The times. [volume] (Washington [D.C.]) 1897-1901, 1901-02-10
BY PROF. ELlHU THOMSON

rent and that the direction of turning de
ponds on the direction of the current. The
study of the magnetic effects of electric
currents by Aragc, Ampere, and the pro-
/ duction of the electromagnetic by Sturgeon,
together with the very valuable work OF
I Henry and Others made possible the COM
! pIetion of the electric telegraph. This was
! done by Morse and Vail in America. and
almost simultaneously by workers abroad.
but before Morse had entered the field
Prof. Joseph Henry had exemplifed by ex-
periments the working of electric signal
ing by electromagnetic over a short line
II was Henry. in fact who first made
practically useful electromagnetic of sott
, iron. The history of the electric telegraph
teaches us that to no single individual is
the invention due. The Morse system had
been demonstrated in 1887. but not until
| 1874 was the first telegraph line built. II
connected Baltimore and Washington and
! the funds for defraylng its cost were only
! obtained from Congress after severe
! struggle This can easily be understood,
| for electricity had not up to that time ever
/ been shown to have any practical useful
| ness. The success of the Morse telegraph
was soon followed by the establishment of
| telegraph lines as means of communica-
! ton between all the large cities and popu-
lous districts Scarcely ten years elapsed
before the possibility of transatlantic
| telegraph was mooted. The cable laid in
| 1858 was a failure A few words passed
and then the cable broke down completely.
! This was found to be due to defects IN
| construction. A renewed effort to lay
| cable was made in 1865. but disappoint-
/ ment again followed; the cable broke in
| mid-ocean and the work again ceased.
| The great task was successfully accom-
| plished in the following year; ana the
pluck and pertnacity of those who were
stalking their capital il not their reputa-
| lions for business sagacity, were amply
rewarded Even the lost cable of 1866 was
found. spliced to new cable, and COM
pieted soon after as a second working line.
The delicate instruments for the working
of these long cables were due to the gen.
Jus of Sir William Thomson, now Lord
Kelvin. whose other Instruments for cleo
trical measurement have for years been a
great factor in securing precision both in
scientific and practical testing. The num-
Der of cables joining the Eastern and
Western hemispheres has been increased
from time TO time and the opening of a
new cable is now an ordinary occurrence
calling for little or no especial note.
! The introduction Of the electric tele>
/ graph was followed by the invention Of
various signaling systems, the most i'm
/ portant being the fire alarm telegraph as
| suggested by Charming and worked out
! by Farmer We now, also, have auto
matte clock systems in which a master
clock controls or gives movement to the
hands Of distant clock dials by electric
currents sent out over the connecting or
circuit wires Automatic electric signals
are made when fire breaks out in build
ing, and alarms are similarly rung when 4
burglar breaks In. Not only do We have
teIegraphs which print words and char
acters. as in the stock ticker" but in the
form known as the teIautograph, invented
| by Dr. Elisha Gray, the sender writes his
message, which writing is at the same
/ time being reproduced at the receiving end
| of the line. Even pictures for drawings
are wired by special Instruments The
| desirability of making one wire connect-
| ing two points do a large amount Of work,
| and thus avoiding the addition of new
lines. has led to two remarkable develop
ments of telegraphy. In the duplex, quad
| ruplex and multiplex systems several mes
| sages may at the same time be traversing
| n single wire lire without interference one
| with the other In the rapid automatic
systems the working capacity OF the line
| is increased by special automatic trans
hitting machines and rapid recorders, and
the electric impulses in the line itself fol-
low each other with great speed.
| improvement in this field has by no
means ceased, and new systems for rapid
transmission are yet being worked out.
The object is to enlarge the carrying ca
| pacity of existing lines connecting large
centres of population. The names of
| Wheatstone. Stearns, Edison, and Delaney
| are prominent in connection with this
| work. For use In telegraphy the original
~ crude forms of voltaic battery, such as
| Davy used, were replaced by the more
perfect types. such as the constant bat
| terry of Daniel. the nitric acid battery of
Grove, dating from 1896, and the carbon
| battery Of Bunsen first brought out in
1872 Such was the power of the Grove
| and Bunsen batteries that attention was
! again called TO the electric arc and to the
| possibility of its use for electric illumina-
| ton. Accordingly we find that suggestions
| were soon made for electric arc lamps to
| be operated by these more powerful and
| constant sources OF electric current. The
| first example of a working type of an arc
lamp was that brought 10 notice by W. L.
| Static in lSi7. and his description Of the
| lamp ard the conditions under which 1t
| could be worked Is remarkably exact
| and fun statement. considering the time
| of its appearance. Static even anticipated
the most recent phase OF development in
| arc lighting, namely. the enclosure of the
light In a partially air-ight globe to pre-
| vent too rapid waste of the carbons by
| combustion in the air. In public address
| at Newcastle-on-Tyne In 1877 he advocated
| the use of the arc, so enclosed. in mines as
| obviating the danger of fire. But 1t was a
| long time before the electric arc acquired
| any Importance as 4 practical illuminant.
| There was, indeed. no hope of Its success
| so long as the current had to be obtained
! from batteries consuming chemicals
| and zinc. The expense was too great, and
| the batteries soon became exhausted In
| spite of this fact occasional exhibitions OF
| arc lighting were made, notably in 1885, by
la Cassagne and Theirs, in the "treets OF
| Paris.
| For this service they had invented an
are lamp Involving what Is known as the
differentlal principle, afterward applied 50
/, extensively TO are lamps. Tie length of
The arc or the distance between the car
hons of the lamp was controlled with
| great nicely and the light thus rendered
| very steady. Even as late as 1915 batteries