AttBQBICULTURAL FEATURES OF BUTESHIRE. 65 



ception being found in the small islets forming the harbour of Mill- 

 port, which consists of white and grey sandstone. Strata of conglo- 

 merate structure are occasionally met with ; and the ridges on the 

 west formerly showed some thin limestone beds interstratified with 

 sandstone, but these have been worked out. No fossils have been 

 met with ; but there can he little doubt that the sandstone is of the 

 same age as that of South Bute, most probably lower carboniferous. 



Little Cumbrae. — The Lesser Cumbrae is about two miles long and 

 one mile broad, and in its bolder outlines strongly contrasts with the 

 sister isle; its highest point has an elevation of about 800 feet. In 

 geological structure and in altitude it corresponds with the southern 

 division of Bute. 



Pladda. — This islet is attached to Arran by a whin dike, over 

 most parts of which there is broken water at low tide. The island 

 consists almost wholly of a dark-coloured trap rock, the sandstone 

 foundation appearing only on the north-eastern shore. 



II. Arboricultural Features of Buteshire. 



Island of Bate. — The extent of enclosed plantations in Bute is 

 about 1600 acres. The principal portion is the policy woods of 

 Mount Stuart, the remainder being a number of detached belts and 

 plantations in the south and north parts of the island. 



The plantations to the south of Bothesa} 7 rest on the carboni- 

 ferous formation, those to the north on the slate formation. Though 

 there is a considerable breadth of trap rock in the middle and south 

 portions of the island, there is no wood of any consequence to afford 

 conclusive evidence of the advantages or disadvantages of such under- 

 lying formation to the growth of trees. At the same time, from the 

 character of the herbage, the dry nature of the soil and substratum, 

 caused by the numerous intersects with which the underlying rock 

 abounds, we should suppose that trees would grow well where there 

 is sufficient depth of soil. 



The policy woods of Mount Stuart have an elevation of from 10 

 to 150 feet, with an east exposure, and are completely sheltered from 

 the west storms. The portion immediately round the mansion- 

 house is of considerably older date than the outer portions, in all 

 probability dating back to the commencement of the mansiomhouse 

 — 1712 — -which gives an age of 160 years. The outer portions 

 average from 30 to 62 years old. The part of the policy woods 

 along the sea-shore rests at the bottom of the old sea terrace, and is 

 very few feet above high-water mark. The rock in a groat many 



