592 C. H. Mathewson — Metallographic Description 



no sense comparable to the copper-tin alloys known as speculum 

 metal which contain in the neighborhood of 30 per cent tin 

 and retain their lustre for a long time. 



The order of curvature possessed by this disc may be sensed 

 by referring to the diagram, fig. 78, which was prepared by 

 running the pencil around the edges of a centrally located trans- 

 verse section of the object placed face down on the paper. 

 This serves as a diagram of position and two representative 

 photo-micrographs are shown on the same plate. Tig. 79 

 represents the structure of the handle. This is an unworked 

 casting structure, nearly homogenized by heat treatment, as 

 shown by the faint, but readily distinguishable cores (shadowy 

 markings all over the surface). Passing from the handle into 

 the disc, the large irregularly bounded casting grains give 

 place to a much finer recrystallized structure of the usual 

 characteristics. This is quite uniform all over the section of 

 the disc and is fairly represented by fig. 80, which, at the 

 stated magnification (72X)> practically spans the section from 

 one side to the other at the point indicated. The grain count 

 of 22 indicates a moderate annealing temperature; neighbor- 

 hood of 750°. As in the case of most of these specimens, it 

 is not possible to decide whether hot-working did or did not 

 occur during some stage of the shaping process. The section 

 examined bears evidence of undisturbed annealing after the 

 hot- or cold-working had been effected and subsequent alteration 

 in some places by cold-working, notably in the vicinity of the 

 handle. Thus, whatever may have preceded, the final changes 

 were produced by cold-working and the last severe work was 

 probably done in the region of the handle. 



Object No. 13 (cf. Table I). 



This piece is chiefly of interest as an example of a partially 

 completed object. By comparing fig. 22, illustrating the 

 present object, with fig. 27, illustrating a form of tweezers 

 commonly used for removing hair (cf. Joyce (6), p. 130), it 

 is readily seen that the finished tweezers, except for the per- 

 foration, will result when the present shape is bent around into 

 proper form. A section was prepared by sawing the piece 

 along its middle line from end to end. A diagram of this 

 section is given in fig. 81, and a photo-micrograph of the spot 

 indicated is shown in fig. 82. 



The grain count varies along the section from 13 to 25. This 

 indicates that some parts were worked considerably more than 



