536 Geological Society. 



after giving the definition of resistance, to state that the quantity 

 so defined is, for a given conductor maintained under given physical 

 conditions, independent of the current. It is this constancy of 

 the resistance which is an experimentally verifiable and experi- 

 mentally verified fact, and which constitutes the essence of 

 Ohm's law. 



LI1. Proceeding* of Learned Societies. 



GEOLOGICAL SOCIETY. 

 [Continued from p. 444.] 



June 6th, 1900.— J. J. H. Teall, Esq., M.A., F.ft.S., President, 

 in the Chair. 



'TVELE following communication was read : — 



-*- 1. ' Mechanically-formed Limestones from Junagarh and other 



Localities.' By Dr. J. W. Evans, LL.B., F.G.S. 



After reviewing the conditions under which granular limestones 

 may be accumulated by current- or wind-action, the author proceeds 

 to describe the limestone of Junagarh, a deposit some 200 feet 

 thick, resembling in hand-specimens the Oolites of this country, 

 though less firmly cemented together. It is mainly formed of grains 

 consisting of a nucleus of a fragment of a marine organism or 

 foraminiferal test, surrounded by a layer of deposited carbonate of 

 lime. Particles derived from the igneous rocks of the neighbour- 

 hood and rounded quartz-grains also occur, but amount to only 

 a small percentage of the rock. The whole is bound together by 

 colourless calcite-cement. The deposit is situate at a distance of 

 30 miles from the sea, and contains no large fossils of any kind. 



Calcareous rocks of similar character are described from other 

 parts of Kathiawar, Kach, the south-eastern coast of Arabia, and the 

 Persian Gulf — some of these contain unbroken marine shells and 

 other fossils. These beds are included by Dr. H. J. Carter under 

 the name of miliolite, on account of the frequent presence in them 

 of the genus Miliola. 



The author discusses the origin of these deposits, and comes to 

 the conclusion that the grains were formed in sea-water saturated 

 with carbonate of lime : some being deposited by currents in shallow 

 water, and others thrown up as a calcareous beach, from which a 

 portion were sifted out by the wind and blown inland to form geolian 

 deposits, as contended by Prof. Blake in the case of certain superficial 

 limestones in Kach. The Junagarh limestone falls into the last 

 group, but must have been formed when the land was at a low level 

 and the sea-shore was at no great distance. 



A rapid survey is then taken of similar rocks in other parts 

 of the world, which may be grouped into the same three classes. 

 The remarkable wind-blown foraminiferal deposit of Dog's Bay 

 (Gralway) is referred to in some detail ; and the author concludes 

 by suggesting that in the Oolites of the Jurassic period we have 

 representatives of all three groups. 



