which we have before described as physiological; the colours evoking each other. Instead of blue, we should thus see red-yellow; instead of red, green, &c., and vice versâ. We reserve experiments in detail, the rather as we have ourselves still some doubts on this point.
451.
If we were now called upon to give some general explanation of these epoptical colours, as they appear under the first condition, and to show their connexion with the previously detailed physical phenomena, we might proceed to do so as follows:—
452.
The glasses employed for the experiments are to be regarded as the utmost possible practical approach to transparence. By the intimate contact, however, occasioned by the pressure applied to them, their surfaces, we are persuaded, immediately become in a very