208 Jaggar— Yolcanologic Investigations at Kilauea. 



the surface crusts liigli euougli to melt those crusts when 

 foundered ? How are the temperatures graded from lake to 

 grotto, or to blowing cone on the bench? How hot are the 

 burning gases ? Are thej hot enough for refusion of the 

 basalt 1 



Reconnaissance and 3Iethod. 



The floor of Halemaumau around the liquid lake was recon- 

 noitered from the east by a steep trail, and from the west with 

 rope ladders, on January 8, 4, 5 and 7, 1917. The north- 

 eastern rampart, a place of repeated overflow and largely 

 built by spatter over grottoes, was found to be a favorable 

 location for work at the actual edge of the liquid lake. We 

 were here standing on the bench magma, and could thrust iron 

 pipes into the lake magma. On January 4 an iron pot of lava 

 was dipped up from the lake (flg. 17a), with three immersions, 

 in the hope that such a pot might imprison the volcanic gas. 

 This pot was sent to the Geophysical Laboratory'. On January 

 7, the high western crag mass (fig. 6J) of the bench magma 

 was climbed to its summit, and photographs made in all 

 directions from this central position. It became evident that 

 Seger cones enclosed in series in the ends of common " gal- 

 vanized* iron '' (rolled steel) pipes, would be sei'viceable for 

 determining approximate temperatures, and as the tempera- 

 ture in the lake magma was expected to be at least 1000° C, 

 the first Seger cones used were of fusibilities near that figure 



The conditions of this sort of experimentation are arduous, 

 and the thrusting of a one-inch (2*51"°) steel pipe into the lava 

 and withdrawing it, are by no means simple operations. The 

 floor or bench was covered with pahoehoe lava flows freshly 

 overflowed nearly every day, crusted with shells three to five 

 inches (eight to thirteen centimeters) thick, and red hot 

 beneath (fig. 17«). Several times I crossed flows which had 

 poured out within four or five hours. The ranipart was three 

 to eight feet (one to two meters) high, built of glossy fling 

 from the fountains, which incessantly spattered over it, with 

 changing locations of activity. Consequently the surface of 

 the rampart was hot enough to burn shoe leather, but one 

 could stand on it with hob-nailed boots, by keeping in motion. 

 The high lake when near to overflowing (PL I^, lower view) 

 was most favorable for access and on account of its quietness, 

 brimming close to the rampart edge and above the level of the 

 floor behind. Work at such times, however, had to be rapid, 

 as at any moment sudden rising might start overflow, or the 

 rampart might collapse, or fountaining might begin at the 



* Zinc oxide would act as flux and make readings too high. Black steel 

 was used later. 



