042 TRANSACTIONS OF ROYAL SCOTTISH ARBORICULTURAL SOCIETY. 
fertility. The variety of the geological formation produces a 
corresponding diversity in the soil, and the physiological character 
a marked influence on the climate. Apart from these, however, 
its geographical position bears very directly on its climate, for, 
situated as it is almost on the verge of the Atlantic, the island 
enjoys a much greater uniformity of temperature, and a more 
copious rainfall, than almost any other place in Scotland; and as 
these are very important factors in the rearing of forests and the 
production of timber, it follows that if the soil is suitable arbori- 
culture could be very successfully practised. 
Including, as it does, the granite, slate, old and new red sand- 
stone, whinstone, lime, hornblend, porphyry, quartz, basalt, 
claystone, pitchstone, and various sections of the Coal formation, 
including shale, Arran may be said to be quite a geological 
museum; but it is not needful to go minutely into the 
geological details of the island. For my purpose it will be 
sufficient to divide the island into two parts—a northern and a 
southern, of nearly equal area. The northern portion is mainly 
composed of granite, slate, and old red sandstone; while the 
southern consists principally of the Carboniferous series, with 
porphyry, greenstone, basalt, etc., and the disintegration of these 
different rocks has given to the soil of Arran its present character. 
The lapse of time has in many places covered the rock with 
rich alluvial soil, in some parts attaining the depth of many feet, 
and generally of sufficient depth to grow large sized forest trees. 
From what is indicated above, it will be quite understood that 
the variety of soil to be found in the island is very great. About 
Brodick it is of a loamy nature—argillaceous in places—while 
farther south it becomes of a lighter and more sandy character, 
but with patches of alluvial loam interspersed throughout. The 
subsoil is generally of a gravelly marl. In the southern parts of 
the island the soil is of a clayey consistency, and the subsoil is 
also clay mixed with gravel and sand, and very retentive of water. 
The western side of the island is gravelly and moorish, but with 
frequent patches of excellent alluvial soil. In the northern parts 
the soil is generally of a light sandy nature. 
Perhaps it might be argued that the physical features of Arran 
are not such as to encourage any desire to plant timber, for its 
exposure to the Atlantic gales, and the lie of its principal mountain 
ranges, are not very favourable for forest culture. This difficulty, 
however, is not so real as apparent, and could easily be overcome 
