Unless the field artillery is directed with most particular care, it is liable to expose its infantry to heavy losses, which are not only regrettable in themselves but affect considerably the morale of the troops. For the very reason that the 75 mm. gun is a weapon of great precision, its accuracy is disturbed by very slight causes, such as atmospheric perturbations, and the quality and condition of the different powders. The officers commanding the batteries, immediately upon their arrival in new regions, prepare firing-tables based on the local conditions of the atmosphere and temperature, to guide the firing at the different hours of the day. They correct also the errors resulting from the different propulsive qualities of the various powders. As a rule all the projectiles belonging to the same lot give similar results. Directly it is in position, the field artillery calculates the distance that separates it from the various points on which it may have to fire. It complies with all the requests of the infantry, when informed of dangerous moves of the enemy; executing rapid barrages on the signalled objectives. By barrages, at about one hundred metres ahead of the advance, it protects the assaulting waves of infantry. It increases the range in proportion as the advance moves on. The groups of 105 mm. may be advantageously used in order to reinforce the action of the 75 mm. field artillery. Since it has been possible to increase the proportion of 155 mm. quick-firing guns, batteries of this calibre have often been brought in to reinforce the barrages kept up by the 75 mm. guns. In the recent operations on the Anglo-French front this combination has often been used on a large scale, and with disastrous effect whenever fire was opened in time on troops assembled for the purpose of counter-attack. Heavy artillery has a twofold part to play. It is an artillery for destruction and an artillery for counterfiring; it executes also neutralizing fire. It is guided by the information furnished by scouting airplanes and captive balloons. _Destructive fire_ is executed against important dugouts, blockhouses, shelters for machine-guns, and everything on the enemy’s front that can check the advance of the infantry. _Counterfiring_, guided by the same agencies, is executed in order to put enemy batteries out of action. It is certain, indeed, that the one of the two adversaries that succeeds in silencing the opposing artillery can more easily collect his forces, and, at the time of launching an attack or resisting a counter-attack, the task of the infantry will be made easier of accomplishment. At the time of the preparation of the attacks, the fire of the various artilleries continues for seven and even eight days with unabating or even (if necessary) increasing intensity.