40. In forcing the passage of a river, what is the most advantageous position for artillery? The bridge being generally laid in a re-entering angle, batteries should be posted on each side of the bridge, and far enough from it to secure a cross fire on the opposite bank. 41. Should the indiscriminate expenditure of ammunition be permitted in the field during action? Upon no account; ammunition should at all times be carefully husbanded, particularly at the commencement of an action, as the want of it at the close may decide the fate of the day; it should also be sparingly used in skirmishes and minor affairs, especially when at a distance from supplies, or in anticipation of a general action. [Sidenote: 49]] 42. When should the reserve be employed? When a particular point of the line requires additional support, a favorable position is to be seized, an impression has been made on the line by the enemy, a forward or retrograde movement is in contemplation, or when a determined attack is to be made on him, then the reserve should come up and take part in the action; and it is of the utmost importance that this should be done as expeditiously as circumstances will permit. 43. Where should the reserve be placed previous to an engagement? In rear with the second line, out of the range of shot, and as little exposed as circumstances will admit, but always in such a position as to have ready access to the front or rear. 44. Should guns be lightly abandoned before an enemy? Never until the VERY LAST EXTREMITY. An artilleryman must never forget that his gun is his proper ARM; that here lies his strength; that here is his post of honor and of duty; also, that the LAST DISCHARGES are always THE MOST DESTRUCTIVE, and MAY POSSIBLY INSURE THE SAFETY OF THE WHOLE ARMY, or TURN THE TIDE OF VICTORY IN THEIR FAVOR. 45. What is the position for cavalry when placed in support of a battery? On its flank, about the distance of 100 yards, and as much concealed as possible. [Sidenote: 50]] 46. What is the proper position of field batteries when infantry squares are attacked by cavalry?