NEW ORLEANS, May 25, 1864.

Major GEORGE B. DRAKE, A. A. G., Dept. of the Gulf:

SIR: I have the honor to submit the following as the best estimate of the cavalry forces in the Department of the Gulf which can be made up from the data now in this office.

I am, sir, very truly, your obedient servant,

W. BARCOCK,

Lieutenant Colonel Seventy-fifth N. Y. Vols., Acting Aide-de-Camp.

[Inclosure.]

Regiments. Numb Estima Conditi Station Remarks.

ers ted on. s.

of aggreg

comp ate

anie streng

s. th.a

CAVALRY BRIGADED.

First Brigade:

14th New York 6 - - In the

Cavalry. field.

16th Indiana 10 - - do.

Mounted Infantry.

2nd Louisiana 10 - - do.

Mounted Infantry.

6th Missouri 6 b2,136 - do. Howitzer

Cavalry. battery

included

in this

regiment.

12th Illinois 12 b1,200 Well Eight

Cavalry. armed. compani

es in

field

and

four

compani

es at

Greenvi

lle, La

Second Brigade:

118th Illinois 10 468 - Port

Mounted Infantry Hudson

3rd Illinois 5 365 - do.

Cavalry

Third Brigade:

1st Louisiana 8 500 - In the

Cavalry field

87th Illinois 10 400 - do.

Mounted Infantry.

2nd Maine Cavalry. 12 b1,200 A new Nine

regimen compani

t, well es at

appoint Greenvi

ed. lle and

three

compani

es in

field.

Fourth Brigade:

3rd Massachusetts 12 - - In the

Cavalry. field

6th Massachusetts 10 - - do.

Cavalry.

2nd New Hampshire 10 - - do.

Cavalry.

2nd Illinois 12 b2,946 - do. One

Cavalry battalion

of this

regiment,

mounted

and armed,

is at

Memphis

awaiting

shipment

here. One

battalion

dismounted

and

unarmed,

is at

Baton

Rouge.

3rd Maryland 10 645 - do. One

Cavalry company is

on duty at

Thibodeaux

and one

company on

pioneer

duty.

Fifth Brigade:

2nd New York 12 1,200 A do. One

Veteran Cavalry. veteran company at

regimen Brashear

t, and 250

nearly men, one

all company

mounted and

recruits,

at

Greenville

18th New York 12 1,000 Two do. Two

Cavalry compani companies

es at Pass

lately Cavallo;

capture three

d in companies,

the dismounted

field., at

Greenville

.

3rd Rhode Island 9 500 - do. Only two

Cavalry battalion

in this

department

Total 12,500

aTaken from latest report at hand.

bThese figures will be slightly reduced by excess of losses in late campaign over gain in recruits, but not very greatly.