192 



Mr. W. C. D. Whetham. 



<jommeiicing at X 4736-18, which so far has not been observed in the 

 ■chromosphere. The other flutings of carbon which are present in the 

 chromosphere do not appear in the coronal spectrum. 



The reductions indicate that there may be feeble indications of the 

 presence of some of the chromospheric gases in the inner corona. 

 Thus in photograph 3d, on the north-eastern edge, fragments of rings 

 corresponding to lines of helium at XX 4472, 4714, and 4922 have 

 been recorded ; these occur also on the south-western limb, where the 

 chromosphere itself is coming into view, but as the chromosphere was 

 completely eclipsed in the north-east at this stage, the radiations 

 mentioned as occurring there perhaps belong to the inner corona. 



A very interesting result of this detailed examination of the photo- 

 graphs is that the chief coronal ring in the green is very closely 

 •associated with the form of the inner, and appears to have no distinct 

 connection with the outer, corona. This suggests that the green line 

 •of the coronal spectrum is not produced in the outer corona, and that 

 the indications of its presence there on previous occasions, as obtained 

 by slit spectroscopes, were simply due to glare, as in the case of hydro- 

 gen and calcium. So far as the photographs taken with the prismatic 

 cameras are concerned, the spectrum of the outer corona gives no indi- 

 ■cations of bright rings. 



The measurements of the coronal rings and the diagram which 

 accompanies this paper have been made by Mr. Fowler. 



Dr. Lockyer has investigated the coronal spectrum in relation to 

 ■carbon, and Mr. Baxandall has made comparisons with the spectra of 

 stars and nebulae. 



The lonisation of Dilute Solutions at the Freezing Point." By 

 W. C. D. Whetham, M.A., Fellow of Trinity College, Cam- 

 bridge. Communicated by E. H. Griffiths, F.K.S. Keceived 

 February 14,— Bead February 22, 1900. 



(Abstract.) 



It is known that the depression of the freezing point of water, pro- 

 duced by dissolving molecularly equivalent amounts of different acids 

 -and salts in a given quantity of it, is approximately proportional to 

 the number of ions which these substances must be supposed to yield 

 in order to explain their electrical conductivities. Again, as the con- 

 centration of a solution of one such substance is gradually increased, 

 the molecular depression of the freezing point, and the equivalent 

 electrical conductivity, both vary, and vary by amounts which seem in 

 :Some cases to correspond, but in others to differ considerably. 



There appeared reason to suppose that it was desirable to increase 



