4 
ἣ ON THE FACTS OF EARTHQUAKE PHEZ NOMENA. 81 
explosions of powder being first recorded as earthquakes, and, subsequently, 
the shock ascribed to the true cause; for example, the blowing up of the 
Amphion frigate at Portsmouth about the end of last century, was taken for 
an earthquake over all the south of England. On oceasion of the explosion 
of the powder-mills at Hounslow this year, 1850, it was stated in the papers 
that the shocks, corresponding in number to the explosions (three in all), 
were distinctly felt at Sussex, a distance of between 50 and 60 miles from 
Hounslow ; and at Petworth, 40 miles off, the people ran out of their houses, 
supposing it to be an earthquake; yet here the weight of powder fired was not 
very large. The same circumstances were remarked when the great Spanish 
powder magazine was purposely blown up during Sir John Moore's retreat, 
said to have contained 1500 barrels of powder; it was felt as an undulation 
of the ground for miles away ; and again, in a less degree, when early in last 
century one of the great lintel stones of Stonehenge fell down upon the 
ground, it was felt all over Wiltshire, and thought at first to have been an 
earthquake. In fact all these were earthquakes, though not originating in 
natural causes*. 
Finally, it remains to make a few remarks upon the directions in which it 
is desirable that earthquake inquiries should be in future extended, and what 
are the chief desiderata of the subject. In the article drawn up for the Ad- 
miralty Scientific Manual, and published in that volume, on the observation 
of earthquake phenomena, the general character and classification of earth- 
quake observations will be found, and to this I refer. 
But altogether the most valuable and important additions that this branch 
of physics can now receive, must come— 
Ist. From a large and careful determination of the moduli of elasticity 
of rocks and of the other substances forming our geological forma- 
tions, and of the changes due to increase of temperature, upon such 
moduli. 
2nd. From systematic and connected observations of the direction, di- 
mensions, and other conditions of earthquake shocks or waves by self- 
registering instruments suitably placed in countries which are subject 
to very frequent shocks. 
3rd. From the co-ordination and comparison of such self-registered ob- 
servations, with those of self-registering meteorological and magnetic 
instruments. 
These observations must be continued for a considerable period, and those 
at distant points of observation must be in connexion as to time, &c. The 
᾿ς island of Zante, as being almost hourly shaken by earthquakes, almost all of 
_ which are of a manageable degree of force, and capable of exact registration, 
_ would be an excellent station for a first trial of such instruments, in con- 
 nexion with some other Mediterranean station; but when a complete self- 
_ registering seismometer shall have been constructed, it would be most de- 
sirable that every astronomical and magnetic observatory on the globe 
should be furnished with one, and this kept constantly in action, and its indi- 
* cations systematically recorded in connexion with those of meteorology, 
electricity, &c. 
_ Thave to regret that in the latest edition of his work on volcanoes, Dr. 
| Daubeny has discouraged the employment of such instruments, by an ob- 
᾿ς καὶ While these sheets have.been passing through the press, an explosion of some tons of 
᾿".. 5 
gunpowder, effected at Seaford on the south coast of England, for the purpose of removing 
seaward a large mass of chalk cliff, produced so real an earthquake, that a chimney was 
thrown down in an adjacent village, and houses shook at a distance of three miles, yet no 
_ sound or shock was transmitted through the air.—See ‘ Times,’ Sept. 1850, 
