Extract

When the Sketch of the Mineralogy of Sky was drawn up for the Society’s volume in 1813,* I had no prospect of again visiting that remote country. Circumstances having led me to traverse the same ground in much greater detail, I have been enabled to supply the deficiencies which were acknowledged in that paper, and to correct the errors into which I had unwarily fallen. I hold it my duty to supply the one and to correct the other; and consider that an acknowledgment of the latter is the greatest mark of respect I can pay to that body under whose protection they were laid before the readers of its Transactions.

No apology can be offered for want of industry; but the extent of this island, the difficulty of traversing it, and the intricate disposition of its rocks, offer some excuse for deficiencies, where want of time was further superadded to all other obstacles, For errors there is no excuse, but in correcting them it will not be useless to point out the causes from which they arose, since other observers may take warning from them, and learn to mistrust all observations which are not founded on rigid investigation, free from conjecture, and free from system.

To conclude respecting what is, from that which ought to be, will lead, as it has already led, to greater errors than those which I shall have to record. Equal hazard arises from judging of the structure of a district by the examination of