132 EEPORT UNITED STATES GEOLOGICAL SITEVEY. 



Leaving this group and proceeding northward througli the timber we 

 come to No. 85, a collection of mud pots 2 to 3 feet in diameter, with 

 white mud. 



JS'o. 86. A collection of simmering holes and steam vents. 



No. 87. Sulphur holes and vents. These are not far from the main 

 creek that is north of the basin. 



Eeturning through the timber, the next subgTOup is opposite that of 

 No. 79, and is composed of the following: 



No. 88. Double sulphur spring. 



No. 89. Milky green sulphur spring 10 by 12 feet. 



No. 90. Small green spring. 



No. 91. Steam hole in rocks. 



No. 92. Large green pool, about which there are numerous sulphur 

 simmering holes. 



No. 93. Mud pot, with thick white mud. 



No. 94. White mud pot, 10 feet diameter, surrounded by vents and 

 mud-holes. 



The two following are near the large pool, No. 80, already mentioned, 

 viz: 



No. 96. Sulphur spring 10 feet long, with temperature of 161° F. 



No. 97, Green sulj^hur pool, 10 feet in diameter, with temperature of 

 142° F. 



There are several points in connection with this Geyser Basin that 

 are particularly noticeable when we review its numerous springs. They 

 are: 



First. The absence of any very great accumulation of deposits, such as 

 are seen in the Geyser Basins of Fire Hole Eiver. 



Second. The newness of some of its most important geysers. 



Third. The abundance of iron and sulphur in the deposits. 



It is, I think, evident that here we have the newest development of 

 thermal action to be found in the Park, not only because we have a 

 geyser which dates only from 1878, but because when we examine the 

 other geysers we find that the deposits have not yet reached any con- 

 siderable development. The oldest geyser in the group, if we judge 

 from the accumulation of deposits, is the Pebble Geyser. 



Southwest of the springs just described and about a mile distant, in 

 what he calls the Upper Canon of the Gibbon, Mr. Norris says there is 

 a collection of red pulsating geysers.* In his report for 1878t he speaks 

 of them as follows : 



Along and near the upper canon of tlie Gibbon are pulsating geyser cones of both 

 yellow and crimson, paint springs, and rivulets of nearly every color, geysers throwing 

 their jets, some at least 100 feet, at an angle of 40° to 60°, instead of vertically, as in 

 the old basins. 



This is probably the same as the Eed Geyser Basin he speaks of in 

 his report for 1877 (page 13). 



MONIBDENT GEYSERS. 



This collection of geysers, named by Col. P. W. Norris, is on a spur of 

 the plateau on the south side of the open valley above the head of the 

 lower caiion of Gibbon Eiver. The group is about 1,000 feet above the 

 level of theriver, and the columns of steam can be distinctly seen from the 

 open valley. I was unable to visit them from lack of time, and the 



* Eeport on the Yellowstone National Park 1879, p. 16. 

 t Eeport on the Yellowstone National Park 1878, p. 6. 



