304 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1909. 
The problem is admittedly very complex, and is one which has 
not yet been studied enough to do much more than enable us to make 
a few broad guesses at the truth. But we are beginning to discern 
some glimmer of light, and the fact that we can not make out 
clearly our guiding stars, veiled as they are by the mists of imperfect 
_ knowledge, should not cause us to disdain such help as glimpses 
of them may now afford, or underrate their possible importance when 
the mists shall have been dispelled. 
