The visitor can readily trace the Grinnell from place to place throughout the entire park area, and can thus easily visualize that it as well as all other formations at one time filled the intervening spaces between the mountains. (See color of cover pages.) SIYEH FORMATION. Next above the Grinnell is a thick limestone formation which, because of its weathered buff color, stands out in sharp contrast to the red beds upon which it rests. It is the greatest cliff-maker in the park and in several places its entire thickness of 4,000 feet may be exposed in a single nearly vertical cliff. Since it is younger than the three preceding formations, it is confined mainly to the higher elevations, capping many of the loftiest peaks within the Lewis and Livingstone Ranges. In the Many Glacier area such peaks are Mount Gould and the Garden Wall, Mounts Siyeh, Grinnell, Allen, Wilbur, and Henkel. A number of others, including Little Chief, Jackson, Gunsight, Fusillade, Going-to-the-Sun, Piegan, Pollock, Cannon, and Heavens Peak, are visible from Going-to-the-Sun Highway. The huge peaks—Kinnerly, Kintla, Carter, and Rainbow—which stand guard at the heads of Kintla and Bowman Lakes are composed of the Siyeh. The list also includes Cleveland, highest and largest of all. [Illustration: ALGAE COLONIES IN SIYEH LIMESTONE NEAR GRINNELL GLACIER. (DYSON PHOTO)] [Illustration: GENTLY TILTED STRATA OF THE SIYEH FORMATION IN GRINNELL MOUNTAIN. (DYSON PHOTO)]