88 EIGHTH REPORT — 1838., 



30 feet apart, and they are not portions of continuous siliceous beds 

 in a vertical position, but piles of single flints running through the 

 chalk, like so many wooden stakes driven into mud. Few of the sepa- 

 rate flints are symmetrical, but some are pear-shaped. They are very 

 unequal in size — usually from a foot to three feet in their longest dia- 

 meter. At the point of intersection between a row of potstones and 

 one of the horizontal beds of flints, there is no mutual interruption 

 or shifting, but they are united as if both Avere formed at one time. 

 Each potstone is not siliceous throughout, like the nodules of flint in 

 the horizontal beds, but contains invariably within it a cylindrical 

 nucleus of chalk, which, when deprived of its siliceous envelope, has 

 the form and smooth surface of a tree when stripped of its bark. This 

 internal mass of chalk is much harder than the ordinary chalk sur- 

 rounding the flints, and does not fall to pieces when exposed to frost: 

 it penetrates the flinty covering at the top and bottom of each potstone. 

 A ventriculite was observed in the chalky nucleus in one instance. 

 The author concluded by inviting those geologists who resided near 

 Norwich to examine these phenomena more minutely ; and adverting 

 to the late discoveries of Ehrenberg, declared his expectation that the 

 origin both of the vertical and horizontal masses of flint would be 

 found to be intimately connected with the fossil remains of Infusoria, 

 sponges, and other organic beings. 



On the Straiijication of Rocks. By John Leithart. 



The strata in Alston Moor, to which Mr. Leithart's personal obser- 

 vations have been chiefly confined, consist of numerous alternations of 

 limestone, argillaceous shale or ' plate,' and sandstone. The definite 

 order in which these rocks succeed one another, the variety of inclina- 

 tions Avhich they present, the phenomena of faults which interrupt the 

 continuity of the strata, and other facts, appeared to the author inex- 

 plicable as the result of deposition from water, followed by elevatory 

 action or the influence of heat. 



Being engaged in the study of galvanism, he remarked that many 

 other substances besides metals would, when piled in alternate layers, 

 develop electrical action, and became impressed with the opinion that 

 the stratified rocks might be likened to a galvanic battery, and that the 

 peculiar appearances above noticed might receive an explanation ui^on 

 this supposition, provided there was a communication across the enor- 

 mous 'pile' of rock : such a communication is made, the author thinks, 

 by mineral veins. 



Upon this hypothesis he proceeds to show the probability that mixed 

 sediments would be re-arranged by the electrical action into alternating 

 distinct zones or strata, and confirms his reasoning by the result of 

 direct experiments. In the first of these, a battery of 28 cylindrical 

 plates of copper and zinc was used, but the author finds 18 or 20 pairs 

 answer better. The copper plates had about 9 and the zinc plates 

 about 6 square inches of surface. They were placed in jars, containing 



