he at once abandons his original plan of turning the
Enemy's right, and determines on "going around his left, where the
country is more open, and the roads broad and good."

McDowell now orders a concentration, for that night, of the four
divisions, with two days cooked rations in their haversacks, upon and
about Centreville,--the movement to commence as soon as they shall
receive expected commissariat supplies. But, later on the 18th,
--learning that his advance, under Tyler, has, against orders, become
engaged with the Enemy--he directs the concentration to be made at once.

Let us examine, for a moment, how this premature engagement comes about.
We left Tyler, accompanied by Richardson, with a squadron of Cavalry and
a battalion of light Infantry making a reconnaissance, on Thursday
morning the 18th, toward Blackburn's Ford. They approach within a mile
of the ford, when they discover a Rebel battery on the farther bank of
Bull Run--so placed as to enfilade the road descending from their own
position of observation down to the ford,--strong Rebel infantry pickets
and skirmishing parties being in front.

Tyler at once orders up his two rifled guns, Ayres' Battery, and
Richardson's entire Brigade--and later, Sherman's Brigade as a reserve.
As soon as they come up,--about noon-he orders the rifled guns into
battery on the crest of the hill, about one mile from, and looking down
upon, the Rebel battery aforesaid, and opens upon the Enemy; giving him
a dozen shells,--one of them making it lively for a body of Rebel
Cavalry which appears between the ford and Manassas.

The Rebel battery responds with half a dozen shots, and then ceases.
Tyler now orders Richardson to advance his brigade and throw out
skirmishers to scour the thick woods which cover the Bull Run
bottom-land. Richardson at once rapidly deploys the battalion of light
Infantry as skirmishers in advance of his brigade, pushes them forward
to the edge of the woods, drives in the skirmishers of the Enemy in fine
style, and supports their further advance into the woods, with the 1st
Massachusetts Regiment.

Meanwhile Tyler, discovering a favorable opening in the woods, "low down
on the bottom of the stream," for a couple of howitzers in battery,
sends Captain Ayres of the 5th U. S. Artillery, and a detached section
(two 12-pound howitzers) of his battery, with orders to post it himself
on that spot, and sends Brackett's squadron of the 2d Cavalry to his
su