J. D Dana — History of the Changes in Kilauea. 21 



government, under Professor Alexander's charge, completed 

 in 1886. For convenient comparison the reduced copies of 

 Wilkes's and Brigham's maps are here reprinted ; that of the 

 Government survey is reproduced in Plate 1 of this volume. 

 In using the maps a difficulty is encountered at the outset in 

 consequence of a discrepancy between the first two of the maps 

 and that of the Government survey as to the dimensions of 

 the crater. Accepting the latter as right, the scale of each of 

 the others should be diminished about an eighth to bring the three 



maps into correspondence. The maximum diameters in Wilkes's 

 map, using his own scale, are 16,000 and 11,000 feet; while 

 according to the Government map they are about 14,000 and 

 9800 feet ; and the length of the line from K to B on the for- 

 mer is 10,000 feet and on the latter 8500 feet. It is certain 

 that the crater in 1840 was not larger at top than now. Mr. 

 Brigham's map appears to have been carefully made, but for 



