Editorial Couiincnt. 375 
The distribution of the volcanoes in Ecuador, Cohmibia, 
Bohvia, ChiH, and Mexico, Central America, and the Aleutian 
group is very remarkable, for it is evident that a great nucleal 
centre would not discharge the excess of its igneous fluid by 
narrow channels, but by great orifices in the regions of flow, 
which would be kept permanentl}- open during the eruptive 
period. 
He leaves the same dilemma which his object was to solve. 
Either the earth is surrounded by a thin crust although its in- 
terior is in a state of fusion, which is in contradiction with cer- 
tain geological and astronomical facts, although offering an 
easy explanation of volcanic action : or the earth is solid to a 
great depth and contains only a relatively unimportant kernel 
of igneous materials, which conforms to the astronomical and 
geological facts but leaves the eruptive phenomena unaccount- 
ed for. r. F. 
gilbert's summary history of NIAGARA FALLS. 
Numerous partial descriptions and discussions of Xiagara 
river and Xiagara falls have been published in late years, ow- 
ing to the rapid growth of the Pleistocene geology of the re- 
gion of the great lakes. Some views have not been in accord 
with others, and some geologists have amended their own 
views. The result is that those who have not closely noted the 
development of this history find some difficulty in forming a 
consistent idea of the actual result arrived at by these re- 
searches. Below is the summary of this result as given by Mr. 
G. K. Gilbert in connection with the new map of Xiagara river 
and the Pan-American Exposition, dated May, 1901. 
N. II. w. 
"The beginning of the river is intimately associated with 
the Glacial or Pleistocene period. Before that time lake Erie 
and lake Ontario did not exist and there was a very different 
system of rivers in the region. In the early part of the period 
glaciers were formed on the highlands of Canada, and gradu- 
ally grew and spread until they covered all the region of the 
great lakes. They eroded the land in places and deposited the 
eroded material elsewhere in the fomi of drift. Then they 
melted back so as to uncover the lake region, making an inter- 
glacial epoch, and afterwards they again grew large. These 
