKCIPAL MRgmiAIIS AHP RA8R UWM.

All surveys in a given area are referred to two priRMfy Uttes, a
principal meridian and a base line, passing tbfOU|^ «l isM^I poiRt;

i All puMic^aad Mill iii—wrti III iwi 1 jn riinim spf Bijpt. Achaia«fioo
links is equivalent to 66 feet u—mutt lamme, aad 9o cfaaiai eflQislv

184 INSTRUCTIONS TO TOPOGRAPHERS.

the one is a true north-south line and the other a true east- west line,
that is, a parallel of latitude. These two lines constitute the axes
of the system, and the township units are numbered with reference
to them in consecutive tiers to the north and to the south, respec-
tively, beginning at the base line; and in consecutive ranges to the
east and to the west, respectively, beginning at the principal me-
ridian. Any township, accordingly, may be designated by tier and
range number, as T. 14 N., R. 7 W. fourth principal meridian, or T.
10 N., R. 28 E. Moimt Diablo principal meridian. The principal
meridian must be added to each designation; there are about 30
separate systems in the United States, each with a separate set of
axes and a separate system of numbers. The number or name of the
principal meridian serves to distinguish these from each other.

STANDARD PARALLELS Ain> GUIDE MERIDIANS.

From the principal meridian, commonly at intervals of 24 miles,
auxiliary base lines called standard parallels, or correction lines, are
extended east and west. They are numbered each way from the
base line, thus, first standard parallel north, third standard parallel
south.

From the base line, usually at intervals of 24 miles, auxiliary
meridians called guide meridians are run due north. They are
numbered each way from the principal meridian, thus, first guide
meridian east, second guide meridian west. As they converge ap-
preciably in a distance of 24 miles (the exact amount depending on
the latitude), they are not continued beyond the first standard parallel
north, but end at closing corners on that line and start afresh from
standard corners a full 24 miles apart. It will therefore be seen that
standard parallels have two sets of corners, one set referring to lines
north of the parallel, and the other being established by township
and section lines from the south, closing on the parallel. The process
is repeated at the second standard parallel and at all succeeding ones.
Each guide meridian thus runs due north from parallel to parallel,
and on each of the latter is an offset to correct for convergence.

South of the base line guide meridians are run not south, but north,

so that the blocks inclosed between them and the parallels there are

essentially similai to those north of the base line. In case conditions

UNITED STATES SYSTEM OF PUBUC-LAND SURVEYS. 1 85

require that a guide meridian be run south it must be begun at a
properly established closing comer.

The standard distance of 24 miles between parallels and meridians,
it is to be noted, is not always strictly adhered to. Thus, in many
parts of the far West there are live tiers of townships (30 miles)
between parallels and six, seven, or more ranges between guide
meridians. In some places these irregularities in the spacing of the
standard lines necessitate the introduction of intermediate meridians
and parallels. These are designated by local names.

Certain data are of special importance in the platting of guide
meridians and standard parallels, and these the topographer should
not fail to secure from the Land Office. They are the offsets of the
meridians on the parallels and their closing distances.

The meridional convergence increases proportionately to the dis-
tance from the principal meridian. Therefore the offset of the sec-
ond guide meridian is double that of the first guide meridian
(between the same parallels); that of the third guide meridian is
three times as great; and so on in proportion (assuming the intervals
to be regular). Again, the convergence increases slightly northward
with the latitude. Thus the offset of a first guide meridian in lati-
tude 50° is more than double what it would be in latitude 30°. Of
course the actual offsets depart somewhat from the theoretical ones
because of inaccuracies in surveying, and this makes it all the more
imperative that they be noted on the plats.

It is to be remembered that all errors of closure in distance are
thrown in the last mile and are not distributed over the entire lene:th
of the line. The spacing of the comers along the line is thus not
affected by the amount of the closiue .

TOWNSHIP EXTERIpRS.

Whenever practicable the siu^ey of township exteriors within a
block boimded by standard lines begins with the southwest town-
ship and continues northward tmtil the entire west range is com-
pleted; thence it goes from south to north through the next range
east, etc. The mode of procedure is first to run the east boundary
of a township due north a full 6 miles. Then to run its north bound-
ary on a random or trial line from east to west, correcting back on a

1 86

INSTRUCTIONS TO TOPOGRAPHERS.

true line after the ''falling" north cm* south of the northwest township
comer has been ascertained. The closure in distance, however, is
thrown in the last half mile at the west end of the line; that is.
between the last quarter-sectioa comer and the town^iip corner.
The purpose of this is to t]u«M¥ the meridional convergence and all
irregularities arudag (voas inacciuwle surveying toward the west
bouxuiary ol the towulili. The last quarter-section corner accord-
ingly lies n0t mtdwiy im the last mile, but always an even 40 chains,
from the mile comer east of it, whatever the distance between it
and the towaAip comer may be.

In getting data for platting township exteriors, therefore, special
note shftuld be made oi the closing distances at the west ends of the
latitudinal townsllip boundaries. The accuracy of the surveys may
be gaged ffom a ooflBparison of the actual closing distances with tlie
theoretical ones, as indicated below:

Theoretical closing distances at different latitiides.

Latitude.

CloBiiig distance.

■ ■

Feet.

5,252
5,246
5,240
5,232
5,223

<
50"

79.58
79>49
79.39
79.27
79- X4

In the northernmost tier of townships in a block it is further neces-
sary to take note of the closing distances of the range lines on the
standard parallel. Theoretically these distances should be an even
80 chains, but inaccuracies in the azimuth of the standard lines on
the one hand, and of* the township lines on the other hand, tisually
cause discrepancies. It frequently happens that the length of chain
used for the one set of lines differs appreciably from that used for the
other, and the closure errors may then amount to several chains.
Such discrepancies should be marked on the plats.

UNITED STATES SYSTEM OF PUBLIC-LAND SURVEYS. 1 87

SECTION USES,

Each township is divided by section lines into 36 sections, which
are numbered consecutively, commencing with No. i at the north-
east angle of the township and proceeding west to No. 6; thence pro-
ceeding east to No. 12; thence west to No. 18; and so on, alternately
east and west, to No. 36 in the southeast comer. In all fractional
townships the sections bear the same numbers they would have if
the township was full.

As townships are trapezoidal and not square, they do not contain
a full 36 square miles each, but fall short of that amount by a num-
ber of acres. It being undesirable to distribute this shortage among
all of the 36 sections, the law provides that it shall be thrown into
the westernmost range of sections, and that the other sections shall
be laid out so as to contain a full 640 acres each, as near as may be.
Accordingly, the longitudinal lines between sections are run not
due BorUi, but parallel to the east boundary of the township. Each
bears sHghtly west of north, according to the latitude of the town-
ship and its distance from the east boundary. The latitudinal sec-
tioa lines are run parallel to the south boundary of the township ;
that is, as a rule they nm practically east and west.

The subdividing of all normal townAips begins \vith the south-
east section. Its west boimdary is run N. 0° i"" W. a full 80 chains;
its north boundary is then run east on a random or trial line, a quar-
ter section comer being temporarily placed at 40 chains. The "fall-
ing" north or south from the appropriate comer on the town^ip
boundary having been meastu'ed, the quarter section comer is then
shifted proportionately and set exactly midway between the section
cofners. In many of the older contracts these mles were not faith-
fully carried out, and in consequence little dependence is to be
placed on the position of the quarter section comers on the latitu-
dinal section lines. The west boundary of the nesct section north
is then rtm out, and then its north boundary as before, and so on
up through the entire east range of sections. The other ranges are
taken up consecutively from east to west, each being surveyed from
south to north. The range lines of the northernmost tier differ from
the others in that they are connected with the comers along th«*

1 88 INSTRUCTIONS TO TOPOGRAPHERS.

township boundary, and consequently are not always parallel to the
east boundary nor measure an even 80 chains in length. Theoret-
ically they should do so, but in practice the inacciu'acies in the sur-
vejring of the township exteriors on the one hand and of the section
lines on the other hand cause discrepancies. Accordingly, these
lines are run first on a random or trial line parallel to the east bound-
ary and then corrected back according to their falling. In order
to confine the irregtilarities in acreage to the northernmost tier of
lots, the excess of deficiency in measurement is thrown north to the
quarter section comer, and the latter consequently is set not mid-
way but an even 40 chains from the south end of the line.

In the west range of sections, again, the latitudinal lines are con-
nected to comers along the west township boundary. Each is there-
fore run first on a random parallel to the south boundary of the sec-
tion and then corrected back according to its falling. Here again,
in order to confine the irregularities in acreage to the westernmost
range of lots, the error (which normally is a deficiency equal to the
meridional convergence) is thrown west of the quarter section cor-
ner, and the latter is set not midway but an even 40 chains from
the east end of the line.

MBANDBRS.

Where land lines cross rivers, the right-angle width of which is
three chains and upward, lakes, bayous, and deep ponds of 25 acres
area and upward, meander comers are established on each bank,
and from these are run meanders (corresponding to traverse lines)
along the banks, to close on other meander comers. Similarly, water
bodies of 25 acres area and upward, lying within sections, are sur-
rounded by a meander tied to the two nearest section or quarter
section comers. Islands, finally, are located by triangulation from
meanders on the shore, an auxiliary meander comer being estab-
lished on each one of them.

Meanders are run for the sole purpose of providing a definite

boundary for the land areas in the lots abutting on water bodies, so

that the acreage of such fractional lots may be computed with accu-

racv. There is consequently no object in publishing meanders on

^graphic maps, and they are to be omitted. At the same

UNITED STATES SYSTEM OF PUBUC-LAND SURVEYS. 1 89

time, distances to meander comers and notes or plats of meander
lines are often of great value in the construction of the maps in the
field, and such data should therefore be secured in all important
cases.

Care should be taken in drafting the field sheets to discontinue
land lines at river banks and lake shores. They should not be rep-
resented as crossing the water body.

BLAZING LINES.

Trees on line have two chops or notches cut on the sides facing
the line. Other trees standing within 50 links of the line, on either
side of it, may be blazed on two sides diagonally or quartering to-
ward the line; the blazes approaching nearer each other the farther
the tree stands from the line.

Random lines are not blazed.

MARKING CORNERS.

Classes, — Land-siu^ey comers are divided into the fourteen fol-
lowing classes, each of which has a distinctive set of marks and is
marked in accordance with definite rules:

Standard township conier$r
Closing township comers.
Comers common to four townships.
Comers common to two townships only.
Comers referring to one township only.
Standard section comers.
Closing section comers.
Comers common to four sections.
Comers common to two sections only.
Comers referring to one section only.
Quarter section comers.
Standard quarter section comers.
Meander comers.

Comers on reservation or other boundaries not conforming to the regular sys-
tem.

Each of these fourteen classes of comers may be constructed as
the character of the cotmtry and the availability of the materials
permit, in eight different ways, as follows:

Stone, with pits and mounds of earth.
Stone, with mound of stone.

I90 INSTRUCTIONS TO TOPOGRAPHlSRS.

Stone, with bearins trees.

Post, with pits and mounds of earth.

Post, with bearing trees.

Mound of earth, with deposit and stake pit.

Tree comer, with pits and mound of earth.

Tree ccMtier, with bearing trees.

No less than 112 different combmations may be met in the field.
There is, however, no need of describing each combination sepa*
rately; the marks follow a definite simple system and in a measure
are self-explanatory.

Notches and grooves. — Stones and posts on all township and section
comers (except those on standard parallels) are set diagonally to the
lines; that is, with an edge on each line. On the edges are cut
notches, the number of which indicates the number of miles to tlK
nearest township comer in the directioii of the edfe. Thus, tiie
first mile comer on a range line between two towiiihips bos one
notch on the south edge and five notches on the north edge; and the
second mile comer, two notches on the south edge and four m^^^^fg
on the north edge. On a latitudinal townabip boundary, the Hot
mile comer west of the township comer has ooenoldi on tte east edge
and five notches on the west edge; and the seeond corner west has
two notches on the east edge and four notches on the west edge. A
oomer common to four townships has six notches on each of its four
edges.

Section comers within a township are notched on their south and
eaft edges only. The number of notches on them, thetefioce, mdt-
cates the distance in miles to the south and east township extefioo,
respectively. Thus, the comer between sees. 35, 26, 35, and 36 hss
ooe notch on its south edge and one notch on its east edge; the ooner
between sees. 10, 11, 14, and 15 has four notches on its louth edge
and two notches on its east edge; the comer between sees. 5, 6, j,
and 8 has five iiotches on both its south and east edges.

Sloaes and potts on standard parallels are set square with the lines;
that is» with a flat face on each line. Their faces are graavtd, tbft
mtmhtt ai gnx)ves on any face indicating the number of fltttea to
the nearest township comer in the direction of the face. AmDotd'
ingly, standard township comers have six grooves on their ttordi,
cMt, and west facts; closing township comers have six grooves oa

UNITED STATES SYSTEM OF PUBUC-LAND SURVEYS. 191

thcdr south, east, and west faces. Staadard aection coraers are
grooved only on their east axid west faces with respect to the stand-
ard township coniecs. Closaig section comers are ^milarfy marked
with respect to the closing townsliip comtts.

Tree comers are notched iso correspcmd with the notdies or groores
which stones or posts would bear in the same situation.

Additional mwrks. — Standard comers of all kinds are marked s c
on the north face; closing comers, c c on the south face. If posts
or trees are used the town^p and range numbers also are indicated
on the appropriate sides of standard and closing township comers;
and the township, range, and section ntunbers on the appropriate
sides of standard and closing section comers.

Posts at ordinary township corners have each town^ip and range
marked on the appropriate face; tree comers bear the same marks
on large blazes.

Posts at section comers are similarly marked with the ntunbers of
the surrounding sections, and in addition, with the number of the
township and range on the northwest and northeast faces,
respectively.

Quarter-section comers are marked "X s " on their north face if on a
latitudinal line, on their west face if on a meridicxud line. If stones
are used the s is omitted.

Pits mnA mounds, — In open country, where the soil is soft enoui^ to
permit digging, square pits are dug aboat each oomer, and the earth
taken from them is heaped up into a oonlcal mound. At comers
cu mi Mm to fottr townships the moisad is placed inunediately sooth
of the nomunent; at comen comaion to ficmr sections, west of the
nww M P i rnt ; at standard comers nortii, and at domag coraen aooth,
of the monument; and at quarter-section comers, north or west«f tke
monument acootdiQi^ as the line is a latitodtnal or meridianalone.

The pits ate plaacd on eadi line about all oofBem except aection
comers; at these last the pits are placed d i a f onally, one in each
section.

Where neither stone nor wood is available for snitahk corr
monuments a maifccd stone, cbatred stake, or qamt of dharto'
deposi t e d i foot bek>w the suifsce of the ground and the r
placed aborve it. ^

J

192 INSTRUCTIONS TO TOPOGRAPHERS.

Where the ground is stony and does not permit the digging of pits,
a pyramid of stones is built in lieu of a mound.

Bearing trees. — Bearing trees, each with a large blaze facing the
comer monument, are used wherever the required number of trees
within proper distance is available. They are disposed and marked
as follows:

At township comers one in each sturveyed township, marked with
township, range, and section number, followed by the letters **b T "
(bearing tree). At section comers, one in each section, marked with
township, range, and section number. At standard comers of all
kinds, two trees, one in each section north of the parallel; at closing
comers, two trees, one in each section south of the parallel. At
quarter-section comers, two trees, one in each section.

Witness corners. — When the true point for any comer falls in a
place where its destruction by natural or other causes would be cer-
tain, a witness comer is established in a secure position on a surveyed
line, if possible, and within 20 chains of the comer point thus
witnessed.

A witness comer bears the same marks that would be placed on the
comer for which it is a witness with the addition of the letters "w c "
conspicuously displayed above the markings. Its bearing trees,
similarly, are marked " w c."

• REQUISITIONS.

STATIONERY.

In ordering stationery it is advisable to request not more than
three months* supply at one time. Requisitions should be made
on triplicate form 9-002 and should designate articles by ntimbers
if any are known. Below are summarized the amount and kinds of
stationery suitable for the several classes of field parties. Attention
is called to the schedules of general articles (pp. 198-199), any of
which may be supplied any class of party.

.^ Precise-level party.

fll^ X account book, 9-9x8, (3o-page.
j ^yi^ a address, notification of, 9-966.
"J*^ 'S bill of loding. 9-060.
^^^f * employment contracts, 9-009.

REQUISITIONS. 193

6 employees, temporary, report of, to Civil Service Commission, 9-946.
6 employment, field, application ior, 9-9ax.
10 frdght or express shipment, label for, 9-948.
a instruments, transfer of, 9~i39.
a leave of absence, x-«i34.
X level book, bench mark descriptions, 9-9x6.

4 level notebooks, yard rod, 9-940.
as level party, weekly report, 9-933.

a4 mail forwarding card, postmaster, 9-977.
Z5 mail, second class, label for, 9-X60.
20 postal cards, plain.
35 precise levels, computation form. 9-933.
15 precise levels, abstract form, 9-937.

a property, inventory of, 9-054.
xo proposal for general suppUes livery, etc., 9-005.

a requisition, instnmients, 9-445.
zo requisition, stationery, 9-003.
13 topographic party, monthly report, 9-908.

6 envelopes, blue, cloth-lined, 5 by zo inch.
Z3 envelopes, addressed for Topography.

6 envelopes, white, extra letter size, 4J4 by loH inch.
25 envelopes, standard letter size, 3H by SH inch.

6 envelopes, maziila. 9 by X3>^ inch.

a ink, fotmtain pen, wood case.

6 pencils, Dixon's No. 4.

z paste tube.

z rubber bands, box.
zo tags, linen, express shipment.

5 tags, linen, penalty or plain.

3 tags, linen, instrument repair.

6 voucher, pay, 9-oz3a.

6 voucher, party pay and subsistence, 9-0Z5.
z5 voucher, purchase, 9-0Z3.

a voucher, subvoucher book, 9-0Z7 (camping parties 3 additional).
6 voucher, traveling expense, with detached memorandum copy, 9-016.

Primary-level party,

1 account book, 6o*page, 9-9Z8.
13 address, notification (tf, 9-966.

6 bill of lading, 9-060.
Z5 employment contracts, 9-^x)9.

6 employees, temporary, report of, to Civil Service Conmiission, 9-^46

6 employment, field, application for, 9-93 x,
zo freight or express shipment, label for, 9-948.

665x3 — Z3— — Z3

194 INSTRUCTIONS TO TOPOGRAPHERS.

3 instruments, transfer of. 9-139-

2 leave of absence, 1-034.

1 level book, bench mark description. 9-9x6.

3 level notebooks, primary, black cover. 9-903.

3 level notebooks, primary, yellow cover, 9-903-
25 level party, weekly report, 9-922.

24 mail forwarding card, postmaster. 9-977'
15 mail, second class, label for, 9-160.

20 postal cards, plain.

2 property, inventory of, 9-054-

10 proposal for general supplies livery, etc., 9-005.

2 requisition, instnmients. 9-445-
10 requisition, stationery, 9-002.
12 topographic party, monthly report. 9-908.

6 envelopes, blue, cloth-lined, 5 by 10 inch.
12 envelopes addressed for Topography.

6 envelopes, white, extra letter size, 4H by 10^ inch.

25 envelopes, standard letter size, 3H by S!H inch.

4 envelopes, manila, 9 by xaH inch.
I ink, fountain pen, wood case.

X paste, tube,
xo pencils, Dixon's No. 4.
I rubber bands, box.

5 tags, Unen, penalty or plain.
10 tags, linen, express shipment.

4 tags, instrument repair.

6 voucher, pay, 9-oi3a.

6 voucher, party pay and subsistence, 9-015- •

15 voucher, purchase, 9-012.

X voucher, subvoucher book, 9-017 (two additional for camping parties).
6 voucher, traveling expense, with detached memofandum, 9-016.

Secondary-level party.

1 account book, 6o-page. 9-918.
X2 address, notification of. 9-966.

2 bill of lading. 9-060.

XO employment contracts. 9-009.

2 employees, temporary, report of, to Civil Service Commission. 0-9 1'^.
a employment, field, application for. 9-931.
4 freight or express shipment, label for, 9-948.

2 leave of absence, 1-034.

3 level notebook, yellow cover, 9-903.
25 level party, wedcly report. 9-922.

xa mail forwarding card, postmaster, 9-977.
10 mul, second class, label for, 9-160.
^o postal cards, plain.

REQUISITIONS. 1 95

6 proposal for general supplies, livery, etc., 9-005.

1 requisition, instruments, 9-445.

5 requisition, stationery, 9-002.

6 topographic party, monthly report, 9-908.
3 envelopes, blue, cloth-lined, 5 by 10 inch.

12 envelopes, addressed for Topography.

1 2 envelopes, standard letter size, 3H by SH inch.

2 envelopes, manila, 9 by 12M inch.
I ink, fountain pen. wood case.

6 pencils. Dixon's No. 4.

5 tags, linen, express shipment.

3 tags, instrument repair.

3 voucher, pay. 9-0138.

4 voucher, party pay and subsistence 9-015.
15 voucher, purchase, 9-012.

I voucher, subvoucher book, 9-017 (two additional for camping party).

3 voucher, traveling expense, with detached memOTandum, 9-016.

Triangulation party.

I account book, 60-page, 9-918.
ID address, notification of, 9-966.

6 bill of lading, 9-060.

1 computation book, large, 9-889.
IS employment contracts, 9-009.

6 employees, temporary, report of, to Civil Service Commission, 9-046.

4 employment, field application for, 9r-92i.

6 freight or express shipment, label for, 9-948.

2 geodetic coordinates, computation of, 9-902.

1 geodetic coordinates, computation of, 9-901.

2 instruments, transfer of, 9-139.
2 leave of absence, 1-034.

10 mail forwarding card, postmaster, 9-977.
10 mail, second class, label for, 9-160.
20 postal cards, plain.

2 property, inventory of, 9-054.

6 proposal for general supplies, livery, etc., 9-005.

2 requisition, instruments, 9-445.
10 requisition, stationery, 9-002.
12 topographic party, monthly report, 9-90S.

6 envelopes, blue, cloth-lined, 5 by 10 inch.
12 envelopes, addressed for Topography.

6 envelopes, white, extra letter size, 4J4 by io\i inch.
25 envelopes, standard letter size, 3^ by 8^ inch.

6 envelopes, manila, 9 by i2>^ inch.

I ink, fountain pen, wood case.

I paste, tube.

196 INSTRUCTIONS TO TOPOGRAPHERS.

6 pencib, Dixcm's No. 4.

3 pencil tips, metal and rubber,
z rubber bands, box.

5 tass, linen, penalty or plain.

5 tags, linen, express shipment.

4 tags, instrument repair.

4 triangulation fidd notebook, 9-9x2.

6 votsdier, pay, 9-ox3a.

6 voucher, party pay and subsistence, 9-015-
15 voucher, purchase, 9-0x3.

2 voucher, subvoucher book, 9^0x7 (a additional for camping party).
6 voucher, travding expense, with detadied memorandum, 9-016.

Primary-traverse party.

X account book, 60-page, 9-9x8.
30 address, notification of, sr966.
Z3 bin of lading. 9-060.
25 employment contracts, 9-oo9>

6 employees, temporary, report of. to Civil Service Commission, 9-94

8 employment, field, application for, 9r^2x.
xo freight or express shipment, label for, 9^48.

3 instrument, transfer of. 9-X39.
3 leave of absence, x-034.

34 mail forwarding card, postmaster, 9^77*
Z5 mail, second class, label for, 9-X60.

xo pocket notebook, detachable leaves, $)-896a.
30 postal cards, plain.
Z3 primary-traverse field notd>ook. 9-938.
zo primary- traverse distance record notebook, 9-929.
3 property, inventory of, 9-oS4'
10 proposal for general supplies, livery, etc., 9-005-

3 requisition, instruments. 9-445«
xo requisition, stationery. 9-002.

13 topographic party, monthly report, 9-908.

35 traverse party, weekly report, 9-923.

6 envelopes, blue, cloth-lined, 5 by zo inches.
Z2 envelopes, addressed for Topography.

6 envelopes, white, extra letter size, 4^^ by xoH inch.
35 envelopes, standard letter size, 3H by 8H inch.

6 envelopes, manila, 9 by 12I4 inch.

X ink, fountain pen, wood case.

z paste, tube.
ZO pencils, Dixon's No. 4.

4 pencil tips, metal and rubber.

REQUISITIONS. 197

z rubber bands, box.

5 tass, linen, penalty or plain,
zo tags, linen, express shipznent.

3 tags, instruznent repair.

6 voucher, pay, g-ozja.

6 voucher, party pay and subsistence, 9-015.
z5 voucher, purchase, 9-oza.

3 voucher, subvoucher book, 9-0Z7 (a additional for camping parties).
6 voucher, traveling expezise, with detached memorandum, 9-016.

Topographic party (i topographer).

z accotmt book, 60-page, 9-9Z8.
zo address, notification of, 9-966.
za bill of ladizig, 9-060.
z5 employment contract, sroo9.

6 employees, temporary, report of, to Civil Service Coztmiission. 9*946.

6 employment, field, application for, 9-93 z.
zo freight or express shipment, label for, 9-948*

a instruments, transfer of, 9-Z39.

a leave of absence, z-034.
zo znail forwarding card, postmaster, 9-977.
zo zziail, second class, label for, 9-Z60.
zo postal cards, plain.

4 property, inventory of, 9-054.

24 proposal for general supplies, livery, etc., 9-005.

a requisition, instruments, 9-445.

6 requisition, stationery, 9r-ooa.
za topographic party, monthly report, 9-908.

8 traverse party, weekly report, 9-923.

6 envelopes, blue, cloth-lined, 5 by zo inch.
a5 envelopes, addressed for Topography.

6 envelopes, white, extra letter size 4H by zoH inch .
a5 envelopes, standard letter size, zH by 2,H inch.

6 envelopes, manila, 9 by zaK inch.

z izik, fountain pen, wood case.

z paste, tube.

3 pencil tips, metal and rubber.

z pizis, pyramid.

z rubber bands, box.

a Ruby erasers.

z sandpaper pencil pointer,
za tags, linen, express shipznent.

6 tags, instrument repair.

a vertical-angle traverse record, 9-913.

198 INSTRUCTIONS TO TOPOGRAPHERS.

3 voucher, pay, 9-oi.ia.

3 voucher, party pay and subsistence, 9-015.
I a voucher, purchase. 9-013.

I voucher, subvoudier book, groi-j (3 additional for camping party)..

4 voucher, traveling expense, with detached memorandum, 9-^16.

The following articles are usually required in camping parties only :

Additional outfit for camping parties only.

Auction sale, advertlseflnent, 9-051.

Auction sale, report of, 9-040.

Pasturage public animals, proposal, acceptance, and receipt, 9-008.

Property affidavit, 9-048.

Property, abandoned or lost, certificate for, 9-974.

Property, inspection report ol, 9-047.

Proposal for rations and forage, 9-006.

Proposal for supplies, field, 9-947C'

Storage public property, proposal, acceptance, and receipt, 9-007.

The following articles may also be had on requisition, if not already
supplied :

Additional outfit for all parties.

Topographic Instructions.

Regulations of Geological Survey.

Telegram book, carbon duplicating, 9-431.

Blotting-paper sheets.

Clips, Gem, Mogul, etc.

Fasteners, paper, McGill, O. K.

Letter file. Favorite.

Paper, carbon copy books, official.

Paper, ruled, 8 by loK inch.

Paper, scratch, note size.

Paper, carbon sheets.

Pencils, Kohinoor, 6-H, 7-H, 8-H, 9-H.

Pencils, red, blue.

Sealing wax.

Tacks, thumb.

Tracing linen, lo-yard rolls.

Tracing paper, thin sheets.

Water colors, burnt sienna, Prussian blue.

Paper, manila covers, 18 by 34 inch or 34 by 31 inch.

RE^^UISITIONS. 199

The following articles should be on requisitions separate from those
for other stationery:

Articles for which separate refuisiiiens are required.

Solar transit tables.

Stadia tables, new or old style.

Stadia tables. Anderson's.

Wheel tables.

Vertical-angle tables.

Geographic tables and formulas, Gannett.

Logarithms, 7-place.

Natural sines and cosines.

Nautical almanacs.

Tracing paper, 30-yard rolls, thick.

The following are miscellaneotis articles that may be had on requi-
sition when required:

Miscellaneous siationery.

Account book, 140-page, 9-9i9>

Primary traverse computation notebook, 9-931.

Transit record. 9-905.

Envelopes, note size, 3M by 6 inches.

Envelopes, return-penalty, 3H by 8H inches.

Penholders, drawing, writing.

Pens, drawing, K. & E.. Gillott's, 390, 291, 303.

Pens, writing, stub, falcon, etc.

Ink, indelible, black, red, green.

Water colors, saucers, and brushes.

INSTRUMENTS.

Requisitions for instruments for mdiiridtial field men of the classes
named below should be on form 9-445 only:

Plane-table triangulator,

I aUdade, 25-inch telescopic.

I compass, 4-inch.

I compass, declination.

I glasses, field.

I level, circular.

I plane-table board, 34 by 31 inches.

3 scale, triangular, metal, projection.

INSTRUCTIONS TO TOPOGRAPHBRS.

I tape, (ted, s»toat.
I tripod, Johun.
I lunbrdte, menu.

Tapt travtrtetatm.

I aUdsde, naht, BuAland.

I compug, ^4adi.
1 omtMM, poAet.

ilevcL drcular.

■ kvd,Lod[c

I pluic-tabk boud, 9 by g iadia. wltli compua.

I pkiifrtibleboaid. i; by II iochct. itith compus.

I tiipod, (nroM.

Foot travtrt^ian.
I Blldwle. tlfht.

I plui^tAble booid. 15 by ij inches, iriUt compAss.

Wheel tTaverieimm,
dt, nght, Biufcknd.

I tripod, tiavcnc

Stadia travtrtmaan.

I ptuic-Uibk board, ij by i] indici.
le board, \t by 14 Inche.
r. ceOulMd.

REQUISITIONS. 20I

Topographer.

I alidade, sight, Burkland.

z aneroid.

z compass, 4-inch.

X compass, declination.

X counter, hand.

I glasses, field.

I level, circular.

X level. Locke.

z plane-table board, 9 by 9 indies, with compass.

X plane-table board, 15 by 15 inches, with compass.

z plane-table board, z8 by 94 indies.

X plane-table board. 34 by 31 inches.

z protractor, celluloid.

z rod, stadia.

z scale, triangular, metal, projection.

z tape, zoo-foot, steel.

z tripod. Johnson.

z tripod, traverse.

z umbrella, wagon.

Precise leveltnan.

Dies, figures, z set.
Dies, letters, z set.
z level, Locke,
z level, prism,
a pins, turning.
3 rods, precise,
z tape, steel, 35 foot.

Primary leveltnan.

Dies, figures, z set.
Dies, letters, z set.
z levd. plumbing,
z level, Y, so-inch.
3 pins, turning,
z rod. New York,
z tape, 50 foot, metallic,
z tape, 35 foot, steel.

Secondary leveltnan,

X glass, fidd.

1 levd, Z5 indi.

I rod, Philaddphia.

z tape, metallic, 50 foot.

202 INSTRUCTIONS TO TOPOGRAPHl^RS.

Tri€n§ui9tar.

1 aneroid.

2 compasses, prismatic.
I glass, field.

I lamp, electric, hand.
I plumb bob.
I protractor, celluloid.
I tape, steel, 6 foot.
I tape, steel, 35 foot.
I theodolite.

1 umbrella, wagon.

Primary traverseman,

3 counters, hand.
Dies, figures, i set.
Dies, letters, i set.
z glass, field.

2 lamps, electric, hand,
lerel, plumbing, stadia.

II pins, tally.
2 plumb bobs.
2 rods, range.
I rod, stadia.

1 tape, icx) foot, steel.

2 tapes, 300 foot, steel.
I tape stretcher.

I tape repair outfit.
I transit, 30 second.

FOUNTAIN PENS.

One fountain pen only will be issued to each emplayee wjbo holds
a Secretary's appointment, the item to be the only one on a copy of
Form 9-002, which must be approved by the division chief. The
recorder, as well as the chief of each precise-level party, must be sup-
plied with a foimtain pen.

MISCELLANEOUS ARTICLES.

The following articles may be secured on Form 9-002 or 9-445,
whichever may be more convenient:

Bags, book, large or small.

Batteries, for flash lamps, round or flat.

Bench marks, copper nails with washers.^

Bench-mark posts.^

Bench-mark tablets.^

f

' Bstimatc number reQuired for each locality and order accordingly. Por coopcct*
tive work give the State name.

REQUISITIONS. 203

Canteens, 2 quart.

Celluloid sheets, opaque or transparent, 15 by 15, or 18 by 24 inches.

Cement, cans.*

Drills, i><-mch bit.

Flags (for camping parties only).

Hammers.

Hatchets.

Keel, red or blue.

Level bubbles (specify size wanted).

Paint cans, with brushes.

Paper, double-mounted, 18 by 24 or 24 by 31 inches.

Paper, single-moimted, 9 by 9, 15 by 15, or 18 by 24 inches.

Paper, tracing, 20-yard rolls or less.

Post-hole diggers.

Scales, flat boxwood, 1:240,000, 1:125,000, 1:96,000, 1:62,500, 1:48,000, 1:31,680,
1:24,000; inches, tenths, and fiftieths; inches, tenths.and eightieths; also
1:48,000 for chains. (Either of these may be made into Burkland sight alidades
on request.)

1 Estimate number required for each locality and order accordingly.

INDEX

A.

Page.

Abbreviations, authorized forms of aaS

Adjustments of instrimients, general rules for 30-32

See also Particular instruments.

Afternoon, observing in 49, 50-51

Agricultural data, mapping of 151-154

patterns and symbols for, figures showing 151, 152, 153

Alidade, adjustment of 32, iia

micrometer eyepiece for Z2Z-Z29

Aneroids, care of 24, 124-125

range of 24

use of 124

Angle equations, tabulation of 62-63

Angles, reading of 52, 78

tabulation of > 56-57

Appointment, application for 14

Aqueducts, mapping of 13^

Arable land, mapping of X53

patterns and symbols for, figure showing 152

Arcs, cleaning of 27

Atlas sheets, approval of 171

borders of 132-133, 177

lettering on 167-168

data regarding 131

features to be shown on 131

identification of 133

inspection of 171

lettering on 166-168, 171

names on 133-135

preparation of, for engraving 159-168

See also Engraving.

proof reading of 171, 172-174

Author diagram, use of 168

Azimuth, computation of 58-60, 82-83

correction of 84

observations for 54-56, 78-80

66512 — 13 14 aa.%

230 « INDEX.

®- Page.

Baggatie. personal. limitation of , 18

Baldwin solar chart, errors in use of 129

explanation of 125

orientation by 125. 128-129

plate showing 126

preparation of, for use 126-128

time correction from 130

Barren land, mapping of , 153

Bars, representation of 144

Base line, measurement of ^ 4a

measurement of, correction of, figure showing 122

Base lines and meridians, land-siuvey system of 183-185

Beaman stadia arc, use of 1 19-1 20

Bearing trees, use of 192

Bench marks, description of 8i, 90-91

location of 75. 88-89

mapping of 143-144, 161-162

representation of, conventional sign for .^ 211

Bench-mark posts and tablets, supply of 27

types of 75

for cooperative work 27

plate showing 46

Blazing lines, method of X89

Bluffs, inking of 164

Borders of atlas sheets, joining of i32"i33. 171

lettering on 167-168

Botmdaries, lettering at 166-167

mapping of 141-142, x6o-i6x

representation of, conventional signs for 211

Bridges, mapping of 138, 162

Bruises, treatment of 177-17S

Bubbles, prism level, adjustment of 97-98

setting of 30

specifications for 25

Buildings, mapping of 137-138. 160

Bums, treatment of 175

C.

Camp, administration of i6-iS

equipage for X8-19, 193

storage of , 19-30

subsistence in 15-16

Camping parties, stationery for 198^199

Canal locks, location of symbol for 139

Canals, mapping of X39> 160

INDEX^ 231

Page.

Cemeteries, mapping of 140

Chainmen, duties of 76, 123-124

Chief of party, reports by 21-23

Churches, when shown 137-138

ClifTs, inking of 164

Closure error, adjustment of, in level circuits 92, 95, 1 11

adjustment of, in primary traverse 84, 87

distribution of, among angles 56

Coke ovens, when shown 141

Compass, care of 28^

Computers, suggestions to 39-41

Contour figures, placing of ..... .* 165-166

Contour interval, range of 131 . 155-156

Contours, use of 146-148, 164-165

See also Depressions.

Conventional signs 205-228

Cooperation, with other bureaus ii-ia

with States 12, 89, 168

Comers, land, identification of 142-143, 151, 157

marking of i89-i9a

Comers, witness, use of zga

Correlates, table of 65

Courtesy, enjoinment of ., 12

Criticism . rules concerning 11

Cross wires, motmting cf 30-3a

Cultural features, lettering of 166

mapping of ^ 135-144, 160-161

names of , . . 133-135

representation of, conventional signs for i6o-i6i, 207-210

Cuts and fills, land, symbol for 140

Cuts, treatment of ^. 177

D.

Dams, representation of 139

Dam sites, mapping of 156-157

Death, tests for 177

Departures in primary traverse, computation of 84-85

Depressions, mapping of 164-165

Discipline in camp, rules for 16-1 7

Distances, computation of 7o-7t

determination of 93, 1 17-124

See a/.ro Stadia traverse; Wheel traverse; Tape traverse; Foot traverse.

Ditches, mapping of 139- *6o

Drainage. See Hydrographic features.

Drowning, aid in case of , i "v\*r'^'v^

232 INDEX.

E. Page.

Editing, regulations for 172, 174

Elevution figures, inking of i6a

Elevations, establishment of 89-90, X1&-119

See also Bench marks.

Emergency, first aid in 175-177

Employment contracts, terms of .' 14

Engraving, preparation of field sheets for 159-168

transmission for 172

See also Inking; Cultural features; Hydrographic features; Topographic
features; Lettering; etc.

Equations, triangulation, adjustment of 62-70

Equipage, care of 18-19

loss of 19

purchase of, in field 19

storage of '. 19-20

See also Triangulation; Traverse; etc.

Express, transportation by 29

Eyepiece, micrometer, description of X2i-i2a

F.

Ferries, mapping of 138

Field employees, appointment of 14

grades of 14

insurance for 15

traveling expenses of 14

Field parties, organization and management of 14-22

personnel and outfit of 43-44» 74

reports from 21

Field reports, scope of ai-22

Field sheets, engraving of. See Engraving.

identification of 133

Field work, for map construction 131-159

preparation for 131-133

Figures, triangulation, adjustment of 6o-6z

adjustment of, figure for 60

desirable groups of 45

tabulation of triangles for 60

Fills, symbol for 140

First aid, rules for 175-177

Flags, display of x6

Flesh -wounds, treatment of 177

Foot traverse, instrimients for aoo

method of 124

Fords, mapping of 139

Forest land, mapping of 259, Z7x, 171

^Tus and symbols for, figure showing 151

INDEX. 233

Page.

Form lines, use of 14B

Fotintain pens, issuing of 20a

Fractures, treatment of 178

Freight, transportation by 29

Frost bite, treatment of 175

Furnaces, location of 141

G.

Geodetic coordinates, computation of 71-73

Glaciers, mapping of 146

Grazing land, mapping of 153

patterns and symbols for, figure showing 153

Grooves, system of, on land survey corners 190-191

H.

Heliotrope, use of 49

Horizon, closing of, at triangulation stations 56

Hydrographic features, lettering of 167

mapping of 144-146, 16^-163

representation of, conventional signs for 162-163; 212, 2x9

Hygiene, laws of, adherence to, in camp 17

I.

Information, giving of 12, 13

Injury, first aid in case of 175-178

transportation in case of 178

Inking, conventions and symbols shown by 160

directions for 159-164

sequence of 159

Inks, list of 159

Instruments, accessory articles for 26-27

adjustment of 30~39» SO

See also Particular instruments.

care of ^ . . 37-29

cleaning of 27

delivery and return of , . . 2a

packing of 28-29

protection of, against weather 28, 50

responsibility for 22

requisitions for 199-202

specifications for 24-25

transfer of 2a

types of 23-24

transportation of 28-29

Insurance, provision for ^^

234 INDEX.

Page.

Intermittent streams, mapping erf ^^^^ x6a

Inventories, when required ao

Invoices, essential information in 22

L.

Lakes, mapping of 146

Land-classification board, data desired by i4Srx5i

transmission to i-a

Land-classification data, mapping of 149-159, 171, 172

See also Agricultural data; Water-supply data.

representation of, conventional signs for 151-154, 215-217

Land comers, mapping of 142-143, 151, 157

marking of 189-192

Land lines, mapping of 157

Land-Office plats, use of 132, 1^7

Latitudes, computation of 7 1—72, 84-86

Least-square adjustment, figure for 60

method of 62-70

Lenses, care of 27

Lettering, position of 166-167

punctuation of ^ 167

rules for 166, 171

style of 167, 226-228

Levees, representation of 140

Level circuits, computation and adjustment of ^. . io6-iii

orthometric correction for 106

See also Leveling, precise; Leveling, primary.

Leveling, precise, adjustment of 106-107

instruments for '. 201

observations in loo-ioi

recording in loi-ios

stationery for 192-193, 198-199

Leveling, primar>', adjustment of 107-111

adjustment of, figure showing 109

distribution of 87-88

instruments for • 201

stationer>' for 193-ISW, 198, 199

See also Bench marks; Elevations; Wye level; Prism level.

Leveling, secondary, instruments for 201

stationery for 194-195. 198-199

Level net, adjustment of 107-111

figure showing 109

Lighthouses, representation of J40

Locke level, adjustment of 34» 95

Longitude, computation of 71-72,85-86

INDEX. 235

M. Page.

Mad-dog bite, treatment of 176

Magnetic declination, measurement of 80

Mail, transportation by 39

Manuscript, transmission of, rules for 173

Map construction, field work of 131-159

field work of. See also Names; Cultural features; Hydrographic features;
Topographic features; Land-classification data.

office work of 159-174

See also Engraving; Photolithography; Editing; etc.

Marches for pack train, length of 182

Marginal lettering, rules for 167-168

Marks. See Stations; Bench marks.

Marshall, R. B., preface by 9

Marshes, mapping of ^ 144, 146

Meanders on land surveys 188-189

Medical attention, data on 175-177

outfit for, in field 178-180

Meridians and base lines, public land surveys . . .^ 183-185

Military symbols, conventional forms of 224-325

Mine dumps, representation of 140

Mineral lands, reports on 150

Mines, representation of 140-141

Monuments, boundary, location of 141, i43' 161

Mounds, at land-survey corners 191-193

N.

Names, authority for ^ 134

choice of 134-135

lettering of 166-168

♦Navigation, aids for, conventional signs for 233-333

Notches, system of, at section comers 190-191

O.

Observing, hours for angle reading 49

hours for leveling 93

method of 50-51.76-80,113-115

preparation for 49-SO

Orientation of plane-table, method of ii?- 125> 128-129

method of, plate showing , 126

Sec also Baldwin solar chart.

Owners, consent of 1 2-13., 46

P.

Packing instruments, care in 18-19

Pack animals, care of 183

forage f or . . » "^^

236 INDEX.

Page.

Pack train, carrying capacity of 181-181

equipment of i8o-i8x

organization of iji

speed of igj

transportation by 28-29, 180-18:

Paper, quality of !„, ug

Parcel post, use of 29

Pasturing, rules governing 1^20

Personnel of field parties , 14-15,43-44, 74.9194

See also Triangulation; Traverse; etc.

Photolithography, preparation for 169-170. 1:2

Pipes, oil and water, mapping of ij5

Pits at land-survey corners 191-193

Plane-table, orientation of 116. 117, 125, 198-129

Plane-table boards, packing of j3

sizes of 2^

Plane-table traverse, general methods of zz6-ii6

See also Stadia traverse; Wheel traverse; Tape traverse; Foot traverse.

Poisoning, antidotes for 2^5_j.^

Plane-table triangulation:

general instructions for 112-113

instruments for 199-200

observing and recording for 113-X15

stations for, choice of X13

Polaris, observations on 54-55, 78-79, 8a

Ponds, mapping of 146

Precise leveling. See Leveling, precise.

Press, information to 13

Primary control, establishment of 42-111

general methods of 42-43

See also Triangulation; Traverse; Leveling.
Primary leveling. See Leveling, primary.
Primary traverse. See Traverse, primary.

Prismatic eyepieces, supply of 24

Prism level, adjustment of 96-9S

care of 98

precise leveling with 100-105

primary leveling with 94-100

limit of error in 95, xoo

I>ersonnel and outfit for 94-95

record of observations with 99, 104-Z05

Private property, entry on 12-13, 46

Projection, method of xi2, 131, 132

Proofreading, instructions for ^71, 172-174

INDEX. 237

Page.

Public, relations of topographers to 23-13

Public land lines, mapping of i43'Z43, z6z

Public land siu^eys, system of i83-x9a

Public property. See Equipage.

Purchase of property, regulations governing 19

Q.

Quadrangles, nature of 131

Quarries, representation of 140

R.

Railroad crossings, representation of *^

Railroads, mapping of i*7» *38

Range number, placing of , ^. *6x

Rations, list of 1S-16

Reconnaissance, data required in 44""4S

Record forms, field, for azimuth observation SSf 78~79

for plane-table "3

for precise leveling 99i 101-105

for primary leveling 94

for primary traverse 8o-8i

for triangulation Si~S3

Reports, requirement of ai-aa

Requisitions, rules for 192-203

Reservoir sites, mapping of i56~iS7

Reservoirs, mapping of 139

River profiles, delineation of 170

Rivers, mapping of 144-145, i54"IS7j 162-163

topography along, mapping of i5S~xs6

River surveys, maps and reports of iS4-iS7

preparation of, for photolithography 169-170

scale of X54~*5S

Roads, classification of 136-137

representation of 136, x6o

Rod level, adjustment of 34

Rupture, treatment of 178

S.

Scaffolds, erection of, at triangulation station 48

Scalds, treatment of 175

Scale of maps, position of 168

varieties of 131

Secondary control, establishment of 1x2-130

5e« o/^o Plane-table triangulation; Plane-table traverse; Aneroid; Baldwin
solar chart.

338 INDEX.

Page.
Secondary leveling. See Leveling, secondary.
Section comers. See Corners.

Section numbers, use of 161

Section lines, description of 187-188

Shore line, definition of 144

Sickness, principal causes erf 17

Sights, length of, on level lines 93, 99

Signals, centering of 48-49

location and construction of 47-48, 113

Sine equations, table of 64

Sinks, mapping of 146

Slopes, inking of ^ 164

Smelters, location of 141

Snake bite, treatment of 176

Solar chart. See Baldwin solar chart.

Spherical excess, computation of 61-62

Sprains, treatment of 178

Springs, importance of 145-146

data required concerning 154

Stadia arc, use of 1 19-121

Stadia rods, specifications for 25

Stadia traverse, instruments for 122-123, aco

methods of 118-123

State surveys, relations of topographers to 12

Stationery, requisitions for 192-199

Stations, establishment of 44. 113

location of, by three-point method 115-116

figure showing 116

marks for 46-47

plate showing 46

names for 45, 114

necessary number of 44

symbol for 143

See also Bench marks.

Stations, eccentric, reduction of, to center 57-58

Steamboat routes, mapping of 139

Stock, forage for 16

Storage of property, rules governing 19-20

Stream flow, reports on 157-158

Streams, mapping of 117

See also Rivers.

Subsistence, supplies for 15-16

Surgical aid, outfit for , 178^180

rules for » 175-178

Sunstroke, treatment of 175

INDEX. 239

T. Page.

Tanks, location of Z46

Tapes, cleaning c^ 27

cloth, marking of 123

use of 76-78

Tape traverse, instruments for 300

making of 123-124

Taping, chainmen for, duties of 76

errors in 77

method of 77

Telescope lenses, cleaning of 27

Telescopic alidade, adjustment of 32

Theodolite, adjustment of 36-39

Three-point method, description of 115-116

figure showing , 116

Timber cutting, owner's consent to 46

Topographic branch, organization of 71

relations of, to Government 11-12

to public ^ 12-13

to State surveys 12

Topographic expression, importance of 148-149

Topographic features, lettering of 166

mapping of 146-149, 164-166

representation of, conventional signs for 164-166, 213

Topographic maps. See Atlas sheets; Engraving; etc.

Tbpographic field party, instruments for 201

stationery for 197-199

Topography, sketching of ii4» n7-"8, 147-149

Township numbers, placing of i6z

-Townships, exteriors of, running of 185-186

section lines, running of 187-188

system of 183

Trails, mapping of 139

Transit, adjustment of 34-36

Transmission of manuscript, rules for 172

Transportation of instruments, rules for 28-29

of persons, expense of X4

of property, care in 18-19

See also Pack train.

Traveling expenses, rules governing 14

Traverse, plane-table. See Plane-table traverse.

Traverse, primary, azimuth for 78-80

azimuth for, computation of 82-84

computations for 82-87

general methods <rf 421 7S-7&

instruments for *«''>•

240 INDEX.

Page,

Traverse, primary, outfit for 74

preparation for 75-76

recording for 80-82

stationery for , 196-197, 19^-199

Traverse boards, attachments for 24

Triangles, tabulation of 6oh5i

See also Figures.

Triangulation, azimuth observation for 54-56

computation of 56-74

in field ^4

distances in, computation of 70-71

equations for, adjustment of 62-74

field work of 43-56

figures desirable for 45

general methods of 42

instruments for 202

observing methods for 49-54

outfit for 43-44

plot of 54

preparation for 44-49

reconnaissance for 44-45

recording for 51-54

signals for 47-48

spherical excess in 61-62

stationery for 195-196, 198-199

stations for 44. 46

conventional sign for 143, an

Triangulation, plane-table. See Plane-table triangulation.

Triangulation parties, personnel of 43

Triangulation systems, connection of, with determined positions 42-43

Tunnels, representation of 139

Typhoid fever, prevention of ;• 17-18

V.

Venomous insects' stings, treatment of 176

Verniers, cleaning of j •

Visitors in camp, rules governing i3

W.

Waste land, mapping of 153

Watch, error of 55»8o, 129

Water elevations, mapping of 162

Watering places, mapping of 154

See also Wells; Springs; etc.

INDEX. 241

Page.

Water-power data, mapping of * 158-159

reports on 150, i5»-xs9

Water-supply data, mapping of 154-159

reports on 150, 155, 157-159

Weather, protection of instruments against 28

Wells, location of 140, 146

reports on 154

Wharves, representation of 140

Wheel traverse, instruments for aoo

method of laj

Witness comers, land surveys, use of 19a

Woodland sheets. See Forest land.

Wye level, adjustment of 32-34

leveling with 91-94

adjustment of 9a-93

limit of error in 9a

personnel and outfit for 91-93

records of 94

rod for, reading of 93

Y.

Yard rod, care of 98

graduation of 95

reading of 95-96

testing of 98

Y level. See Wye level.

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