Life has now and then some supreme moments of pure happiness,
which in reminiscence give to single days the value of months
or years. Two or three such moments it has been my good fortune
to enjoy with you, in talking over the mysteries which forever
fascinate while they forever baffle us. It was our midnight talks
in Great Russell Street and the Addison Road, and our bright May
holiday on the Thames, that led me to write this scanty essay on
the "Unseen World," and to whom could I so heartily dedicate it
as to you? I only wish it were more worthy of its origin. As for
the dozen papers which I have appended to it, by way of clearing
out my workshop, I hope you will read them indulgently, and
believe me
