_First_, most of them are made of unusual materials; that is, the ancient Indian selected a bright, clear stone, a stone with well-defined bands, or a fine-grained, dark brown sandstone, or a bright granite. He did not use ordinary limestone, and he employed gray slate or black slate without bands when he could obtain nothing else. He preferred brighter colors. The very material and its treatment indicate that these objects in their purpose stand apart from the ordinary run of common artifacts. _Second_, he brought these objects to a state of high finish, all of which involved a deal of labor. [Illustration: FIG. 310. (S. 1–1.) Carved animal figures on both sides of a flat piece of catlinite. North Dakota. Collection of Henry Montgomery, Toronto, Canada. ] _Third_, he was very particular how he made them, and I shall show pictures illustrating the progress of the double-winged problematical form from the block of slate to the chipped specimen. _Fourth_, he cast away broken axes or celts, and we seldom find a broken spear that is re-chipped, unless for use as a scraper. But it is significant that he made use of at least half of the broken problematical forms. This may seem trivial, but it is important; for we must inquire into every detail with reference to these objects because it is only by such study that we shall learn anything about them. _Fifth_, he made his perforations at right angles to the grain or bands of the stone, which should be noted. The exceptions are rare. If he drilled with the grain, the stone would chip, and before he finished the object, it might break. _Sixth_, he drilled the specimen before it was completed, knowing that the drilling was a dangerous process at best. And if he did not prize the specimen very highly, he would not have cared when he drilled it. _Seventh_, he placed these objects with his dead. He buried them in altars, or under other conditions which stamped them as peculiar and valuable. After ascertaining that slate pebbles were rare, he looked about for material and discovered veins of slate which outcropped in certain portions of the United States. He quarried slate even as he quarried flint, though on a less extensive scale. He blocked out this slate after the fashion of “turtle backs,” in order that he might conveniently transport it and work it into desired forms at his leisure. There is a village-site on Martin’s Creek, Pennsylvania, where numbers of these problematical forms have been found. There are thirty or more of them in our museum from this site alone. [Illustration: