48 



springs take an eastward direction, breaking out along the 

 edge of the marshes, and joining the river at Pluck's 

 Gutter. There are two other remarable streams joining at 

 Sandwich, called the north and south streams, the latter 

 rising at Eastry and Northbourne and supplying the towa 

 of Sandwich with abundance of pure water. The most re- 

 markable features in this supply are the streams called 

 "nailbournes" or periodical streams, some of which break out 

 every winter, running for a limited period and then stopping 

 suddenly ; others run only once in every five, sis, or seven 

 years. Some of these rise above Elham andBishopsbourne, 

 particularly that called the Pott, and another above Pethara 

 which runs to Shalmsford Bridge. The same process occurs 

 on the southern face of the chalk hills at longer intervals, 

 and I have frequently had occasion professionally to remedy 

 the mischief they have caused, which has led me to investi- 

 gate their origin and cause, for at times they cover a 

 large space, giving the surface the character of a sponge. 

 They appear to be solely cau3ed by the " overcharge " of 

 the chalk strata, viz., when the water line rises above the 

 edge of the gault, the water finds vent through an upper line 

 of pores, and having driven out all the air in its rise, it 

 starts running like a syphon, or series of syphons, and con- 

 tinues to discharge the water in the chalk basin below the 

 level of the orifice with one continuous stream until this 

 basin is discharged low enough to admit the air press- 

 ing from above, when it ceases as suddenly as it commenced, 

 and stops until a series of years or an extraordinary quantity 

 of moisture again supply the basin to overflowing. The con- 

 stant springs, which so evenly supply this river with 

 their waters, rise from a lower level and break through and 

 over the gault, and the fissures through which they are sup- 

 plied are probably of considerable length and depth ; whether 

 in some cases these fissures penetrate through the entire 

 bed of galut into the lower green sand is uncertain though 

 not impossible ; but as their level is too near that of the 

 summit of the rock range I should much doubt if it be the 

 case. However there are many springs in the gravel and 



