Repository: UIHistories Project: Board of Trustees Minutes - 1886 [PAGE 244]

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236

The results obtained in a series of tests by this method were tabulated and reduced by my friend and colleague Prof. N. Clifford Bicker, so that the samples of wools of any breed could be compared not only with eacli other but with wools from other breeds, or even with different kinds of material as well. Li this work all the results of this series of tests were specially tabulated, and from them curves were plotted, the idea being to secure averages corresponding with the several units employed. Thus first it was necessary for each sample to determine for the purposes of the comparasons the average tensile strains required to produce in permanent stretch, in even and half millimetres, from one-half millimetre to the maximum produced, while for the total stretch they were computed for each successive millimetre. For each sample tests of ten fibres were taken, and the averages secured in this way for the sample above represented, 189 Co us wold, are the following,—stretch in millimetres, strain in grammes:

For permanent stretch: Stretch Average strains F o r total s t r e t c h : Stretch Average strains 0.25^ o.5o; 19.58 20.81j j__ 1.00 22.96J 1.50| 24.25| 2.00! 25.36| 2.501 3.00 28.89 20.76 1 3.50 31.84 4.W 33.05

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19.58!

2.00 21.13

3.00! 23.55

4.00i 24.83

5.00! 26.20

6.00 29.38

7.00 33.86

8.00 38.28

To determine averages for each breed represented the averages obtained above wTere collected for ten samples, and corresponding reductions made. But in order to compare results for different samples and secure averages for a class or breed, the fibres must be theoretically reduced to a common diameter, which for convenience was assumed for the material under examination to be four centimillimetres. Any other diameter could equally well be assumed. For reduction of all fibres to this uniform diameter Prof. Ricker made use of the following proportion and formula: I) 2 : 4 2 : : S : S 1 or, 16 S1 = S —

In which: 4 = the assumed common diameter of the fibre. D = the actual diameter of fibre for the given sample. 5 = the actual tensile strain on the fibre in grammes, producing a certain elongation, total or permanent. S 1 = the tensile strain in grammes that should be required to produce identical elongation in a fibre 4 centimillimetres in diameter. The strains must be to each other as the squares of the diameers of the fibres, supposing the section to be of similar form.