TRANSACTIONS OF SECTION A. 



777 



In presenting this brief introduction to the physics of smell, I have aimed at 

 indicating the vast territory that waits to be explored. That it will be found to 

 contain mines of theoretical wealth there can be no doubt ; while it is probable that 

 a luxuriant growth of technical application would spring up later on. Already, lor 

 example, Mrs. Ayrton unintentionally picks out inferior glass by the repugnance 

 she shows at drinking water out of certain cheap tumblers. To conclude, I may 

 say that one of my fondest hopes is that an inquiry into the physics of smell may 

 add another to the list of wide regions of knowledge opened up by the theoretical 

 physicist in his search for answers to the questions of the technical man. 



The following Report and Papers were read : — 



1. Report on Comparing and Reducing Magnetic Observations. 

 See Reports, p. 80. 



2. Lenses not of Glass. By J. W. Gifford. 



Glass passes light to X = 3612, calcite to X = 2064, and quartz to X = lSo2, the 

 most refrangible line of aluminium. Seventy deviations were measured between 

 A = 7951 and X = 2147. Over that range an uncorrected quartz lens F = ll" gives 

 1'76" of chromatic aberration; when corrected by calcite this may be reduced to 

 0-24". A partially achromatised lens where error = 0'71J8" gives less spherical 

 aberration and a flatter held. In this the achromatism curve is so nearly a straight 

 line that a glass plate once tilted at the angle required, the spectrum may be 

 photographed from A = 7051 to X = 2147 with good detinition throughout. 



There are only four elements known which give lines bejond the range of cal- 

 cite. These lenses are therefore suitable for spark photography of projectiles. 



The best lens for achromatism was calculated not from the dispersive powers, 

 but from the refractions for X = 1852, an imaginary deviation for calcite being 

 obtained by graphical extrapolation. Fluor-spar corrected by quartz gives better 

 achromatism. 



3. On the Articulation and Acoustics of the Spirate Fricative 

 Consonants.^ By R. J. Lloyd, D.Lit., M.A., F.R.S.E. 



The writer compared the results of his recent paper '• with those of foreign 

 observers. 



The best German results ■■ compare as under : — 



The diflerences between the first and third lines are probably personal for s, 

 but national lor sh and ch. They represent, in V.D. per. sec, the strongest sound 

 heard in these consonants when articulated in isolation ; and they are in each case 

 created by the resonance of the oral cavity, before or behind the frictional passage. 

 But this fixity of articulation and resonance is simply the combined result of con- 

 venience and habit. They may be easily made to vary through the wide ranges 

 given in the fourth line ; and in actual speech they do vary, under the influeuce of 



' Nettcre Sprachen, vol. vii. = Roy. Sue. Edhn., Proc. vol. xiii. 



' Trautmann, Sprachlaiite, 1885. 



