J. D. Dana — History of the Changes in Kilauea. 15 



From which x— + 5*0, y = - 379. The resulting speed is 

 2*638 ± 0-105 miles, or 4245 ± 168 meters per second. If the 

 correction for the systematic error has a value approximately 

 that which has been derived from the comparisons of the 

 stopped clocks with well determined times of particular locali- 

 ties, or not less than one-fifth the amount, the corrected speed 

 would be from 5100 to 5200 meters. 



We may now proceed to combine the results of the first three 

 groups and obtain from them a single mean. The probable 

 error of the fourth group being uncertain it is necessary to 

 omit it. TaMng the weights inversely as the squares of the 

 probable errors we have : 



Group I, 

 Group II, 

 Group III, 



5205 m ± 168 m 

 5192 m ± ^36 m 

 5 1 7 1 m =fc 116 m 



W't. 



2 

 1 

 4 



Mean result, 



5184 m ± 80 m 





It remains to inquire whether the data indicate any variation 

 of the speed. The answer is in the negative. The data are 

 inconsistent with any variation of a systematic character and 

 there is no apparent means of detecting an unsystematic one. 

 A small irregular variation, such as might be caused by varying 

 density and elasticity of the propagating medium, would not 

 be inconsistent with the data ; but the evidence of it cannot be 

 separated from the errors of observation. 



Art. II. — History of the changes m the Mt. Loa Craters', 

 by James D. Dana. Part I. Kilauea. (With Plate I). 



[Continued from vol. xxxiii, p. 433 (June), vol. xxxiv, p. 81 (August), and p. 349 



(November).] 



4. General Summary, with Conclusions. 

 From the foregoing review of publications on Kilauea, 

 it appears that we have already much real knowledge about 

 the changes in the crater, and that this knowledge embraces 

 facts that are fundamental to the science of volcanic action. 

 This will be made more apparent by the Summary and Con- 

 clusions which follow. It will be convenient to consider, first, 

 the Historical conclusions, and secondly, the Dynamical. 



I. HISTORICAL. 



1. Periodicity or not in the discharges of Kilauea. 



In the sixty-three years from 1823 to 1886, there appear 



to have been at least eight discharges of Kilauea. Four of 



them were of prime magnitude — those of 1823, 1832, 1840 



