268 PHYSICAL GEOGRAPHY. 



the fountain ; when he is awake, he stops the water ; when he sleeps, it flows.' " The far- 

 famed pool of Siloam is thus to be classed with the ebbing and flowing wells, though it 

 does not appear that any character of periodicity belongs to the phenomenon, 



We have similar examples nearer home. In the diocese of Paderborn, in Westphalia, 

 there is a spring which disappears twice in every twenty-four hours, returning always 

 with considerable noise after six hours, and hence called by the inhabitants the bolder- 

 born, or boisterous spring. Lay Well, near Torbay, also ebbs and flows very visibly, 

 several times every hour, the distance between high and low-water mark, according to 

 one observer, being somewhat less than half a foot. Another irregularly reciprocating 

 spring occurs in the neighbourhood of Giggleswick, in Yorkshire, at the foot of the Saar, 

 an almost perpendicular cliff of limestone and gravel, apparently about 150 feet high, 

 and extending above three miles in length. The water discharged from the rock falls 

 immediately into a stone trough, in the front of which are two holes near the bottom 

 the outlets of two streams that flow constantly from the artificial cistern. An oblong 

 notch is also cut in the same side of the trough, which extends from the brim of it nearly 

 to the level of the two holes already mentioned. This aperture is intended to show the 

 fluctuations of the well : for the water subsides in the notch when the stream issuing from 

 the rock becomes languid ; on the contrary, the surface of the water rises again in the notch, 

 so soon as the influx into the trough begins to be more copious. The reciprocations of the 

 spring are easily observed by this contrivance ; and they appear to be very irregular, 

 both in respect of duration and magnitude. The interval of time betwixt any two suc- 

 ceeding flows is sometimes greater, and at other times less, than a similar interval which 

 the observer may happen to take for his standard of comparison. The rise of the water 

 in the cistern, during the time of the well's flowing, is also equally uncertain ; for it varies 

 from one inch to nine or ten inches in the course of a few reciprocations. The spring 

 discharges bubbles of air, more or less copiously, into the trough. These appear in the 

 greatest abundance at the commencement of the flow, and cease during the ebb, or at 

 least issue from the rock very sparingly at that time. The water is limpid, cold, and 

 wholesome, and has no particular taste. Weeding Well, in the Peak of Derbyshire, other- 

 wise called the Ebbing and Flowing Well in the locality where it is situated, exhibits the 

 same characteristic. It lies in a field by the road-side in the neighbourhood of Castletori 

 Dale, surrounded with mud and weeds. The motion of the water depends upon the 

 quantity of rain during the season, and is by no means regular, as it has ceased to flow 

 for several weeks during a drought ; but, in very wet weath,er, it will flow and ebb more 

 than once in an hour. The time which it continues to flow varies ; but it is sometimes 

 four or five minutes, the water appearing at first slightly agitated, and then issuing forth 

 from nine small apertures with a gurgling sound. After remaining stationary, it then 

 ebbs to its ordinary level. The well is scarcely inclosed, and has the appearance of a 

 pool ; but the height to which it would rise would probably exceed a foot, if the margin 

 were protected so as to prevent the overrunning of the water. It has been known to 

 discharge twenty-three hogsheads in a minute. No theory has yet been proposed to 

 account for the peculiarity of these springs which is perfectly satisfactory ; but probably 

 Pliny's comparison of their fluctuations to the interrupted and irregular stream which 

 issues from an inverted bottle may have some portion of truth, as well as the common 

 hypothesis of an interior cavity of water discharging itself by a siphon-formed channel. 



.4. Thermal. Springs characterised by a higher temperature throughout the year than 

 the mean of the latitude where they are situated, abound in active volcanic districts, as 

 in the Neapolitan territories and Iceland, and are obviously referable to the action of 

 subterranean fire. They are frequent also in localities which have been the scenes of 

 volcanic activity in past ages, as in Asia Minor, the neighbourhood of Rome, and Au- 



