It is the policy of all Nations at all times, especially such as at present exist in our Confederacy, to make every effort to develop its internal resources, and to diminish its tribute to foreigners by supplying its necessities from the productions of its own soil. This observation may be considered peculiarly applicable to the appropriation of our indigenous medicinal substances of the vegetable kingdom, and with the view of promoting this object the inclosed pamphlet embracing many of the more important medicinal plants has been issued for distribution to the medical officers of the Army of the Confederacy now in the field. You are particularly instructed to call the attention of those of your corps to the propriety of collecting and preparing with care such of the within enumerated remedial agents or others found valuable, as their respective charges may require during the present summer and coming winter. Our forests and Savannahs furnish our _materia medica_ with a moderate number of narcotics and sedatives, and an abundant supply of tonics, astringents, aromatics and demulcents, while the list of anodynes, emetics and cathartics remains in a comparative degree incomplete-- "Very good! The next, Jarrow--" RICHMOND, FREDERICKSBURG AND POTOMAC RR. PRESIDENT'S OFFICE. HON. GEORGE W. RANDOLPH: _Dear Sir_,--At the risk of seeming tedious, permit me to say that my impression that you were mistaken last night in your recollection of the extent to which Louis Napoleon used railroads in transporting his army into Sardinia is this morning confirmed by a gentleman who is a most experienced and well-informed railroad officer, and is also the most devoted student of geography and military history, with the most accurate and extraordinary memory for every detail, however minute, of battles and all other military operations that I have ever met with. He is positive in his recollection that not less than 100,000 and probably more, of that army were gradually concentrated at Toulon and sent thence by sea to Genoa, and the rest were during some weeks being concentrated at a little town on the confines of France and Italy, whence they were transferred, partly on foot and partly on a double-track railroad, into Sardinia. The capacity of a double-track railroad, adequately equipped like the European railroads, may be moderately computed at five times that of a single-track road like those of the Confederate States. For the sudden and rapid movement of a vanguard of an army, to hold in check an enemy till reinforced, or of a rear guard to cover a retreat, or of any other portion of an army which must move suddenly and rapidly, and for the transportation of ordnance, ammunition,