288 Messrs. J. T. Bottomley and A. Tanakadate. [June 20, 



the fibres makes it easy to do with these fine filaments that which is 

 otherwise scarcely possible. The fibre is attached to the galvano- 

 meter mirror with the smallest possible speck of shellac varnish, the 

 greatest care being taken not to varnish any part of the spider line. 

 When the varnish has dried, the mirror can be lifted np by the spider 

 line ; caution being used at the moment of raising the one mirror off the 

 surface of the other on account of the vacuum which is liable to be 

 formed at the moment of separation. The mirror should be allowed 

 to hang on the fibre inside a glass beaker for twenty-four hours at 

 least, as the spider line stretches considerably for some time after the 

 weight comes on it. A spider line which will carry a galvanometer 

 mirror and magnet weighing 0"2 gram may have, according to au 

 estimate made by one of the present writers, about of the torsional 

 rigidity of a single cocoon silk fibre. 



Eor the heating of the junctions, a number of glass vessels were 

 blown, resembling the flasks, with neck and condensing tube, used 

 for fractional distillation, but with the condensing tube projecting' 

 upwards into the air, so that the steam of a liquid boiling in tbe 

 flask runs back into the flask on being condensed. Into the shorter 

 neck of the flask was introduced a cork, which carried the thermo- 

 j unction and a mercurial thermometer ; the thermo- junction being 

 loosely bound to the bulb of the thermometer, or, at any rate, kept in 

 close contact with the middle part of the thermometer-bulb. The 

 cool junction was bound to the bulb of a second thermometer, which 

 dipped into a vessel containing water at the temperature of the 

 laboratory. The water was kept thoroughly stirred from top to 

 bottom by a properly arranged stirrer. 



In the heating flasks the vapours of the following liquids were used : 

 alcohol, water, chlorobenzol, aniline, methyl salicylate, and bromo- 

 benzol.* The liquids were boiled vigorously, and the temperatures of 

 the vapours were determined by means of the mercurial thermometer. 

 Both the mercurial thermometers were compared directly with the 

 air thermometer, f The obtaining of a set of points of temperature 

 by this means was very satisfactory in every case except that of the 

 liquid of highest boiling point, bromobenzol. In this case a curious 

 phenomenon was observed. J In spite of the fact that the vapour of 

 the substance was rushing strongly into the condensing tube and, 

 indeed, out into the open air, at an elevation of 2 feet above the surface 

 of the liquid it was found exceedingly difficult to keep the temperature 

 ot the various parts of the boiling flask anything like uniform. The 

 vapour formed itself into layers of different temperatures, the parts 

 of the flask nearest the surface of the liquid being the hottest. At 



* Kamsay and Young, ' Chem. Soc. Journ. (Trans.),' 1885. 

 f J. T. Bottomley, ' Phil. Mag.,' August, 1888. 

 X Perhaps due to want of purity of the suhstance. 



