For what it's worth, I find it interesting that Bearss censures McPherson for reporting to Grant that he had been in contact with 5000-6000 men with two batteries during the day.

Wirt Adams: 800 men
Gregg's Brigade: 3100 men + 1 battery
WHT Walker's Brigade: 1100 men + 1 battery
-----------------------------------------------

5000 men + 2 batteries

No indication that McPherson was aware that Walker's men were on the field during the battle, but interesting nonetheless, especially given that 2 hours into the battle McPherson reported to Grant that he had been in contact with only 1000 Confederates ... which was pretty close to the total that he had faced to that point. Intentially or not, McPherson was nearly spot on about the size of the force between him and Jackson.