PEALE.J LOWER GEYSER 'BASIN ^FOUNTAIN GROUP. 155 



times the water of 'iSo. 18 evidently connects with that of ^o. 17. l^o. 

 ISa is oue of the two large cavern-like bowls in the basin, and is the only 

 one in which I could obtain the temperature. Back of No. 18 are a num- 

 ber of sizzling holes. 



Nos. 20-23 are back of Na 17 and are sufBLciently described in the 

 table. 



Nos. 24 and 25 are back of No. 18. They are really within the limits 

 of one basin when full of water. Na 25 spouts irregularly to the height 

 of a foot or two. 



No. 26. Tliis is a large pool^ probably a geyser, north of No. 18. It 

 was estimated to be about 100 feet in diameter. It has a gray basin, 

 in which there is a fissure over which the water has a greenish hue. 

 The temperature (169° F.) was taken at the edge of the basin. 



No. 27 includes a number of springs on the line of a fissure. They 

 represent only a few of the springs on the flat. The surface is perfor- 

 ated with steam holes and bubbling and spouting springs. No. 27^ is 

 one of those nearest to No. 28. No. 31 is in the opposite direction. 



No. 28. This one of the handsomest springs on the lower level. It Is 

 somewhat irregular in shape, 100 feet in length by 30, 50, and 75 feet 

 in width, and has a white, scalloped, overhanging edge. As far as seen 

 it is a quiet spring, no boiling centers having been noted. It receives 

 some of its water from the subgroup on the Fountain terrace. It has 

 a beautiful sky-blue hue over the deeper parts of the pool. The tem- 

 X)erature (157° F.) was taken on the edge. 



No. 28a is a circular spring, 4 feet in diameter, with a grayish-whit« 

 basin and yellow and white rim. From the center of this basin a small 

 jet of water is thrown a couple of feet into the air. 



The map made in 1871 shows only seventeen springs in this group, and 

 of these No. 4 is the only one in which I can compare the temperature. 

 In 1871 it had a temperature of 140° F., and in 1878, 120° F. On the ter- 

 race of the Fountain the springs are so crowded that is difficult to show 

 them on the map, and in the fiat below only the most important are 

 given on the accompanjdng map. 



FOUJiTH OR FISSURE GROUP. 



This group might well have been named the Lake Group, for it is 

 characterized by hot lakes and ponds. A large quantity of water 

 goes from the springs and ponds, flowing over steps and terraces in an 

 intricate network of streams. Some of the latter are wide and deep, 

 ajid are filled with a luxuriant vegetation. Below the lakes and ter- 

 races the water spreads out on the flat and unites with the drainage 

 from the springs about the White Dome Geyser. In this area there are 

 large numbers of dead trees that have been killed by the flow of hot 

 water. This group is interesting also as containing a few springs in 

 which sulphur is deposited, which is rarely found to be the case in the 

 Lower and Upper Geyser Basins. The springs are situated mainly on 

 the sides of the ravine or valley in which the Low^r lake is situated, and 

 at the east end of the main or upper lake. There are four lakes^ the 

 largest of which is about 1,000 feet long and 800 feet wide. There are 

 two i)riiicipal geysers, although the height to which they throw the 

 water is not great. The following table contains the principal sj^rings 

 of the group : 



