The effluvium is not a luminous phenomenon. I have described it in order to be complete, and not to omit a fact which is interesting for more than one reason. It can, moreover, be seen by certain subjects in the dark. Here is an interesting experiment, which I have sometimes realised, but which presents certain difficulties. One of the mediums, with whom I experimented, appeared to have an exceptional acuteness of vision in reference to the effluvium. He saw it escape from the hands of the sitters, and spread itself over the seance-table. Desirous of finding out what the medium would see in total darkness, I put out all the lights, and invited the medium to touch my hand if he saw it. The experiment did not succeed every time, but the proportion of success was superior to probabilities; but as the medium might have been able to guide himself by the sense of hearing, I thought of testing him by touching the table. The sensitive quickly recognised the finger-tips, claiming to perceive a kind of milky phosphorescence at the spot where my finger was. To make doubly sure I tested him still further by tracing letters on the table with the tip of my forefinger, taking the precaution to avoid all sound. The medium read nearly all the letters drawn. I then traced some words; he read them off also. I was able to make him read words of five letters; he was not able to read longer words, he recognised the last letters, but declared that the first were blotted out. Nearly all the words of three or four letters were read correctly, and the errors were often significant: _e.g._ the word ‘foi’ became ‘loi.’ Now, in a running hand-writing, it suffices to suppress the lower part of the ‘f’ for the letter thus amputated to take the aspect of an ‘l.’ I cannot say if the sensitive really saw what he claimed to see, or if he were guided by the sound of my finger. I am obliged to trust to his sincerity on this point; but I have reason to believe that this medium is sincere and honourable. He is a man of education, and is not a professional medium; he follows a liberal profession, and does not wish his name to be mentioned. I have much esteem for him. On the other hand, his senses would need to have been extraordinarily developed, to have enabled him to recognise the movement of my finger from the very slight sound it may have made. No sound was perceptible to myself. I wrote on a small varnished table of blackwood, on which my finger glided easily and silently. Again, the errors made now and then—by reading ‘loi’ for ‘foi,’ etc., seem to prove that the sense of sight and not sound was in operation.