In order that the reader can follow easily the narrative of that remarkable life-system which is conducted by the fur-seal as it annually rests and breeds upon the Pribylov group, I present a careful chart of each island and the contiguous islets, which are the only surveys ever made upon the ground. The reader will observe, as he turns to these maps, the striking dissimilarity which exists between them, not only in contour but in physical structure, the Island of St. Paul being the largest in superficial area, and receiving a vast majority of the _Pinnipedia_ that belong to both. As it lies in Bering Sea to-day, this island is, in its greatest length, between northeast and southwest points, thirteen miles, air-line; and a little less than six at points of greatest width. It has a superficial area of about thirty-three square miles, or twenty-one thousand one hundred and twenty acres, of diversified, rough and rocky uplands, rugged hills, and smooth, volcanic cones, which either set down boldly to the sea or fade out into extensive wet and mossy flats, passing at the sea-margins into dry, drifting, sand-dune tracts. It has forty-two miles of shore-line, and of this coast sixteen and a half miles are hauled over by fur-seals _en masse_. At the time of its first upheaval above the sea, it doubtless presented the appearance of ten or twelve small rocky, bluffy islets and points, upon some of which were craters that vomited breccia and cinders, with little or no lava overflowing. Active plutonic agency must have soon ceased after this elevation, and then the sea round about commenced a work which it is now engaged in—of building on to the skeleton thus created; and it has progressed to-day so thoroughly and successfully in its labor of sand-shifting, together with the aid of ice-floes, in their action of grinding, lifting, and shoving, that nearly all of these scattered islets within the present area of the island, and marked by its bluffs and higher uplands, are completely bound together by ropes of sand, changed into enduring bars and ridges of water-worn boulders. These are raised above the highest tides by winds that whirl the sand up, over and on them, as it dries out from the wash of the surf and from the interstices of rocks, which are lifted up and pushed by ice-fields.