What are some of the things they note?
First of all, it was night. That wonderful light coming through the clouds to highlight General Washington was far from the reality of the night. The crossing began in the late afternoon of December 25th...the sun, if it had been out, would have set by then. Very little light would have been visible outside of a few lanterns with candlelight.
Compounding the darkness and certainly indicating that no sun was available, is the fact that diary account after diary account talk of the horrible weather that accompanied the crossing. Rain to sleet to snow pelted the troops and made the conditions difficult and disheartening. One account mentions that it was supposed to be a nearly full moon that night, yet you could barely see the moon as the clouds made it impossible to view.
The darkness of the night and the darkness of the murky river water made for a dangerous mission. The Delaware River was believed to be at flood stage at the time of the crossing. However, the river in the painting is not modeled after the Delaware, but rather the Rhine River in Germany. Mr. Leutze's family was originally from Germany. (At the time this region of Europe comprised individual provinces and city-states rather than the united country we think of today.) Emmanuel had gone to Germany to study art and painted this work, his most popular, while there. The ice that forms in the Delaware River tends to be large, solid sheets that break into floes in the River. Some of these would have been quite large and would have constantly pounded into the side of the boats as the current pushed them down river. However, in the painting, the ice tends to be depicted as ice caps and crags instead of the way the Delaware River still looks when ice forms.
Did the artist get anything right?