CHAPTER LI.
ROME.
THE next day, I was prostrated by fever and pleurisy, by cold caught in examining the extinct, volcanic tract between Velletri and Rome, where I was delayed thus a fortnight, and was able to make but few inquiries, before leaving by the first Marseilles steamer after my recovery, as to the distance and extent to which the shock had been felt, in the Roman states far away to the eastward, and towards the Adriatic shore.
At the Collegio Romano I found, on visiting the Padre Secchi, the able and active astronomer, that he had reason to believe that the shock had been instrumentally sensible, even as far as Rome.
He has at work at the college, a self-registering barometer, the principle of construction of which is based, upon the large iron tube of the instrument being balanced, its lower end dipping into a fixed cistern of mercury. The rise and fall of the whole tube, as its balance is disturbed by change of pressure, acts upon the registration apparatus, marking upon a band of ruled paper, moved by the clock.
Almost at the instant of the occurrence of the shock, allowance being made for the difference of times at the two cities
