“Whoever follows these thoughts will be afraid of himself and, considering himself sustained by the weight which nature has given him, between those two abysses of the infinite and nothing, he will tremble in face of those marvels, and I believe that as his curiosity changes to admiration, he will be more disposed to contemplate them in silence than to seek them with presumption. “For indeed what is man in nature? A nothing in comparison with the infinite, a universe in comparison with nothing, a mean between nothing and all. Infinitely removed as he is from comprehending the extremes, the goal and principle of things are invincibly concealed from him in an impenetrable secret; he is equally incapable of seeing that nothingness whence he sprang or that infinite which swallows him up.” More than one of our contemporary savants has republished this conception of “the atom as a world system,” imagining that it is new and without appearing to recollect either Bernoulli or Pascal. * * * * * As we have seen before, the invisible world is the basis of creation and the visible universe is composed of invisible bodies. What we see is made up of things which we do not see. In the sky every star of the Milky Way being below the seventh magnitude is quite invisible to our eye. Yet we see the Milky Way. On the Earth we see and touch crowds of molecules every particle of which could be neither seen with our eyes nor felt with our touch nor perceived with any of our senses. And yet one meets very often so-called scientific men in the world who say peremptorily: “I only believe what I see.” A large number of different measurements of the speed of light agree in proving that this speed is 186,000 miles a second. That is a fact of observation absolutely proved by astronomy and by physics. These 186,000 miles amount to 982 million feet or 11,785 million inches. Now, certain measurements of the same degree of precision show that in a ray of red light there are 42,300 waves to the inch or 1,666 to the millimetre. Each of these waves therefore measures 6/10,000 of a millimetre. Those of the extreme red measure 7/10,000; beyond the red, wave-lengths of 8 or 9/10,000 are found; the blue waves measure 4 to 5/10,000 and the violet 4/10,000. Expressed in millionths of a millimetre, as is usual in spectroscopy, these wave-lengths are the following:— WAVE-LENGTHS OF LIGHT Infra-red 900 or more Extreme-red (A) 760 Red (B) 687 Orange (C) 666 Yellow (D) 689 Green (E) 617 Blue (F) 486 Indigo (Q) 431 Violet (H) 897 Ultra violet 380 and less