I have now to report not only that the line has been constructed and opened to the public, but that its success, telephonic and commercial, has exceeded the most sanguine anticipations. Speech has been maintained with perfect clearness and accuracy. The line has proved to be much better than it ought to have been, and the purpose of this paper is to show the reason why.
The lengths of the different sections of the circuit are as follows:
| London to St. Margaret's Bay | 84.5 | miles. |
| St. Margaret's Bay to Sangatte (cable). | 23.0 | " |
| Sangatte to Paris. | 199.0 | " |
| Paris underground. | 4.8 | " |
| ——— | ||
| Total. | 311.3 | " |
The resistances are as follows:
| Paris underground. | 70 | ohms. |
| French line. | 294 | " |
| Cable. | 143 | " |
| English line. | 183 | " |
| —— | ||
| Total (R) | 693 | " |
The capacities are as follows:
| Paris underground. | 0.43 | microfarads. |
| French line. | 3.33 | " |
| Cable. | 5.52 | " |
| English line. | 1.32 | " |
| —— | ||
| Total (K). | 10.62 | " |
693 × 10.62 = 7,359 = K R
a product which indicates that speech should be very good.
2. Trials of Apparatus.—The preliminary trials were made during the month of March between the chief telegraph offices of the two capitals, and the following microphone transmitters were compared: