SECTIONAL TRANSACTIONS.— A. 303 



fineness from quality to quality proceeds in geometrical progression, it would 

 seem that the qualities themselves proceed in arithmetical progression. 

 A logarithmic law apparently gives the sorter's relationship between quality 

 and fibre fineness for all countries in the world. It is found further that 

 the wool-sorter's work is based on the same psychological factors wherever 

 performed. 



Dr. R.A.HousTOUNand Dr. L. F. Richardson. — Quantitative mental 

 estimates of saturation with colour. 

 As a preliminary, the results of estimating large intervals of (i) loudness, 

 (2) redness, (3) distance on the skin, were exhibited as lantern slides. 



A rotating disc was next shown. Its outer zone appeared grey ; its 

 central portion a saturated orange-red ; and its intermediate zone was of 

 the same hue but less saturated. All three areas were nearly equally bright. 

 Each spectator was provided with a segment of a line 100 millimetres long, 

 and was asked to put a mark on the line to show where the intermediate tint 

 came on a scale of saturation extending from grey at one end to the saturated 

 colour at the other. 



Five persons stated that they could not perform the task. 

 Fifty-four persons made estimates. The positions, which they marked on 

 the lines, were subsequently measured in per cents., calling the grey o per 

 cent, and the saturated colour 100 per cent., with the following results : 

 Least estimate .... 5 per cent. 



Lower quartile . . . .- 29 ,, ,, 



Median . . . . • 38,,,, 



Upper quartile . . . . 59 >. >> 



Greatest estimate . . • 86 ,, ,, 



Five unsigned forms were excluded. Multiple marks on the same line 

 were averaged. Various suggested improvements are gratefully acknow- 

 ledged. 



On the disc the intermediate zone consisted of nearly equal angles of the 

 papers forming the outer zone and central portion. But to reduce contrast, 

 the full colour occupied 46 per cent, of the circumference next the grey 

 and 56 per cent, at the inner edge of the zone. These facts were not known 

 to the observers at the time they made their estimates. 



The median estimate of 38 per cent, is significantly less than the angle of 

 SI per cent. A similar deviation towards the unsaturated side was found 

 in previous experiments on white, pink and scarlet. 



Friday, September 2. 



Presidential Address by Prof. A. O. Rankine, O.B.E., on Some aspects 

 of Applied Geophysics. (See p . 2 1 .) 



Discussion on Supra-conductivity (Prof. J. C. McLennan, F.R.S., 

 Prof. W. J. de Haas, Dr. W. Meissner, Prof. O. W. Richardson, 



F.R.S.): — 



Prof. W. J. DE Haas. 

 From the experiments previously made, it seemed probable that the 

 metals go over into a new phase when they become supra-conduc- 

 tive. In order to support this point of view experiments have been carried 

 out. Formerly the region of disappearance of resistance was about 0-03°. 

 We found that for good single crystals and small measuring current this 



