W. T. Brighamr-Kiicmea in 1880. 19 



the angular motion of the index (p 1 for a given wire must be 

 expressible as a function of the time during which twisting has 

 taken place and the rate at which the strain is increased. In 

 other words, if c be the rate of rotation of the lower end of the 

 lower wire, the experimental results may be symbolized by 



i\ =/,(«, O 

 #;=/.(*. O 



i\ =/»(*, c„), 



where t is the symbol of time. It follows that the strain per 

 centimeter of the total length X, at any time t, will be ct/L 

 diminished by the amount of viscous motion.* Hence it is ex- 

 perimentally possible and fully feasible to pass from the family 

 of curves <p t , (p„ .. . . . <p n to a similar family, 



cp=-F(t,r), 

 by an appropriate method of graphic solution. <p thus expressed 

 as a function of time and strain, for all degrees of hardness and 

 all degrees of temperature T, is the complete solution of the 

 problem in hand. 



I take pleasure in acknowledging that the greater number of 

 experiments in this paper are due to Mrs. Barus. 

 Laboratory U. S. G-. S., Washington, D. C. 



Art. II. — Kilauea in 1880 ; by William T. Brigham. 



May 1, 1880, an outbreak from the summit crater of Mauna 

 Loa, in the Hawaiian Islands was reported. Some persons 

 made the ascent and found a fire fountain from the floor of the 

 small crater adjoining Mokuaweoweo, but this soon ceased and 

 no lava escaped from the crater or from any visible rent on the 

 mountain side. This was unusual, and thinking the slight 

 summit eruption was probably a prelude to a more extensive 

 outbreak, I started in June for the Hawaiian Islands taking 

 with me Mr. Charles Furneaux, a well-known artist, that I 

 might be able to preserve for scientific study, should we be so 

 fortunate as to see an eruption, those appearances that the 

 camera does not retain and which are so difficult to describe. 



As soon as possible after our arrival in Honolulu we sailed 

 for Hilo and made the ascent to Kilauea. The road had cer- 

 tainly not improved during the fifteen years since I had last 



* If c' be the rate of the index for perfectly elastic wires, then ip—c't, and 

 2c't—il> correspond respectively to the viscous motion and the strain intensity at 

 the time t. The curves ip will in general be circumflex, passing from an initial 

 tangent c' to an asymptote which is the rate of rotation of the lower end of the 

 wires. • 



