Hi 
ON CYCLES OF SEDIMENTATION. 
J. L.vwTOX Williams, llonifllsvillc. X. V. 
The ftict of cycles of sedimentation is well known to strati- 
5i;rapliical geologists. The following tal)le, from Dr. .Alexander 
Wincliell. is a good illustration of what is meant l»y the term: 
Tablk of Cycles of Sedimentation. 
Palai'ozoic 
Systfiiis 
Coars,. 
FraKinental. 
Fine Fiairmental. 
Calcareous. 
Calcareo- 
Fragmental. 
I'pptn- 
Carbonifei-ouii. 
Parma 
ConirlomeratP. 
Coal Measures. 
(Broken into 
small epoch, i 
Laramie 
Limestone. 
Permian. 
Ldwpi- 
Carbon iftn-oiis. 
Wavcrlv SaiidstDni' Wavcrly Sandstone 
(Marshall Tliasc. i (Chouteau Pha.se. ) 
Mountain 
Limestinii'. 
False Coal 
Measure.*. 
Di'voniaii. 
Oriskany 
Saudstone". 
Sclndiarie Crit . 
Cornif<'roiis 
LiuK'stone. 
Hamilton 
andCheinung 
Siliii-iaii. 
Medina Sandstoiie 
and Oneida 
CoiiLrlomerate. 
Xiajrara Shale 
and Clinton. 
Niagara 
"Limestone. 
Salina. 
Cambrian. 
Potsdam. 
Calciferoiis and 
Chazv. 
Trenton 
Limestone. 
Cincinnati. 
While these divisions may l)e somewhat artiticial and arbitrary, 
they seem to illustrate the general fact of a detinite sequence in 
sedimentary deposits. Similar relations have l)een observed in 
the strata of Great Britain. ]\Ir. Hull ((^nait. -Jour. Sci.. .July. 
1S(>!).) makes a triple rather than a (piadruple sulxlivision : 1st. a 
lower stage of sandstones, shales and other sedimentary deposits, 
representing prevalence of land with downward movement: 2d, a 
iniddle stage, chiefly of limestones, representing, prevalence of 
sea with general ([uiescence and elaboration of calcerons organic 
formations: IJd. an upper stage, once more of mechanical sedi- 
ments indicative of ijroximity to land. 
The identity l>et\vecn this and A\'incheirs tal»le is appai'ent. In 
both we nitiy begin with a given stratigraphical structure, and. 
after passing through a definite succession of intermediate struc- 
tures we again encounter one like the lirst. We are to Iteai' in 
mind, however, that this succi'ssion is not a rigid one. Often- 
times we meet with intercalated beds which have no i(>})res{Mita- 
tives in the otiiei- niembei's of the series. Hi>sides. there ai'e wide 
