In the winter of 1886–7 a boring was made at Bletchley Junction for the London and North-Western Railway Company, and acquired importance from the report that, after passing through the Oxford Clay, it had entered a mass of granitic rock. Probably many readers of this Magazine wondered why no detailed account of the boring was published after this announcement; but the reason was, that when inquiries came to be made, some uncertainty was found to exist as to the position and mode of occurrence of the granitic rock. My attention was recently called to the boring by learning that the water obtained from it was salt. I then obtained all the information I could with regard to the rocks passed through, and think the results are of sufficient importance for publication.