The final question is, do the lines as depicted and described by various observers exist on the surface of Mars? Those who have made the greatest addition to our knowledge of the character of these lines, and have constructed maps based on Martian latitude and longitude are accredited on other grounds as being endowed with remarkable acuteness of vision coupled with persistence and painstaking care in observation. The most successful work has been accomplished with instruments of fine definition in regions of steady atmosphere and high altitude, or at intervals of clarity and steadiness in regions otherwise unfavorable. Finally, and most convincing of all, Mr. Lowell's assistant, Mr. Lampland, after many attempts has succeeded in photographing the more conspicuous linear markings. _The lines do exist essentially as figured by Schiaparelli and Lowell._ It now rests with the objectors to suggest any better interpretation of the markings of Mars than that they are the results of intelligent effort. The mediæval attitude of some astronomers regarding this question recalls the story of Scheiner, a Jesuit brother, who, independently of Galileo and Fabricius, discovered spots on the Sun. Eager with enthusiasm he informed his Superior of his remarkable discovery and begged to be allowed to publish it to the world. The Superior replied, "Go, my son; tranquilize yourself and rest assured that what you take for spots on the Sun are the faults of your glasses or of your eyes." This happened three hundred years ago, and yet to-day a few astronomers of this class still survive. If one will calmly reason about the matter, let him consider a parallel case of interpretation. He digs out from the ground a fragment of stone; its somewhat symmetrical shape suggests to him the idea that it may be a rude stone implement. If he wishes to know what kind of rock it is and its geological age, he refers it to a geologist; if he wishes to know its composition, he asks a mineralogist, who, if necessary, will analyze it for him. If, however, he is curious to know whether its peculiar, fractured surface is due to frost or other natural agency, or whether it is the work of some rude savage, he inquires of an archæologist, who alone will be able to tell him whether it is a worked stone or natural fragment. He will probably tell him whether it was shaped by paleolithic man, and whether it is a rough stone implement or a core, _reject_ or chip. So with the study of Mars, as we have already pointed out, there are certain matters of information about the planet which the astronomer alone can impart, while the superficial markings are just as certainly to be interpreted by another class of students who may or not be familiar with astronomical methods. * * * * *