Linda Hall Library of Science, Engineering, & Technology
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60. The Trotternish Sill, 1832

Leonhard, Karl Cäsar von (1779-1862). Die Basalt-Gebilde in ihren Beziehungen zu normalen und abnormen Felsmassen. Stuttgart: E. Schweizerbart’s Verlags-Handlung, 1832.

Salisbury Crags and Stirling Castle became quite well known to geologists as places to observe the intrusion of whinstone into pre-existing limestone. A third site was discovered by John MacCulloch on the Isle of Skye. There is a location on the northern shore, at Trotternish, where there is a long three-fingered sill of whinstone that intrudes between the layers of limestone. MacCulloch first illustrated the Trotternish sill in a paper, and it was picked up by many other writers as further evidence of the volcanic origin of whinstone.

Leonhard’s book on basalt formations illustrates a great number of intrusions, often putting five or six on a single plate. We reproduce a detail of the plate that depicts the Trotternish sill.