ON THE FACTS OF BARTHQUAKE PHENOMENA. 13 
which is yet never attained, of which the history of all observational science 
is full. 
The author begins by stating that a horrible earthquake had occurred on 
the 6th of April, 1667, which had almost thrown down the whole of Ragusa, 
and then proceeds in a very clear way to relate the observations which he 
had made during its occurrence, while at Venice, the earthquake having 
shaken the whole of Romagna, &c. He then describes the motions of the 
earth, “ moveri multiplicatis vibrationibus, ab occidente ad orientem et 
reciproce ;” then the wave motions of the water in the Venetian canals, no- 
ticing the relations of the directions in length of these channels to that of 
the shock, the waves running along the canals, whose lengths were from west 
to east, and from bank to bank, or across all others. He then describes the 
directions in which belfries and other buildings were shaken; then the mo- 
tions of pendulous bodies, as church lamps, and describes his own sensations 
as like those of a man in a boat in motion which had struck some obstacle. 
From all his observations he concludes, “ Ecce igitur, mi lector, ex obser- 
vatione communi in eodem terremotu, quasi tres gradationes seu facies; 
prima qua motus illi est mixtus ex succussatione atque ex laterali illa vibra- 
tione, ita tamen ut lateralis ista vibratio minor sit succussatione, quod accedit 
eo loco ubi maxime deszevit causa movens. 
“ Altera qua motus iste etiamnum mixtus minore preefert succussationem, 
quam vibrationem, quod contingit in locis remotioribus abs causa movente, 
ubi plus minusve desidit illa succussatio pro ratione, majoris aut minoris suze 
remotionis causa movente. 
“ Tertia denique, ubi sola lateralis illa vibratio percipitur, quod contingit 
in locis remotissimis ab illa causa movente, que tamen sint intra spheram 
activitatis illius, cujusmodi erat Venetia nostra respectu motus Ragusei.” 
Having found that all the lateral vibrations were from west to east and the 
contrary, he proceeds further to inquire into the physical conditions that 
will satisfy the above complex motions, and without troubling himself much 
to inquire as to the nature of the first mover, but merely glancing at the 
opinions commonly held up to his time, he at once assumes any force what- 
ever to break through the crust of the earth. 
‘Ex natura inquam cum semper tempore terreemotu aliquid videatur ali- 
cubi foras prorumpere certe quicquid illud sit ut sic foras prorumpat debet 
revera terram supra stantem succutere, sed nihil omnino quod prorumpendo 
debeat sic lateraliter eandem vibrare: enimvero ita si foret sequeretur totum 
terre globum eodem motu tune sic vibrari et ex equo vibrari super axem 
suum, quod experientia ipsa arguit falsitatis manifestissime.” 
In illustration of this he gives the following figure: “Terra sit A, loco ubi 
sunt vel sulphura vel nitrum, vel aque bullientes, 
&c., sit B. Sentiatur motus corporis exiturientis 
a D per B usque ad E. Si motus iste esset 
etiam vibrationis lateralis a B ad D, necessario 
deberet etiam terra vibrari a D in F, et ab F in 
E ob solidam continuitatem totius globi, secun- 
dum omnes sue partes.” 
This last expression is a very remarkable one ; 
it is the first glimpse, as it were, that I can find in 
any author, of a true conception of pulse forces 
moving in solids, a notion that none of the ancient 
_ authors on earthquakes seem ever to have approached; all of them insisting 
_ upon the cavernous and perforated interior of the globe being the condition 
essential to the transmission of earthquakes. 
