ISLE OF MAN. GEOLOGY. ,533 



a good substitute for other colours as a paint in oil ; but, 

 being unknown to the inhabitants, it has not been applied 

 to any purposes. 



The next most extensive and important rock after the 

 schist, is the limestone. The boundary of the principal 

 mass cannot every where be defined with absolute preci- 

 sion, since in the interior parts it is covered with a deep 

 soil. This however is easily done on the shore, and it is 

 indicated in the accompanying map ; while, by tracing its 

 termination in the schist near Ballasalla, its limit at that 

 place is also determined. The intermediate line on each 

 side of that point, towards the Santon river on one hand 

 and Pool vash on the other, is laid down as well as the 

 map would allow, from a consideration of the form of the 

 land; since there is a sensible difference between the 

 undulation of the surface above the limestone, and that 

 above the schist. A small detached piece also occurs 

 on the point near Port la Marie, which is there, like 

 the former, capable of being accurately defined, since 

 its junction with the schist is visible on both sides. 



There are two very different kinds of limestone in these 

 places, and there are also several varieties of each of 

 them, to which more or less importance in an econo- 

 mical view is attached. The two leading distinctions are, 

 a stratified limestone containing shells, and an unstrati- 

 fied and irregular one rarely containing any, and com- 

 monly of a crystalline texture. These are mixed in an 

 irregular manner over the whole tract; a mass of the 

 unstratified rock occurring unexpectedly in the midst of 

 the stratified, without any certain order or arrangement. 

 In general, all the varieties of the unstratified rock are 

 rejected by agriculturists. In some cases it seems to have 

 been ascertained that they are ill adapted for land; in 

 others it has been so imagined without sufficient trial. 

 There is another objection to the use of the unstratified 

 limestone, arising from the greater difficulty of quarrying 

 it ; while it is also less easy to burn. Differences in 



