Radiography is particularly useful for the nondestructive investigation of complete ceramic vessels, such as the Peruvian whistling pot in the shape of a macaw shown in Plate 4.1. The radiograph reveals clearly the whistle concealed within its head. But radiography can also be useful when applied to broken potsherds. Indeed, the earliest published radiographic examination of archaeological ceramics appears to be that of Titterington (1935), who published a radiograph (ibid. figure 7) of some potsherds from Indian burial mounds in Jersey County, Illinois. Inclusions in the clay are clearly visible in the radiograph; it can be seen that the different sherds contain different amounts of these inclusions. Another early study was published in 1948, reporting work carried out at the British Museum some years earlier by Digby and Plenderleith, who were interested in the methods used to make some spout-handled Peruvian pots (Digby 1948) (see below for further discussion).