A series of measurements of wire diameter, length of side, and area of holes, has been made on new and used sieves, all of which were originally of the “100 mesh” size, i.e. the square holes were supposed to be ·01″ in length of side and the wire to be ·01″ in diameter. The measurements have been expressed as frequency curves.In the case of unused sieves woven to the I.M.M. specification, the sieve on the whole compared well with the specification, but in used sieves the variations were much greater. The divergence from specification in the new and old sieves is shown by Tables I and II respectively.In one sieve (No. 2) the holes elongated more in one direction than the other. In fact in one direction the alteration which has taken place is a contraction rather than a stretch. This effect was probably connected with the manner in which the sieve was attached to its metal framework, and also to difference in tempering of the wires and the tension in weaving.A number of the frequency curves showed double peaks, and the actual observations showed that there was a systematic distribution of values corresponding to these two peaks. It is probable that some of the guides in one of the combs through which the warp wires are led during the weaving were displaced sideways, thus giving alternate strands of wire and narrow holes. This was particularly the case in the single weave.