P. S.-I received the inclosed telegram at 6 o'clock to-night, and send this communication by Captain Neill, to be delivered early to-morrow. No delay in the execution of the order will result, if, after what I have stated, the order be reiterated in these words: "Execute the order,"

R. PATTERSON,

Major-General.

[Inclosure.]

WASHINGTON, D. C., May 5, 1861.

Major General R. PATTERSON:

Send immediately six regiments of Pennsylvania volunteers to this city via York, Pa.

SIMON CAMERON.

WASHINGTON, May 6, 1861.

Lieutenant-General SCOTT, Commander-in-Chief, U. S. Army:

DEAR SIR: I deem it important that our railway from Washington to the Relay House (within nine miles of Baltimore) should be well guarded by the military department.

The Annapolis Branch is now protected. Colonel Scott, in charge of the railway and telegraph departments, recommends that a regiment (if possible to spare it) be stationed along the line as a permanent guard, say one company each four miles, with tents and equipments complete. This would require eight companies, the two remaining companies to encamp at or near Bladensburg, which it is believed is not a loyal district. With our railway and telegraph protected, we could move this regiment for you at any time on short notice to Annapolis, Relay House, or Washington.

Our telegraph has been destroyed twice since yesterday morning. We much fear that evil-disposed persons may interfere with tracks and cause serious accidents and delay in many of our movements.

Respectfully, yours,

SIMON CAMERON,

Secretary of War.

DEPARTMENT OF ANNAPOLIS, May 6, 1861.

Lieutenant-General SCOTT:

GENERAL: In obedience to your command, I have occupied the station at the Relay House, nine miles from Baltimore, with the Eighth New York Regiment. I have learned however that a force of two regiments of dragoons had been raised and were in force at Ellicott's Mills, some eight miles from this point, and I therefore ordered up Major Cook's light battery, Massachusetts Volunteer Militia, which was with me at Annapolis; and as I was moving Colonel Jones' Sixth Regiment Massachusetts Volunteer Militia from the capital, I ordered them also here, so that I am here in considerable force, to wit:

Colonel Lyons, Eighth Regiment

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1,000 men.

Colonel Jones, Sixth Regiment

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600 "

Major Cook

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100 "

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Total

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1,600 "