Below this was hard 'pot-earth,' which Wren thought would be sufficiently firm to bear the great weight about to be laid upon it, but to ascertain its depth he had dry wells dug, and found it very unequal, in one place hardly four feet; he searched lower and found loose sand, then sand and shells; he speaks of them as sea shells, but it is now thought that they were probably river; below this again hard beach, and then London clay. He took great precautions when he laid any foundations here, fearing lest the sand should slip. The bed of sand is a danger still, for if pierced by a drain or other underground works the sand might run off, leaving a hollow under the pot-earth. The Cathedral authorities are accordingly wisely jealous of any excavations near S. Paul's. When the north-east portion of the choir was reached, in digging the foundations a pit was found, from which all the pot-earth had been taken, containing many fragments of vases and urns, all of Roman pottery. This pit was a very serious difficulty, occurring as it did at the very angle of the choir. Sir Christopher's assistants suggested to him to drive in piles of timber; but he knew that, though timber lasted well under water, yet in this case, where it would be half in dry and half in wet sand, it would rot in the course of time, and 'his endeavours were to build for eternity.' He dug down more than forty feet, till he came to the hard beach, below which was the London clay, and upon the beach built a pier of solid masonry ten feet square, till within fifteen feet of the ground, and then by turning an arch brought it level with the rest of his foundation. The theory commonly received was that a temple of Apollo stood where Westminster Abbey now stands, and that the site of S. Paul's Cathedral was occupied by a temple of Diana. Wren, however, believed in neither legend. The temple of Apollo he thought was invented merely that the monks of Westminster might not be behind the Londoners in antiquities. In spite of the horns of stags, tusks of boars, and the like, said to have been found during former repairs of S. Paul's, in spite of an image of Diana dug up hard by and in the possession of Dr. Woodward,[144] he wrote to Bishop Atterbury[145] that he 'changed all the foundations of old S. Paul's, and rummaged all the ground thereabouts, and being very desirous to find the footsteps of such a temple, I could not discover any, and therefore can give no more credit to Diana[146] than to Apollo.' In the September of 1675, when the work with which her husband's name is for ever connected was but little advanced, Lady Wren died, and was buried, as her son Gilbert had been, in the chancel of S. Martin's-in-the-Fields, leaving her husband with a baby son hardly seven months old. The 'Parentalia,' with characteristic carelessness, gives neither the date of her death nor the place of her burial. [_SECOND MARRIAGE._]