Éleuthère Élie Nicolas Mascart

“ We may ask, then, What would be the condition of nature if the light that shines upon us were absolutely homogeneous? Some bodies would absorb it completely, and would appear dark like black velvet; others would reflect it more or less actively, and would have a corresponding degree of brilliancy. ”

“ It has been known since Newton's experiments that white light, or, to be more precise, the light of the sun, is formed of a large number of different colors, and that the union of all these in equal proportion, acting upon the eye, either simultaneously or at very close intervals, produces the impression of white. Starting from a preconceived analogy with the notes of the gamut, Newton divided the solar spectrum, or the image obtained by decomposing white light with a refracting prism, into seven different colors. ”

“ About ten persons in a hundred make mistakes in the comparison of colors marked enough to be detected by an attentive examination. Generally the imperfection is not accompanied with grave inconveniences, and is corrected unconsciously by the operation of habit, the recollection of objects, and the judgments of others. But the annoyance becomes extreme when one can not distinguish, for example, red from green, a cherry or a ripe strawberry amid the foliage, or a green from a red light in railway or ship signals. Artists sometimes have marked predilections for certain colors. ”

“ In the case of light, we are in the presence of rays that are not luminous in sunlight, or at least are not seen by us, which are energetically absorbed by most transparent media and especially by the humors of the eye, for which we give ourselves no concern whatever in current life, and which nevertheless act upon the retina. ”

“ In white light, the bacteria will be seen to precipitate themselves upon the grains of chlorophyl, to get the oxygen disengaged from them. They thus constitute a very delicate reagent. To witness the effect of the different colors, we let the microscopic spectrum fall upon a filament of conferva, or a transverse leaf-section. The bacteria will collect upon the plant in the red, at the point of maximum absorption, next in the blue, and the density of the population will nearly follow the absorption-curve of the coloring-matter. ”

“ The estimation of color being connected with the impression produced upon the retina, it is readily to be seen that the human eye will not always equally well perform that function. The different points of the retina are not alike ready to appreciate colors. To distinguish the details of au object, it is necessary to direct the look toward it, or, in other words, to produce an image upon the central region of the retina, where the acuteness of physiological perception is much the greatest. ”

“ We are able to go still further into the mechanism of nutrition. Besides the loss of water by evaporation, plants have two kinds of respiration—one which is continuous day and night, disengaging carbonic acid, a kind of combustion correlative with life and quite analogous to the respiration of animals; and the other intermittent, and taking place only in the light, the result of which is to borrow from the carbonic acid of the atmosphere the carbon from which the plant makes sugar and wood, and to disengage oxygen. ”

“ A common plant, like those we have habitually under our eyes, increases, develops itself in every quality, adds to its weight, produces leaves, flowers, and fruits, and respires, or keeps up a constant exchange between the elements it contains and the gases of the atmosphere. These different acts of vegetable life are very unequally affected by the various luminous or calorific radiations. The growth of plants, by the elongation and multiplication of cells, takes place mostly under the influence of the calorific rays, and there is for each plant a preferred temperature. ”

“ Organization, feeling, spontaneous movement, and life exist only at the surface of the earth, and in places exposed to the light. We might say that the fable of the torch of Prometheus was the expression of a philosophical truth that did not escape the ancients. Without light, nature would be bereft of life, dead, inanimate. A beneficent God in giving light has spread organization, feeling, and thought over the surface of the earth. ”

“ Outside of the colors we are accustomed to see, the solar spectrum includes other rays, some less refrangible than the red, which make themselves manifest by their calorific properties, and others more refrangible than the violet, which are remarked by their photographic effects, and by the action they exercise on fluorescent substances. The solar ultra-violet spectrum produced in the prism occupies an extent nearly equal to that of the luminous spectrum ”

“ The color of seawater varies according to the thickness through which we observe it, on account of the unequal absorption of the different rays; hence a marine plant will find itself in a condition more or less favorable, and be better or less equipped for the struggle for existence, according to the depth of the soil on which it rests. ”

“ If we examine a bottom which the tide has just left, we will find blue sea-weeds on the edges of the deepest waters, farther down green sea-weeds, beyond these brown ones, and, lastly, red plants in the places which are least frequently uncovered. ”

“ Visibility, on the other side of the spectrum, persists in a remarkable manner. Helmholtz had already discovered that with certain precautions he could perceive the whole ultra-violet spectrum as it is revealed by photography. Having had occasion to study the light emitted by metallic vapors, I have ascertained that, with a prism of Iceland spar, an ordinary sight can distinguish an ultra-violet spectrum three or four times as extended as the luminous spectrum; one of my co-laborers saw much farther still, and pointed out in advance all the rays which it was possible for me to photograph. ”

“ Even if mankind were capable of a rapid progress toward perfection, it might be supposed that peoples who have continued in the conditions of the Stone age, like the natives of Cape Horn, should not have participated in the general progress. The French expedition, that recently spent a year at Terra del Fuego, made a special study of the natives in respect to this point. The Fuegian language has terms for only two colors, one for red and analogous tints, the other for blue and green. ”

“ But it is thus poor only because colors do not play an important part in Fuegian life, for it was found that with a little practice the people learned to distinguish and classify colors and their different shades with all the exactness of the most civilized European. The organic development of their visual apparatus, therefore, leaves nothing to be desired. The question whether the vision of animals is the same as that of man, or whether some of them may not have the faculty of perceiving rays to which we are insensible, has been taken up by M. Paul Bert. ”

“ If we examine the aërobes of a liquid with the microscope, we will find them collected around bubbles of an*, where they can find oxygen. If the liquid is deprived of air-bubbles and incloses a filament of a green alga, the bacteria will distribute themselves indifferently in the medium so long as it is illuminated with a very weak light, or, which is better, with a light that has been filtered through a solution of chlorophyl. ”

“ Without doubt, light and colors act upon the condition of our mind, and the moral impression thus produced can be nothing but the translation of a physiological action. In some sanitary establishments, where mental disorders are treated, patients are sometimes kept in a yellow light, which seems to exercise a happy influence on their disposition, and to promote calmer feelings. ”

“ The comparison of two lights of the same color can be made without the assistance of our eyes, and by physical means alone, but it is impossible to compare different colors without bringing in the intervention of the physiological impression. ”

“ It might be worth while to investigate whether the choice of their favorite colors by some painters is wholly intentional, or is a consequence of a physiological state. Color-blind persons are generally so by birth, but the affection may sometimes be the result of an accident. ”

“ A question has been raised on this subject that presents a very great interest in the philosophical point of view, as to whether man is susceptible of an organic development, and if it is possible to detect a trace of any progress that may have been accomplished in the vision of colors, and consequently in the structure of the eye. ”

“ The rays of greater wave-length are, therefore, the more active ones. Hence results a very simple explanation of heliotropism, or of the marked tendency of plants to bend toward the light. When a plant is exposed to a lateral light, the illuminated parts lengthen less rapidly than those which remain in the shade, and the plant bends its head toward the light. ”

“ Most animals show a similar disposition, and seek the light when it is not too glaring. When a spectrum was thrown upon the vessel, the Daphnias still spread themselves over the illuminated region, but with some quite remarkable peculiarities of arrangement. ”