38 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 76

NO. 2

HISTORY OF

ELECTRIC

LIGHT SCHROEDER

₃₉ designedtofittherequirementsof the seriesarclamp.

The Thomson- Houston machine was

^{a bipolar,} having an armature ^{consisting of} threecoils, one end ofeachof the three coils havinga

common

termi- nal, or ^"

Y

" connected, as it is called.

The

other end of each coil

was

connectedtoa

commutator

segment.

The machine was

toa great extentself-regulating,that isthe current

was

inherently constantwith fluctuating load, as occurs

when

the lamps feed or

when

the

number

of lamps burning at one time should change for

any

^{reason. This} regulation

was

accomplished

by what

^is called "armature reaction,"

which

is the effectthe magnetization of the

armature

has on the field strength. Close regulation

was

obtainedby a separate electro-magnet.

0^mi

Diagram uf T-li Arc Lighting System.

in series with the circuit,

which

shifted the brushes as the load changed.

As

there

were

but three

commutator

segments, one foreach

coil, excessive sparking

was

preventedby an air blast.

The

^"

T-H

^"

(Thompson-Houston) lamp employed

the shunt feed principle.

The

carbons

were

normallyseparated, being in

most

^types

drawn

apart

by

a spring.

A

^{high resistance} magnet, shunted

around

the arc, served to

draw

the carbons together. This occurred on starting the

lamp and

thereafterthe voltage of the arc

was

held con- stant by the balance between the spring

and

the shunt magnet.

As

the carbon

burned away

the

mechanism advanced

to a point

where

a clutch

was

tripped, the carbons brought together,

and

the cycle re- peated.

Both

the

T-H and Brush

systems

were

extensively used in street lighting, for

which

they

were

the standard

when

the

open

arc

was

superseded

by

the enclosed.

40 SMITHSONIAN MISCELLANEOUS COLLECTIONS

^{VOL. ye}

OTHER AMERICAN ARC LIGHT SYSTEMS

Beginning with about 1880, several arc^lightsystems

were

developed.

Among

these

were

the Vanderpoele,

Hochausen,

Waterhouse,

Maxim,

Thomson-Houston

Arc Lamp, 1878.

This is an early model with a single pair of carbons.

Thomson

Double Carbon Arc Lamp.

This later model, having two pairs of carbons,was commer-

cially used for

many

years. This lamp is in the collection of the Smithsonian In- stitution.

Schuyler

and Wood. The

directcurrentcarbonarcisinherently

more

efficient than the alternating current lamp,

owing

tothe fact that the continuous flow of current in one direction maintains

on

the positive

NO. 2

HISTORY

OF ELECTRIC

LIGHT — SCHROEDER

4I carbona larger crater ^atthe vaporizing point of carbon. This source furnishes the largest proportion of light, the smaller crater in the negative carbon

much

less.

With

the alternating current arc, the large crateris

formed

first

on

theupper

and

then

on

thelowercarbon.

On

^accountof the cooling

between

alternations, the

mean

temperature

falls below the vaporizing point of carbon, thus accounting for the lowerefBciency of the alternating current^arc.

For

this reason ^all these systems used direct current

and

the 10

ampere

ultimately displaced the 20

ampere

system.

The

10

ampere

Maxim Dynamo.

This dynamo is in the collection of the Smithsonian Institution.

circuit

was

later standardizedat 9.6amperes, 50 volts per lamp.

The lamp

therefore

consumed 480

watts giving

an

efificiency of about 15

lumens

per watt. This

lamp

gave an average of 575 candlepower (spherical) in alldirections,

though

^it

was

called the

2000

cp (candle-

power)

arc as under the best possible conditions it could give this candlepower in onedirection. Latera 6.6

ampere

arc

was

developed.

This

was

called the ^" 1200 cp^"

lamp and was

not c^uite as efficient as the 9.6

ampere

lamp.

42

SMITHSONIAN MISCELLANEOUS COLLECTIONS

VOL. '](i

SUB-DIVIDING

THE

ELECTRIC

LIGHT

While

the arc

lamp was

being commercially established, it

was

at onceseen thatit

was

too large a unit forhousehold use.

Many

inven- tors attacked the

problem

of

making

a smaller unit, or, as it

was

called, "sub-dividing the electric light." In the United States there

were

four

men

prominentin this

work

^:

WilHam

E. Sawyer,

Moses

G.

Farmer, Hiram

S.

Maxim and Thomas

A. Edison.

These men

did not

make

smaller arc lamps butallattemptedto

make

an incandescent

lamp

that

would

operateon the arc circuits.

Sawyer's Incandescent Lamp, 1878.

This had a graphite burner operating in nitrogen gas.

Farmer's Incandescent Lamp, 1878.

The graphite burner oper- ated in nitrogen gas. This lamp is in the collection of the Smithsonian Institution.

Sawyer made

several

lamps

in the years 1878-79 alongthelines of the Russian scientists. All his lamps

had

a thick carbon burner operating in nitrogen gas.

They had

a long glass tube closed ^at one

end and

the other

cemented

to a brass base through

which

the gas

was

put in.

Heavy

fluted wires connected the burner with the base to radiate the heat, in order to keep the joint in the base cool.

The

burner

was

renewable

by

openingthe

cemented

joint. Farmer's

lamp

consisted of a pair of

heavy

copper rods

mounted on

a rubber cork,

between which

a graphite rod

was

mounted. This

was

inserted in a glass bulb

and

operated ^{in nitrogen} gas.

Maxim made

a

lamp

having a carbon burner operating in a rarefied hydrocarbon vapor.

He

also

made

a

lamp

consisting of a sheet of platinumoperating in air.

NO. 2

HISTORY

OF ELECTRIC

LIGHT SCHROEDER

₄₃