The great authority of Napoleon is on record upon the necessity of fortifying national capitals. He gives his opinion that 50,000 men, national guards or volunteers from the citizens, and 3,000 artillerymen will defend a capital against an army of 300,000 and that had Vienna, Berlin and Madrid been fortified and defended, the countries of which they are the capitals would have been preserved from the fatal results of his campaigns of 1805, 1806,and 1808 against them, and that, had Paris been fortified in 1814, his own Empire would have been saved from overthrow.

The position of Washington on the very borders of the insurgent territory, exposes it to great danger in cases of serious reverse to our arms in Virginia, and twice already have its defensive works been the means of saving the capital and enabling us to reorganize our defeated armies.

JOS. G. TOTTEN,

Brevet Brigadier-General and Colonel of Engineers.

M. C. MEIGS,

Quartermaster-General.

WILLIAM F. BARRY,

Brigadier-General of Volunteers.

J. G. BARNARD,

Brigadier General and Chief of Engineers, Defenses of Washington.

G. W. CULLUM,

Brigadier-General and Chief of Staff of the General-in-Chief .

WASHINGTON, December 30, 1862

Major General AMBROSE E. BURNSIDE, Falmouth:

MY DEAR GENERAL: You were good enough to say that you would be pleased to hear from me, and I venture to say a few words to you which neither the newspapers nor, I fear, anybody in your army is likely to utter.

In my position as Quartermaster-General much is seen that is seen from no other stand-point of the Army.

The Secretary of the Treasury has always felt the pressure of the difficulty of providing means to carry on the war, but he has thus far succeeded,so that the credit of the Government has not much suffered. Our contracts for supplies have not been made at prices higher than the consumption of the material might justify. Contractors have been content to wait a few weeks or months for their pay,and to receive it in certificates of debt, instead of in Treasury notes or gold. Hay and oats, two essentials for an army, have risen, however, until it is difficult to find men willing to undertake their delivery, and the prices are higher than ever before. A ton of hay costs not less than $30,and a bushel of oats costs $1 by the time it gets to Aquia. I begin to fear that the supply will fail. Should this happen, your army would be obliged to retire, and the animals would be dispersed in search of food.

Every day's consumption of your army is an immense destruction of the natural and monetary resources of the country. The country begins to feel the effect of this exhaustion,and I begin to apprehend a catastrophe. Your army has, I suspect, passed its period of greatest efficiency, and, by sickness, disability, and discharge, is decreasing in numbers. The animals have been recruited by rest, and are in better condition than they will be a month hence. The weather and the roads will not in months be again as favorable as during the weeks which have elapsed