PEALE.] 



SHOSHONE GEYSER BASIN MINUTE MAN GEOUP. 



26: 



August 18. — Eruptions to-day have occurred as usual, but the water 

 in the pool back of the geyser has been low whenever seen. 



In the table of observations taken on the IGth, it will be seen that 

 43 spurts occurred in an hour in the morning, while in the afternoon 

 there were only 34 to the hour. It is probable that at times the height 

 attained may be 30 or 40 feet, although the highest measured by us 

 was only 23 feet above the top of the mound. There appears to be no 

 regularity about the length of the spurt nor of the interval between 

 them. The steam appears to escape rapidly, causing the frequent spurts. 

 The following temperatures were taken: 



August 16. — 2| feet below top of crater 180 



5 feet below top of crater 187 



6 feet below top of crater 200 



6 feet below top of crater 200^ 



These temperatures were all taken immediately after spurts. Th« 

 water was in such constant agitation that it was impossible to say how 

 far below its surface these temperatures were taken. It was difficult to 

 take the temperatures that were obtained. The temperature in the 

 pool back of the geyser was 171° F. The temperature of the air during 

 these observations was 01° F. 



Shield Geyser. — The Shield Geyser (shown in the foreground to the 

 left in Plate XXXII«) w^as named in 187U. It is about 70 feet from the 

 Minute Man, which is seen in the background of the illustration, to- 

 wards the north, and has a beaded mound, which is from 18 inches to 

 2 feet above the general surface. It measures about 11 by 7^ feet. It 

 has a shield-shaped basin, which is brilliant white, and measures about 

 8 feet on two sides and 7 on the third. At the bottom is an opening 

 about 3 feet in diameter, which is the top of the tube. A depth of 5 

 feet 8 inches was measured. The following are the observations made : 



August 16. — While observations were being made on the Minute Man, 

 the basin of the Shield was full, and every lew seconds the water spouted 

 a foot or two. At 1.2.00 p. m. the basin was empty; at 1.3.00 it was fill- 

 ing, and surface temperature was 190 ^F., air 60 ^F. 



1 02 





03 





V.i 





10 





18 





20 





22 





23 





27 





30 





35 





40 





50 



2 



00 



3 



25 



4 



13 





15 





10 





21 





23 





24 





25 





ao 





28 





29 



Time- of observation. 



h. m. s. 



00 p. m., basin is empty 



00 p. m., basin is filling 



00 p. in., basin is empty 



00 p. m., basin is fillinii 



30 p. m., bisin is emp^y 



00 p. ni., basin is flllin<i 



00 p. n"., l):)sin is empty 



00 p. m.. liiisin is filling 



00 p. m., basin is full and spouts 3 or 4 feet 



00 p. m., biisin is empty 



00 p. ni., water is down several inches in the tube 



00 p. m., water still down in tube 



0;J p. ni., water still down in tube 



00 p. m., water st ill down in tube 



00 1). ru., visited the Shield and found the ba-in fidl and water spouting two or 



th^(•,<^ feet, as in Iho moiuiug; considcraljlt! overflow 



00 p. m., water down in the tube 



00 J), in., basin filling and bubbling 



00 (>. tn., si)uiting as usual 



00 )). lu., (juiet and water falling 



00 p. in., water down in tube boiling moderately 



00 p. in., basin (illinj' 



30 \). m.. liasin is full but not spouting 



30 1). m., water is falling 



00 p. in., water is down in the tube 



00 i>. m., water is rising 



£ 4) fl 



+? B o 



5 30 



3 30 



"s" '66 



10 00: 



5 00 



