PKALK.l LOWER GEYSER BASm THUD- GROUP. 145 



DESCRIPTION. 



Ko. 1. Loiie Spriyig. — This spring ia somewhat isolated from the rest 

 of the group, being quite a distance to the east of them, on the side of a 

 hill, at an elevation of about 40 feet higher. It has an ash-colored basin 

 measuring 9 feet by 16 feet, with a white border, and the basin, which 

 is somewhat funnel-shaped, is 4J feet in depth. The water has a milky 

 hue and a temperature of 174°. 



No. 2. Stirrup Spring. — This spring has a basin measuring 9 by 8 feet, 

 with a white rim raised about 6 inches. It is 5 feet deep, and the overflow 

 is carried away through a lemon-yellow colored water-way. There are 

 two holes in the bottom of this spring, from which the steam escapes, 

 and a fissure also, which makes the spring resemble the head of an old 

 woman with a cap on ; the scalloped edge of the spring representing the 

 ruffles of the cap, and the fissure the mouth, while the other steam-vents 

 represent the eyes. The temperature at the surface was 186° F., and at 

 2 feet below 187° F. This agrees closely with that (188° F.) taken in 

 1872. Close to the spring are several small holes, in three of which 

 temperatures of 195°, 194°, and 181° were obtained. The latter is 

 probably the one which in 1872 gave a temperature of 182° F. 



No. 3. Fungoid Spring, or Thud Qeyser (Fig. 1, Plate VII). — This is 

 the spring called Thud Geyser on the map published in 1871, but in 1872 

 was renamed from the fungoid-like masses that form the margin. It is 

 140 feet west of the Thud Spring (No. 4) and 345 feet south of the Oak- 

 leaf Spring (No. 5). Its basin measures 13 by 17 feet and averages 

 about 6 inches in depth. The deposit is pure white silicious, sinter- 

 coated with yellow in the shallow basin. In the center of the latter is 

 an inner or central basin, 5 feet in diameter and 7 feet deep, over which 

 the water has a light-greenish tinge, which contrasts well with the 

 white and yellow colors of the basin and rim. The latter resembles a 

 margin of fungoid giowths on short pedestals. They are gray -brown 

 on top. The temijerature over the central orifice was 165° F., and in 

 the basin near the edge 163° F. This was taken when it was quiet. 

 During the thumpings it is probably higher. Surrounding the basin is 

 a mound of sinter over which two small streams, lined with orange- 

 colored deposit, carry off the surplus water. On this mound, close to 

 the main spring, are two small basins. One of them (a) has four open- 

 ings, in which the water had a temperature of 190° F. just after the 

 thumping in the main spring occurred. During the latter the holes 

 were emi^ty, but as soon as the thumping ended the water began to 

 flow steadily from them. 



The following are the observations on the main spring : 



Began. Duration. 



Interval. 



11. 00 a, m. 

 11.23 a.m. 

 11. 38. 30 a. m. 



10- 



7m 



23" 

 15"30» 



During the action the basin is full, but immediately afterwards the 

 water falls. The observations were too limited to determine anything 

 in regard to the regularity of this spring. The noise made is a dull, 

 suppressed thud, which seems to be below the surface somewhere. 

 There is a slight escape of bubbles. 



No. 4. Thud Spring. — This sirring is 375 feet southwest from the 

 10 n, PT II 



