On the following day (February 1) the French began to move forward from Santa Engracia towards the Coso, always clearing their way by explosions, and risking as few men as possible. Nevertheless they could not always keep under cover, and this day they suffered a severe loss: their chief engineer, General Lacoste, was shot through the head, while reconnoitring from a window the houses against which his next attack was to be directed[137]. He was succeeded in command by Colonel Rogniat, one of the French historians of the siege. That officer, as he tells us, discovered that his sappers were using too large charges of powder, which destroyed the roofs and four walls of each house that they undermined, so that the infantry who followed had no cover when they first took possession. He therefore ordered the substitution of smaller measures of powder, so as to throw down only parts of the wall of the building nearest to the French lines, and to leave the roof and the outer walls uninjured. In this way it was much more easy to establish a lodgement, since the storming-party were covered the moment that they had dashed into the shattered shell. The only plan which the Spaniards could devise against this method of procedure, was to set fire to the ruins, and to prevent the entry of the assailants by burning down all that was left of the house. As the buildings of Saragossa contained little woodwork, and were not very combustible[138], the besieged daubed the walls with tar and resin to make them blaze the better. When an explosion had taken place, the surviving defenders set fire to the débris of floors and roofs before retiring[139]. In this way they sometimes kept the French back for as much as two days, since they could not make their lodgement till the cinders had time to cool. Countermining against the French approaches was often tried, but seldom with success, for there were no trained miners in the city: the one battalion of sappers which Palafox possessed had been formed from the workmen of the Canal of Aragon, who had no experience in subterranean work. On the other hand the French had three whole companies of miners, beside eight more of sappers, who were almost as useful in the demolition of the city. They maintained a distinct ascendent underground, though they not unfrequently lost men in the repeated combats with knife and pistol which ensued when mine and countermine met, and the two sides fought for the possession of each other’s galleries. [137] There is a full account of his death in Legendre, i. 149; that officer was in the room with him, when he and his aide-de-camp, Lalobe, were simultaneously shot through the head as they peered out of a side window where they thought themselves unobserved. [138] The ceilings in all the better sort of houses were made of vaulted arches, not of beams and boards. [139] See Cavallero, p. 120, and compare Belmas, ii. 253.