Page:Bird-lore Vol 01.djvu/344

 are, however, rare instances where the conditions are such that identification of a bird as to its order, or even more detailed identifications, are possible, and it is this chance which buoys up the enthusiasm while keeping your patient vigil.

When the small cone of atmosphere between the eye and the moon is compared with the entire dome over any point of observation, the mind may grasp the extent of this movement of the birds that pass in a night in any longitude, and when this is again multiplied by the number of nights in the migrating season, and again by the width of our land from the cliffs of Newfoundland to the Golden Gate of the Pacific, some conception may possibly be had as to the vast importance in the economy of nature of this movement of the feathered army as it sweeps northward on its summer campaign.