( 618 ) 



i'^spect to the wavelength : ).*Dr^'^F=^ 2.129, is to be explained in 

 this way ^). 



About the influence of what was mentioned under 3 we have 

 made a separate measurement. See for this ^ 5. 



After the corrections indicated in this § have been applied, the 

 data of table IV may serve to give an idea of the size of the par- 

 ticles by the aid of developments such as are given by Lorenz ^), 

 From the change of vf.d in table IV on approach to the critical 

 temperature may already be deduced that the light-scattering particles 

 must no longer be considered as small with regard to the wave- 

 length at and below 11°.86^ (i.e. 0°.5 above Ti). 



§ 5. On the quantity of substance luhich is condensed in the 

 light-scattering particles at different temperatures '). To get to know the 

 intensity of the scattered light at different temperatures, only a correc- 

 tion has to be applied to table III on account of the circumstance men- 

 tioned p. 617 under 3. Therefor the condition of polarisation of 

 the scattered light at different temperatures must first be known 

 (cf. p. 613 note 2). An upper limit for this correction may already 

 be given as follows. 



In the measurement mentioned in § 4 it appeared that light 

 polarized normal to the slit was weakened to a greater degree in 

 the spectroscope than light polarized parallel to the slit, in such a 

 way that the ratio of the intensities in the spectrum is ") : 

 R/)jHü// = 0.82, HfJHf/i = 0.70. 



If we now suppose that at 13°. 53 all the light of wavelength D 

 scattered in a direction normal to the incident light is polarized 

 in the plane of incidence, and that at 11°. 24 this light would be totally 

 unpolarized, it follows from this measurement, that at 11°. 24 the 

 weakening of the D-light in the spectroscope would be J. 10 times 

 the weakening of the D-light at 13°. 53. 



To be able to derive from the intensity of the scattered light at 

 different temperatures how the quantity of condensed substance 

 depends on the temperature, we should have to get a somewhat 

 complete insight into the way in which the light is scattered by such 



1) Also the fact that the light scattered by the mist must pass through a 

 layer of a certain thickness (± 2 cM.) in the direction of propagation, may cause 

 a deviation in the same direction. 



2) L. LoRENz. Vidensk. Selsk. Skr. Copenhagen 6 (1890). Oeuvres Scientifiques 

 1 p. 405. 



3) Gf. § 1 p. 612. 



4) Gf. with this the calculations of Ghristie Proc. Roy. Soc. 26 (1877) p. 24. 



