x AQUATIC INVERTEBRATE FAUNA OF* WYOMING AND MONTANA. 215 



travel. The shores are bold but not much broken, steepest on the south and west, 

 where the 8,000- foot line runs a quarter to half a mile from the margin of the lake. 

 On the northeast a peak about half a mile back rises to 8,GOO feet, and others nearly 

 as high lie not far north of the eastern end. To the south the Pitchstone Plateau lifts 

 its black and forbidding mass patched with snow all summer to a height of nearly 

 9,000 feet; and to the southeast, 7 or 8 miles away, but seemingly less than half as 

 far, the Eed Mountains rise, culminating in Mount Sheridan, 10,200 feet above the sea. 

 The rampart of hills surrounding the lake opens out on the northeast, where Heron 

 Creek comes in ; on the west, to form the valley of Shoshoue Creek ; on the south, 

 where Moose Creek drains a swampy tract about 1 mile across and 5 miles long; and 

 on the southeast, where the waters of the lake pass out through Lewis River. Some 

 smaller tributaries empty at the Geyser Basin, on the eastern end; and a number of 

 little rivulets, dry at times, drain the hills at various points. Near the mouths of the 

 larger streams, ponds or small lagoons occur, connected with the lake at high water, 

 and in midsummer thick with vegetation and swarming with animal life. The imme- 

 diate shores are commonly rocky except for an occasional narrow beach of black 

 volcanic gravel. There is little weedy water in this lake, the sandy bottom bearing 

 at best a sparse growth of Potamogeton and plants of similar habit. 



The only soundings made by us were in the nortli arm or bay of the lake, where 

 depths of 40 and 50 feet were reached from a third to half way across the mouth of this 

 bay, starting from the eastern side. The bottom at these depths varied from sand to 

 soft mud, the latter without vegetation, the former with a growth of Cladophora. 



Our camp was placed in a small grove on the Hat at the mouth of Heron Creek, 

 where we had at hand the creek itself and a small, very weedy, and very muddy lagoon, 

 filled earlier with overflow waters, but then disconnected from the lake. Our collec- 

 tions were made chiefly in the north bay of the lake, but a few things were taken 

 from the western end, and a few collected alongshore as we made our way to the 

 outlet. In the north bay, besides making collections along shore and with hand nets 

 in the shallow water, we hauled the surface net repeatedly from the boat, from 8 a. m. 

 to 9 p. m., in both clear and rainy weather, and dredged at various depths from 6 to 40 

 feet. Our larger apparatus was useless, as there were no fish in -this lake.* 



* Here we first heard, while out on the lake in the bright still morning, the mysterious aerial sound 

 for which this region is noted. It put me in mind of the vibrating clang of a harp lightly and rapidly 

 touched high up above the tree tops, or the sound of many telegraph wires swinging regularly and 

 rapidly in the wind, or, more rarely, of faintly-heard voices answering each other overhead. It begins 

 softly in the remote distance, draws rapidly near with louder and louder throbs of sound, and dies 

 away in the opposite distance ; or it may seem to wander irregularly about, the whole passage lasting 

 from a few seconds to half a minute or more. We heard it repeatedly and very distinctly here and at 

 Yellowstone Lake, most frequently at the latter place. It is usually noticed on still, bright mornings 

 not long after sunrise, and it is always louder at this time of day ; but I heard it clearly, though 

 faintly, once at noon when a stiff breeze was blowing. No scientific explanation of this really 

 bewitching phenomenon has ever been published, although it has been several times referred to 

 by travelers, who have ventured various crude guesces at its cause, varying from that commonest 

 'catch-all of the ignorant, "electricity," to the whistling of the wings of ducks and the noise of 

 the "steamboat geyser." It seems to me to belong to the class of aerial echoes, but even on that 

 supposition I can not account for the origin of the sound. 



