CONTENTS.
Page
Introduction ........
Telegraphs generally:
Telegraphs by means of light.
-direct sight ......
-electricity.
On the production of electricity.
Electricity from friction.
-chemical action.
On the production of electricity from the magnetThe production of electricity by a change of temperature .
Electricity from animals.
-- other sources ......
The means employed for making the presence of the electric power
cognizable to the senses.24
On the means usually employed for transmitting electricity to adistant place . . . , . . . . . .29
First principles of an electric telegraph.34
Telegraphs invented prior to any of those which have been patented 37Brief Summary of Telegraphs prior to the year 1838 . . 38
Description of Telegraphs prior to 1838 :
Lesarge’s Telegraph.40
Lomond’s Telegraph.41
Betancourt's Telegraph. .id.
3
468
ib.
12
16
18
20 ,
22