No general description of the methods of experimental psychology would be instructive to one unfamiliar with the instances of their application, so we will waste no words upon the attempt. _The principal fields of experimentation_ so far have been: 1) the connection of conscious states with their physical conditions, including the whole of brain-physiology, and the recent minutely cultivated physiology of the sense-organs, together with what is technically known as 'psycho-physics,' or the laws of correlation between sensations and the outward stimuli by which they are aroused; 2) the analysis of space-perception into its sensational elements; 3) the measurement of the _duration_ of the simplest mental processes; 4) that of the _accuracy of reproduction_ in the memory of sensible experiences and of intervals of space and time; 5) that of the manner in which simple mental states _influence each other_, call each other up, or inhibit each other's reproduction; 6) that of the _number of facts_ which consciousness can simultaneously discern; finally, 7) that of the elementary laws of oblivescence and retention. It must be said that in some of these fields the results have as yet borne little theoretic fruit commensurate with the great labor expended in their acquisition. But facts are facts, and if we only get enough of them they are sure to combine. New ground will from year to year be broken, and theoretic results will grow. Meanwhile the experimental method has quite changed the face of the science so far as the latter is a record of mere work done. * * * * *