18 THE MAMMOTH CAVE. 
In preparing this history of the Mammoth 
Cave, we make as much use as possible of the 
materials just mentioned, collating their agree- 
ments and disagreements with our own obser- 
vations. We are chiefly indebted, however, to 
the valuable Manual of Professor Wright for all 
measurements and material facts, such as can 
be acquired only by a protracted series of obser- 
vations; and we trust that this general an- 
nouncement of the authorities that we draw ~ 
upon will serve us in many instances instead of 
quotation-marks. 
