266 Dr, Draper on the Use of a Secondary Wire as a 



But if all this be granted, those geologists who have examined 

 Norfolk will admit that the denudation here alluded to must be 

 that which gave to this district its actual valleys, and many of 

 the leading features of its present geographical configuration. 

 We are thus brought round to the conclusion that land in 

 this country must have emerged from the sea after the depo- 

 sition of the Norwich crag, and yet at a period anterior to 

 that of the denudation just alluded to. But as we know of 

 no denuding agency capable of excavating great valleys in a 

 flat country like Norfolk, except the power of the ocean, ope- 

 rating either at the time of the submergence of land or that 

 of its emergence from the waters, we must infer from all the 

 facts and reasonings above set forth, that land, consisting of 

 chalk covered by crag, was first laid dry before the origin of 

 the sand-pipes, and then submerged again before it was finally 

 raised and brought into its present situation. 



For my own part I readily adopt the hypothesis of these 

 oscillations of level, because 1 have found them indispensable 

 to explain other geological appearances on the coast of Nor- 

 folk, not many leagues distant from Norwich, where there is 

 independent evidence of the land having been first laid dry, 

 after the deposition of the crag, so as to support a forest; 

 then submerged again, so as to subside to the depth of 400 feet 

 or more, the signs of the forest being buried under strata 

 several hundred feet thick ; and, lastly, of the same tract 

 having been re-elevated, so as to bring the monuments of 

 this remarkable succession of events into view. On this sub- 

 ject I shall shortly enlarge, when treating of the age and 

 origin of " the Mud Cliffs" of Eastern Norfolk. 



XXXVI. On the Use of a Secondary Wire as a Measure of the 

 Relative Tension of Electric Currents. By John W. Draper, 

 M.D.i Professor of Chemistry in the University ofNe'w York ; 

 late Prof, of Physical Sciefice in Hampden Sydney College, 

 Virginia*. 



[With Figures : Plate I.] 



IT is the object of this memoir tcf^establish the following 

 -* propositions : — 



1st. That by means of a secondary wire, we may always 

 determine the relative tension of electric currents. 



2nd. That there is reason to doubt whether the processes 

 usually supposed to affect the condition of an electric current, 



* Communicated by the Author. 



