38 REPORT—1850. 
tione fuit Solis Colossus Rhodi......... septuaginta cubitorum altitudinis fuit. 
Hoe simulacrum post quinquagesimum sextum annum terre motu prostra- 
tum, sed jacens quoque miraculo est......... spectantur intus magne molis 
saxa, quorum pondere stabiliverat constituens.”—Plin. Nat. Hist. ].xxxiv. 18. 
It was thus overthrown, according to Eusebius, in the second year of the 
139th Olympiad, or 221 years before the Christian zra. 
In coherent formations, or rocky strata, there seems ἃ priori ground to 
suppose that the velocity of the earth-wave is not less than 10,000 feet per 
second, but it may be much less in loose and incoherent material. 
I trust in a future Report to be able to give the results of some actual 
admeasurements of the velocity of earth-waves in various formations, co- 
herent and incoherent, the experiments for which are now in progress. 
22nd. The direction and velocity of translation of the earth- 
wave or shock change occasionally in passing from the boun- 
daries of one formation to those of another. 
This part of the subject demands much additional careful observation. 
It has been long remarked, that buildings have been variously affected in 
the same earthquake in different localities, which varied in the nature of 
their subjacent formations, or in their levels or elevations. 
The change in destructive effect from the same shock has generally been 
most evident along the lines of boundary separating different formations, 
And along such junctions, shocks have been described as succeeding each 
other in opposite directions, but with a difference in force, with scarcely any 
interval in time betwixt them, and the second shock being the weaker one. 
Thus in the New Zealand earthquake of 1848 most of the shocks came from 
the North or N.N.E., but very few of the shocks appear to have come 
from the opposite direction, ἐ. 6. S.E. and §.S.E. “ May these,” says the nar- 
rator, “ be a sort of subsidence from the southward after some upheaving from 
the northward?” He appears, however, to zvfer the directions from the move- 
ments of furniture only. The Lisbon shock was felt all over Spain, except 
in Catalonia, Aragon and Valentia; it is difficult to see why these should 
be excepted ; but the difficulty may arise (assuming the fact) only from our 
ignorance of the nature of the intervening formations. (Encyc. Londinensis, 
in verb.) 
Dolomieu, in his dissertation on the Great Calabrian Earthquake, says, the 
shocks sustained by the houses and villages situated upon the hills on the 
solid rock, were less felt and did less damage than those which occurred in 
the plain. 
It is to be recollected that the general formation of Calabria, from the axis 
of mountains towards the sea, as described by Dolomieu, may be roughly 
represented by the following section :— 
a 
6 
a. Granite. e. Sand, or scarcely coherent sandstone, 
a®, Slates. ἢ. Clay of great de! 
ὃ, Decomposed granite. e. Alluvium ; black rich earth. 
: 
a 
4 
ἢ 
) 
3 
' 
Ἷ 
᾿ 
a 
4 
ς 
: 
; 
“ 
