Still more serious is another problem. When the mining operations were commenced, in December, 1604, Parliament was appointed to meet on the 7th of February following, by which time, as is evident, the preparations of the conspirators could not have been completed. While they were working, however, news came that the session was to be postponed till October. This information the conspirators appear to have received quite casually before Christmas, for it is said that on the strength of it, they thought they could afford to take a holiday.[153] Early in January they were again at work,[154] and they continued their operations thenceforth, without any circumstance intervening to interrupt or alarm them, of which we hear anything either from themselves or from subsequent writers. Nevertheless, it is quite certain that the Lords actually met on February 7th--that is while the mining operations were going on--and not only went through the ceremony of prorogation, but transacted some little business besides, Lord Denny being introduced and his writ of summons read.[155] It is equally incomprehensible that the miners should have known nothing of so startling an occurrence, or that knowing of it they should never have made the slightest mention thereof. It is even more difficult to explain how the Peers thus assembled, and their attendants, could have failed to remark the mine, then actually open, in premises belonging to themselves, or any suspicious features of earth, stones, timber, or barrels. The difficulties presented by the stubborn nature of the foundation-wall proved well-nigh insuperable, but, as is observed by Father Greenway,[156] one still more grave awaited the diggers had they succeeded in making their way through. The "concavity" to be excavated within, to contain the large number of powder barrels required for their purpose, would have involved engineering work of the most hazardous kind, and heavily laden as the floor above proved to be, it must, according to all rules of calculation, have collapsed, when thus undermined. But at this juncture, when the wall had been half pierced, a circumstance occurred, not less extraordinary than others we have considered, to change the whole plan of operations.