¶This separate printing of Q's 1916 lecture to the Royal Institution is unrecorded by Copac or Worldcat. Quiller-Couch died in 1944 after he had been hit by a car and presumably this lecture was printed with the permission of his daughter Foy fairly soon after his death. It was Foy that asked Daphne Du Maurier to complete her father's unfinished novel, Castle Dor, which was eventually published in 1962. The Commerce of Thought first appeared in Studies In Literature, 1918. It ends: '... in the commerce and transmission of thought the true carrier is neither the linotype machine, nor the telegraph at the nearest post office, nor the telephone at your elbow, nor any such invented convenience: but even such a wind as carries the seed, 'it may chance of wheat, or of some other grain': the old, subtle, winding, caressing, omnipresent wind of man's aspiration. For the sec ret - which is also the reward - of all learning lies in the passion for the search'.