"But though I have written this report without stopping to answer the objections and difficulties which arise at every line, though I have been contented myself with setting forth the logical and almost inevitable sequence of the deductions which led up to my theory. I should be failing in respect to the academy and to the public if I allowed it to be believed that I am not fully conscious of the weight of those objections and difficulties. I did not, however, consider this a reason for abandoning my task. Though it be our duty to bow when science utters a formal veto, on the other hand duty orders us to persist when science is content merely to confess its ignorance. This is the twofold principle which I observed in seeking no longer the source of the projections, but rather the manner in which they were able to appear, for that is where the whole problem lies. It is easy to declare that they emanate from Venus; it is not easy to explain how they travel through space and how they exercise their action, at a distance of many millions of miles, on an imperceptible screen with a surface of three or four hundred square feet. I am confronted with physical laws which I am not entitled to transgress. I am entitled at most to advance where science is obliged to be mute. "Therefore and without any sort of discussion I admit that we are debarred from supposing that light can be the agent of the transmissions which have been observed. The laws of diffraction indeed are absolutely opposed to the strictly rectilinear propagation of luminous rays and hence to the formation and reception of pictures at the exceptional distances actually under consideration. Not only are the laws of geometrical optics merely a somewhat rough approximation, but the complicated refractions which would inevitably occur in the atmospheres of the earth and Venus would disturb the optical images. The veto of science therefore is peremptory in so far as the possibility of these optical transmissions is concerned. "For that matter, I should be quite willing to believe that the inhabitants of Venus have already tried to correspond with us through the intermediary of luminous signals and that, if they abandoned their endeavours, this was precisely because the imperfection of our human science made them useless. We know in fact that Lowell and Schiaparelli saw on the face of Venus brilliant specks and a transient gleam which they themselves attributed either to volcanic eruptions or, as is more probable, to the attempts at communication of which I have spoken.