1874.] Alternating Currents. 161 
sometimes of thousands of miles,* instead of their being 
merely the reaction, the rebounds or refluxes of the imme- 
diately preceding effluxes occasioned, as I have shown, by local 
submarine earth-shocks. And writers in some of our leading 
periodicalst, having adopted the same idea, have ascribed 
the extraordinary disturbances of the Sea in California, New 
Zealand, Australia, and other islands in the Pacific, on the 
13th and 14th of August, 1868, immediately after the 
destruction of Arica, to one of these great sea waves 
produced by a submarine earthquake near Peru, and moving 
onwards in all directions with varying velocity (like other 
great sea waves) according to the square roots of the 
varying depths which they traversed. But such waves are 
only imaginary; they have never been seen, nor can their 
existence be proved. None such existed at any of the 
similar agitations in the West of England which I have 
described during the last thirty years; and, therefore, none 
such can be rightly assumed to have existed at any other 
similar agitations. To remove all doubt, however, on this 
point, I invite attention to what was observed at Plymouth, 
on the 29th of September, 1869, during the extraordinary 
disturbances of the sea that day, on the northern as well as 
on the southern coasts of Devonshire and Cornwall. Ex 
uno disce omnes. 
The alternating current in Cattewater, an anchorage 
outside Plymouth pier (Sutton Pool), rushed in and out of 
the pier every 15 or 20 minutes, whirling about the boats 
and vessels, parting their hawsers, and carrying a schooner 
which had almost reached the pier back two or three furlongs, 
and then to and fro so helplessly that a steam tug was 
despatched to her assistance, and towed her in. This com- 
motion was almost universally believed to have come in from 
the offing, through the two entrances at the ends of the break- 
water. I wassure from past experience that it did not, and so 
it proved. One of the keepers of the lighthouse on the break- 
water, and one of the labourers there, informed me that they 
were on the breakwater all that day, and that the sea there 
Was quite undisturbed. Moreover, the foreman of the 
labourers, who was absent that day, told me that, after 
having witnessed the extraordinary disturbance in Catte- 
water, he was so convinced of its having proceeded from 
outside the breakwater, that he fully expected, when he 
* Quarterly Journal of Science for January, 1864. 
+ See the articles on Earthquakes in the “Times” of November 3, 1868, and 
the “ British Quarterly Review” for January, 1869, and ‘‘ Blackwood’s Edin- 
burgh Magazine” for July, 1869. 
