and the Distortion of Fossils. 413 



clathratus. The normal measurements assumed for these fossils 

 were — 



Length. Breadth. 



Orthis crenistria ... 1 1 



Athyris concentrica . , 294 341 



I Spirifer clathratus . , 1 2 



Wlien the angle between cleavage and bedding was 44°, I 

 found from two distinct specimens of Orthis crenistria, one lying 

 with its hinge-line parallel to the intersection of cleavage and 

 bedding, and the other with its hinge perpendicular to this line, — 



.A\ ..*f. 6=44°. .— =1*860 Orthis crenistria 



- = 1*820 Orthis crenistria 



P 



Mean . . 1*840 



When the angle between the planes of cleavage and bedding 

 became 10°, I found as follows, expressing by the numbers hun- 

 dredths of half-inches : — 



Athyris concentrica . Length distorted =213 

 Breadth ... =269 



{i') , Spirifer clathratus . Length distorted =136 



Breadth ... =300 



Calculating the distortion from these data and the normal 

 measurements before given, by means of equation (1), we find — 



</>' = 10°, ry =1*088 Athyris concentrica 



dofifw ,- biw -i. =1-102 Spirifer clathratus 



'^*''*'^ Mean . . 1-095 



Introducing the values of ^, (j>'j /o, p' here given into equations 



(4) and (5), we obtain — > ^^ 



1^0X1 llexia i. joq^h 



(A) 



From these results I infer that the slate of Ardoginna has 

 been relatively compressed perpendicular to its cleavage nearly 

 two and a half times, and that this result has been brought 



