[Illustration: FIGURE 8.--Views of opening of oven in figure 7, photographed before its removal from house. This illustrates how oven was built into corner of fireplace and concealed from view. At right, the oven door is in place. (_Photos by A. C. Littlejohns._)] The clay with which all the potters worked came from three similar deep clay deposits in a valley running parallel with the River Taw in the parishes of Tawstock and Fremington between Bideford and Barnstaple. A geologist in 1864 wrote that the clay is "perfectly homogeneous ... exceedingly tough, free from slightest grit and soft as butter."[35] When fired at too high a temperature, he wrote, the clay would become so vesicular that it would float on water. The kilns were bottle-shaped and, according to tradition, originally were open at the top, like lime kilns; the contents were roofed over with old crocks.[36] Apparently all the potteries made the same types of wares, "coarse" or common earthenware having comprised the bulk of their product. The utilitarian red-ware was indeed coarse, since it was liberally tempered with Bideford gravel in order to insure hardness and to offset the purity and softness of the Fremington clay. An anonymous historian wrote in 1755:[37] Just above the bridge [over the River Torridge] is a little ridge of gravel of a peculiar quality, without which the potters could not make their ware. There are many other ridges of gravel within the bar, but this only is proper for their use. John Watkins wrote that Bideford earthenware "is generally supposed to be superiour to any other of the kind, and this is accounted for, from the peculiar excellence of the gravel which this river affords, in binding the clay." His claim that "this is the true reason, seems clear, from the fact that though the potteries at Barnstaple make use of the same sort of clay, yet their earthenware is not held in such esteem at Bristol, &c. as that of Bideford"[38] is scarcely supportable, since the Barnstaple potters also used the same Bideford gravel. The fire dogs found in Barnstaple with the date 1655, referred to above, were tempered with this gravel, as were "ovens, tiles, pipkins, etc.," in order "to harden the ware," according to Charbonnier, who also observed that "The ware generally was very badly fired.... From the fragments it can be seen that the firing was most unequal, parts of the body being grey in colour instead of a rich red, as the well-fired portions are." He noted that the potters applied "the galena native sulphide of lead for the glaze, no doubt originally dusted on to the ware, as with the older potters elsewhere."[39] A sherd of gravel-tempered ware is displayed in the window of Brannam's Barnstaple pottery, while a small pan from Bideford, probably of 19th-century origin, is in the Smithsonian collections (USNM 394440).