IIIK srcCKSSlOX (»!•' I>KI'()SlT.s. :,;{ 



()tlii\sa. iirc (»cciisi(»imlly richly Inssilit'ciKiis, Imt \\\*nv 

 UMimlly lire ilcslitutc. of t'ossil rcinuiiiM. Wlicii drictl, tliu 

 LimIu cliiy iM'cdiiit's of stony Imnliu'ss, and wlit'ii Itiinicd, 

 it iissiiiiu's ii Idick-icil cdjour. Wlicii diicd and Irs ii,'al<'d, 

 it, nearly iilways iill'ords sonic t'oianiinitcra ami sliclls of 

 ostnu'oids ; and in this, as well as in its cojuur and 

 tuxt\irc, it, closely resenildcs l he lihie nind now in |adcess of 

 de]iosition in the dee|>ei' purls of the <^\\\\' of Si. Lawrence. 



The laniiiialion of the LimIu clay and its inclnded sand 

 layers, show that it was deposited at, int,ervals, hetween 

 which intervened s])aces when cnrreiits caiiied small 

 ([niinlities of sand oxer the snil'ace. In these intci\als 

 shells as wtdl as sand were washed oNcr the bottom, while 

 ordinarilv Le(lu, Nucnla and Astarli; lairrowed in the (dav 

 itself. The layers and ]tat(dies of stones I allrilaite to 

 dei)osit from lloatinu; ice, and to the same canse mnst he 

 attrihnted the lar^n Laurent ian houMers, occasionally 

 though rarely seen iuihedded in tlu; clay. 



The material of the Leda clay has been derived mainly 

 from the waste of the; lower Silurian shales of the (^)iiehec 

 and I'tica eroups, whi(di occupy a <freat space in the basin 

 of the ^ulf and river St. Lawrence. The driftaj^'c, of this 

 material has been to the south-west, ami in that diicction 

 it becomes thinner and liner in texture. The sup[)ly of 

 this mud, under the action of the waves, of streams, of 

 the .arctic currents and tidal currents, and tloatinj,' ice, 

 must have Ijeen constant, as it now is in the gulf and 

 river St. Lawrence. It woidd l)e increased by the meltin<,' 

 of the snows in spring and )>y any oscillations of level, 

 and it is probal)ly in these w^ays that we should account 

 for the alternations of layers in the deposit. 



The modern deposit in the gulf of St. Lawrence, the 

 chemical characters and coloration of which I explained 



