Morning journal and courier., 1885-06-09

to put ourselves in imagination in the con- dition of creatures under the sea, and ask what the sun may appear to them; for if the fish who had never risen above the ocean floor were an intelligent being, might he not plausibly reason that the dim greenish light of his heaven--which is all he has ever known was the fnll splendor of the sun, shining through medium which all his experience shows is transparent?
 We ourselves are, in very fact, living at the floor of the great aerial sea, whose pillows roll hundreds of miles above our heads. It is not at any rate conceivable that we may have been led into like fa1lacy of assuming that the intervening medium above us is colorless because the light which comes through it is so?
 I freely admit that all men, educated or ignorant, appear to have the evidence of their senses that the air is colorless, and that pure sunlight is white, so that if venture to ask you to listen to considerations which have lately been brought forward to show that it is the sun which is blue, and the air really acts like an orange veil or like a sieve which picks out the blue and leaves the white, do so in the confidence that I may appeal to you on other grounds than those 1 could submit to the primitive man who has his senses alone to trust to; for the educated intelligence possesses those senses equally, and in addition the ability to interpret them by the light of reason, and before this au- dience it is to t-interpretation thatI ad= dress myself.
 My own attention was first directed this way many years ago, when measuring the heat and light from different parts of the suns disk. It is known that the sun has an atmosphere of it's own which tempers it's heat, and, by cutting off certain radiations and not others, produces the spectral lines we are familiar with. These lines we cus- tomarily study in connection with the ab- sorbing vapors of sodium, iron, and so forth, which produce them; but my own attention was particularly given to the regions of ab- sorption, or to the color it caused, and I found that the suns body must be deeply bluish, and that it would shed blue light ex- cept for it's apparently colorless solar atmos- phere, which really plays the part of red dish veil, letting little of the blue appear in the center of the suns disk where it is thin nest, and staining the edge red, so that to delicate tests the center of the sun is pale aqua-marine, and it's edge garnet. The eff feet l found to be so important that if this all but invisible solar atmosphere were diminished by but 8 third part, the tempera- ture of the British Islands would rise above that of the torrid zone, and this directed my attention to the great practical importance of studying the action of our own terrestrial atmosphere on the sun, and the antecedent probability that our own air was also and in dependently making the really blue sun into an apparently white one. We actually know then, beyond conjecture, by comparison of the suns atmosphere, where it is thickest and where it is thinnest, that apparently co1orless atmosphere can have such an effect, and analogous observations which I have carried on for many years, but do not now detail, show that the atmosphere of our own planet, this seemingly clear air in which we exist, like creatures at the bottom of the sea, does do so. We look up through our own air as through something so impid in it's purity that it appears scarcely matter at all, and we are apt to forget the enormous mass of what seems of such Eghtness, but which really presses with nearly ton to each square foot, so that the weight of all the buildings in this great city, for instance, is less than that of the air above them.