The most interesting feature of Giraldus’ tidal studies, however, are not these general speculations regarding causes but some very neat observations made on the British and Irish coasts. In the first place, he remarks on the choppy water of the Irish Sea, which presumably he connects with tide rips.[882] He then goes on to discuss the difference in the hour of high water at various Irish ports, at Milford Haven in Wales, and at Bristol in England. When the tide is at the half-ebb in Dublin, at Milford Haven it is at the half-flood, and near Bristol just beginning the rise. Let us see what the facts of the case are at the present day.[883] On February 1, 1919, half-ebb occurred at Dublin at about 2:30 P. M., half-flood at Milford Haven only about an hour and a half later, and low water had occurred at Bristol half an hour earlier. In other words Giraldus’ observations on the relative times of the tides at these three points were unusually accurate. Furthermore, he explains that at Wicklow, on the Irish coast opposite Wales, the water falls at the same time that it rises throughout the sea in general. When Giraldus here speaks of the “sea in general” he perhaps had in mind tidal observations made at other points on the coast not far to the south. Modern tide tables show that near Arklow, only about fourteen miles away, it is low water some two hours and a half earlier than at Wicklow. The water, consequently, is rising at Arklow for two hours and a half while it is still falling at Wicklow. That Giraldus was familiar with Arklow is shown by the fact that he mentions a river entering the sea there and describes a curious rock in the harbor.[884] Finally, Giraldus states[885] that when the moon has passed the meridian the waters first recede from the coasts of Britain but that on the Irish coasts in the vicinity of Dublin full flood corresponds to this recession of the waters. In the vicinity of Wexford, however, flood waters do not correspond with the flood at Dublin but rather with the flood waters on the British coast at Milford Haven. Giraldus was mistaken, if we are right in interpreting his words to mean that he thought that the tidal undulation which produces high water at Dublin is a different wave from that of Wexford or Milford Haven. No tidal undulation enters the Irish Sea from the north, and consequently the ebb and flood at all of these places is caused by the same wave. On the other hand, this wave reaches Dublin nearly five hours later than it reaches Wexford and Milford on the opposite shore, and the accuracy of Giraldus’ data on the time of these tides is further confirmed by modern tide tables, which show that flood water at the Welsh port may occur only twenty-four minutes earlier than at Rosslare Point, the entrance to Wexford Harbor.