6. A certain number of pieces of horse-artillery must always be _kept in reserve_, so that, if an artillery fire at any point should be suddenly wanted, it may be furnished with the least possible delay. 7. Guns of _various calibres_ should never be in the same battery, to prevent confusion as to the respective ranges, and in the supply of their ammunition. 8. An independent section or battery should never consist of _howitzers alone_, for the proper fire of these pieces is too slow to be effective in repulsing an attack on them. 9. There should always be _wide intervals_ between the pieces; otherwise the battery would offer too good a mark to the enemy. V.--How used. First, GENERALLY. Secondly, IN OFFENSIVE COMBAT. Thirdly, IN DEFENSIVE COMBAT. Fourthly, AGAINST INFANTRY. Fifthly, AGAINST CAVALRY. Lastly, AGAINST ARTILLERY. A. GENERALLY. 1. So far as is possible, guns should be kept _hidden from the enemy_ till the moment of opening on him. They may be masked by the ground, or other cover, natural or artificial, or by troops placed in front of them. The surprise will add much to their effect. Moreover, concealed, they will be less exposed to be taken. Nothing discourages troops more than the loss of a battery at the beginning of an action. 2. A desultory and indiscriminate artillery fire will accomplish nothing. To effect any thing important, it must be _concentrated on some object_; and the fire must be persevered in till the desired effect has been produced. 3. It is a general principle that artillery should not reply to the enemy's batteries, unless compelled to by their effect on our own troops. To obtain the most decisive effects from artillery fire, it should be directed _on the enemy's troops_, instead of his guns. 4. If it should become advisable to silence one of his batteries, it will be done more promptly and effectually by the employment, for this purpose, of _two_ of our own batteries, than of a single one. 5. There is usually great advantage in keeping our batteries constantly _shifting their position_; for then-- (1.) They have the effect of a surprise, by opening on the enemy at some unexpected point. (2.) They make the enemy believe our guns to be more numerous than they really are. (3.) They are in less danger of being captured. But these changes of position are attended with this inconvenience, that they expose the horses to be taken in flank by the enemy's batteries and sharpshooters. 6. The movements of a battery in the field should be _as rapid as possible_; for, while moving, it is helpless and exposed. Moreover, celerity of movement and accuracy of fire will often more than compensate for inferiority in the number of guns; as was the case at the battle of Palo Alto, in the Mexican War, where the enemy's guns outnumbered ours two to one. B. IN OFFENSIVE COMBAT.