BIllTISII ASSOCIATION MEKTINa. 
441 
Tliis cavern was niiicty f^"'"'' loii"-, and cxtciulcd in a diicction from iiortli- 
norl li-(!a.sl to south-sou tli-WL'si, or very nearly thai of tlu' dip of the liuieslouc- 
heds. It eomuieuccd about, eiglit feet below tlie to[) of t lie elill', and eoaliuucd 
to its base, so tiiat it is about lifty-two feet high; indeed its heiglit exceeds 
this, as the bottom has not been " reached. At the top it is about two feet 
X 
Lign. 2.— Vertical transverse section, on the scale of 1-20 inch to the foot, of a Cavern dis- 
covered at Oreston, near Plymouth, in the winter of 1858-9. 
a, c, d, h, Roof of Cavern, composed of large angular masses of limestone. 
<-'. ''i " Gravel" of the workmen, i. «., angular limestone, with a comparatively small 
amount of sand, the whole imccmented. 
«i Angular hmestone, sand, and tough dark clay with bones. 
/, h, k, " CaUis" of the workmen, i. e., a nearly vertical dyke of stalactite, with masses of 
Umestone-breccia., the whole containing bones. 
g, I, m, k Tough dai'k clay without traces of bones. 
wide, gradually increasing do\rawards, and reaching a width of ten feet at its 
bottom. The first or upper eight feet were occupied with what the workmen 
called " gravel," which consisted of angular portions of the adjacent lunestonc, 
mixed with a comparatively small amount of sand. The lunestone debris 
varied in dimensions from fragments of the size of hazel-nuts to pieces ten 
pounds in weight. This accunuilation was entirely free from stalagmite, and 
was in no part cemented. No traces of fossils were found in it. The next 
thirty-two feet in depth were occupied with similar materials to those just men- 
tioned (the sand being somewhat more abundant), with the addition of a 
considerable quantity of tough, dark, unctuous clay. 
