In the Neapolitan earthquake, the sound was only heard in a district of about 3,300 square miles immediately surrounding the epicentres, while the whole area disturbed by the shock was not less than 39,000 square miles. A similar limitation was noticed in the Andalusian earthquake. According to the Spanish Commission, the sound was heard at only one place (Cordova) outside the provinces of Granada and Malaga; and its audibility was a rule confined to the area within which buildings were damaged by the shock. It was compared at different places to the noise of a passing train or a carriage heavily laden running on a paved road, of distant thunder, a great storm, or the discharge of heavy guns. At every place where the sound was heard, it distinctly preceded the shock, frequently allowing time for escape from houses that were afterwards ruined. Its duration within the meizoseismal area was on an average about five or six seconds, rarely perhaps did it exceed ten seconds. At some places in the same area, it overlapped the beginning of the shock, but generally it was separated from the latter by a very short interval, estimated at a second. From this precedence of the sound, the Italian Commission conclude that the sound-waves travelled more rapidly than those which formed the shock, an inference that depends on the assumption that both waves started simultaneously from within precisely the same focal limits. A different explanation, not based on these assumptions, will be considered more fully in Chapter VIII, dealing with the recent earthquakes of Hereford and Inverness. VELOCITY OF THE EARTH-WAVES. If, in a highly-civilised country, the time-records of an earthquake vary within wide limits, it is not surprising that those given for the Andalusian earthquake should be wholly untrustworthy. Even the clocks in public buildings and railway stations differed by as much as 25 minutes in their indications. An interesting observation is, however, described in the French report and is worth repeating, though it does not lead to any accurate result. At the time of the principal shock, two telegraph-clerks were in communication, one at Malaga and the other at Velez-Malaga. The latter, surprised by the shock, suddenly stopped his message; and, about six seconds later, the arrival of the earth-waves at Malaga explained the interruption to his colleague. As, according to the French report, Velez-Malaga is 9 kms. (or about 5-1/2 miles) nearer than Malaga to the mean epicentral point, it follows that the velocity of the earth-waves must have been about 1.5 kms., or nearly a mile, per second.[34]