------------+--------------------------+------- Load | Thickness in mm | Δ per sq.cm. +------------+-------------+------- in grm. | Limed skin | Puered skin | ------------+------------+-------------+------- 0 | 3·45 | 1·78 | 1·67 20 | 3·43 | 1·58 | 1·85 40 | 3·33 | 1·43 | 1·90 60 | 3·28 | 1·35 | 1·93 80 | 3·22 | 1·23 | 1·99 100 | 3·15 | 1·13 | 2·02 120 | 3·08 | 1·08 | 2·00 140 | 3·03 | 1·05 | 1·98 160 | 2·95 | 1·01 | 1·94 180 | 2·90 | ·98 | 1·92 200 | 2·83 | ·95 | 1·88 300 | 2·73 | ·88 | 1·85 All off | 2·98 | -- | -- 380 | 2·61 | ·82 | 1·79 600 | 2·43 | ·76 | 1·67 All off | -- | ·76 | -- ------------+------------+-------------+------- Δ = difference in thickness of the skin--i.e. compression under the same load. [Illustration: Fig. 11.--Apparatus for Measuring Degree of Falling _m_ = micrometer dial. JJ = jaws between which the skin is placed. _b_ = balance-weight attached to cord passing over pulleys _p p_, to counterbalance weight of frame _f f_. _k_ = knife edge supporting pan and weights _w_.] Fig. 11 shows the apparatus[72] that was employed to obtain these results. It consists essentially of a commercial form of micrometer for measuring the thickness of leather. To one of its jaws a pan for weights is attached, by means of the frame _f f_, in such a manner as to secure a perfectly straight pull. The weights of the frame and pan are counterbalanced in the manner shown by a counterpoise _b_. The delicacy of measurement may be increased by inserting larger jaws in the form of suitably fashioned disks, but even when this is done the results are to a certain extent vitiated by the rather considerable friction of the micrometer. [72] The apparatus was constructed by Mr. W. Linney, of the University College, Nottingham. Since this apparatus was constructed Professor H. R. Procter has informed me that an appliance devised by Mr. Anderson, of the Leeds University, for measuring the thickness of leather under varying pressures, has been in use in the leather industries department for some months for the purpose of measuring the proportion of the permanent to elastic compression. [Illustration: Fig. 12.--Curve obtained by Measuring Apparatus. (The dotted lines show the pressure on taking off the load.)]