S E L d S E L d S E L d SSS 24 13 13 - 11 7 30 13 + 6 10 31 9 - 1 WSS 33 9 8 - 25 20 24 6 - 14 17 27 6 - 11 SSW 19 15 16 - 3 23 16 11 - 12 10 31 9* - 1 WWW 19 12 19 0 13 26 11 - 2 1 40 9 + 8 SWW 18 30 2 - 16 23 21 6* - 17 7 38 5 - 2 WWS 13 16 21 + 8 12 30 8 - 4 15 25 10 - 5 *Transcriber's Note: Original "16" changed to "6", "19" to "9". Analysis of this table shows that in every case a difference between the intensities of the first and second taps lengthens the first interval in comparative estimation. In the case of subject _Mm_ a difference in the intensities of the second and third taps lengthens the second interval subjectively. But in the cases of the other two subjects the difference shortens the interval in varying degrees. The intensity difference established for the purposes of these experiments was not great, being less than that established for the work on the first two subjects, and therefore the fact that these results are less decided than those of the first work was not unexpected. The results are, however, very clear, and show that the lengthening effect of a difference in intensity of the stimulations limiting an interval has its general application only to the first interval, being sometimes reversed in the second. From the combined results we find, further, that a uniform change in the intensity of three stimulations is capable of reversing the direction of the constant error, an intensity change in a given direction changing the error from positive to negative for some subjects, and from negative to positive for others. III. INTERPRETATION OF RESULTS. We may say provisionally that the _change_ from a tactual stimulation of one kind to a tactual stimulation of another kind tends to lengthen subjectively the interval which the two limit. If we apply the same generalization to the other sensorial realms, we discover that it agrees with the general results obtained by Meumann[15] in investigating the effects of intensity changes upon auditory time, and also with the results obtained by Schumann[16] in investigations with stimulations addressed alternately to one ear and to the other. Meumann reports also that the change from stimulation of one sense to stimulation of another subjectively lengthens the corresponding interval. [15] _op. cit._ (II.), S. 289-297. [16] _op. cit._, S. 67. What, then, are the factors, introduced by the change, which produce this lengthening effect? The results of introspection on the part of some of the subjects of our experiments furnish the clue which may enable us to construct a working hypothesis.