precious book I found almost all I wanted.  I obtained, by means of it, a knowledge of, and gained access to, the great authorities of Adanson, Moore, Barbot, Smith, Bosman and others.  It was of great consequence to know what these persona had said upon this subject.  For, having been themselves either long resident in Africa, or very frequently there, their knowledge of it could not be questioned.  Having been concerned also in the trade, it was not likely that they would criminate themselves more than they could avoid.  Writing too at a time, when the abolition was not even thought of, they could not have been biassed with any view to that event.  And, lastly, having been dead many years, they could not have been influenced, as living evidences may be supposed to have been, either to conceal or to exaggerate, as their own interest might lead them, either by being concerned in the continuance of the trade, or by supporting the opinions of those of their patrons in power, who were on the different sides of this question.

Furnished then in this manner, I began my work.  But no person can tell the severe trial, which the writing of it proved to me.  I had expected pleasure from the invention of the arguments, from the arrangement of them, from the putting of them together, and from the thought in the interim that I was engaged in an innocent contest for literary honour.  But all my pleasure was damped by the facts which were now continually before me.  It was but one gloomy subject from morning to night.  In the day-time I was uneasy.  In the night I had little rest.  I sometimes never closed my eye-lids for grief.  It became now not so much a trial for academical reputation, as for the production of a work, which might be useful to injured Africa.  And keeping this idea in my mind ever after the perusal of Benezet, I always slept with a candle in my room, that I might rise out of bed and put down such thoughts as might occur to me in the night, if I judged them valuable, conceiving that no arguments of any moment should be lost in so great a cause.  Having at length finished this painful task I sent my Essay to the vice-chancellor, and soon afterwards found myself honoured as before with the first prize.

As it is usual to read these essays publicly in the senate-house soon after the prize is adjudged, I was called to Cambridge for this purpose.  I went and performed my office.  On returning however to London, the subject of it almost wholly engrossed my thoughts.  I became at times very seriously affected while upon the road.  I stopped my horse occasionally, and dismounted and walked.  I frequently tried to persuade myself in these intervals that the contents of my Essay could not be true.  The more however I reflected upon them, or rather upon the authorities on which they were founded, the more I gave them credit.  Coming in sight of Wades Mill in Hertfordshire, I sat down disconsolate on the turf by the roadside and held my horse.  Here a thought came into my mind, that if the contents of the Essay were true, it was time some person should see these calamities to their end.  Agitated in this manner I reached home.  This was in the summer of 1785.