CHEMICAL STUDY OF MATERIAL 585 



cessive earlier overflows (plate 22), which individually rarely exceeded 

 2 or 3 feet in thickness. The (Halemaumau) pit as a whole was about 

 1,500 feet in diameter, roughly circular in plan, and with nearly perpen- 

 dicular walls except for the talus pile at the base, which extended about 

 half way up the wall. All these dimensions vary somewhat from day to 

 day and considerably from year to year with the state of activity in the 

 basin. The appearance of the lake and its surroundings is perhaps best 

 shown by a photograph (plate 23) made from a slight elevation above 

 the floor of the active basin on May 23, 1912. 



Analyses op the Lava 



The composition of the liquid lava in the lake and of the solid floor 

 of the Kilauea crater near the Halemaumau pit may be seen from analy- 

 ses 1-a and 1-b which follow. The sample 1-& was dipped from the 

 middle of the lava lake on July 23, 1911, by Mr. Frank A. Perret and 

 one of the authors (Shepherd) 10 with the help of a cable and trolley, 

 stretched directly across the center of the pit, and appropriate tackle. 

 The sample 1-a- was taken from one of the recent overflows on the main 

 floor of the Kilauea crater and may perhaps be fifteen or twenty years old. 

 The substantial identity of the analyses with each other and with other 

 recent analyses of the lavas of Hawaii 11 shows that no material change in 

 its composition has taken place in recent years. The most noticeable fea- 

 ture of the new analyses is perhaps the presence of a small amount of 

 molybdenum, which appears not to have been detected hitherto. The 

 analyses were most carefully made by Mr. John B. Ferguson of this 

 laboratory, to whom we take this opportunity to express our thanks. 



10 This expedition was sent out by the Massachusetts Institute of Technology (Prof. 

 T. A. Jaggar) In the summer of 1911 for the purpose of securing a trustworthy measure- 

 ment of the temperature in the lava lake. The record of the expedition has not been 

 published. 



u R. A. Daly: Magmatic differentiation in Hawaii. Journal of Geology, vol. 10. 1911. 

 p. 305. 



W. T. Brigham : Loc. citi, p. 33. 



