"I find in the Crystal a bit of dark wall, covered with white jessamine, and I ask myself, 'Where have I walked to-day?' I have no recollection of such a sight, not a common one in the London streets, but to-morrow I will repeat my walk of this morning, with a careful regard for creeper-covered walls. To-morrow solves the mystery. I find the very spot, and the sight brings with it the further recollection that at the moment we passed this spot I was engaged in absorbing conversation with my companion, and my voluntary attention was preoccupied." This is a very simple case. A visual image, recently yet unconsciously received, springs up from the subterranean strata of the soul into which it had sunk. No. 68 affords a similar instance: "I had carelessly destroyed a letter without preserving the address of my correspondent. I knew the county, and searching in a map, recognised the name of the town, one unfamiliar to me, but which I was sure I should know when I saw it. But I had no clue to the name of the house or street, till at last it struck me to test the value of the crystal as a means of recalling forgotten knowledge. A very short inspection supplied me with 'Hibbs House' in grey letters on a white ground, and having nothing better to suggest from any other source, I risked posting my letter to the address so strangely supplied. "A day or two brought me an answer, headed 'Hibbs House' in grey letters on a white ground." Tricks of the memory like these appear still more strange when they are due merely to an indirect excitation. It may happen that one is suddenly reminded of a friend who is long since dead, by the accidental sight of his favorite dish. No direct excitation is here presented, but the image of the friend remembered is indirectly revived through a certain concatenation of ideas. This we find in the eleventh experiment: "One of my earliest experiences was of a picture, perplexing and wholly unexpected—a quaint oak chair, an old hand, a worn black coat-sleeve resting on the arm of the chair,—slowly recognised as a recollection of a room in a country vicarage, which I had not entered and but seldom recalled since I was a child of ten. But whence came this vision, what association has conjured up this picture? What have I done to-day?... At length the clue is found. I have to-day been reading Dante, first enjoyed with the help of our dear old vicar many a year ago." The process here carried on, which takes place for the most part outside of the sphere of consciousness, is therefore the following: The reading of Dante revives the image 'Vicar'; the image 'Vicar' produces the image of the room; the latter image is externalised.