| Description | Contains eight figures. 
 Subject: Geology
 
 Relates to 'An enquiry into the original state and properties of spars, or crystals found in the Cornish mines, called Cornish Diamonds. In a letter to Emanuel Mendez da Costa, Esq; F. R. S. From the Rev. Mr. Wm. Borlace.' by William Borlase
 
 Read 3 May 1750
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