When the stone was firmly secured, the next step was to liquefy a certain portion of mortar; and the joints having been carefully pointed, up to the upper surface, this mortar or cement was poured in with iron ladles so as to occupy every empty space. The more consistent parts of the cement naturally fell to the bottom, and the watery were absorbed by the stone; the vacancy thus left at the top was repeatedly refilled, until all remained solid; then the top was pointed, and, where necessary, defended by a layer of plaster.
The whole of the foundation having thus been elevated to a proper level, some other means was required to obtain a similar amount of security for the substructure.
A hole of one foot square was accordingly cut right through the middle of the central stone in the sixth course; and at equal distances in the circumference were sunk eight other depressions of one foot square and six inches deep. A strong plug of hard marble, from the rocks near Plymouth, one foot square, and _twenty-two inches_ long, was set with mortar in the central cavity, and driven firmly into it with wedges. As this course was _thirteen inches high_, it is evident that the marble plug which reached through it rose _nine inches_ above the surface. Upon this was fixed the central stone of the next course, having a similar bore in its middle, bedded with mortar, and wedged as before. By this means, no force of the sea acting horizontally upon the central stone, unless it was able to cut in two the marble plug, could move it from its position; and the more effectually to prevent the stone from being lifted, in case its bed of mortar should chance to be destroyed, it was fixed down by four trenails. The stones surrounding the central were dove-tailed to it in the same manner as before, and thus one course rose above another, with no other interruption than the occasional violence of the waves or inclemency of the weather.
In every stage of the laborious and difficult work Smeaton himself was foremost. When it had proceeded so far as to present the appearance of a level platform, he could not deny himself the gratification of enjoying the limited promenade which it afforded; but making a false step, and being unable to recover himself, he fell over the brink of the work, and among the rocks on the west side. The tide having retired, he sustained no very serious injury; but he dislocated his thumb, and as no medical assistance could be procured, set it himself, and returned to his work. The incident is characteristic of the courage and tenacity of the man.