Evans describes his mediumistic development (in his own words).

I first secured a pair of 5x7 school slates. I appointed my time of sitting from 10:30 to 11 every evening, for I was certain of being alone and undisturbed at that hour. The next plan was to make my room perfectly dark during my sittings. I might pause here and discuss the question as to why darkness was necessary, but I will not, further than to say that it seems a law of Nature that darkness is necessary in many of her most wonderful operations. The seeds of nearly all vegetable formations can only grow and mature in the midst of a profound darkness; and then, again, before they can germinate and grow, they must be covered with darkness and mother earth. The embryotic animal is unfolded and developed in the dark, and not until the form is fully perfected does Nature permit it to behold the light which thenceforward is its life sustainer. Why it is so none can answer. But that it is so all must admit, and so I found it in developing myself. I sat in my darkened room holding my slates for a half-hour each evening for two months, and never received a manifestation. I began to get discouraged, and determined that I should sit no longer for development, so I put my slates away and retired. I had been in bed about three minutes when I could see a bright luminous light at the foot of my bed. I thought it might be caused by the light creeping through the blinds and reflecting on the white door knob which was opposite the foot of my bed. Although I felt a little nervous I arose and hung my black coat on the door knob, so that it would not cause any delusion. I covered every thing that was white with some black material. I next turned my attention to the only window in the room, and covered it so that not a ray of light could get in; the room was so dark that I could not see an inch before me. I groped my way back to bed, determined that if any light should appear it must surely be spirits. I had no sooner got into bed than several luminous lights were seen floating at the foot of my bed. Some would be about the size of a dollar and others would be about the size of a man's hand. I was determined to see in reality what they were, and was half out of bed with the intention of going to where the lights seemed to be located, when the lights suddenly came within an inch of my face. I jumped into bed and covered my head with the clothes to see whether I was being deluded in any way, when the clothes were suddenly pulled off the bed by invisible hands; forms floated about the room, and the whole room seemed to be filled with a white vapor. My bed began to shake, and loud raps sounded on the foot and head of my bed, then on the walls and doors. After standing this for about ten minutes I arose and made a light and smoked a cigar. After I had finished my cigar I felt more confident, and made up my mind that if I heard any more raps I would ask some questions. On retiring I again heard raps, and on questioning them learned that they wished me to continue my evening sittings, which I did, and from that date the rapid unfoldment of powers was marked. In holding the slates I felt as though I were holding on to a small battery. I then began to hear distinct raps on the slates, and a few nights later I realized that they were manipulating the crumbs of pencil I had placed between the slates, and after I had sat my usual time I found a number of small pencil marks on the slates. Each evening brought new, developments, until one evening I found a letter "A" on the slates, and a few nights later I found the word " Patience" written on the slates; and so it went on every day improving, until in February, 1885, by the advice of my spirit friends, I gave up all other pursuits and devoted myself to the exercise of my mediumship as an independent slate-writer.

I found that each month improved my mediumship, and that one phase developed another, so that with my continued sittings I not only developed independent slate-writing but also automatic writing, rapping, clairaudience, clairvoyance, physical manifestations, and materialization, and have demonstrated all the above gifts to thousands in California. I gave my first public seance after sitting three months and a half for development. I found that darkness was only necessary during my sitting for development, and when I commenced to sit for the public, all my slate-writing manifestations were given in broad daylight, with the sun shining on the slates held in the investigator's own hands.