[311] This came from the extreme hardness of the soil, which induced the builders of the 18th-century enceinte to put less earth into the glacis than was needed, since it had to be scraped up and carried from a great distance, owing to the fact that the coating of soil all around is so thin above the rock. For some days after the investment of Almeida had been completed the 6th Corps remained quiescent, and made no attempt to break ground in front of the place. Ney was waiting for the Grand Park and the train, which had now started in detachments from Ciudad Rodrigo, but were advancing very slowly on account of the lack of draught animals. For a moment Wellington thought it possible that the enemy was about to mask Almeida, and to advance into Portugal with his main army without delay[312]. This hypothesis received some support from the facts that Junot had moved up from the Agueda, and that Reynier had shown the head of a column beyond the Pass of Perales. This last appeared a most significant movement; for if the 2nd Corps was about to march up from the Tagus to join Masséna, the deduction was that it was required to join in a general invasion, since it was clear that it was not needed for the mere siege of Almeida. Wellington accordingly wrote to urge Hill to keep a most vigilant eye on Reynier, and to be ready to move up to the Mondego the moment that it was certain that his opponent had passed the Sierra de Gata and linked himself to the main French army. As a matter of fact there was, as yet, no danger from Reynier. The advance of one of his flanking detachments to Navas Frias beyond the Pass of Perales, and a raid made upon Penamacor on July 31 and upon Monsanto on August 1, by another, were pure matters of foraging and reconnaissance. Reynier had no orders to move up his whole force to join Masséna, and was only amusing himself by demonstrations. His actions became most puzzling to Wellington when, a few days later, he called back all the troops that had moved northward, and concentrated his force at Zarza la Mayor, on the road to Castello Branco, so as to threaten once more to invade Central Portugal by the line of the Tagus. This was no device of his own, but the result of a dispatch from Masséna dated July 27, ordering him to keep more to the south for the present, to threaten Abrantes, and to afford Hill no chance of joining Wellington. [312] Wellington to Hill, Alverca, July 27, ‘There is not the smallest appearance of the enemy’s intending to attack Almeida, and I conclude that as soon as they have got together their force, they will make a dash at us, and endeavour to make our retreat as difficult as possible.’